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Research Article
Review of the fish parasitic genus Elthusa Schioedte & Meinert, 1884 (Crustacea, Isopoda, Cymothoidae) from South Africa, including the description of three new species
expand article infoSerita van der Wal‡§, Nico J. Smit|, Kerry A. Hadfield|
‡ North-West University, Potchefstroom, South Africa
§ Ludwig-Maximilians-University, Munich, Germany
| North West University, Potchefstroom, South Africa

Corresponding author: Kerry A. Hadfield ( kerryh26@yahoo.com )

Academic editor: Tammy Horton
© 2019 Serita van der Wal, Nico J. Smit, Kerry A. Hadfield.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: van der Wal S, Smit NJ, Hadfield KA (2019) Review of the fish parasitic genus Elthusa Schioedte & Meinert, 1884 (Crustacea, Isopoda, Cymothoidae) from South Africa, including the description of three new species. ZooKeys 841: 1-37. https://doi.org/10.3897/zookeys.841.32364
ZooBank: urn:lsid:zoobank.org:pub:4D023A1C-B64C-4278-8C8A-F23D55266E2F
Open Access

Abstract

The branchial-attaching cymothoid genus, Elthusa Schioedte & Meinert, 1884 is a genus with a worldwide distribution of 36 species, including the three species described here. Elthusa raynaudii (Milne Edwards, 1840) is the only species that has been described from southern Africa. All South African material held at the National Museum of Natural History, Paris, France (MNHN) and the Iziko South African Museum, Cape Town (SAMC) identified as, or appearing to belong to, Elthusa was examined. Four species were identified, Elthusa raynaudii and three species that proved to be undescribed. Elthusa xena sp. n. can be distinguished by an evenly rounded pereonite 1 anterior margin, a roughly rectangular pleotelson, and narrowly rounded uropod apices that extend to more than half the length of the pleotelson. Elthusa acutinasa sp. n. is identified by the produced and narrowly rounded cephalon anterior margin, acute uropods that are shorter than half the length of the pleotelson, and pereonite 1 anterior margin with medial projection. Elthusa rotunda sp. n. is characterised by the round body shape, broadly rounded uropod apices, and protrusions on the proximal and lateral margins of the merus and carpus of pereopod 7. A key to the South African Elthusa species is provided, together with a table summarising the hosts and localities of the 33 previously known species of Elthusa.

Keywords

Alexander Bay, Atlantic Ocean, Clinus superciliosus, Elthusa raynaudii, fish parasites, Indian Ocean, taxonomy

Introduction

Elthusa Schioedte & Meinert, 1884 is a branchial cavity-inhabiting cymothoid genus that was described as a monotypic genus for Elthusa emarginata (Bleeker, 1857). Elthusa was subsequently largely overlooked until Bruce (1990) provided a new diagnosis based on one of Bleeker’s (1857) syntypes and the Australian species of the genus. Most species of Elthusa were originally described and placed within the genus Livoneca before their revision and redescription by Bruce (1990).

Currently, there are 33 known and accepted Elthusa species (Öktener et al. 2018a). Elthusa is one of the more speciose genera within the family Cymothoidae Leach, 1818, however many species of Elthusa still need to be studied and redescribed due to their original descriptions being inadequate, lacking morphological detail and illustrations. The high morphological intraspecific variability that exists within this genus (Hadfield et al. 2017) has also contributed, in some cases, to misidentifications and confusion regarding the placement of species.

Most species of Elthusa inhabit the branchial cavities of their fish hosts (Smit et al. 2014), with the exception of two species. Elthusa neocytta (Avdeev, 1975) ovigerous females have been recorded from the buccal cavity of the spiky oreo, Neocyttus rhomboidalis Gilchrist, 1906 (see Stephenson 1987), and Elthusa splendida (Sadowsky & Moreira, 1981) has been described from the buccal cavity of the spiny dogfish Squalus cubensis Rivero, 1936 (see Sadowsky and Moreira 1981).

Elthusa is considered to be cosmopolitan, except for polar waters (Bruce 1990, Bruce et al. 2002, Rocha-Ramírez et al. 2005, Hadfield et al. 2017), and is predominantly recorded from the Indo-West Pacific (see Bruce 1990, Trilles and Justine 2006) with only occasional records of species from the Eastern Pacific (Brusca 1978, Espinosa-Pérez and Hendrickx 2001), the Atlantic (Kensley and Brusca 2001) and the Mediterranean (Trilles and Justine 2006, Öktener et al. 2018a). Elthusa raynaudii (Milne Edwards, 1840) is the only species of Elthusa that has been described from sub-Saharan Africa. The lack of species records is most likely due to the lack of studying cymothoid isopods from this region and is not a true representation of the biodiversity of this genus. This paper forms part of a detailed study on the cymothoids from sub-Saharan Africa and confirms this postulation with the identification of three new species from the region.

Materials and methods

Twenty-seven specimens of Elthusa were examined. Material loaned from the National Museum of Natural History, Paris, France (MNHN) and the Iziko South African Museum, Cape Town (SAMC) was included in the examination. These specimens were collected as early as 1840 (MNHN) and 1960 (SAMC). Non-museum material was collected during 1993 in the intertidal zone of Alexander Bay, as well as from deep-sea trawlers during January 1999 and April 2003 off the south coast (RV Africana), and during February 2010 off the west coast of South Africa (RV Dr Fridtjof Nansen).

Specimens were identified by illustrating all body parts and appendages using a Nikon SMZ1500 Stereo Microscope and a Nikon Eclipse80i Compound Microscope, both equipped with drawing tubes. The position of specimens and dissected parts were manipulated to obtain the most accurate direct and complete view in order to minimise errors in illustrated ratios of segments. Material loaned from national museums was not dissected. Species descriptions were made with the aid of the taxonomy software package DELTA (Descriptive Language for Taxonomy) (see Coleman et al. 2010), following a general Cymothoidae character data set originally developed by Hadfield et al. (2010) and recently updated for other genera (Hadfield et al. 2013, 2016b). Ratios and measurements for the descriptions were made using the maximum values at the middle of the specific measured segment, and all proportional measurements were rounded to one decimal place. Higher-level classification follows that of Brandt and Poore (2003). Host authorities are not included in the text or references; host nomenclature and distribution were sourced from FishBase (see Froese and Pauly 2018) and Catalog of Fishes (see Eschmeyer 2018).

Abbreviations:

DELTA Descriptive Language for Taxonomy

MNHN National Museum of Natural History, Paris, France

NWU North-West University, Potchefstroom Campus

OH other hosts

OL other localities

RV research vessel

SAMC Iziko South African Museum

Syn synonym

TH type host

TL total length

TLoc type locality

W width

Taxonomy

Suborder Cymothoida Wägele, 1989

Superfamily Cymothooidea Leach, 1814

Family Cymothoidae Leach, 1814

Elthusa Schioedte & Meinert, 1884

Elthusa: Schioedte and Meinert 1884: 337; Bruce 1990: 254; Trilles and Randall 2011: 453; Hadfield et al. 2017: 3.

Type species

Livoneca emarginata Bleeker, 1857; by monotypy (Schioedte and Meinert 1884). The original number of type specimens that were available to Bleeker (1857) is unknown. A single female syntype, examined by Bleeker (1857), is deposited at the Naturalis Biodiversity Center (previously the Rijksmuseum von Natuurlijke Historie), Leiden (RMNH.CRUS.I.66). Another type specimen from the latter museum has been lost. The specimen examined by Schioedte and Meinert (1884) is held at the Natural History Museum in Paris (MNHN241) (Trilles 1976).

Remarks

Species from Elthusa can be distinguished from other genera by having a weakly vaulted dorsum with a wide pleon; antennulae that are shorter than, or subequal in length to antennae, bases not in contact; a cephalon posterior margin that is not trilobed; and lamellar pleopods. Other diagnostic characters include a slender maxilliped palp article 3, with setae present; as well as pereopods with relatively short dactyli (see Bruce 1990 for a revised diagnosis of the genus).

Trilles and Randall (2011) redescribed the type species for the genus, E. emarginata. This redescription provided a more detailed description and more accurate drawings of the species that had previously not been possible due to the fragility of the syntype. It also allows for a diagnosis and description of the genus based on the type material. However, Trilles and Randall (2011) designated one of the examined specimens [material deposited by Schioedte and Meinert (1884) into the Natural History Museum in Paris, MNHN No. 241] as the lectotype for the species. This does not follow the ICZN rules (Article 74.1) for lectotype designation as there is extant type material (RMNH.CRUS.I.66). Furthermore, no figures were provided of the designated lectotype material to ensure recognition of the specimen designated (ICZN Article 74.7.2). As such this lectotype designation is invalid and set aside (ICZN Article 74.2).

