Paragiopagurus acutus (De Saint Laurent, 1972)

Lemaitre, R., 1996, Hermit crabs of the family Parapaguridae (Crustacea: Decapoda: Anomura) from Australia: species of Strobopagurus Lemaitre, 1989, Sympagurus Smith, 1883 and two new genera., Records of the Australian Museum 48 (2), pp. 163-221 : 211-214

Paragiopagurus acutus (DeSaint Laurent, 1972)

Figs 25 , 26

Parapagurus acutus acutus De Saint Laurent, 1972: 113 , figs 7, 18 (type locality: Philippines, Albatross sta. 5222).

Sympagurus acutus acutus .- Lemaitre, 1989: 37.- Lemaitre, 1994: 412.

Holotype. Male (SL 5.6 mm), Philippines, 9.2 mi (17 km) NW of W San Andreas Is., between Marinduque and Luzon, Albatross sta. 5222, 13°38'30"N, 121°42'45"E, 357 m, 24 Apr 1908, USNM 168309 .

Australian Material. WESTERN AUSTRALIA: 1 male (SL 4.6 mm), NW of Leveque , FRV Soela, sta. 01184/065, 14°49.0'S; 121°36.1'E, 302 - 300 m, 12 Feb 1984, colI. S. Slack-Smith, WAM 1239 -86 .

Other material. (For meaning of asterisks see Materials and Methods). JAPAN: 1 male (SL 6.1 mm), Honshu , Uraga Strait, Albatross sta. 5094, 35°04'42"N, 139°38'20"E, 161 m, 26 Oct 1906, USNM 168973 *.

PHILIPPINES: 14 males (SL 3.4-6.0 mm) , 9 females (SL 2.8-4.8 mm), Verde Is. Passage, off Matocot Point, Albatross sta. 5268, 13°42'N, 120°57'15"E, 311 m, 8 JUll 1908, USNM 168980 *. 7 males (SL 2.1-3.5 mm), between Cebu and Bohol, off Lauis Point, Albatross sta. 5412, 10009'15"N, 123°52'E, 296 m, 23 Mar 1909, USNM 168977 *. 2 males (SL 2.7, 3.2 mm), between Cebu and Bohol, off Lauis Point, Albatross sta. 5411, 1O°1O'30"N, 123°51'15"E, 265 m, 23 Mar 1909, USNM 168976 *. 2 males (SL 4.2, 4.8 mm) , Verde Is. Passage, off Matocot Point, Albatross sta. 5297, 13°41'20"N, 120058'E, 362 m, 24 Jul 1908, USNM 168975 *. 1 female (SL 4.1 mm) , Verde Is. Passage, off Matocot Point, Albatross sta. 5269, 13°39'50"N, 120059'30"E, 402 m, 8 JUll 1908, USNM 168974 *.

INDONESIA: 1 male (SL 5.2 mm), Borneo , Darvel Bay, off Sibutu Is., Albatross sta. 5579, 04°54'15"N, 119°09'52"E, 320 m, 25 Sep 1909, USNM 168978 *. 1 female (SL 6.4 mm), Borneo , Sibuko Bay, off Silungan Is., Albatross sta. 5592, 04°12'44"N, 118°27'44"E, 558 m, 29 Sep 1909, USNM 168979 *. 1 female (SL 5.8 mm), Den danske Kei Ekspd. 1922, sta. 59, 05°28'S, 132°36'E, 385 m, 12 May 1922, ZMK . 4 males (SL 3.3- 7.4 mm), Den danske Kei Ekspd. 1922, sta. 44, 05°39'S, 132°23'E, 268 m, 30 Apr 1922, ZMK . 1 male (SL 6.7 mm), Den danske Kei Ekspd. 1922, sta. 51, 05°40'1O"S, 132°21'E, 263 m, 3 May 1922, ZMK . 3 males (SL 2.1- 8.0 mm), 2 females (SL 2.0, 3.3 mm), 4 females ovig. (SL 2.6-6.8 mm), Th. Mortensen's Java-S. Afrika Exp. 1929-30, sta. 7, 08°29'S, 114°40'E, 200 m, 5 Apr 1929, ZMK *.

