Research Article |
Corresponding author: Rafael Lemaitre ( lemaitrr@si.edu ) Academic editor: Sammy De Grave
© 2018 Rafael Lemaitre, Dwi Listyo Rahayu, Tomoyuki Komai.
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:
Lemaitre R, Rahayu DL, Komai T (2018) A revision of “blanket-hermit crabs” of the genus Paguropsis Henderson, 1888, with the description of a new genus and five new species (Crustacea, Anomura, Diogenidae). ZooKeys 752: 17-97. https://doi.org/10.3897/zookeys.752.23712
|
For 130 years the diogenid genus Paguropsis Henderson, 1888 was considered monotypic for an unusual species, P. typica Henderson, 1888, described from the Philippines and seldom reported since. Although scantly studied, this species is known to live in striking symbiosis with a colonial sea anemone that the hermit can stretch back and forth like a blanket over its cephalic shield and part of cephalothoracic appendages, and thus the common name “blanket-crab”. During a study of paguroid collections obtained during recent French-sponsored biodiversity campaigns in the Indo-West Pacific, numerous specimens assignable to Paguropsis were encountered. Analysis and comparison with types and other historical specimens deposited in various museums revealed the existence of five undescribed species. Discovery of these new species, together with the observation of anatomical characters previously undocumented or poorly described, including coloration, required a revision of the genus Paguropsis. The name Chlaenopagurus andersoni Alcock & McArdle, 1901, considered by
Diogenidae , hermit crab, new species, Paguropsina gen n. Paguropsis, symbiotic anemone
“In the case of Paguropsis typica the association with a colonial sea-anemone of a genus related to Mamillifera is even more remarkable. Here there is no shell to play the part of “Sir Pandarus of Troy,” but the sea-anemone settles upon the hinder part of the young hermit-crab’s tail, and the two animals grow up together, in such a way that the spreading zoophytes form a blanket which the hermit can either draw completely forwards over its head or throw half-back, as it pleases.”
(
Two unusual hermit crab specimens collected in the Sibuyan Sea, the Philippines, on board the HMS Challenger Expedition in 1874, were considered so unique by
Paguropsis Henderson, 1888 has remained a monotypic genus since its original description. The single representative of this genus, P. typica, has been presumed to have a broad distribution across the tropical Indo-West-Pacific, from the Philippines, Japan, and Indonesia, to off eastern Africa, where adults have been reported in depths ranging from 110 to 350 m (
Despite the uniqueness of Paguropsis among the Diogenidae and even Paguroidea as a whole, the morphology of P. typica has not been studied in sufficient detail in light of the modern concept of paguroids. Furthermore, aside from the inclusion of this genus and species in phylogenetic studies related to the origin of lithodids and the phenomenon of carcinization (
List of species, collection site, museum catalog number of vouchers, and GenBank accession numbers for which mitochondrial COI barcode region and partial sequences of 12S and 16S rRNA were obtained in this report.
Species | Locality | Voucher deposition | COI GenBank no. | 16S GenBank no. | 12S GenBank no. |
---|---|---|---|---|---|
Paguropsis typica | Philippines |
|
MG759674 | MG759703 | MG773703 |
Philippines |
|
– | MG759705 | – | |
Philippines |
|
MG759677 | MG759704 | MG773704 | |
Paguropsis andersoni | Indian Ocean |
|
– | MG950177 | MG950176 |
Madagascar |
|
MG759673 | MG759692 | MG773702 | |
Paguropsis confusa | Philippines |
|
MG759683 | MG759696 | MG773707 |
Locality uncertain |
|
– | MG759695 | MG773705 | |
Philippines |
|
MG759682 | MG759694 | MG773706 | |
Paguropsis gigas | South China Sea |
|
MG759678 | MG759697 | MG773709 |
South China Sea |
|
MG759679 | MG759698 | MG773710 | |
Paguropsis lacinia | Papua New Guinea |
|
MG759665 | MG759699 | MG773711 |
New Caledonia |
|
MG759666 | MG759700 | MG773712 | |
Solomon Islands |
|
MG759668 | MG759701 | MG773713 | |
Paguropsina pistillata | New Caledonia |
|
MG759672 | MG759689 | MG773695 |
New Caledonia |
|
MG759675 | MG759690 | MG773696 | |
New Caledonia |
|
MG759676 | MG759691 | MG773699 | |
Paguropsina inermis | Philippines |
|
MG759669 | MG759686 | MG773700 |
New Caledonia |
|
MG759681 | MG759684 | MG773701 | |
New Caledonia |
|
MG759670 | MG759687 | MG773698 | |
New Caledonia |
|
MG759667 | MG759685 | MG773697 | |
South China Sea |
|
MG759680 | MG759688 | MG773693 |
Specimens used for this study remain deposited in the following museums: The Natural History Museum, London, UK (formerly British Museum) (
General morphological terminology follows that of
CC otter trawl;
CP beam trawl;
DW Warén dredge;
FB fishing boat;
INVMAR Invertébrés Marins (for collections of
NO navire océanographique;
ovig ovigerous female(s);
sta station;
RV research vessel;
ROV remotely operated vehicle;
TRV trawling vessel;
USFC United States Fish Commission.
The station data for the following French collaborative campaigns have been obtained from the
Vouchers, tissue samples, and sequence data of specimens for DNA Barcoding or other genetic analysis were deposited in the
Paguropsis Henderson, 1888: 98 (type species by monotypy: Paguropsis typica Henderson, 1888, gender feminine); Stebbing, 1893: 169; Alcock, 1905: 27; Gordan, 1956: 325; McLaughlin and Lemaitre, 1997: 112 (phylogeny); McLaughlin, 2003: 114 (key); McLaughlin et al., 2010: 23; McLaughlin, 2015: 153, fig. 6.3D.
Chlaenopagurus Alcock, 1899: 113 (type species by monotypy: Chlaenopagurus andersoni Alcock, 1899, gender masculine).
Thirteen pairs of quadriserial gills [no pleurobranchs on thoracomere VIII (last)], gills consisting of series of twin lamellae each ending on distolateral and distomesial angles in filamentous or stub-like extensions (e.g., Fig.
Subtropical to tropical Indo-West Pacific. Depth: 30 to 1125 m.
Several cnidarian names have been reported in the literature as symbionts of what has been presumed to be P. typica, including: Epizoanthus paguropsidis [e.g.,
Paguropsis typica Henderson, 1888, by monotypy. Gender: feminine.
In addition to the type species, P. typica, the genus includes: P. andersoni (Alcock, 1899), and three new species described herein.
During this study, several important characters previously overlooked or not sufficiently discussed have been added to the diagnosis of Paguropsis. Among these are the shapes of mouthparts (maxillule external lobe of endopod, and maxilliped 3 exopod); presence on posterior carapace of a well delimited calcified lateral lobe (e.g., Fig.