The original description by Bleeker (1857) did not specify any host species, genus or even family (“the skin of various species of fish”) and Trilles and Randall’s (2011) redescription is not supported by or based on specimens being from the same host species or genus. Trilles and Randall (2011) did not examine Bleeker’s remaining syntype, and comparison of the two accounts suggest that there are some differences between the Bleeker (1857) figures and those of Trilles and Randall (2011); most notably being the shape of the cephalon, which is truncate or subtruncate in the syntype but anteriorly concave in Trilles and Randall’s redescription; and the pleotelson in the syntype is broadly rounded (“semi-circular”) while distally narrowed in Trilles and Randall’s redescription. Trilles and Randall (2011) made no direct reference to Bleeker’s (1857) description and did not comment on any perceived character difference. These differences suggest that direct comparison to Bleeker’s syntype is needed to confirm conspecificity of the specimens identified by Trilles and Randall (2011) as E. emarginata.

Key to the species of Elthusa from southern Africa
1 Pleonite 5 lateral margins visible; uropods half the length of pleotelson or longer; pereonite 1 anterior margin without medial projections; pereonite 1 anterolateral margin extending to medial region of the eye 2
– Pleonite 5 lateral margins largely concealed by pleonite 4; uropods short, less than half the length of pleotelson; pereonite 1 anterior margin medially pointed; pereonite 1 anterolateral margin extending to posterior margin of the eye Elthusa acutinasa sp. n.
2 Cephalon with rounded anterior margin; uropod rami apices broadly rounded; pleotelson evenly rounded 3
– Cephalon anterior margin narrowly rounded; uropod rami apices narrowly rounded; pleotelson sub-quadrate Elthusa xena sp. n.
3 Pereon 1.2–1.4 times as long as wide; cephalon anterior margin blunt; pereopod 7 without bulbous protrusions; uropods more than half the length of pleotelson; pleonites subequal in length Elthusa raynaudii
– Pereon as long as wide; cephalon anterior margin concave; pereopod 7 merus and carpus with bulbous protrusions; uropods half the length of pleotelson; pleonite 5 longest Elthusa rotunda sp. n.

Elthusa raynaudii (Milne Edwards, 1840)

Figures 1, 2, 3, Table 1

Livoneca Raynaudii: Milne Edwards 1840: 262; Krauss 1843: 66; Bleeker 1857: 30; Schioedte and Meinert 1884: 367, pl. 12, figs 9–13; Thielemann 1910: 42; Hale 1926: 215–217, figs 10a–j.

Cymothoa Novae-Zealandia: White 1847: 110 (nomen nudum).

Lironeca novae-zealandia: Miers 1874: 228; 1876: 106, pl. III, fig. 2; 1881: 64, 67.

Lironeca laticauda: Miers 1877: 677, pl. 69, fig. 5; Ellis 1981: 124.

Livoneca Raynaudi.–Gerstaecker 1882: 259.

Livoneca Novae Zelandiae.–Gerstaecker 1882: 263.

Lironeca Stewarti: Filhol 1885: 450, pl. 4, fig. 6.

Lironeca neo-zelanica.–Thomson and Chilton 1886: 154.

Livoneca raynaudii.–Whitelegge 1902: 236; Chilton 1909: 606; 1911: 309; 1912: 135; Stebbing 1910: 125; Young 1926: 283; Hale 1926: 215, fig. 10; 1929: 261, figs 253, 259; 1940: 303; Barnard 1940: 491; 1955: 6; Hurley 1961: 268; Hewitt and Hine 1972: 108; Sivertsen and Holthuis 1980: 34; Beumer et al. 1982: 33.

Livoneca epimerias: Richardson 1909: 88, fig. 13; Kussakin 1979: 301, figs 69, 170.

Livoneca raynaudi.–Nierstrasz 1915: 97; 1931: 145; Barnard 1920: 358; Pillai 1954: 16.

Livoneca laticauda.–Nierstrasz 1931: 143.

Lironeca raynaudii.–Brian and Dartevelle 1949: 176; Avdeev 1975: 250; 1978: 281; Trilles 1976: 778, pl. 1, fig. 4; Poore 1981: 341.

Lironeca raynaudi.–Menzies 1962: 115, fig. 36A–B; Kensley 1978: 80, fig. 33B; Moreira and Sadowsky 1978: 111.

Lironeca magna: Mañé-Garzón 1979: 18, figs 1–5.

Elthusa raynaudii.–Bruce 1990: 263; Bruce et al. 2002: 177; Williams et al. 2010: 99–101.

Elthusa raynaudi.–Ghani 2003: 218.

Type material

Type material held at the Museum national d’Histoire naturelle, Paris (syntypes MNHN-IU-2016-9885; MNHN-IU-2016-9884).

Type locality

Cape of Good Hope, South Africa.

Type host

Unknown.

Material examined

(all from South Africa). Syntype. SOUTH AFRICA • 1 ♀ (ovigerous, 26.7 mm TL, 14.1 mm W); south coast of South Africa, Cape of Good Hope; MNHN-IU-2016-9885. Other material. SOUTH AFRICA • 1 ♀ (ovigerous, 26.0 mm TL, 14.0 mm W); Indian Ocean, south coast of South Africa, RV Africana (fish sorting table); 34°38'S, 25°38'E; April 2003; coll. Nico J. Smit; dissected; in the collection of the authors at NWU • 1 ♀ (ovigerous, 26.0 mm TL, 15.0 mm W); Atlantic Ocean, RV Dr Fridtjof Nansen trawl (Station NAN401T062); January 2007; coll. L Atkinson; SAMC-A47881 • 1 ♀ (ovigerous, 20.0 mm TL, 12.0 mm W); Atlantic Ocean, RV Dr Fridtjof Nansen (fish sorting table); 32°17'S, 16°54'E; 269 m; February 2010; coll. KA Hadfield; dissected; SAMC-A089957.

Description

(ovigerous ♀). Figs 1–3. Body ovoid, slightly twisted to the left, 1.7 times as long as greatest width; dorsal surfaces smooth and polished in appearance, widest at pereonite 5, most narrow at pereonite 1; pereonite lateral margins mostly posteriorly ovate, medially indented. Cephalon 0.9 times longer than wide, visible in dorsal view, sub-truncate with blunt anterior margin. Frontal margin thickened, ventrally folded. Eyes oval with distinct margins; one eye 0.2 times width of cephalon, 0.4 times length of cephalon. Pereonite 1 smooth; anterior border medially straight, curved laterally; anterolateral angle narrowly rounded, extending to the medial region of eyes. Posterior margins of pereonites smooth, slightly curved laterally. Coxae 2–3 wide, with posteroventral angles rounded; coxae 4–7 with rounded point, not extending past pereonite posterior margin. Pereonites 2–5 subequal, becoming more progressively rounded posteriorly; pereonites 6 and 7 slightly narrower. Pleon 0.4 times as long as total body length, with pleonite 1 largely concealed by pereonite 7, slightly visible in dorsal view; pleonites posterior margin mostly concave. Pleonite 2 partially overlapped by pereonite 7. Pleonites 3–5 similar in form to pleonite 2; pleonites subequal in length, with posterolateral angles narrowly rounded, posterior margin straight. Pleotelson 0.6 times as long as anterior width, dorsal surface smooth; lateral margins weakly convex; posterior margin evenly rounded.

Figure 1. 

Elthusa raynaudii (Milne Edwards, 1840) ♀ (ovigerous, 20.0 mm TL, 12.0 mm W) (SAMC-A089957) from Dr Fridtjof Nansen research vessel A dorsal body B lateral body C oostegites D dorsal view of cephalon and pereonite 1 E uropod F ventral cephalon G pleopod 1 H dorsal view of pleon I pereopod 1 J pereopod 7.

Figure 2. 

Photos of Elthusa raynaudii (Milne Edwards, 1840) ♀ (ovigerous, 26.0 mm TL, 15.0 mm W) (SAMC-A47881) from Dr Fridtjof Nansen research vessel A dorsal view B ventral view C lateral view.

Figure 3. 

