Research Article |
Corresponding author: Kerry A. Hadfield ( kerryh26@yahoo.com ) Academic editor: Panakkool Thamban Aneesh
© 2022 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:
Smit NJ, Hadfield KA (2022) Gnathia pipinde sp. nov. (Crustacea, Isopoda, Gnathiidae), a temporary parasite of the pufferfish, Amblyrhynchotes honckenii, from temperate southern Africa. ZooKeys 1129: 1-19. https://doi.org/10.3897/zookeys.1129.90986
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A new species, Gnathia pipinde sp. nov., is described from specimens taken from pufferfish, Amblyrhynchotes honckenii, at Chintsa and De Hoop Nature Reserve on the southern Indian Ocean coast of South Africa. Gnathia pipinde sp. nov. is characterised by the straight frontal margin, presence of conical superior frontolateral process, a strong and bifid mediofrontal processes, pronounced and pointed supraocular lobes, mandible strongly curved with a dentate blade, and the claviform penes produced more than a third the length of the pereon. A summary and key to the males of all known species of the Gnathiidae from the Temperate Southern African marine realm is provided.
Chintsa, De Hoop Nature Reserve, Indian Ocean, marine fish parasite, taxonomy
The Western Indian Ocean is a region of known high but underexplored marine invertebrate diversity. The Temperate Southern African (TSA) marine realm (a realm identified by
Summary of the location, depth, size and references of 9 gnathiid species from the Temperate Southern African (TSA) realm, including the 8 previously known species and the new species, Gnathia pipinde sp. nov.
Species | Location | Size (mm) | Depth (m) | Substratum / Host | References |
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Afrignathia multicavea Hadfield & Smit, 2008 | South Africa (Eastern and Western Cape) | 1.5–2.0 | 26–73 |
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Caecognathia cryptopais (Barnard, 1925) | South Africa (Eastern and Western Cape) | 2.0–3.9 | 160 |
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Gnathia africana Barnard, 1914 | South Africa (Eastern and Western Cape) | 0–5.1 | Tubes of serpulid worms; sponges; Caffrogobius caffer (Günther, 1874); Chorisochismus dentex (Pallas 1769); Clinus cottoides Valenciennes, 1836; Clinus superciliosus (Linnaeus, 1758) |
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Gnathia disjuncta Barnard, 1920 | South Africa (Western Cape) | 3.5 | 73 |
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Gnathia nkulu Smit & Van As, 2000 | South Africa (Eastern Cape) | 3.3–4.9 | 80–200 | Smit and Van As (2000) | |
Madagascar (Nosy-Be) | 4 | 1.5 |
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Gnathia pantherina Smit & Basson, 2002 | South Africa (Eastern and Western Cape) | 3.7–6.8 | intertidal | Haploblepharus edwardsii (Schinz, 1822); Poroderma pantherinum (Müller & Henle, 1838); Torpedo fuscomaculata Peters, 1855 |
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Gnathia pilosus Hadfield, Smit & Avenant-Oldewage, 2008 | South Africa (Kwazulu-Natal) | 1.6–2.0 | intertidal | Abudefduf sordidus (Forsskål, 1775); Acanthurus triostegus (Linnaeus, 1758); Antennablennius bifilum (Günther, 1861); Diplodus capensis (Smith, 1844); Epinephelus marginatus (Lowe, 1834); Halichoeres nebulosus (Valenciennes, 1839); Istiblennius dussumieri (Valenciennes, 1836); Istiblennius edentulus (Forster & Schneider, 1801); Omobranchus banditus Smith, 1959; Plectroglyphidodon leucozonus (Bleeker, 1859); Psammogobius knysnaensis Smith, 1935; Pterois miles (Bennett, 1828); Rhabdosargus sarba (Forsskål, 1775); Scartella emarginata (Günther, 1861); Terapon jarbua (Forsskål, 1775); Thalassoma purpureum (Forsskål, 1775) |
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Gnathia pipinde sp. nov. | South Africa (Eastern and Western Cape) | 4.6–5.1 | Intertidal-shallow; subtidal | Amblyrhynchotes honckenii (Bloch, 1795) | Current study |
Gnathia spongicola Barnard, 1920 | South Africa (Western Cape) | 5 | 238–347 | hexactinellid sponges |
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These small crustaceans (<15 mm, most species <6 mm) have three larval stages that feed on the blood and lymph of their hosts, before dropping to the ocean floor where they moult into the subsequent larval stage or into adult males or females (
Gnathiid isopods have traditionally been described from the free-living adult males collected from dredge sampling, elutriation and sorting of coral rubble, from sponge collections, and other standard techniques used to collect small marine crustaceans. However, since the early 2000s, new gnathiid species have been described by moulting final (P3) larval stages into adults, either collected by light (