Paguropsis typicus Henderson, 1888: 99, pl. 10, fig. 4 (type locality: HMS Challengersta 204A or B, off Tablas Island, Philippines); Murray, 1895: 789.
Paguropsis typicus : Pzibram, 1905: 199; Boas, 1926: 1, figs 1, 7, 8–11; Rabaud, 1941: 263; Gordan, 1956: 325 (in part). (See “Remarks”).
Paguropsis typica : Estampador, 1937: 55; Balss, 1924: 775, figs 31, tbl. 2 (see “Remarks”); Balss, 1956: 1429 (in part); Nicol, 1967: 583; Kaestner, 1970: 299; Miyake, 1982: 98, pl. 33, fig. 6 (color photo); Schäfer et al., 1983: figs 12 (in part, see “Remarks”); Ross, 1983: 171; Baba et al., 1986: 192 (fig. 141, color photo), 193 (Japanese text), 299 (English text); Richter and Scholtz, 1994: 189 (phylogeny); Ates, 2003: 42, tbl. 1; Williams and McDermott, 2004: 16, tbl. 1; McLaughlin et al., 2010: 23; McLaughlin, 2015: 152, fig. 6.3D; Malay et al., 2018: 55.
Paguropsis tyica (misspelling): Schäfer et al., 1983, fig. 12 (in part, see “Remarks”)
Not Paguropsis typica: Schäfer et al., 1983: 229, figs 1, 2; Williams and McDermott, 2004: 12, 66, tbl. 1 (= glaucothoë stage of Parapaguridae, see “Remarks”)
Lectotype (herein selected), male 6.0 mm, Tablas Island, Philippines, HMS Challenger, sta 204A to 204B, 12°43' to 12°46'N, 122°09' to 122°10'E, 182.9–210.3 m, 2 Nov 1874 (
Japan: Intensive Research of Unexploited Fisheries Resource on Continental Slopes, Japan Fisheries Resources Conservation Association, FBShin’ei-maru No. 53, Kita-Koho Seamount, Kyushu-Palau Ridge, 26°46'09"N, 135°20'03"E, 360 m, 17 Nov 1978, trawl: 4 males 10.2–16.4 mm (
South China Sea: NANHAI 2014, cruise OR5: staDW 4105, 13°57.8902'N, 115°25.5073'E, 297–565 m, 3 Jan 2014: 1 male 3.6 mm (
Philippines: USFCAlbatross, Philippines Expedition: Quezon, Luzon Island, Tayabas Bay, Lucena City, sta 5369, 13°48'00"N, 121°43'00"E, 193.8 m, 24 Feb 1909: 1 male 10.7 mm, 1 female 5.7 mm (
Papua New Guinea: BIOPAPUA, NOAlis: Manus Island SE point, staCP 3693, 02°10'S, 147°17'E, 300 m, 29 Sep 2010: 2 males 5.2, 6.7 mm (
Indonesia: Danish Kai Islands Expedition: sta 44, 05°39'S, 132°23'E, 268 m, 30 Apr 1922: 1 female 12.2 mm (
Fiji: BORDAU 1, NOAlis: Lau Ridge, Lakeba, staDW 1463, 18°10'S, 178°44'W, 300–400 m, 6 Mar 1999: 1 male 10.7 mm (
New Caledonia: MUSORSTOM 5, NOCoriolis: Coral Sea, Lord Howe Ridge, Capel Bank, staCP 275, 24°46.60'S, 150°40.30'E, 285 m, 9 Oct 1986: 1 male 4.3 mm (
Eastern Australia: Queensland, Nimbus 1/68, sta 29, 26°30'S, 153°44'E, 184 m, 29 Jul 1968, coll. AJ Bruce: 1 male 7.0 mm (
[Locality uncertain]: INVMAR: sta 15, [coordinates on label in error], 240 m, [no day] April 1929: 1 male 10.3 mm, 1 female 3.9 mm (
Shield (Figs
A–C Paguropsis typica Henderson, 1888, after
A, B Paguropsis typica Henderson, 1888 male, 14.6 mm, Philippines, USFCAlbatross, sta 5409 (
Ocular peduncles ca. 0.5 length of shield, constricted medially and noticeably broadened distally, glabrous or at most with row of short dorsomedian row of short setae; corneas strongly dilated, diameter 0.5–0.6 total peduncular length (including the cornea). Ocular acicles small, triangular, each armed with distal or dorsodistal spine often directed anterodorsally.
Antennular peduncles when fully extended overreaching distal margins of corneas by full length of ultimate peduncular segments. Ultimate and penultimate segments glabrous or at most with scattered short setae. Basal segment with ventromesial tuft of setae distally; lateral face with distal subrectangular lobe, small medial spine, and setose lobe proximally.
Antennal peduncles overreaching distal corneal margins by 0.3–0.4 lengths of ultimate segments. Fifth and fourth segments unarmed except for scattered setae. Third segment with spine at ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in small, usually bifid spine; mesial margin rounded, setose, dorsomesial distal angle with small, usually blunt spine. First segment unarmed. Antennal acicle reaching level of distal portion of optic calathus, slender, terminating in sharp spine, with long setae mostly distally; usually armed with row of 2 or 3 minute spines lateroproximally. Antennal flagellum long, reaching to distal end of cheliped fingers, articles with scattered short setae (< 1 flagellar article in length) and 1 or 2 longer setae (ca. 2 flagellar articles in length) every 12 articles or so.
Mandible (Fig.
Paguropsis typica Henderson, 1888, Philippines, USFCAlbatross, sta 5409: A, B, D male, 14.6 mm, C female, 7.1 mm (
Chelipeds (Figs
A, B Paguropsis typica Henderson, 1888 male, 14.6 mm, Philippines, USFCAlbatross, sta 5409 (
Pereopods 2 and 3 (Figs
Pereopod 4 (Fig.
Paguropsis typica Henderson, 1888, male, 14.6 mm, Philippines, USFCAlbatross, sta 5409 (
Pereopod 5 (Fig.
Male gonopod 1 (Fig.
Paguropsis typica Henderson, 1888, Philippines, USFCAlbatross, sta 5409 (
Female with unpaired pleopods 2–5 usually on left side or less frequently on right side, as follows: pleopods 2–4 biramous, well developed, and reduced biramous or uniramous vestigial pleopod 5. Brood pouch (Fig.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Figs
A, B Paguropsis typica Henderson, 1888, Philippines, PANGLAO 2004, sta T2 [#48] (A) and T2 [#54] (B) (photographs: T-Y Chan): A habitus, with carcinoecium B habitus, with carcinoecium removed C Paguropsis andersoni (Alcock, 1899), habitus, MAINBAZA staCC 3159 (#29) (
Western Pacific: from Japan, off Daito Islands, Ryukyu Islands (
Found with indeterminate species of acontiate anemone (see “Remarks” under genus).