Photos of syntype material Livoneca raynaudii Milne Edwards, 1840 ♀ (ovigerous, 26.7 mm TL, 14.1 mm W) (MNHN–IU–2016–9885) A dorsal view B ventral view C lateral view.

Antennula shorter than antenna, consisting of eight articles; antennula peduncle articles I and II distinct and articulated, extending to anterior of pereonite 1. Antenna consists of eleven articles, extending to middle of pereonite 1.

Pereopod 1 basis 1.6 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion; carpus with rounded proximal margin; propodus 1.4 times as long as wide; dactylus slender, 1.6 times as long as propodus, 2.9 times as long as basal width. All pereopods without robust or simple setae. Pereopod 7 basis with carina, 2.5 times as long as greatest width; ischium without protrusions, 0.5 times as long as basis; merus 0.7 times as long as wide, 0.4 times as long as ischium; carpus without bulbous protrusion, 0.7 times as long as wide, 0.3 times as long as ischium; propodus 0.8 times as long as wide, 0.3 times as long as ischium; dactylus slender, 2.3 times as long as propodus, 3.5 times as long as basal width.

Pleopods simple, exopod larger than endopod. Pleopod 1 exopod 1.3 times as long as wide, lateral margin weakly convex, distally narrowly rounded, mesial margin straight; peduncle 2.3 times as wide as long.

Uropod more than half the length of pleotelson; peduncle 0.5 times longer than rami, lateral margin without setae; rami not extending beyond pleotelson, apices broadly rounded. Endopod apically rounded, 2.7 times as long as greatest width, terminating without setae. Exopod extending to end of endopod, 2.2 times as long as greatest width, apically rounded, terminating without setae.

Variations. Intra-specific variations can cause difficulty in identification and should be taken into consideration. One of the more obvious variations is the overall body shape of examined individuals, as seen from the dorsal view. While the syntype (MNHN–IU–2016–9885) has weakly convex, symmetrical lateral margins, specimen SAMC-A089957 is not as symmetrical, with the right margin being strongly convex and that of the left margin, weakly convex. The latter specimen therefore appears to be less symmetrical. Bruce (1990) mentioned this occasional asymmetrical body shape as an observed variation, as a result of slightly twisted individuals. The body shape of the South African specimen (SAMC-A089957) accords to the shape of individuals illustrated and described by Bruce (1990). In addition, the widest part of this species may vary between pereonite 4 and pereonite 5. This variation may also cause individual body shapes to appear dissimilar. The anterior margin of the cephalon of the syntype (MNHN–IU–2016–9885) appears to be rounded rather than subtruncate. The posterior margin of pleonite 5 can be roughly straight (AM G2181 from Bruce 1990), have a slight medial point, or be weakly concave (Bruce 1990, present study). Although Bruce (1990) described the uropods as being short, most measure more than half the length of the pleotelson.

Size. Ovigerous females 20.0–26.7 mm TL, 14.0–15.0 mm W. Other material: ovigerous females 22.0–67.0 mm TL (average 30.83 mm TL) (Bruce 1990).

Distribution

Records listed from west to east. North Pacific Ocean: Bering Sea (Kensley 1976). South America: Punta Quillaipe (Menzies 1962) and Chile (Nierstrasz 1931); Uruguay (Mañé-Garzón 1979). South Atlantic Ocean: Saint Helena and Tristan da Cunha (Sivertsen and Holthuis 1980). South Africa: Table Bay (Barnard 1920); Cape of Good Hope (Milne Edwards 1840); Durban (Barnard 1955). India: Travancore (Pillai 1954). Southern Indian Ocean: Amsterdam Island (Kensley 1976). Australia: southern and south-eastern Australia (Schioedte and Meinert 1884, Hale 1926, Bruce 1990, Whitelegge 1901). Japan: Yokohama (Schioedte and Meinert 1884). New Zealand (Filhol 1885, Chilton 1909, Nierstrasz 1915, Hurley 1961, Bruce 1990).

Hosts

Elthusa raynaudii has been recorded from various fish hosts of multiple orders and families. These hosts are: Chelidonichthys kumu (Cuvier, 1829) (see Avdeev 1978); Chorisochismus dentex (Pallas, 1769) (see Barnard 1920); Cyttus australis (Richardson, 1843) (see Avdeev 1978, 1984, Bruce 1990); Cyttus novaezelandiae (Arthur, 1885) (see Avdeev 1978, 1984); Cyttus traversi Hutton, 1872, previously Cyttoidops mccullochi (Whitley, 1947) (see Avdeev 1984, Bruce 1990); Genypterus blacodes (Bloch and Schneider, 1801) (see Hewitt and Hine 1972); Gnathanacanthus goetzeei Bleeker, 1855 (see Bruce 1990); Hyporhamphus intermedius (Cantor, 1842) (see Powell 1959, Stephenson 1969); Latris lineata (Forster, 1801) (see Kensley 1976); Meuschenia freycineti (Quoy and Gaimard, 1824) (see Bruce 1990); Mustelus antarcticus Günther, 1870 (see Hewitt and Hine 1972); Nemadactylus monodactylus (Carmichael, 1819), previously Acantholatris monodactylus (Carmichael, 1819) (see Sivertsen and Holthuis 1980); Nematalosa nasus (Bloch, 1795) (see Ghani 2003); Notacanthus sexspinis Richardson, 1846 (see Avdeev 1978, 1984); Notothenia microlepidota Hutton, 1875, previously Notothenia colbecki (see Chilton 1909, Hewitt and Hine 1972, Avdeev 1978, 1984); Notolabrus tetricus (Richardson, 1840), previously Pseudolabrus tetricus (see Bruce 1990); Paranotothenia magellanica (Forster, 1801), previously Notothenia macrocephala (see Avdeev 1978); Ilisha melastoma (Bloch and Schneider, 1801) previously Pellona brachysoma (see Pillai 1954); Pelotretis flavilatus Waite, 1911 (see Chilton 1911); Pseudophycis bachus (Forster, 1801), previously Physiculus bachus (see Hewitt and Hine 1972); Physiculus sp. (see Bruce 1990); Pseudophycis barbata Günther, 1863, previously Physiculus barbatus (Günther, 1863) (see Bruce 1990); Pseudolabrus miles (Schneider and Forster, 1801) (see Poore 1981, Bruce 1990); Pseudophycis bachus (Forster, 1801) (see Chilton 1911, Bruce 1990); Rexea solandri (Cuvier, 1832) (see Bruce 1990); Rhombosolea sp. (see Hewitt and Hine 1972); Sardinops sagax (Jenyns, 1842), previously Clupea neopilchardus Steindachner, 1879 (see Chilton 1911); Scorpaena cardinalis Solander and Richardson, 1842 (see Poore 1981); Sebastes capensis (Gmelin, 1789), previously Sebastichthys capensis (Gmelin, 1789) (see Sivertsen and Holthuis 1980); Stolephorus commersonnii Lacepède, 1803 (see Pillai 1954); Thyrsites atun (Euphrasen, 1791) (see Sivertsen and Holthuis 1980); Zenopsis nebulosa (Temminck and Schlegel, 1845), previously Zenopsis nebulosus (see Bruce 1990); Zeus faber Linnaeus, 1758 (see Hale 1926, Avdeev 1984). Unidentified by scientific names: banded perch (Serranidae), flathead (Platycephalidae) (see Bruce 1990).

Remarks

Elthusa raynaudii can be distinguished by the cephalon having a narrowly truncate rostrum; pereonite 1 with anterior margin straight; pleonites subequal in shape and width; and broadly rounded uropod apices that extend to more than half the length of the pleotelson.

Originally described in 1840, from the Cape of Good Hope in South Africa, from an unknown host, Elthusa raynaudii has been recorded numerous times from a wide range of localities within the Indo-Pacific region. It is the only species of Elthusa that has been described from sub-Saharan Africa. It has been recorded from an unknown host from the Cape of Good Hope (see Milne Edwards 1840); from the rocksucker, Chorisochismus dentex (Pallas, 1769) near Cape Town (Table Bay) (see Barnard 1920); from a wrasse in Durban (see Barnard 1955); as well as from the striped trumpeter, Latris lineata (Forster, 1801) (see Kensley 1976).

Elthusa sigani Bruce, 1990, which is only known from its type locality in Queensland, Australia, seems to be most similar to E. raynaudii. Elthusa sigani can be distinguished from E. raynaudii by having an evenly concave pereonite 1 anterior margin; a flat, straight cephalon anterior margin; and coxae 7 that extend past the posterior margin of pereonite 7. In addition, E. sigani is a much smaller species in overall body length range (9.0–13.0 mm), compared to E. raynaudii (20.0–26.7 mm).