Nine Amblyrhynchotes honckenii were collected from the De Hoop Nature Reserve (4 specimens) and the small coastal town of Chintsa (5 specimens) on South Africa’s south coast during October 1999 and October 2020, respectively. Fish from De Hoop Nature Reserve (34°28'44"S, 20°30'38"E) were captured by luring them into deep pools during evening low tide and then catching them with hand nets (see
Following capture, live pufferfish were screened for external parasites and fish with gnathiid larvae present were kept alive in fresh, aerated seawater until the gnathiids completed feeding and detached from the host. All the larvae were attached to the dorsal and lateral areas of the body just posterior to the fish’s head. Fish were kept alive until the fully fed larvae detached 6–8 h following capture. In order to rear the larvae into the next stage, they were kept alive in fresh seawater. Free swimming gnathiids were collected by pipettes and transferred into small 50 ml bottles with fresh seawater until moulting into adults (see
From the collected samples, a single third stage larva and male were cleaned and prepared for scanning electron microscopy (SEM). The fixed specimens were hydrated from 70% ethanol to fresh water. The organisms were then washed and cleaned by brushing them with a soft sable hairbrush to remove salt crystals and debris. Clean specimens were dehydrated through a series of ethanol concentrations and critical-point dried using standard techniques. Dried specimens were mounted on inverted conical stubs with a rapid-drying varnish (Japan Gold Size, Winsor and Newton) normally used in gilding. Specimens were sputter coated with gold and studied with the aid of a JEOL WINSEM JSM 6400 scanning electron microscope. Optimum results were obtained when SEM work was done at 10 kV with a working distance of 39 mm and the stage tilted at 70° to 90°. For light microscopy, temporary slides of lignin pink stained specimens were prepared as whole mounts or dissected appendages. These were examined with a Leitz Laborlux D compound and a Wild M5 dissection microscope and drawings were made from projections using drawing attachments on these microscopes.
The species descriptions of both male and larva were prepared in DELTA (DEscriptive Language for TAxonomy) using a modified Gnathiidae character set (as used in
Research permits for fish collection were provided by the Department of Agriculture, Forestry and Fisheries (DAFF) (RES2019/103 and RES2020/29), and ethical clearance was through the North-West University AnimCare animal ethics committee (NWU-00440-16-A5 and NWU-0051-19-A5). Type material is deposited in the
National Museum, Bloemfontein (
Suborder Cymothoida Wägele, 1989
Superfamily Cymothooidea Leach, 1814
Gnathia termitoides Leach, 1814, by monotypy (
A restricted synonymy and diagnosis of Gnathia was provided in
Holotype
. South Africa • 1 ♂ (4.6 mm TL, dissected); De Hoop Nature Reserve (34°28'44"S, 20°30'38"E); October 1999; leg. N.J. Smit; from Amblyrhynchotes honckenii (
(Figs
Pereon lateral margins subparallel, with few setose setae; anteriorly smooth. Pereonite 1 partially fused dorsally with cephalosome; dorsolateral margins partly obscured by cephalosome. Pereonite 2 wider than pereonite 1. Pereonite 4 with prominent anterior constriction separating it from pereonite 3, median groove present. Areae laterales present on pereonite 5. Pereonite 6 with weak lobi laterales; lobuii absent or weak, conical. Pleon epimera dorsally visible on all pleonites. Pleonite lateral margins with 2 pairs of simple setae, long setose setae randomly distributed on posterior margins. Pleotelson as long as anterior width, covered in pectinate scales; lateral margins finely serrate, anterolateral margins concave, with 3 submarginal setae; posterolateral margin weakly convex, with 2 submarginal setae; mid-dorsal surface with 2 submedian setae, apex with 2 setae.
Antennula shorter than antenna; peduncle article 1 with 2 penicillate setae; article 2 0.8 times as long as article 1, with 2 penicillate setae; article 3 2.1 times as long as article 2, 3.8 times as long as wide. Antennula flagellum 0.8 times as long as article 3, with 5 articles; article 1 with 2 plumose setae; article 3 with 1 aesthetasc seta; article 4 with 1 aesthetasc seta, and 2 simple setae; article 5 terminating with 1 aesthetasc seta, and 3 simple setae. Antenna peduncle article 1 covered in pectinate scales and marginal setae; article 3 2.9 times as long as wide, twice as long as article 2, with 1 penicillate seta, and 12–14 simple setae and 1 penicillate seta; article 4 1.3 times as long as article 3, 3.7 times as long as wide, with 2 penicillate setae, and with 40–50 simple setae; flagellum as long as article 4, with 7 articles, terminating with 4 simple setae.