Aside from the meristics accounted for in the above redescription, this species is relatively constant in morphology. The only remarkable variation is in the position of unpaired pleopods 2–5 in females, and presence and degree of development of pleopods 3–5 in males. Females of Paguropsis typica have unpaired pleopods 2–5 on either side, with pleopods 2–4 well developed, biramous and ovigerous, whereas pleopod 5 is considerably reduced or absent. Males have unpaired pleopods 3–5 on either side, all considerably reduced, uni- or biramous, although pleopod 5 or occasionally all pleopods 3–5, can be absent.
Except for the drastic difference in coloration, Paguropsis typica and P. confusa sp. n. are remarkably similar in morphology, and can thus be easily confused unless fresh specimens that still retain their color patterns are available (Figs
General similarities exist between Paguropsis typica and P. andersoni, in particular the cephalic appendages (i.e., dilation of corneas, development of antennular and antennal peduncles), and shape of shield (i.e., posterior half of shield narrowly subtriangular). However, the two species can immediately be differentiated by the shape of the dactyls of pereopods 2 and 3 (Figs
Since
Chlaenopagurus Andersoni Alcock, 1899: 115, pl. 1 (type locality: Indian Marine Survey Investigator, off Comorin).
Chlaenopagurus andersoni Alcock & McArdle, 1901: pl. 53, figs 1, 1a, 2, pl. 54, figs 1, 1a; Alcock, 1901: 229; Alcock, 1902: 67, fig. 2.
Paguropsis typica : Alcock, 1905: 28, pl. 2; Balss, 1924: 775, figs 30, 32 (see “Remarks” under P. typica); Balss, 1927: 963, fig. 1059; Thompson, 1943: 414 (see “Remarks”); Balss, 1956: 1429 (in part); Barnard, 1962: 240; Russell, 1962: 19, fig. 12; Sarojini and Nagabhushanam, 1972: 250, fig. I, fig. A, B, C; Kensley, 1981: 33 (list); Thomas, 1989: 59; Schäfer et al., 1983: figs 12 (in part, see “Remarks” under P. typica); Emmerson, 2016: 449 (list).
Paguropsis typicus : Thompson, 1943: 413 (see “Remarks”); Kamalaveni, 1950: 77, fig. 1 (see “Remarks”); Gordan, 1956: 325 (in part, see “Remarks” under P. typica).
P. tyica (misspelling): Schäfer et al., 1983, fig. 12 (in part, see “Remarks”)
Lectotype herein selected: off Cape Comorin (Kanyakumari), Laccadive Sea, Indian Ocean, HM Indian Marine Survey Steamer Investigator, [probably sta 258, see “Remarks”], 23 Apr 1899, 08°23'N, 76°28'E, 186.5 m (102 fm): male 18.3 mm (
Philippines: NW coast of Panglao Island, 146.3–548.6 m, [no day] Jan-Mar 2011, coll. J Arbasto: 4 males 14.2–16.3 mm (
Indonesia: KARUBAR, RVBaruna Jaya 1: off Tanimbar Island (Arafura Sea), staCP 46, 08°01'S, 132°51'E, 271–273 m, 29 Oct 1991: 7 males 9.3–16.1 mm (
Indian Ocean: southwestern India: off Neendakara, Munambam, Kerala State, 30 m, 2006, commercial trawler, coll. A Biju Kumar: 4 males 14.1–18.2 mm (
[Locality uncertain]: INVMAR: sta 17, 155–165 m, 3 Aug 1964, coll. OT Chan: 1 ovig female 11.2 mm (
Shield (Figs
Paguropsis andersoni (Alcock, 1899) lectotype male, 18.3 mm, Laccadive Sea, Indian Ocean, HM Indian Marine Survey Steamer Investigator (
Ocular peduncles ca. 0.4 length of shield, constricted medially and noticeably broadened distally, glabrous except for scattered short dorsodistal setae; corneas strongly dilated, diameter 0.5–0.6 total peduncular length (including the cornea). Ocular acicles small, triangular, each armed with distal or dorsodistal spine often directed anterodorsally.
Antennular peduncles when fully extended overreaching distal margins of corneas by 0.2 length of penultimate peduncular segments. Ultimate and penultimate segments glabrous or at most with scattered short setae. Basal segment with ventromesial tuft of setae distally; lateral face with distal subrectangular lobe, small medial spine, and setose lobe proximally.
Antennal peduncles overreaching distal corneal margins by ca. 0.5 length of fifth segment. Fifth and fourth segments unarmed except for scattered short setae and laterodistal tuft of long setae. Third segment with spine at ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in small simple or less frequently, bifid spine; mesial margin rounded, setose, and small spine on dorsomesial angle. First segment unarmed except for moderately long setae on lateral face. Antennal acicle length variable with growth, reaching from distal margin of optic calathus to slightly exceeding distal margin of cornea, slender, terminating in sharp spine, with long setae distally, at most with 1 or 2 minute proximal tubercles on mesial margin. Antennal flagellum long, reaching to distal end of cheliped fingers, articles with 1 or 2 short setae (< 1 article in length) and usually with 1 or 2 long setae every 12 articles or so.
Mouthparts not markedly different from those described for Paguropsis typica (e.g., Fig.
Chelipeds (Figs
Pereopods 2 and 3 (Fig.
Paguropsis andersoni (Alcock, 1899), lectotype male, 18.3 mm, Laccadive Sea, Indian Ocean, HM Indian Marine Survey Steamer Investigator (
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Male gonopod 1 (Fig.
Female usually with pleopods 2–5 on left side or less frequently on right side, as follows: pleopods 2–4 biramous, well developed, and reduced biramous or uniramous and vestigial pleopod 5 (see “Variations”). Brood pouch large, subquadrate, distal margin scalloped and fringed with setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Fig.
In explaining the etymology of his genus name Chlaenopagurus where this species was originally placed,
Western Pacific: from Philippines and Indonesia (Arafura Sea). Indian Ocean: from Gulf of Martaban, Andaman Sea (
Found with indeterminate species of acontiate anemone (see “Remarks” under genus).
The following morphological features increase with size: length of antennal acicle; density and strength of spines on chelipeds; and density of tufts of setae on chelipeds and ambulatory legs. Larger males have more numerous subdistal spines or rows of spines on the distal margin of gonopod 1 (Fig.
Of the four females examined, one has pleopods 2–5 on the left side, and the other on the right side; both have pleopod 5 reduced. Of the 29 males examined, 53.8% had one or more unpaired pleopods 3–5 on the left side, 15.4% on the right side, 7.7% did not have any unpaired pleopods on either side, and 23.1% had paired pleopods 3–5. As in males of P. typica, the male pleopods 3–5 are reduced, uni- or biramous.
As previously mentioned under the “Remarks” of Paguropsis typica, P. andersoni can be distinguished primarily from that species and other congenerics by the distinct longitudinal concavity present on the lateroproximal surface of the dactyls of pereopods 3 (second ambulatory legs). In addition, the coxae of pereopods 3 (Fig.