Table 1.
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Interspecific character states between Elthusa raynaudii (Milne Edwards, 1840), Elthusa xena sp. n., Elthusa acutinasa sp. n., and Elthusa rotunda sp. n. from sub-Saharan African marine waters.

Morphological feature Elthusa raynaudii (Milne Edwards, 1840) Elthusa xena sp. n. Elthusa acutinasa sp. n. Elthusa rotunda sp. n.
Body shape Ovoid Elongate ovoid Elongate ovoid Round
Shape of cephalon and anterior margin Sub-truncate, blunt anterior margin Sub-triangular, bluntly pointed anterior margin Sub-triangular, pointed anterior margin Sub-triangular, blunt anterior margin
Pereonite 1 anterior margin Straight Medially indented Medial projection Concave
Coxae 7 posterior margin Not extending past posterior margin of pereonite 7 Not extending past posterior margin of pereonite 7 Extending past posterior margin of pereonite 7 Not extending past posterior margin of pereonite 7
Pereopod 7 protrusions Absent Absent Absent Present on merus and carpus
Pleonite length Pleonites 1–5 sub-equal Pleonite 5 longest and indented Pleonite 1 longest Pleonite 5 longest, medially convex
Pleonite 1 width Narrower than other pleonites As long as other pleonites As wide as pleotelson Narrower than other pleonites
Pleonite 5 lateral margins Visible Visible Largely concealed by pleonite 4 Slightly concealed by pleonite 4
Pleotelson shape Evenly rounded Roughly quadrate and curved upwards Rounded Broadly rounded
Pleopod 5 endopod Slightly smaller than exopod Smaller than exopod (not dissected) Half the size of exopod Smaller than exopod (not dissected)
Uropods Broadly rounded, more than half the length of pleotelson Apices narrowly rounded, more than half the length of pleotelson Short, pointed, less than half the length of pleotelson Broadly rounded, half the length of pleotelson

Elthusa xena sp. n.

http://zoobank.org/338A44A2-746F-4D9B-B890-5372D1E45B4C
Figures 4, 5, 6, 7, Table 1

Material examined

Holotype. SOUTH AFRICA • 1 ♀ (ovigerous, 34.0 mm TL, 17.0 mm W); Alexander Bay, mouth of the Orange River; 28°38'S, 16°27'E; July 1993; coll. J Laubscher; from the super klipfish, Clinus superciliosus (Linnaeus, 1758); SAMC-A089958.

Paratype. SOUTH AFRICA • 1 ♂ (intermoult, 8.0 mm TL, 4.0 mm W); same data as holotype; SAMC-A089959.

Description

(ovigerous ♀). Figs 4–5. Body slightly twisted to the left, elongated ovoid, twice as long as greatest width; dorsal surfaces smooth and polished in appearance, widest at pereonite 5, most narrow at pereonite 1, pereonite lateral margins mostly rounded, medially indented. Cephalon 0.8 times longer than wide, visible from dorsal view, sub-triangular with blunt anterior point. Frontal margin thickened, ventrally folded. Eyes oval with distinct margins; one eye 0.1 times width of cephalon, 0.3 times length of cephalon. Pereonite 1 smooth, anterior border slightly concave; anterolateral angle rounded, extending to the medial region of eyes. Posterior margins of pereonites smooth, slightly curved laterally. Coxae 2–3 narrow with posteroventral angles narrowly rounded; coxae 4–7 with rounded point, not extending past pereonite margin. Pereonites 2–5 subequal, pereonites 6 and 7 slightly narrower. Pleon 0.4 times as long as total body length, with pleonite 1 same width as other pleonites, lateral margins concealed by pereonite 7, slightly visible in dorsal view; pleonites posterior margin smooth, slightly curved laterally. Pleonite 2 partially overlapped by pereonite 7; posterolateral angles of pleonite 2 rounded. Pleonites 3–5 similar in form to pleonite 2; pleonite 5 longest, free, not overlapped by lateral margins of pleonite 4, with posterolateral angles narrowly rounded, posterior margin with 3 indentations. Pleotelson 0.6 times as long as anterior width, dorsal surface smooth; lateral margins convex; posterior margin evenly rounded.

Figure 4. 

Elthusa xena sp. n. holotype ♀ (ovigerous, 34.0 mm TL, 17.0 mm W) (SAMC-A089958) from Alexander Bay, South Africa A dorsal body B lateral body C oostegites D dorsal view of cephalon and pereonite 1 E uropod F ventral cephalon G pleopod 1 H dorsal view of pleon I pereopod 1 J pereopod 7.

Figure 5. 

Photos of Elthusa xena sp. n. holotype ♀ (ovigerous, 34.0 mm TL, 17.0 mm W) (SAMC-A089958) from Alexander Bay, South Africa A dorsal view B ventral view C lateral view.

Antennula shorter than antenna, consisting of eight articles; peduncle articles I and II distinct and articulated, extending to anterior of pereonite 1. Antenna consists of eleven articles, extending to past anterior margin of pereonite 1.

Pereopod 1 basis 1.8 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion; carpus with rounded proximal margin; propodus 1.8 times as long as wide; dactylus slender, 0.8 times as long as propodus, 2.3 times as long as basal width. Pereopods 2–3 similar to pereopod 1, all pereopods without robust or simple setae. Pereopod 7 basis with carina, 1.5 times as long as greatest width; ischium without protrusions, 0.9 times as long as basis; merus proximal margin with slight bulbous protrusion, 0.6 times as long as wide, 0.3 times as long as ischium; carpus with bulbous protrusion, 0.9 times as long as wide, 0.5 times as long as ischium; propodus as long as wide, 0.4 times as long as ischium; dactylus slender, 1.9 times as long as propodus, 3.1 times as long as basal width.

Pleopods simple, exopod larger than endopod. Pleopod 1 exopod 1.1 times as long as wide, lateral margin strongly convex, distally broadly rounded, mesial margin weakly convex; peduncle 2.8 times as wide as long.

Uropod more than half the length of pleotelson, peduncle 0.8 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, apices narrowly rounded. Endopod apically rounded, 2.5 times as long as greatest width, lateral margin weakly convex, mesial margin straight, terminating without setae. Exopod extending beyond end of endopod, twice as long as greatest width, apically rounded, lateral margin weakly convex, mesial margin straight, terminating without setae.

Description

(paratype intermoult ♂). Figs 6, 7. Male similar to female but smaller. Specimen mid-moult. Body rectangular, not twisted, twice as long as greatest width. Pereonite lateral margins mostly subparallel. Cephalon 0.7 times longer than wide. Frontal margin rounded to form blunt rostrum. Eyes oval with distinct margins; one eye 0.2 times width of cephalon; 0.5 times length of cephalon. Pereonite 1 smooth, anterior border concave, extending past base of cephalon. Posterior margins of pereonites smooth and straight, except pereonite 4 and 5. Coxae 2–3 wide, with posteroventral angles rounded; coxae 4–7 rounded. Pereonites 6 and 7 narrower, becoming more progressively rounded posteriorly. Pleon 0.3 times as long as total body length, with pleonite 1 largely concealed by pereonite 7, slightly visible in dorsal view; pleonites 1–3 posterior margin posteriorly concave, smooth and slightly curved laterally. Pleonite 5 overlapped by lateral margins of pleonite 4, with posterolateral angles narrowly rounded, posterior margin straight. Pleotelson 0.8 times as long as anterior width, lateral margins straight or weakly convex, posterior margin broadly truncate.

Figure 6. 

Elthusa xena sp. n. paratype ♂ (intermoult) (8 mm TL, 4 mm W) (SAMC-A089959) from Alexander Bay, South Africa A dorsal body B lateral body C pereopod 1 D pereopod 7 E dorsal view of cephalon F penes G uropod H ventral cephalon I dorsal view of pleon J ventral pleopod 2 K dorsal pleopod 2.

Figure 7. 

Photos of Elthusa xena sp. n. paratype ♂ (intermoult) (8.0 mm TL, 4.0 mm W) (SAMC-A089959) from Alexander Bay, South Africa A dorsal view B ventral view.

Antennula shorter than antenna, consisting of eight articles. Antenna consists of ten articles, extending to middle of pereonite 1.