Gnathia pipinde sp. nov. (
Mandible 0.6 as long as width of cephalosome, rectangular, strongly curved, distally; apex cylindrical, 22% total length, distally raised in lateral view; mandibular seta present. Carina present, smooth. Incisor knob-like. Blade present, dentate, straight, dentate along 100% of margin, with tufts of setae along distal margin. Basal neck short; sensory pits with short simple hair-like setae distributed randomly on dorsal surface of blade. Pseudoblade, internal lobe and dorsal lobe absent; erisma present; lamina dentata absent.
Maxilliped 5-articled, mesial border with short simple hair-like setae; article 1 lateral margin with continuous marginal short setae, endite extending to distal margin of article 2, without coupling setae; article 2 lateral margin with 5 plumose setae; article 3 lateral margin with 7 plumose setae; article 4 lateral margin with 6 plumose setae; article 5 with 7 plumose setae and 5 simple setae.
Pylopod article 1 with three distinct areolae, 1.6 as long as wide, without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 38 large plumose setae; mesial margin with scale-setae on distal part only, 2 simple setae and 1 penicillate seta; distal margin with 6 simple setae; article 2 1.3 as long as wide; with 8 simple setae; article 3 minute, with 4 simple setae.
Pereopods 2–6 with long simple setae and randomly covered in pectinate scales (only illustrated on pereopod 2); inferior margins with weak tubercles. Pereopod 2 with tubercles on merus and carpus; basis 2.9 times as long as greatest width, superior margin with 19 setae, inferior margin with 12 setae; ischium 0.7 times as long as basis, 2.5 as long as wide, superior margin with 6 simple setae and 1 long setose seta, inferior margin with 17 setae; merus 0.5 as long as ischium, 1.5 as long as wide, superior margin with bulbous protrusion and 4 setae, inferior margin with tubercles and 7 setae; carpus 0.5 as long as ischium, 1.8 as long as wide, superior margin with 2 setae (1 setose), inferior margin with tubercles and 5 setae (1 serrate seta); propodus 0.7 times as long as ischium, 2.5 times as long as wide, superior margin with 3 simple setae and 1 penicillate seta, inferior margin with 2 simple setae and 2 robust setae; dactylus 0.7 as long as propodus, terminates in sharp posterior pointing unguis. Pereopods 3 and 4 similar to pereopod 2. Pereopod 5 similar to pereopod 6. Pereopod 6 with tubercles on merus and carpus; basis 3 times as long as greatest width, superior margin with 14 setae, and 1 penicillate seta, inferior margin with 11 setae; ischium 0.9 as long as basis, 3.2 as long as greatest width, superior margin with 12 setae, inferior margin with 8 setae; merus 0.5 as long as ischium, 1.8 times as long as wide, superior margin with 6 setae, inferior margin with 4 setae, without dense patch of scale-setae; carpus 0.5 as long as ischium, 2.2 times as long as wide, superior margin with 3 setae, inferior margin with 4 setae; propodus 0.6 as long as ischium, 3.8 times as long as wide, superior margin with 5 setae, inferior margin with 5 setae, and 2 robust setae; dactylus 0.6 as long as propodus.
Penes produced, more than a third length of pereon; penial processes 6.5 times as long as basal width, anterior end ending in sac-like extension dorsal to opening.
Pleopod 2 exopod 1.7 as long as wide, distally broadly rounded, with 9 plumose setae; endopod 1.8 as long as wide, distally broadly rounded, with 8 plumose setae; appendix masculina absent; peduncle 0.8 times as wide as long, mesial margin with 2 coupling setae, lateral margin with 1 simple seta.
Uropod rami extending beyond pleotelson, apices narrowly rounded. Peduncle with 1 dorsal seta. Uropod endopod 2.4 as long as greatest width, dorsally with 4 setae; lateral margin straight, lateral margin with 6 simple setae; proximomesial margin weakly convex, with 6 long plumose setae. Uropod exopod not extending to end of endopod, 3.3 times as long as greatest width; lateral margin weakly sinuate, with 17 simple setae; proximomesial margin straight, distally convex, with 3 long plumose setae.