Coloration is clearly distinct in Paguropsis andersoni when compared to other congeners as well as with all other species discussed herein (see Figs
When
Several studies have reported new specimens collected since
As mentioned under the “Remarks” for Paguropsis typica, a number of reports (
In a summary of the hermit crabs from the Indian Museum,
Holotype, male 13.6 mm, Philippines, Bohol Sea, Maribojoc Bay, PANGLAO 2005, NODA-BFAR, staCP 2331, 09°39'N, 123°48'E, 256–268 m, 22 May 2005 (
Philippines: MUSORSTOM 1, NOVauban: N of Lubang, staCC 12, 14°00'N, 120°17'E, 187–210 m, 20 Mar 1976: 5 males 9.7–11.2 mm, 3 females 7.9–9.7 mm, 2 ovig females 9.2, 10.4 mm (
South China Sea: INVMAR, [off Vietnam], sta 69, Cr. 4/63, 15°55'44"N, 15°57'54"N, 109°8'30"E –109°36'30"E, 260–315 m, 16 Sep 1963: 3 males 7.6–11.8 mm (
Indonesia: CORINDON 2, NOCoriolis: Kalimantan, Makassar Straits, sta CH 208, 00°15'S, 117°52'E, 150 m, 31 Oct 1980: 1 male 10.3 mm (
Western Indian Ocean: MIRIKY: Madagascar, between Nosy-bé and Banc du Leven, staCP 3188, 12°31'S, 48°22'E, 298–301 m, 27 Jun 2009, colls. P Bouchet, N Puillandre & B Richer de Forges: 2 specimens not examined, identified and sexed from color photographs, 1 female (#50), 1 ovig female (#51) (
[Locality uncertain]: INVMAR: sta 8, 5 Dec 1963 [no other data]: 1 male 10.3 mm (
Shield (Figs
Paguropsis confusa sp. n., holotype male, 13.6 mm, Philippines, PANGLAO 2005, staCP 2331 (
Ocular peduncles ca. 0.4 length of shield, constricted medially and broadening distally, glabrous except for dorsal longitudinal row of short setae; corneas strongly dilated, diameter 0.5–0.6 total peduncular length (including the cornea). Ocular acicles small, triangular, each armed with distal spine directed anteriorly.
Antennular peduncles when fully extended overreaching distal margins of corneas by full length of ultimate peduncular segment; ultimate and penultimate segments glabrous or at most with scattered short setae; basal segment with ventromesial tuft of setae distally; lateral face with distal subrectangular lobe, small medial spine, and setose lobe proximally.
Antennal peduncles overreaching distal corneal margins by ca. 0.3 length of ultimate segments. Fifth and fourth segments unarmed, nearly glabrous except for scattered short setae. Third segment with setose spine at ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in small simple or bifid spine; mesial margin rounded, setose, dorsomesial distal angle with small spine. First segment unarmed except for setae on lateral face. Antennal acicle relatively short, reaching at most to distal margin of optic calathus, slender, nearly straight and terminating in sharp spine, with few long setae distally. Antennal flagellum long, reaching to distal end of cheliped fingers, with few, scattered short setae less than 1 flagellar article in length.
Mouthparts not markedly different from those described for Paguropsis typica (see Fig.
Chelipeds (Figs
Pereopods 2 and 3 (Figs
Pereopod 4 (Figs
A Paguropsis typica Henderson, 1888, male, 7.9 mm, MUSORSTOM 3, staCP 90 (
Pereopod 5 (Fig.
Male gonopod 1 with inferior lamella armed on distal margin with posterior row of slender, semitransparent hook-like spines, and 2–4 anterior irregular rows of small, straight or slightly curved corneous spines. Gonopod 2 with distal segment strongly twisted distally, densely setose; usually with unpaired, reduced pleopods 3–5 on left side or less frequently on right side, as follows: biramous pleopods 3 and 4, and uniramous, vestigial pleopod 5 (see “Variations”).
Female with unpaired pleopods 2–5 on left side or less frequently on right side, as follows: pleopods 2–4 biramous, well developed, and reduced biramous or uniramous and vestigial pleopod 5 (see “Variations”). Brood pouch large, subquadrate, distal margin scalloped and fringed with setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Figs
The specific name is derived from the Latin feminine singular of confuso, meaning confusion or disorder, and in reference to the state of morphological confusion that had prevented the unmasking of this and other new species under the name P. typica.
Western Pacific: from Philippines, South China Sea, and Indonesia (Kalimantan) on the Macassar Strait. Western Indian Ocean: Mozambique Channel to off Durban, South Africa. Depth: 150 to 403 m.
Found with indeterminate species of acontiate anemone (see “Remarks” under genus).
Among the 31 males and 16 females examined, 99% of males had pleopods 3–5 on the left side, and 37.5% of females had pleopods 2–5 on the left side. There is no other appreciable morphological variation other than that incorporated in the description.
This new species is superficially similar to P. andersoni, from which it differs drastically in coloration and several other characters. Generally, P. confusa sp. n. has a delicate morphology, in particular the less strongly armed chelipeds and slenderer pereopods 2 and 3 than in P. andersoni (see Figs
Holotype: male 23.0 mm, South China Sea, NANHAI 2014, cruise OR 5, staDW 4105, 13°57.8902'N, 115°25.5073'E, 297–565 m, 3 Jan 2014 (
1 ovig female 20.5 mm, same sta data as holotype (
Shield (Figs
Paguropsis gigas sp. n., holotype male, 23.0 mm, South China Sea, TAIWAN, staDW 4105 (
Ocular peduncles ca. 0.4 length of shield, constricted medially, glabrous except for dorsal longitudinal row of short setae; corneas strongly dilated, diameter 0.5 total peduncular length (including the cornea). Ocular acicles small, triangular, each terminating in blunt, setose distal spine directed anteriorly.
Antennular peduncles when fully extended overreaching distal margins of corneas by nearly full length of ultimate peduncular segment; ultimate and penultimate segments glabrous or at most with scattered short setae; basal segment with ventromesial tuft of setae distally; lateral face with distal subrectangular lobe, and setose lobe proximally.
Antennal peduncles overreaching distal corneal margins by ca. 0.2 length of ultimate segments. Fifth and fourth segments unarmed, nearly glabrous except for scattered short setae. Third segment with setose spine at ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in small simple or bifid spine; mesial margin rounded, setose, and small spine on dorsomesial angle. First segment unarmed except for moderately long setae on lateral face. Antennal acicle almost reaching distal margin of cornea, slender, nearly straight and terminating in sharp spine, with long setae dorsomesially and distally. Antennal flagellum reaching to midpoint of chelae, with few short setae less than one article in length.
Mouthparts not markedly different from those described for Paguropsis typica (see Fig.
Chelipeds (Figs
Pereopods 2 and 3 (Fig.