Pereopod 1 basis twice as long as greatest width; ischium 0.6 times as long as basis; propodus 1.6 times as long as wide; dactylus 1.1 times as long as propodus, 3 times as long as basal width. Pereopod 7 twice as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion, 0.7 times as long as wide, 0.4 times as long as ischium; carpus without bulbous protrusion, 0.7 times as long as wide, 0.4 times as long as ischium; propodus 1.3 times as long as wide, 0.6 as long as ischium; dactylus slender, 1.4 times as long as propodus, 2.7 times as long as basal width.

Pleopod 1 exopod 1.2 times as long as wide, lateral margin weakly convex, distally broadly rounded, mesial margin straight; endopod 2.1 times as long as wide, lateral margin weakly convex, mesial margin straight, peduncle 2.2 times as wide as long. Pleopod 2 appendix masculina with parallel margins, 1.1 times as long as endopod, distally narrowly rounded.

Uropod same length or slightly longer than the pleotelson, peduncle 0.4 times longer than rami, rami extending slightly beyond pleotelson, apices narrowly rounded. Endopod apically slightly pointed, 3 times as long as greatest width. Exopod 2.6 times as long as greatest width.

Penes medially adjacent; penial process 0.7 times as long as basal width.

Etymology

The epithet is constructed in a possessive form of a personal name. This species is named after Xena, the warrior princess, in reference to the strong nature of the female cymothoid isopod.

Size

Ovigerous female (34.0 mm TL, 17.0 mm W), male (8.0 mm TL, 4.0 mm W).

Distribution

Currently only known from the mouth of the Orange River, Alexander Bay, South Africa (Atlantic Ocean).

Hosts

Clinus superciliosus (Linnaeus, 1758). This is the first record of a klipfish (of the genus Clinus Cuvier, 1816), and of the intertidal super klipfish, Clinus supercilious, as a fish host of a species of Elthusa. This host belongs to the fish order Perciformes, and is endemic to the Southeast Atlantic Ocean, from northern Namibia to the Kei River of South Africa (Smith and Heemstra 1986).

Remarks

Elthusa xena sp. n. female can be identified by the elongate, ovoid body shape; coxae 7 that do not extend past the posterior margin of pereonite 7; a bluntly pointed anterior margin of the cephalon; evenly rounded, slightly concave anterior margin of pereonite 1; uropod rami with apices narrowly rounded and more than half the length of pleotelson; pleonite 5 posterior margin with indentations; and the pleotelson is short, roughly quadrate, with margins that curl upward.

Two other Elthusa species have been recorded from related perciform fish hosts from the family Clinidae Swainson, 1839 (blennies). Elthusa californica (Schioedte & Meinert, 1884) was noted from the striped kelpfish Gibbonsia metzi Hubbs, 1927; and Elthusa menziesi (Brusca, 1981) from both the spotted kelpfish Gibbonsia elegans (Cooper, 1864) and the crevice kelpfish Gibbonsia montereyensis Hubbs, 1927. However, this is the first record of Elthusa collected from a Clinus sp.

Elthusa xena sp. n. can be distinguished from E. raynaudii by having a bluntly pointed cephalon anterior margin, compared to the narrowly truncate margin of E. raynaudii. Other differences include the shape of the pleotelson (which is quadrate, wide and short for E. xena sp. n., and evenly rounded for E. raynaudii); pleonite 1 is the same length as the other pleonites in Elthusa xena sp. n. but narrower in E. raynaudii; and the uropod apices of E. xena sp. n. are narrowly rounded compared to the broadly rounded apices of E. raynaudii uropods. See Table 1 for further morphological variation and comparisons.

Elthusa acutinasa sp. n.

http://zoobank.org/D5AFAEC4-F03D-400F-98A0-8D86631E495E
Figures 8, 9, 10, 11, Table 1

Material examined

Holotype. SOUTH AFRICA • 1 ♀ (ovigerous, 39.0 mm TL, 19.0 mm W); Indian Ocean, south coast of South Africa, RV Africana (fish sorting table); 34°38'S, 25°38'E; April 2003; coll. Nico J Smit; SAMC-A089960.

Paratypes. SOUTH AFRICA • 3 ♀♀ (ovigerous, 28.0–30.0 mm TL, 15.0–17.0 mm W); same data as holotype; SAMC-A089961.

Other material. SOUTH AFRICA • 1 ♀ (ovigerous, 29.0 mm TL, 17.0 mm W); same data as holotype; dissected; in the collection of the authors at NWU • 4 ♀♀ (non-ovigerous, 19.0–24.0 mm TL, 10.0–14.0 mm W); same data as holotype; in the collection of the authors at NWU • 9 ♀♀ (three ovigerous, six non-ovigerous, 15.0–40.0 mm TL, 8.0–19.0 mm W); Indian Ocean, south coast of South Africa, RV Africana (fish sorting table); 30°29'S, 16°0'E; 213 m depth; January 1999; SAMC-A091307 • 1 ♀ (ovigerous, 40.0 mm TL, 19.0 mm W); same data as preceding; 30°25'S, 16°9'E; 259 m depth; SAMC-A091308 • 1 ♀ (ovigerous, 30.0 mm TL, 15.0 mm W); same data as preceding; 31°8'S, 15°20'E; 234 m depth; SAMC-A091309.

Description

(ovigerous ♀). Figs 8–11. Body slightly twisted to the right, elongated ovoid, 2.1 times as long as greatest width. Body dorsal surfaces smooth and polished in appearance, widest at pereonite 4, most narrow at pereonite 1, pereonite lateral margins mostly posteriorly ovate, medially indented. Cephalon 0.4 times longer than wide, visible from dorsal view, sub-triangular with narrowly rounded anterior point. Frontal margin thickened, ventrally folded. Eyes oval with distinct margins; one eye 0.2 times width of cephalon, 0.4 times length of cephalon. Pereonite 1 smooth, anterior border with medially produced point, with two indentations; anterolateral angle rounded, extending to posterior margin of eyes. Posterior margins of pereonites smooth and slightly curved laterally. Coxae 2–3 wide; with posteroventral angles rounded; 4–7 with rounded point. Coxae 7 extending slightly past pereonite posterior margin. Pereonites 2–5 subequal, becoming more progressively rounded posteriorly. Pleon 0.4 times as long as total body length, with pleonite 1 longest, lateral margins concealed by pereonite 7, visible in dorsal view; pleonites posterior margin smooth and slightly curved laterally. Pleonite 2 partially overlapped by pereonite 7; posterolateral angles of pleonite 2 rounded. Pleonites 3–5 similar in form to pleonite 2; pleonite 5 overlapped by lateral margins of pleonite 4, posterior margin straight, with slight medial point. Pleotelson 0.7 times as long as anterior width, dorsal surface smooth; lateral margins weakly convex; posterior margin rounded, with slight medial indent.

Figure 8. 

Elthusa acutinasa sp. n. holotype ♀ (ovigerous, 39.0 mm TL, 19.0 mm W) (SAMC-A089960) from Africana research vessel A dorsal body B lateral body C oostegites D ventral cephalon E dorsal view of cephalon and pereonite 1 F uropod G pleopod 1 H dorsal view of pleon I pereopod 1 J pereopod 7.

Figure 9. 

Elthusa acutinasa sp. n. paratype ♀ (ovigerous, 33.0 mm TL, 16.0 mm W) (SAMC-A089961) from Africana research vessel A antennula B antenna C maxilliped D tip of maxillula E maxilla F mandible.

Figure 10. 

Elthusa acutinasa sp. n. paratype ♀ (ovigerous, 33.0 mm TL, 16.0 mm W) (SAMC-A089961) from Africana research vessel A–E dorsal view of pleopods 1–5 respectively F–J ventral view of pleopods 1–5 respectively.

Figure 11. 

Photos of Elthusa acutinasa sp. n. holotype ♀ (ovigerous, 39.0 mm TL, 19.0 mm W) (SAMC-A089960) from Africana research vessel A dorsal view B ventral view C lateral view.