(Figs
Pereon elongate, 2.3 times as long as wide, smooth, with no setae or sensory pits. Pereonite 1 partially fused dorsally with cephalosome; dorsally visible; dorsolateral margins partly obscured by cephalosome. Pereonite 2 and 3 similar in size and shape. Pereonite 4 triangular, 2.1 times as wide as long, posterior margin stretching over pereonite 5, lateral shields at leg attachment. Pereonite 5 consists of elastic membrane fully expanded in praniza stage with blood meal, lateral shields at leg attachment. Pereonite 6 rectangular, posterior margin slightly concave, lateral shields at leg attachment. Pereonite 7 dorsally visible; posterior margin rounded, overlapping pleonite 1. Pleon with all 5 pleonites dorsally visible; pleon and pleotelson 0.4 times as long as pereon. Pleonite 5 almost twice the length of the other articles. Pleotelson 1.3 times as long as anterior width, covered in pectinate scales; lateral margins finely serrate; anterolateral margins concave, without submarginal setae; posterolateral margin weakly convex, with 2 submarginal setae; mid-dorsal surface with 2 submedian setae, apex with 2 setae.
Gnathia pipinde sp. nov. (
Antennula shorter than antenna; peduncle with short hair-like setae on anterior borders of all three articles; article 2 with 3 setae, as long as article 1; article 3 with 2 setae (1 penicillate), 2.3 times as long as article 2, 2.9 times as long as wide. Antennula flagellum 1.1 times as long as article 3, with 4 articles; article 1 with 2–3 setae; article 2 with 1 aesthetasc seta and 1 simple seta, 0.6 times as long as flagellum; article 3 with 1 aesthetasc seta; article 4 terminating with 1 aesthetasc seta and 3 simple setae. Antenna with rows of long simple setae on anterior margins of all 4 peduncle articles; peduncle article 3 2.3 times as long as wide, 2 times as long as article 2, with 4 simple setae; article 4 twice as long as article 3, 4.2 times as long as wide, with 6 simple setae; flagellum 1.1 times as long as article 4, with 7 articles, terminating with 3 or 4 simple setae.
Mandible stout, distal margin styliform with 16 teeth on mesial margin (3 smaller at tip of mandible), conical and posteriorly directed, increasing in size from anterior to posterior.
Paragnaths elongate, gutter-like, terminates in sharp point, no teeth.
Maxillula long, slender, 6–8 small teeth on distal inner margin, lateral border with marginal setae proximally.
Maxilliped cylindrical with elongated base, endite extending to distal margin of palp article 2, with 1 long simple seta and coupling seta. Maxilliped palp 3-articled; article 1 with 6 teeth mesially, lateral margin with setae; article 3 with 5–7 simple setae.
Gnathopod smaller than pereopods, with 7 articles, carpus reduced, few simple setae on articles 1–5, 1 robust seta on article 2.
Pereopods 2–6 with long simple setae, pectinate scales covering inner margins of propodus and carpus, and outer margins of merus. Pereopod 2 with tubercles on carpus; basis 2.6 times as long as greatest width, superior margin with 5 setae, inferior margin with 2 setae; ischium 0.7 times as long as basis, twice as long as wide, superior margin with 2 setae, inferior margin with 1 seta; merus 0.5 as long as ischium, 1.3 as long as wide, superior margin with bulbous protrusion, with 3 setae (2 serrate) and pectinate scales, inferior margin with 2 setae; carpus 0.5 as long as ischium, 1.6 as long as wide, superior margin with no setae, inferior margin with 4 setae (1 serrate) and pectinate scales; propodus 0.7 times as long as ischium, 2.3 times as long as wide, superior margin with 2 setae (1 penicillate), inferior margin with 1 simple seta, 2 robust setae and pectinate scales; dactylus 0.9 as long as propodus, with 5 setae, terminates in sharp posterior pointing unguis. Pereopods 3 and 4 similar to pereopod 2 (differ in setation). Pereopod 5 similar to pereopod 6. Pereopod 6 with tubercles on carpus; basis 3.3 times as long as greatest width, superior margin with 12 setae, inferior margin with 3 setae; ischium 0.7 as long as basis, 2.5 as long as greatest width, superior margin with 4 setae (1 penicillate, 2 setose), inferior margin with 2 setae; merus 0.6 as long as ischium, 1.4 times as long as wide, superior margin with bulbous protrusion and 3 setae (2 serrate), inferior margin with 2 setae, with dense patches of pectinate scales; carpus 0.6 as long as ischium, 2.2 times as long as wide, superior margin with 2 setae, inferior margin with 3 setae (1 serrate) and pectinate scales; propodus 0.8 as long as ischium, 3.6 times as long as wide, superior margin with 9 setae, inferior margin with 1 seta, 2 robust setae, and pectinate scales; dactylus 0.6 as long as propodus, with 4 setae, terminates in sharp posterior pointing unguis.