Pereopod 4 (Figs
Pereopod 5 (Fig.
Male gonopod 1 with inferior lamella armed on distal margin with posterior row of slender, semitransparent hook-like spines, and 2–4 anterior irregular rows of small, straight or slightly curved corneous spines. Gonopod 2 with distal segment strongly twisted distally, densely setose. In only known male, left side with biramous, reduced pleopods 3 and 4, and uniramous vestigial pleopod 5; right side with uniramous vestigial pleopod 3 and lacking pleopods 4 and 5.
Female (only one specimen known) with unpaired left pleopods 2–4 well developed, lacking pleopod 5. Brood pouch large, subquadrate, distal margin strongly scalloped and fringed with setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Fig.
Habitus: A Paguropsis gigas sp. n., holotype male, 23.0 mm, South China Sea, NANHAI 2014, staDW 4105 (
The specific epithet is from the Latin gigas, meaning giant, used as a noun in apposition, and in reference to the large size attained by individuals of this new species.
Western Pacific: known so far only from the South China Sea. Depth: 297 to 565 m.
Found with indeterminate species of acontiate anemone (see “Remarks” under genus).
With only two specimens known, no variations can be evaluated.
Paguropsis gigas sp. n. shares with P. lacinia sp. n. the presence of a prominent patch of dense, capsulate setae on the dorsolateral face and dorsal margin of the palm of the chelae of pereopod 4. The shape and arrangement of the setae on the patch, however, is quite different in both species. In P. gigas sp. n., the capsulate setae are relatively short and arranged in a series of oblique fringes that occupy and oval area from the dorsal margin to midlength of the lateral face of the palm (Figs
Among the species discussed in this revision, Paguropsis gigas sp. n. and P. andersoni are similar in that they grow to the largest size, the former reaching a shield length of 23.0 mm, the latter to a shield length of 20.6 mm. Morphologically they are also generally similar, both having strong, dense spination and bristle-like setation on the chelipeds, and numerous tufts of bristle-like setae on pereopods 2 and 3. The lateral surfaces of the dactyls of pereopods 2 and 3 are concave in both species, although only moderately so and along the proximal half or more of the segment in P. gigas sp. n., whereas the concavity is strongly marked along the proximal one-third in P. andersoni. Despite these similarities, P. gigas sp. n. differs markedly from P. andersoni, the former having a prominent dense patch of thin capsulate setae arranged in oblique fringes on the dorsal margin and dorsolateral face of the palm of the chelate pereopod 4, whereas in the latter there is no patch of setae and only a fringe of long setae on the dorsal margin of the palm. Furthermore, in P. gigas sp. n. the palm of pereopod 4 is often more noticeably lateromesially flattened than in P. andersoni, although there is some variation in this character in both species. The coloration of the ocular peduncles, chelipeds, and pereopods is also clearly different in these two species (compare Figs
Holotype: female 8.4 mm, Solomon Islands, SALOMON 2, NOAlis, NW of Isabel Island, staCP 2201, 07°43.5'S, 158°29.9'E, 307–310 m, 25 Oct 2004 (
Papua New Guinea: MADEEP, NOAlis: NW of Kavieng, staCP 4254, 02°28'S, 150°42'E, 273–324 m, 24 Apr 2014: 1 female 9.8 mm, color photograph (Fig.
Salomon Islands: SALOMON 1, NOAlis: N Buena Vista Island, staDW 1765, 08°43'S, 160°07'E, 325–380 m, 27 Sep 2001: 1 female 6.1 mm (
Tonga Islands: BORDAU 2, NOAlis: NW of Tongatapu, staCP 1643, 21°05'S, 175°22'W, 487 m, 22 Jun 2000: 1 male 7.3 mm, 1 female 7.2 mm (
New Caledonia: NORFOLK 1, NOAlis: Norfolk Ridge, Crypthelia Bank, staCP 1731, 23°21'S, 168°16'E, 310–788 m, 27 Jun 2001: 1 male 8.5 mm (
Shield (Figs
Paguropsis lacinia sp. n., holotype female, 8.4 mm, Solomon Islands, SALOMON 2, staCP 2201 (
Paguropsis lacinia sp. n. holotype female, 8.4 mm, Solomon Islands, SALOMON 2, staCP 2201 (
Ocular peduncles stout, constricted medially and broadening distally, ca. 0.5 length of shield, glabrous except for row of few short dorsodistal setae; corneas strongly dilated, diameter 0.5–0.6 total peduncular length (including the cornea). Ocular acicles small, triangular, armed with distal or dorsodistal spine often directed anteriorly or anterodorsally.
Antennular peduncles when fully extended overreaching distal margins of corneas by nearly full length of ultimate peduncular segments. Ultimate and penultimate segments glabrous or at most with scattered short setae. Basal segment with ventromesial setae distally; lateral face with distal subrectangular lobe with or without small tubercles, small medial spine, and setose lobe proximally.
Antennal peduncles reaching or at most slightly exceeding distal margin of corneas. Fifth and fourth segments unarmed except for scattered short setae and laterodistal tuft of long setae. Third segment with strong spine at ventrodistal angle. Second segment with dorsolateral distal angle produced, terminating in small simple spine; mesial margin rounded, setose, and small spine on dorsomesial angle. First segment unarmed. Antennal acicle reaching to proximal margin of cornea, slender, terminating in sharp spine, with long setae distally, at most with 1 or 2 minute proximal tubercles on mesial margin. Antennal flagellum long, reaching to distal end of cheliped fingers, articles with 1 or 2 short setae (< 1 article in length) and usually with 1 or 2 long setae every 12 articles or so.
Mouthparts not markedly different from those described for Paguropsis typica (see Fig.
Chelipeds (Figs
A–C Paguropsis lacinia sp. n., holotype female, 8.4 mm SALOMON 2, CP 2201 (
Pereopods 2 and 3 (Figs
Paguropsis lacinia sp. n. holotype female, 8.4 mm, Solomon Islands, SALOMON 2, staCP 2201 (
Pereopod 4 with chela (Fig.
Pereopod 5 (Fig.
Male gonopod 1 with inferior lamella armed on distal margin with posterior row of slender, semitransparent hook-like spines, and 1 or 2 irregular rows of small straight or slightly curved corneous spines. Gonopod 2 with distal segment strongly twisted distally, densely setose. Pleon with left unpaired, reduced, biramous pleopods 3 and 4, lacking pleopod 5.
Female with left side having unpaired pleopods 2–4, and reduced biramous pleopod 5 (no unpaired pleopods 2–5 on right side). Brood pouch large, subquadrate, distal margin scalloped and fringed with setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Fig.
The species name is from the Latin lacinia, a fringe, and refers to the characteristic setae of this new species on the dorsal margin of the palm of the chelate pereopod 4.
Western Pacific: from off northern Papua New Guinea, Solomon Islands, Tonga Islands, and New Caledonia. Depth: 135 to 788 m.