Antennula shorter than antenna, consisting of eight articles; antennula peduncle articles I and II distinct and articulated; article II 0.9 times as long as article 1; article III 1.4 times as long as wide, 0.5 times as long as combined lengths of articles I and II; antennula flagellum with five articles, extending to middle of eye, with tufts of setae on articles I–III and article VIII. Antenna consists of twelve articles. Antenna peduncle article III 1.3 times as long as article II; article IV 1.3 times as long as wide, 1.2 times as long as article III; article V 1.5 times as long as wide, 1.1 times as long as article IV. Antenna flagellum with six articles, terminal article terminating in 1–5 short simple setae, extending to past anterior margin of pereonite 1. Mandible palp article II with five distolateral setae, and article III with three simple setae. Maxillula simple with four terminal robust setae. Maxilla mesial lobe not fused to lateral lobe; lateral lobe without simple setae, two recurved robust setae; mesial lobe without simple setae, and two large recurved robust setae. Maxilliped consists of III articles, with lamellar oostegite lobe or second, smaller oostegite lobe on basal part of article, palp article II without simple setae, article III with three recurved robust setae. Oostegites margin covered in numerous plumose setae.

Pereopod 1 basis 1.9 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin with slight bulbous protrusion; carpus with rounded proximal margin; propodus 1.1 times as long as wide; dactylus slender, 1.3 times as long as propodus, 3 times as long as basal width. Pereopod 3 similar to pereopod 2, all pereopods without robust or simple setae. Pereopod 7 basis 1.9 times as long as greatest width; ischium with slight bulbous protrusion on distal margin, 0.9 times as long as basis; merus proximal margin with slight bulbous protrusion, 0.6 times as long as wide, 0.3 times as long as ischium; carpus with bulbous protrusion, 0.7 times as long as wide, 0.3 times as long as ischium; propodus 1 times as long as wide, 0.3 times as long as ischium; dactylus slender, 1.9 times as long as propodus, 3.3 times as long as basal width.

Pleopods simple; exopod larger than endopod, with 4–7 simple setae on peduncle of pleopods 2–5. Pleopod 1 exopod 1.3 times as long as wide, lateral margin weakly convex, distally broadly rounded, mesial margin straight; peduncle 3 times as wide as long. Endopod 1.6 times as long as wide, lateral margin convex, distally narrowly rounded, mesial margin straight, peduncle 2.4 times as wide as long. Pleopods 2–5 similar to pleopod 1, mesial margins becoming more strongly produced, peduncle lobes absent.

Uropod less than half the length of the pleotelson, peduncle 0.7 times longer than rami, peduncle lateral margin without setae, marginal setae absent, apices narrowly rounded. Endopod apically slightly pointed, 3.4 times as long as greatest width, lateral margin weakly convex, mesial margin straight, terminating without setae. Exopod extending to end of endopod, 2.3 times as long as greatest width, apically rounded, lateral margin distally convex, mesial margin straight, terminating without setae.

Variations. Intra-specific variation was observed among the examined specimens of Elthusa acutinasa sp. n. The size of the medial point formed at the anterior margin of pereonite 1 may vary. Some specimens portrayed an obvious, sharp medial point, while others only had a weak medial projection of the anterior margin of pereonite 1. Variation in the length of the uropods are slight, but one specimen had uropod rami extending to half the length of the pleotelson, while all the others specimens’ uropods were remarkably short. The overlapping of pleonite 5 lateral margins by pleonite 4 was consistent, except with one of the other examined paratype females, where pleonite 5 lateral margins were slightly visible. Some variation was also noted in the width of pleonite 1.

Etymology

The epithet is a noun in the genitive singular. The species name acutinasa was derived by the son of one of us (NJS) from a combination of the two Latin words acute and nasus. The word acute translates to a feature that is pointy or ends with a sharp point; while nasus translates to nose. The combined word, acutinasa, therefore means pointy nose, and appropriately describes one of the characters of this species, which is its pointed anterior margin of the rostrum.

Size

Ovigerous females (28.0–40.0 mm TL, 15.0–19.0 mm W), non-ovigerous females (19.0–24.0 mm TL, 10.0–14.0 mm W).

Distribution

Known from the Indian Ocean, off the south coast of South Africa.

Hosts

Not known (type material was collected from the fish sorting table following a trawl and not from a specific fish species).

Remarks

Elthusa acutinasa sp. n. can be identified by its elongate, ovoid body shape; pointed anterior margin of the cephalon; anterior margin of pereonite 1 with short medial point; short, apically pointed uropod rami, which extend to less than half of the length of the pleotelson; coxae 7 that extends past the posterior margin of pereonite 7; pleonite 5 lateral margins that are largely concealed by pleonite 4; pleonite 5 posterior margin with a slight medial point; pleonite 1 the longest of the pleonites; and pleopod 5 endopod approximately half the size of the exopod.

Several characters differentiate between E. acutinasa sp. n. from E. raynaudii (see Table 1). Elthusa acutinasa sp. n. has a prominent, pointed cephalon anterior margin with a medially pointed pereonite 1 anterior margin compared to the straight anterior margin of E. raynaudii cephalon and pereonite 1. Pleon differences include the longer pleotelson of E. acutinasa sp. n. with pleonite 1 widest and pleonite 5 lateral margins concealed by those of pleonite 4 (not seen in E. raynaudii). Elthusa acutinasa sp. n. also has short uropods that do not extend to the half of the pleotelson length, whereas those of E. raynaudii reach to, or extend past, the half of the pleotelson length.

Elthusa acutinasa sp. n. can also be distinguished from E. xena sp. n. by its short uropods and coxae 7 that extend past the posterior margin of pereonite 7. Further differences are found within pleon morphology, where E. acutinasa sp. n. pleonite 5 lateral margins are largely concealed by pleonite 4, whereas those of E. xena sp. n. are visible. Pleonite 1 in E. xena sp. n. is as wide as the other pleonites, whereas pleonite 1 in E. acutinasa sp. n. is narrower than the other pleonites. The pleotelson shape of E. acutinasa sp. n. is evenly rounded, compared to the roughly quadrate pleotelson of E. xena sp. n. (see Table 1).

Elthusa rotunda sp. n.

http://zoobank.org/138FBF0D-2E4B-4561-86C8-F209B78A33E0
Figures 12, 13, Table 1

Material examined

Holotype. SOUTH AFRICA • 1 ♀ (ovigerous, 29.0 mm TL; 20.0 mm W); Cape Town, Sea Point; 33°55'S, 18°23'E; January 1960; coll. G Branch; SAMC A11001.

Description

(ovigerous ♀). Figs 12–13. Body round, not twisted, 1.4 times as long as greatest width; dorsal surfaces smooth and polished in appearance, widest at pereonite 4, most narrow at pereonite 1; pereonite lateral margins mostly posteriorly ovate, medially indented. Cephalon 0.4 times longer than wide, visible from dorsal view, sub-triangular with blunt anterior point. Frontal margin thickened, ventrally folded. Eyes oval with distinct margins; one eye 0.2 times width of cephalon; 0.5 times length of cephalon. Pereonite 1 smooth, anterior border evenly concave; anterolateral angles rounded, extending to the medial region of eyes. Posterior margins of pereonites smooth, slightly curved laterally, posterior margins of pereonites 2–3 uneven. Coxae 2–3 wide; with posteroventral angles rounded; coxae 4–7 with rounded point, not extending past pereonite posterior margin. Pereonites becoming more progressively rounded posteriorly; pereonite 5 most narrow. Pleon 0.4 times as long as total body length; pleonite 1 largely concealed by pereonite 7, slightly visible in dorsal view; pleonites posterior margin slightly concave, smooth, slightly curved laterally. Pleonite 2 lateral margins overlapped by pereonite 7. Pleonites 3–4 similar in form to pleonite 2; pleonite 5 longest, overlapped by lateral margins of pleonite 4, posterior margin medially convex. Pleotelson broadly rounded, 0.7 times as long as anterior width, dorsal surface smooth; lateral margins convex; posterior margin evenly rounded.

Figure 12. 

Elthusa rotunda sp. n. holotype ♀ (ovigerous, 28 mm TL, 19 mm W) (SAMC-A11001) from Sea Point, South Africa A dorsal body B lateral body C oostegites D ventral cephalon E dorsal view of cephalon and pereonite 1 F uropod G pleopod 1 H dorsal view of pleon I pereopod 1 J pereopod 7.

Figure 13. 

Photos of Elthusa rotunda sp. n. holotype ♀ (ovigerous, 28 mm TL, 19 mm W) (SAMC-A11001) from Sea Point, South Africa A dorsal view B ventral view C lateral view.

Antennula shorter than antenna, consisting of eight articles; peduncle articles I and II distinct and articulated; extending to middle of eye. Antenna consists of ten articles, extending to past anterior margin of pereonite 1.