Pleopod 1 exopod 1.9 as long as wide, distally broadly rounded, with 8 plumose setae; endopod 1.8 as long as wide, distally narrowly rounded, with 7 plumose setae; peduncle 0.8 times as wide as long, mesial margin with 2 coupling setae, lateral margin with 1 simple seta.
Uropod rami extending to pleotelson apex, apices narrowly rounded, fringes with short simple setae. Peduncle with 2 dorsal setae. Uropod endopod 1.9 as long as greatest width, dorsally with 3 setae; lateral margin straight, lateral margin with 3 simple setae; proximomesial margin weakly convex, with 6 long plumose setae. Uropod exopod not extending to end of endopod, 3 times as long as greatest width; lateral margin weakly convex, with 5 simple setae; proximomesial margin straight, distally concave, with 4 long plumose setae.
The Xhosa word “pipinde” was chosen, because “pipi” means penis and the post “nde” means long in the language of this southern African tribe and thus referring to the most distinct characteristic of this species. Pronounced as pie-pie-n-dê. The species epithet is a noun in apposition.
South coast of South Africa (Western and Eastern Cape Provinces).
Amblyrhynchotes honckenii (Bloch, 1785).
Gnathia pipinde sp. nov. can be identified by the straight frontal margin; presence of conical superior frontolateral process; a strong and bifid mediofrontal processes; pronounced and pointed supraocular lobes; mandible strongly curved with a dentate blade; and the claviform penes produced more than a third the length of the pereon.
When compared to the other known South African gnathiid species, the shape and size of the frontal process of G. pipinde are very similar to those of G. africana
There are currently 134 species of Gnathia known to science (
The larvae of G. pipinde sp. nov. can be distinguished from the described larvae of the South African species, G. africana and G. pantherina Smit & Basson, 2002, by the presence of 16 teeth on the mandible (G. africana with nine or 10 and G. pantherina with eight). The shape of the pleotelson of G. pipinde (posterior two-thirds convex) also differs from that of G. africana (lateral margins straight) and G. pantherina (anterior half of lateral margins slightly concave).
This species is host-specific to Amblyrhynchotes honckenii and only occurs on the temperate south coast of South Africa (with low intensity and rare infections), despite the wide distribution of the host fish (temperate south coast to subtropical east coast of South Africa). The specific locality preference is also observed with another parasitic isopod on this host fish, Cinusa tetrodontis Schioedte & Meinert, 1884.
This key is based on the morphological characters of the adult male:
1 | Cephalosome wider than pereon; frontal border concave | Gnathia spongicola Barnard, 1920 |
– | Cephalosome not wider than pereon; frontal border produced | 2 |
2 | Frontal border rounded, strongly produced, without any frontal process | Caecognathia cryptopais (Barnard, 1925) |
– | Frontal border slightly produced, with frontal process | 3 |
3 | Pylopod single-articled; two rows of teeth on mandible blade | Afrignathia multicavea Hadfield & Smit, 2008 |
– | Pylopod 2- or 3-articled; absent or single row of teeth on blade | 4 |
4 | Mediofrontal process bifid | 5 |
– | Mediofrontal process absent or not bifid | 6 |
5 | Penes produced, more than a third length of pereon | Gnathia pipinde sp. nov. |
– | Penes not produced, two contiguous papillae as long as wide | Gnathia africana Barnard, 1914 |
6 | Mandibles short and stout (<0.5 length of cephalosome) | Gnathia pilosus Hadfield, Smit & Avenant-Oldewage, 2008 |
– | Mandibles long (>0.5 length of cephalosome) | 7 |
7 | Pereonite 5 completely separated into two lateral halves (pereonite 6 in contact with pereonite 4) | Gnathia disjuncta Barnard, 1920 |
– | Pereonite 5 not separated (pereonite 6 not in contact with pereonite 4) | 8 |
8 | Pereonite 5 areae laterales absent, narrower than pereonite 6; pleopod 2 with appendix masculina > 0.5 length of rami | Gnathia nkulu Smit & Van As, 2000 |
– | Pereonite 5 areae laterales present, as wide or wider than pereonite 6; pleopod 2 with appendix masculina < 0.5 length length of rami | Gnathia pantherina Smit & Basson, 2002 |
This work was in part supported by the National Research Foundation (NRF) of South Africa (NRF Project Grant No. 20403; KA Hadfield, PI). Opinions, findings, conclusions, and recommendations expressed in this publication are that of the authors, and the NRF accepts no liability in this regard. This is contribution number 699 for the NWU Water Research Group.