Found with indeterminate species of acontiate anemone (see “Remarks” under genus).
No appreciable morphological variations were observed other than those incorporated in the description.
See “Affinities” under Paguropsis gigas sp. n.
The most prominent, distinctive morphological character of this species is the presence of a dense patch of capsulate, simple setae on the dorsal margin of the palms of pereopods 4 (Figs
Thirteen pairs of quadriserial gills [no pleurobranchs on thoracomere VIII (last)], gills consisting of series of twin lamellae each deeply divided distally into finger-like extensions (e.g., Fig.
Paguropsina pistillata gen. et sp. n., holotype male, 4.4 mm New Caledonia, EBISCO, CP 2499 (
Paguropsina pistillata gen. et sp. n. Gender: feminine.
In addition to the type species, the genus includes P. inermis gen. et sp. n.
The generic name is derived from the genus name Paguropsis, and using the Latin feminine suffix –ina, in reference to the relatively small size of individuals of the two species of this new genus.
Subtropical to tropical western Pacific. Depth: 52 to 849 m.
The two new species included in this genus have relatively small specimens ranging in shield length from 1.8 to 6.1 mm, with subovate shields, and a general delicate morphology with slender antennal peduncles and pereopods 2 and 3, weakly armed chelipeds having short, simple setation not obscuring the surface features of the segments, stout ocular peduncles, and wide corneas. Aside from the general, subtle appearance, species of Paguropsina gen. n. can be separated from those of Paguropsis primarily by four characters that are drastically different from those in species of Paguropsis. These are: the shape of the gills (lamellae deeply divided distally into finger-like extensions vs. distally divided into filamentous or stub-like extensions in Paguropsis); the shape of the exopod of the maxilliped 3 (broad, 2.4 times as long as broad vs. slender, 4 or more times as long as broad in Paguropsis); the width of sternite XI (ca. length of one coxa of pereopods 3 vs. less than half length of one coxa in Paguropsis); and armature of the cutting edges of dactyl and fixed finger of chela of pereopod 4 (cutting edges of dactyl and fixed finger unarmed or with one distinct corneous spinule vs. cutting edge of dactyl with row of small corneous spines and cutting edge of fixed finger with sharp spines arranged like bear claw in Paguropsis). In several other respects species of Paguropsina gen. n. and Paguropsis also differ albeit the differences are more subtle. The lateral projections of the shield each terminate in a short vertical keel-like ridge in species of Paguropsina gen. n., whereas the lateral projections terminate in a small spines without a keel in Paguropsis species. Additionally, it appears based on the material examined of both new species herein described under this new genus, that the location of pleopods tends to be fixed on the left side [see “Variations” under each species), whereas in species of Paguropsis the pleopods can frequently be present on either side.
Holotype: 1 male 4.4 mm, New Caledonia, EBISCO, NOAlis, staCP 2499, Capel Bank, 24°53'0"S, 159°52'0"E, 286–529 m, 7 Oct 2005 (
Philippines: PANGLAO 2004, W Pamilacan I. Cervera shoal, sta T37, 09°28'N, 123°51'E, 134–190 m, 4 Jul 2004: ovig female 4.2 mm, color photograph (Fig.
Indonesia: Danish Kei Islands Expedition: sta 49, 05°37'10"S, 132°24'E, 245 m, 3 May 1922: 1 ovig female 4.4 mm (
Salomon Islands: SALOMON 1, NOAlis: N Malaita, staDW 1778, 08°19'S, 160°34'E, 157–253 m, 29 Sep 2001: 1 male 2.7 mm (
New Caledonia: MUSORSTOM 6, NOAlis: Loyalty Islands, [sta number lost]: 1 male 3.1 mm (
Chesterfield Islands, Coral Sea: MUSORSTOM 5, NOCoriolis: Lord Howe Ridge, Capel Bank, staCP 269, 24°47'S, 159°37'E, 250–270 m, 9 Oct 1986: 4 males 2.5–3.3 mm, 1 ovig female 3.1 mm (
Shield (Figs
Ocular peduncles strongly broadened distally, ca. 0.5 length of shield; corneas strongly dilated, diameter ca. 0.8 of total peduncular length (including the cornea). Ocular acicles small, obtusely triangular, armed with minute subterminal blunt spine directed anterodorsally.
Antennular peduncles when fully extended overreaching distal margins of corneas by entire or nearly entire length of ultimate peduncular segments. Ultimate and penultimate segments glabrous or at most with scattered short setae. Basal segment with lateral face having distal subrectangular lobe, minute medial spine, and setose lobe proximally.
Antennal peduncles reaching nearly to distal corneal margins. Fifth segment slender, glabrous or with scattered setae. Fourth segment with scattered setae. Third segment with short ventrodistal spine. Second segment with dorsolateral distal angle not noticeably produced, terminating in short spine; mesial margin rounded, setose, dorsomesial distal angle blunt, unarmed. First segment (Fig.
Mouthparts. Mandible with stout palp. Maxillule with recurved external lobe of endopod nearly as long as entire endopod. Maxilla with endopod not exceeding distal end of scaphognathite. Maxilliped 1 with endopod bent medially nearly at right angle, reaching distal end of exopod; epipod elongated. Maxilliped 2 without distinguishing characters. Maxilliped 3 (Fig.
Chelipeds (Figs
Pereopods 2 and 3 (Fig.
Paguropsina pistillata gen. et sp. n., holotype male, 4.4 mm New Caledonia, EBISCO, CP 2499 (
Pereopod 4 (Figs
Pereopod 5 (Fig.
Male gonopod 1 with inferior lamella armed on distal margin with posterior row of slender, semitransparent hook-like spines, and 1 or 2 irregular rows of small straight or slightly curved corneous spines. Gonopod 2 with distal segment strongly twisted distally, densely setose. Left unpaired pleopods 3–5 reduced when present, pleopod 3 biramous, pleopods 4 and 5 uniramous; no pleopods 3–5 on right side (see “Variations”).
Female with left unpaired, well-developed, biramous pleopods 2–4 (ovigerous), rarely with vestigial pleopod 5; lacking or rarely having unpaired pleopods 2–5 on right side (see “Variations”). Brood pouch large, oblong, distal margin weakly scalloped and fringed with sparse short setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Fig.
The species name derives from the Latin pistillum, a club-shaped pounder used in a mortar, and refers to the characteristic shape of the chela of pereopod 4.
Western Pacific: from the Philippines, Indonesia (Arafura Sea), Solomon Islands, and New Caledonia. Depth: 135 to 849 m.
Found with undetermined species of acontiate anemone (see “Remarks” under genus Paguropsis).
Of the 152 males examined, 133 (87.5%) have unpaired pleopods 3–5 (reduced, uni- or biramous) on the left side, and the remaining lack unpaired pleopods on either side. Of the 166 females examined, 99% have unpaired pleopods 3–5 on the left side.