Pereopod 1 basis 1.7 times as long as greatest width; ischium 0.7 times as long as basis; merus proximal margin without bulbous protrusion; propodus 1.4 times as long as wide; dactylus slender, 1.3 times as long as propodus, 2.9 times as long as basal width. All pereopods without robust or simple setae. Pereopod 7 basis with carina, 2.1 times as long as greatest width; ischium with slight bulbous protrusion, 0.8 times as long as basis; merus proximal margin with bulbous protrusion, 0.6 times as long as wide, 0.3 times as long as ischium; carpus with bulbous protrusion, 0.7 times as long as wide, 0.3 times as long as ischium; propodus 1.2 times as long as wide, 0.9 times as long as ischium; dactylus slender, 1.7 times as long as propodus, 2.5 times as long as basal width.

Pleopods simple, exopod larger than endopod. Pleopod 1 exopod 1.3 times as long as wide, lateral margin weakly convex, distally broadly rounded, mesial margin weakly convex; peduncle 2.5 times as wide as long.

Uropod half the length of pleotelson, peduncle 0.9 times longer than rami, peduncle lateral margin without setae; rami not extending beyond pleotelson, marginal setae absent, apices broadly rounded. Endopod apically rounded, 2.6 times as long as greatest width, lateral margin weakly convex, mesial margin weakly convex. Exopod extending to end of endopod, 2.2 times as long as greatest width, apically rounded, lateral margin weakly convex, mesial margin straight.

Size

Ovigerous female (29.0 mm TL, 20.0 mm W).

Etymology

The epithet is a noun in the nominative singular. It is named after its most distinct, defining character, which is the rounded shape of the body. The Latin word for round is rotundus.

Distribution

Currently only known from Sea Point, Cape Town, South Africa.

Hosts

Not known.

Remarks

The diagnostic characters of E. rotunda sp. n. include its circular body shape; a sub-triangular cephalon with blunt anterior margin; pereopod 7 merus and carpus with protrusions on the proximal and lateral margins; pereonite 7 lateral margins that extend to pleonite 4; pleonite 5 longest and medially convex; a broadly rounded pleotelson posterior margin; and uropod rami that are sub-equal in length to the peduncle.

When comparing E. rotunda sp. n. to the rest of the identified Elthusa species, its closest resemblance is to that of E. raynaudii. This is especially in regards to the shape of the uropods, pleon, and cephalon anterior margin. It can be distinguished from E. raynaudii in having a more rounded body shape compared to the ovoid body shape of E. raynaudii; triangular cephalon as opposed to the narrowly truncate cephalon of E. raynaudii; the broadly rounded pereonite 1 anterolateral margins of E. rotunda sp. n. compared to the narrowly rounded to pointed anterolateral margins of E. raynaudii pereonite 1; as well as the uropod rami and peduncles that are subequal in length, as opposed to the longer rami of E. raynaudii (see Table 1).

Elthusa rotunda sp. n. can be distinguished from E. xena sp. n. by the cephalon anterior margin which is more pointed in E. xena sp. n. and more rounded in E. rotunda sp. n.; broadly rounded uropod apices compared to the narrowly rounded ones from E. xena sp. n.; the shape of the pleotelson, which is broadly rounded for E. rotunda sp. n. and roughly quadrate for E. xena sp. n.; as well as the prominent presence of pereopod 7 protrusions on the merus and carpus of E. rotunda sp. n., that are less bulbous on E. xena sp. n.

The main differentiating characters between E. rotunda sp. n. and E. acutinasa sp. n. include the shape of the cephalon anterior margin (bluntly rounded versus produced point); and the uropod morphology, with E. rotunda sp. n. having broadly rounded, longer uropodal rami in comparison to the short, pointed uropodal rami of E. acutinasa sp. n. Elthusa rotunda sp. n. pleonite 5 is the longest, whereas E. acutinasa sp. n. pleonite 1 is the longest; the presence of pereopod 7 protrusions on E. rotunda sp. n. is more prominent and bulbous that those of E. acutinasa sp. n. pereopod 7 (see Table 1).

Conclusions

From previous collections across South Africa, four Elthusa species were recognised. Elthusa raynaudii, the only known Elthusa species from South Africa, was identified along with three new species from this genus. These new species, E. xena sp. n., E. acutinasa sp. n., and E. rotunda sp. n., more than double the known records of Elthusa from this region. Descriptions were provided for the three new Elthusa species along with an identification key with diagnostic characters to distinguish between the sub-Saharan Elthusa species (Table 1). A summative table was provided with currently known information on all species from the genus Elthusa, including host and location records of each (Table 2).

Table 2.
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Summary of the hosts, distribution, and attachment sites of all 33 species from the genus Elthusa Schioedte & Meinert, 1884, as well as the references for each record.