This new species and Paguropsina inermis gen. et sp. n. are very similar. However, the two can be immediately separated by the difference in armature of the cutting edge of the fixed finger on the chela of pereopod 4. In P. pistillata gen. et sp. n. the cutting edge is armed with one distinct, sharp corneous-tipped spine that is often slightly offset laterally from the cutting edge, whereas the cutting edge in P. inermis gen. et sp. n. is unarmed. Coloration also differs in these two congeners (Fig.
Holotype: male 3.7 mm, New Caledonia, NORFOLK 2, Antigonia Bank, staCP 2119, 23°23'S, 168°02'E, 300 m, 1 Nov 2003 (
Japan: Ogasawara Islands: TRVShin’yo-maru 1997 research cruise, sta 17: off Chichi-jima Island, 27°24.58'N, 142°10.21'E, 210–212 m, 16 Oct 1997, coll. T Komai: 1 ovig female 2.9 mm (
South China Sea: ZHONGSHA 2015, ORI cruise 1113: staCP 4160, 20°48.88'N, 116°43.153'E, 251 m, 30 Jul 2015: 1 ovig female 4.5 mm (
Philippines: MUSORSTOM 1, NOVauban: N Lubang, sta CP63, 14°00'N, 120°16'E, 191–195 m, 27 Mar 1976: 1 female 6.1 mm (
Indonesia: KARUBAR, NOBaruna Jaya 1: Kai Islands, sta DW18, 05°18'S, 133°01'E, 205–212 m, 24 Oct 1991: 2 males 3.1, 3.2 mm, 1 female 3.5 mm (
Fiji Islands: BORDAU 1, NOAlis: Lau Ridge, Yangasa Cluster, sta DW1497, 18°44'S, 178°25'W, 335–350 m, 12 Mar 1999: 1 male 2.5 mm, 1 female 3.0 mm (
Tonga Islands: BORDAU 2, NOAlis: Vava’u group, sta DW1583, 18°37'S, 174°03'W, 327–360 m, 13 Jun 2000: 1 female 3.0 mm (
New Caledonia: BATHUS 3, NOAlis: Norfolk Ridge, W of Mont Jumeau, staCP 805, 23°41'S, 168°01'E, 278–310 m, 27 Nov 1993: 1 male 3.4 mm (
Shield (Figs
Paguropsina inermis gen. et sp. n., holotype male 3.7 mm, New Caledonia, NORFOLK 2, sta CP2119, (
Ocular peduncles strongly broadened distally, ca. 0.5 length of shield; corneas strongly dilated, diameter ca. 0.7 of total peduncular length (including the cornea). Ocular acicles small, obtusely triangular, armed with minute subterminal blunt spine directed anterodorsally.
Antennular peduncles when fully extended overreaching distal margins of corneas by entire or nearly entire length of ultimate peduncular segments; ultimate and penultimate segments glabrous or at most with scattered short setae; basal segment with lateral face having distal subrectangular lobe, minute medial spine, and setose lobe proximally.
Antennal peduncles reaching nearly to distal margin of corneas. Fifth segment slender, glabrous or with scattered setae. Fourth segment with few scattered setae. Third segment with short ventrodistal spine. Second segment with dorsolateral distal angle not noticeably produced, terminating in short spine; mesial margin rounded, setose, dorsomesial distal angle blunt, unarmed. First segment (Fig.
Mouthparts similar to those described for the type species Paguropsis pistillata sp. n. Maxilliped 3 (Fig.
Chelipeds (Figs
Pereopods 2 and 3 (Fig.
Paguropsina inermis gen. et sp. n., holotype male 3.7 mm, New Caledonia, NORFOLK 2, sta CP2119, (
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Male gonopod 1 with inferior lamella armed on distal margin with posterior row of slender, semitransparent hook-like, corneous spines. Gonopod 2 with distal segment strongly twisted distally, densely setose. Left unpaired pleopods 3–5 reduced when present (see Variations); when present, pleopod 3 biramous, pleopods 4 and 5 uniramous; no pleopods 3–5 on right side.
Female with left unpaired, well-developed, biramous pleopods 2–4 (ovigerous), rarely with vestigial pleopod 5; usually without unpaired pleopods 2–5 on right side (see “Variations”). Brood pouch large, oblong, distal margin weakly scalloped and fringed with sparse short setae.
Uropodal exopods (Fig.
Telson (Fig.
See Table
(Fig.
The species name derives from the Latin inermis, meaning unarmed, and refers to the lack of armature on the cutting edge and lateral face of the fixed finger of pereopod 4, the main characteristic setting of this species.
Western Pacific: Japan (Ogasawara Islands), South China Sea, Philippines, Indonesia (Banda Sea), Fiji Islands, Tonga Islands, and New Caledonia. Depth: 101 to 397 m.
Found with indeterminate species of acontiate anemone (see “Remarks” under genus Paguropsis).
As noted above, the armature of the dactyls of pereopods 2 and 3 is noticeably variable among the numerous specimens examined of this new species. The dorsomesial and ventromesial margins vary in armature from having bristle-like setae and obscure or altogether lacking any clearly visible corneous spines (e.g., in the holotype, Fig.
In the 25 males examined, the presence of left unpaired pleopods 3–5 is variable, as follows: 77% have reduced, biramous left pleopod 3; 55% have a reduced, uniramous pleopod 4; and 11% have a reduced, uniramous pleopod 5; 22% lack pleopods 3–5 altogether; no male specimens were found to have pleopods 3–5 on right side. Virtually all 22 females examined had pleopods 2–4 only on the left side and lacked pleopod 5. However, 10% of the females had a uniramous, vestigial pleopod 5. Only one ovigerous female (3.8 mm,
See Paguropsina pistillata gen. et sp. n.