Species Distribution Hosts References
Elthusa alvaradoensis Rocha-Ramírez, Chávez-López & Bruce, 2005 TLoc: Alvarado, Veracruz, Mexico. TH: Synodus foetens (Linnaeus, 1766) Rocha-Ramírez et al. (2005)
Elthusa arnoglossi Trilles & Justine, 2006 TLoc: Chesterfield Islands, New Caledonia. TH: Arnoglossus sp. Trilles and Justine (2006)
Elthusa atlantniroi (Kononenko, 1988) TLoc: Bay of Biscay, northeast Atlantic Ocean TH: Cepola macrophthalma (Linnaeus, 1758) Kononenko (1988)
Elthusa californica (Schioedte & Meinert, 1884) Syn: Livoneca californica Schioedte & Meinert, 1884 TLoc: California, near San Francisco TH: Holconoti sp. Schioedte and Meinert (1884); Keys (1928); Hatch (1947); Olson (1972); Iverson (1974); Miller (1975); Waugh et al. (1989); Bennett (1993); Brusca (1981); Brusca et al. (2001); Gamble et al. (2013)
OL: Pacific coast from Alaska to Peru; Canada; USA; Mexico OH: Species from the families Atherinidae; Aulorhynchidae; Clinidae; Clupeidae; Cottidae; Embiotocidae; Fundulidae; Gasterosteidae; Gobiidae; Hexagrammidae; Moronidae; Mugilidae; Pholidae; Osmeridae; Paralichthyidae; Pholidae; Pleuronectidae; Sebastidae
Elthusa caudata (Schioedte & Meinert, 1884) Syn: Livoneca caudata Schioedte & Meinert, 1884 TLoc: Laponica islands, Japan TH: Unknown Schioedte and Meinert (1884); Avdeev (1978)
OL: New Zealand Other hosts: Genypterus blacodes (Forster, 1801)
Elthusa emarginata (Bleeker, 1857) Syn: Livoneca emarginata Bleeker, 1857 TLoc: Java, Indonesia TH: Unknown Bleeker (1857); Miers (1881); Schioedte and Meinert (1884); Nierstrasz (1915); Trilles and Randall (2011)
OL: East India; Malaysia; Indonesia OH: Species from the family Mullidae
Elthusa epinepheli Trilles & Justine, 2010 TLoc: Off Nouméa, New Caledonia TH: Epinephelus howlandi (Günther, 1873) Trilles and Justine (2010)
Elthusa foveolata (Hansen, 1897) Syn: Irona foveolata Hansen, 1897 TLoc: Sri Lanka TH: Unknown Hansen (1897)
Elthusa frontalis (Richardson, 1910) Syn: Livoneca frontalis Richardson, 1910 TLoc: Sablayan, Philippines TH: Balistes sp. Richardson (1910)
Elthusa menziesi (Brusca, 1981) Syn: Lironeca menziesi Brusca, 1981 TLoc: San Quintin Bays, Baja California, Mexico TH: Clinocottus analis (Girard, 1858) Brusca (1981); Ruiz-Campos (1986); Wetzer et al. (1991); Espinosa-Pérez and Hendrickx (2001)
OL: Mexico and Western Baja California OH: Species from the families of Atherinidae; Blenniidae; Clinidae; Cottidae; Gobiesocidae; Kyphosidae; Labrisomidae; Lessoniaceae
Elthusa methepia (Schioedte & Meinert, 1884) TLoc: Rio de Janeiro, Brazil TH: Achirus sp. Schioedte and Meinert (1884)
Elthusa moritakii Saito & Yamauchi, 2016 TLoc: Honshu and east China Sea coast of Kyushu, Japan TH: Ereunias grallator Jordan & Snyder, 1901 Saito and Yamauchi (2016)
Elthusa myripristae Bruce, 1990 TLoc: Escape Reef, outer Barrier Reef, Australia TH: Myripristis violaceus Bleeker, 1851 Bruce (1990)
Elthusa nanoides (Stebbing, 1905) Syn: Irona nanoides Stebbing, 1905 TLoc: Galle, Sri Lanka (old Ceylon) TH: Unknown Stebbing (1905); Monod (1923); Trilles (1976)
OL: Gulf of Suez, Red Sea OH: Species from the families Holothuriidae; Leiognathidae; Molidae; Plotosidae; Scorpaenidae; Sparidae
Elthusa neocytta (Avdeev, 1975) Syn: Lironeca neocytta Avdeev, 1975 TLoc: New Zealand TH: Neocyttus rhomboidalis Gilchrist, 1906 Avdeev (1975, 1984); Stephenson (1987); Bruce (1990)
OL: Tasmania and south-east New Zealand OH: species from the families Cyttidae; Oreosomatidae; Scombridae; Zeidae
Elthusa nierstraszi Hadfield, Bruce & Smit, 2016 Syn: Lironeca parva Nierstrasz, 1915. TLoc: Kisar Island, Moluccas, Indonesia TH: Ereunias grallator Jordan & Snyder, 1901 Nierstrasz (1915); Avdeev (1984); Hadfield et al. (2016a)
Elthusa ochotensis (Kussakin, 1979) Syn: Lironeca ochotensis Kussakin, 1979 TLoc: Sea of Ochosk (near the city of Ayan), western Pacific Ocean TH: Unknown Kussakin (1979)
Elthusa parabothi Trilles & Justine, 2004 TLoc: New Caledonia, off Coëtlogon Bank TH: Parabothus kiensis (Tanaka, 1918) Trilles and Justine (2004)
Elthusa parva (Richardson, 1910) Syn: Ceratothoa parva (Richardson, 1910) TLoc: Opol, Mindanao, Philippines TH: Unknown Richardson (1910); Hadfield et al. (2016b)
Elthusa philippinensis (Richardson, 1910) Syn: Livoneca philippinensis Richardson, 1910 TLoc: Jolo Light, Philippines TH: Unknown Richardson (1910)
Elthusa poutassouiensis (Penso, 1939) Syn: Ceratothoa poutassouiensis (Penso, 1939) TLoc: Babakale Port, Aegean Sea Coasts, Turkey TH: Micromesistius poutassou (Risso, 1827) Brian (1939); Penso (1939); Öktener et al. (2018b)
OL: Genova Gulf, Italy
Elthusa propinqua (Richardson, 1904) Syn: Livoneca propinqua Richardson, 1904 TLoc: Port Heda, Japan TH: Unknown Richardson (1904, 1910); Barnard (1936); Bruce (1990)
OL: Arabian Sea; Laccadive Islands; India; Maldives; Myanmar; Japan; Philippines; Australia OH: “chalinura”; “a macrurid”, “Macrurus”; Ventrifossa cf. nigrodorsalis
Elthusa raynaudii (Milne Edwards, 1840) Syn: Livoneca raynaudii Milne Edwards, 1840 TLoc: Cape of Good Hope, South Africa TH: Unknown See in text.
OL: See text OH: See text
Elthusa sacciger (Richardson, 1909) Syn: Livoneca sacciger Richardson, 1909 TLoc: Bungo Channel; Japan TH: Synaphobranchus sp. Avdeev (1984); Bruce (1990); Hata et al. (2017); Richardson (1909); Shiino (1951); Yamauchi (2009)
OL: North-western Pacific; Australia; Japan and Pacific coast OH: Species from the families Synaphobranchidae; Sebastidae
Elthusa samariscii (Shiino, 1951) Syn: Lironeca samariscii Shiino, 1951 TLoc: Japan TH: Samariscus japonicus Kamohara, 1936 Shiino (1951); Biju Kumar and Bruce (1997)
OL: Kerala coast, India Other hosts: Samaris cristatus Gray, 1831
Elthusa samoensis (Schioedte & Meinert, 1884) Syn: Livoneca samoensis Schioedte & Meinert, 1884 TLoc: Samoa Islands (Samoenses islands) TH: Unknown Schioedte and Meinert (1884)
Elthusa sigani Bruce, 1990 TLoc: North Stradbroke Island, Moreton Bay, southeastern Queensland, Australia TH: Siganus spinus (Linnaeus, 1758) Bruce (1990)
Elthusa sinuata (Koelbel, 1879) Syn: Livoneca sinuata Koelbel, 1879 TLoc: Mediterranean coast TH: Cepola macrophthalma (Linnaeus, 1758) Koelbel (1879); Schioedte and Meinert (1884); Carus (1885); Gourret (1891); Gerstaecker (1901); Galati-Mosella (1920); Brian (1921); Monod (1924); Trilles (1968, 1977, 2008); Trilles and Raibaut (1973); Dollfus and Trilles (1976); Rokicki (1984, 1985); Trilles et al. (1989); Bello and Mariniello (1998); Trilles and Öktener (2004); Öktener et al. (2009, 2018a)
OL: North-West Africa; United Kingdom; Mediterranean; Adriatic Sea; Spain; France; Algeria; Tunisia; Italy; Yugoslavia; Montenegro; Turkey OH: Species from the families Argentinidae; Bramidae; Cepolidae; Gobiidae; Loliginidae; Pleuronectidae; Rajidae; Sepiolidae; Sparidae; Trichiuridae
Elthusa splendida (Sadowsky & Moreira, 1981) Syn: Lironeca splendida Sadowsky & Moreira, 1981 TLoc: South Western Atlantic Ocean TH: Squalus cubensis Howell Rivero, 1936 Sadowsky and Moreira (1981)
Elthusa tropicalis (Menzies & Kruczynski, 1983) Syn: Lironeca tropicalis Menzies & Kruczynski, 1983 TLoc: off Egmont Key, Florida, USA TH: Ogcocephalus parvus Longley & Hildebrand, 1940 Menzies and Kruczynski (1983)
Elthusa turgidula (Hale, 1926) Syn: Livoneca turgidula Hale, 1926 TLoc: Western Australia TH: Unknown Hale (1926); Bruce (1990)
OL: One Tree Island, Great Barrier Reef OH: Species from the families Scaridae; Scaridae
Elthusa vulgaris (Simpson, 1857) Syn: Livoneca vulgaris Stimpson, 1857 TLoc: San Francisco Bay; Tomales Bay; Monterey TH: Unknown Stimpson (1857); Richardson (1904); Turner et al. (1969); Hobson (1971); Brusca (1978, 1981); Bennett (1993); Espinosa-Pérez and Hendrickx (2001); Gamble et al. (2013)
OL: Pacific Ocean including the western coast of USA, Mexico and Colombia OH: Species from the families Carangidae; Chaenopsidae; Cottidae; Cynoglossidae; Embiotocidae;Engraulidae; Gobiidae; Hexagrammidae; Moronidae; Paralichthyidae; Pleuronectidae; Scorpaenidae; Sebastidae; Serranidae; Synodontidae. Also “rock cod”, “flounder”, “lingcod”
Elthusa winstoni Hadfield, Tuttle & Smit, 2017 TLoc: Hawaii TH: Ctenochaetus strigosus (Bennett, 1828); Acanthurus nigroris Valenciennes, 1835 Hadfield et al. (2017)

Acknowledgments

The project was funded through a Western Indian Ocean Marine Science Association (WIOMSA) Marine Research Grant for KA Hadfield. The financial assistance of the National Research Foundation (NRF) (NRF project IFR170210222411 Grant 109352, NJ Smit, PI) and the South African National Biodiversity Institute (SANBI) in conjunction with the Foundational Biodiversity Information programme (FBIP, S van der Wal) supported this research and is hereby acknowledged. Opinions expressed, and conclusions arrived at, are those of the authors and are not necessarily those of the NRF. This is contribution number 336 from the NWU–Water Research Group. Prof Liesl van As, Aquatic Parasitology Research Group, University of the Free State, is thanked for the donation of the specimen here described as Elthusa xena sp. n. We also thank the Captain and crew of the FRS Africana and Sharon du Plessis (Chief Scientist) for the opportunity to collect material during the April/May 2003 South Coast Hake Biomass Survey. We would also like to thank Albé Bosman, curator at the Iziko South African Museum and Lauré Corbari, curator at the National Museum of Natural History, Paris, for providing specimens and information on collections.

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