1 | Exopod of maxilliped 3 slender, 4 or more times as long as broad (e.g., Fig. |
Paguropsis Henderson, 1888)...2 |
– | Exopod of maxilliped 3 broad, 2.4 times as long as broad (e.g., Fig. |
Paguropsina gen. n....6 |
2 | Lateroproximal surface of dactyl of pereopod 3 with longitudinal concavity; sternite XI separating coxae of pereopods 3 by ca. 0.2 length of 1 coxa, posterior lobes of sternite XI strongly compressed | 3 |
– | Lateroproximal surface of dactyl of pereopod 3 convex, without longitudinal concavity; sternite XI separating coxae of pereopods 3 by distinctly more than 0.2 length of 1 coxa, posterior lobes of sternite XI not compressed | 4 |
3 | Lateroproximal surface of dactyl of pereopod 3 with distinct and usually weakly calcified longitudinal concavity (Figs |
Paguropsis andersoni (Alcock, 1899) |
– | Lateroproximal surface of dactyl of pereopod 3 with weak, calcified longitudinal concavity; background coloration mostly white with orange patches on pereopods 2 and 3 (Figs |
Paguropsis confusa sp. n. |
4 | Chela of pereopod 4 lacking dense patch of capsulate setae on dorsal margin of palm (only with fringe of long setae); coloration as in Figs |
Paguropsis typica Henderson, 1888 |
– | Chela of pereopod 4 with dense patch of capsulate setae on dorsal margin of the palm; coloration not as above | 5 |
5 | Patch of capsulate setae on dorsal margin of palm of chela of pereopod 4 arranged in a series of oblique rows or fringes of setae, patch occupying area from dorsal margin to nearly midlength of lateral face of palm (Fig. |
Paguropsis gigas sp. n. |
– | Patch of capsulate setae on dorsal margin of palm of chela of pereopod 4 not arranged in rows or fringes of setae, patch occupying area from dorsal margin to nearly one-fourth of lateral surface of the palm (Fig. |
Paguropsis lacinia sp. n. |
6 | Cutting edge of fixed finger of chela of pereopod 4 armed with 1 distinct corneous-tipped spine often slightly offset laterally from cutting edge (Fig. |
Paguropsina pistillata gen. et sp. n |
– | Cutting edge of fixed finger of chela of pereopod 4 unarmed (Fig. |
Paguropsina inermis gen. et sp. n |
The results of this revision provide a vision of the overall biogeographic distribution of the seven species herein discussed of Paguropsis and Paguropsina gen. n. This vision, however, is preliminary as it is evident that many of the vast marine shelf areas and deep-sea habitats of the Indo-West Pacific where species of these two genera live, still remain to be sampled. Species of Paguropsis are distributed in the tropical and subtropical regions of the Indo-West Pacific, in continental shelf to upper slope depths of 30 to 1125 m. Of the five species of Paguropsis, only two have been found to occur outside the western Pacific: P. andersoni, distributed widely across the Indian Ocean, from off southeastern Africa, both coasts of India, Andaman Sea, to the extreme southeastern coast of Indonesia in the Arafura Sea; and P. confusa gen. et sp. n., found from the southwestern Indian Ocean and the western Pacific from the Philippines and Makassar Straits, Indonesia (Kalimantan). The other three species of Paguropsis, P. typica, P. gigas sp. n., and P. lacinia sp. n., have been found to be distributed exclusively in the western Pacific region. Of these, P. typica occurs the farthest north (off Daito Islands, Ryukyu Islands, Japan) and the farthest south (off eastern Australia), and reaches the Fiji Islands to the east; P. gigas sp. n. is so far known only from the South China Sea; and P. lacinia sp. n. has the easternmost distribution in the South Pacific, distributed from the Solomon Islands to the Tonga Islands. The two species of Paguropsina gen. n. are exclusively distributed in the western Pacific, in depths ranging from 52 to 849 m. Of these, P. pistillata gen. et sp. n. occurs from the Philippines to the New Caledonia region; and P. inermis gen. et sp. n. from Ogasawara Islands, Japan and off Taiwan in the South China Sea, to the Tonga Islands. It is noteworthy that despite extensive sampling during the last three decades in French Polynesia (Tuamotu Archipelago), Marquesas, Society and Austral Islands (e.g.,
The unusual body symmetry and variable presence and position of unpaired pleopods 3–5 in males and unpaired pleopods 2–5 in females, and in the case of females also a brood pouch, indistinctly on the left or right side of Paguropsis typica, has been highlighted by various carcinologists since the time of
Previous to this study, the development of a fully chelate pereopod 4, without a propodal rasp, has been less noted in Paguropsis. This condition is only present in one other paguroid, the semi-terrestrial coenobitid Birgus latro (Linnaeus, 1767) where the abandonment of housing for protection by adults and the non-aquatic life has led to various unusual morphological feeding and respiratory specializations (
The evolution of the specialized morphology of species of Paguropsis and Paguropsina gen. n. can be attributed to the symbiosis with anemones as mode of housing, without the intervention of mollusk shells or other hard habitat at any time during the life of the hermit crab. Aside from symmetry, species of Paguropsis and Paguropsina gen. n. are unique in lacking rasp structures on pereopods and uropods, a character that is a sine qua non for all five families of “asymmetrical” Paguroidea. Only two other species among the “asymmetrical” hermit crabs are known, or at least suspected, to use exclusively a cnidarian as carcinoecia, the ParapaguridaeTylaspis anomala Henderson, 1885 and Sympagurus poupini Lemaitre, 1994 (
Aside from the generic characters that differentiate species of Paguropsis and Paguropsina gen. n., the morphology of the species in these two genera is remarkably homogenous, with species differing only in relatively minor details. This homogeneity can be attributed, at least in part, of the adaptation to a similar symbiotic mode of life with an acontiate anemone as means of protection for the membranous pleon. All species in the two genera live symbiotically with indeterminate species of anemones. The need to manipulate their cnidarian symbiont has evidently led species of Paguropsis and Paguropsina gen. n. to develop fully chelate pereopods 4, the appendage used to grasp and move back and forth the sheet-like coenosarc of the symbiont. It is striking, however, that two species of Paguropsis (P. gigas sp. n. and P. lacinia sp. n.), and both known species of Paguropsina gen. n. (P. pistillata gen. et sp. n. and P. inermis gen. et sp. n.), have developed specialized morphological features on the chela of this appendage, those of the former genus as setal patches (Figs
There is one unusual character discovered during this study that had not been documented before in the single previously known species of Paguropsis, P. typica: the presence on the ventral face of the coxae of the chelipeds of a decalcified longitudinal fissure (e.g., Fig.
Modern studies that have focused on details of anomuran evolution (e.g.,
The molecular data herein included (Table
The most remarkable biological feature of species of Paguropsis and Paguropsina gen. n. is their intriguing symbiotic association with acontiate anemones, without the intervention of snail shells or other hard type of housing. Regrettably, virtually no information exists on the nature and origin of the association except for the brief comments in reports of earlier naturalists (e.g.,
A Paguropsis typica Henderson, 1888: live specimen in sorting tray on board ship (photograph: B Richer de Forges) B Paguropsis andersoni (Alcock, 1899), not collected, ROV, KwaZulu-Natal, South Africa, DST/NRF ACEP Spatial Solutions cruise, Aliwal outer reef, off KwaZulu-Natal, RY Angra Pequena, sta R50: specimen photographed in situ with ROV, not collected (photograph: DST/NRF ACEP – Spatial Solutions project team) C, D Paguropsis confusa sp. n.: C specimen photographed in situ with ROV, not collected, off Durban, KwaZulu-Natal, South Africa, DST/NRF ACEP Spatial Solutions Project cruise, sta R45 Echinoderm Extravaganza (photograph: DST/NRF ACEP – Spatial Solutions project team) D not examined, Philippines, LUMIWAN CP 2867–16 (photograph: T-Y Chan).
This study was conceived during team visits to the