Diagnosis. Phyllobranchiate gills. Shield ( Fig. 25a ) as long as broad; dorsal surface weakly calcified medially; rostrum broadly rounded, with low dorsal ridge; anterior margins weakly concave; lateral projections subtriangular, terminating in small spine; ventrolateral margin with spine (not always visible in dorsal view); posterior margin broadly rounded. Ocular peduncles more than half length of shield; ocular acicles subtriangular, terminating in strong multifid spine; corneae slightly dilated. Maxillule with internal lobe of endopod bearing 4 long seta. Sternite of 3rd maxillipeds with small spine on each side of midline. Epistomial spine straight. Antennular peduncle exceeding distal margin of corneae by 0.75 length of ultimate segment. Antennal peduncle ( Fig. 25b ) reaching distal margin of cornea; 2nd segment with dorsolateral distal angle produced, terminating in strong simple spine reaching to midpoint of antennal acicle; acicles reaching distal margin of corneae, mesial margin with 9 to 14 spines; flagellum with short and long setae <1 to 4 flagellar articles in length respectively. Che1ipeds markedly dissimilar, with moderately dense setae. Right cheliped ( Fig. 25d,e ) with palm broader than long or about as broad as long in large specimens (SL ca 6.0 mm); fingers curved ventromesially, dactyl with strongly concave and smooth ventromesial face; dorsal face of palm with scattered small spines or tubercles, ventral face smooth or with small tubercles; palm with dorsolateral and dorsomesial margins each well delimited by row of spines, ventromesial margin rounded, occasionally with row of 2 or 3 blunt spines proximally; carpus with numerous small spines or tubercles on dorsal surface, and well delimited dorsolateral margin with row of spines. Left cheliped ( Fig. 25c ) usually weakly calcified on lateral face of carpus; carpus with dorsal row of 4 to 6 small, well-spaced spines, and strong dorsodistal spine. Ambulatory legs ( Fig. 25f,g ) with dacty1s having ventromesial row of 7 (3rd pereopod) to 15 (2nd pereopod) small, often minute corneous spines, and dorsal and dorsomesial rows of long setae; carpi each with dorsodistal spine; carpus of 2nd pereopod with dorsal row of 7 small spines. Anterior lobe of sternite of 3rd pereopods setose, armed with 1 spine. Fourth pereopod ( Fig. 25h ) with propodal rasp consisting of 1 row of ovate scales. Vropods and te1son ( Figs 25j , 26 ) markedly asymmetrical; telson lacking transverse suture separating anterior and posterior lobes; posterior lobes separated by shallow V-shaped median cleft, terminal margins armed with often long, curved corneous spines; in large females (SL> 6.0 mm) posterior lobes armed with several rows of corneous spines on distal margin, rows of spines often extending to dorsodistal surface ( Fig. 26a ). Males lacking 1st gonopods, with unpaired, uniramous 2nd left pleopod ( Fig. 25i ). Females with vestigial right 2nd pleopod.

Habitat and symbiotic associations. Found in gastropod shells.

Distribution. Western pacific: Philippines, China Sea, Indonesia, Japan, and now Australia. Depth: 161 to 558 m.

Affinities. Paragiopagurus acutus is most similar to P bicarinatus and P hirsutus . The former can be separated from P bicarinatus by the shape and armature of the mesial face of the right palm. The mesial face of P acutus is not expanded distally, and the ventromesial margin is rounded; the mesial face of P bicarinatus is expanded distally, and the ventromesial margin is well delimited by a row of spines. Paragiopagurus acutus differs from P hirsutus by the armature and setation of the right chela (see Affinities under P hirsutus ). Additionally, P acutus reaches a much larger size than P bicarinatus or P hirsutus , and exhibits a stronger degree of sexual dimorphism in the te1son ( Fig. 26 ).

Remarks. De Saint Laurent (1972) provisionally proposed three subspecies, Parapagurus acutus acutus , P a. bicarinatus , and P a. hirsutus , for specimens that apparently could be differentiated only by the characteristics of the right cheliped. De Saint Laurent did observe that when all specimens of her subspecies were considered, a great range of variability occurred in the relative length of the ocular peduncles, ocular acicles, and the right cheliped. She proposed a subspecific division for the specimens rather than a specific one because of the impossibility she encountered in assigning specimens that were missing the right cheliped. Subsequently, Lemaitre (1989) transferred the subspecies of P acutus to Sympagurus (sensu Lemaitre, 1989).

The study of numerous specimens deposited in various museums previously assigned to De Saint Laurent's (1972) three subspecies, and comparisons with recently collected Australian specimens, clearly show that they are sufficiently distinct morphologically to warrant elevation to specific status. Furthermore, their relatively broad sympatric distributions provides additional support for considering them as full species. The three species are quite similar in a number of characters such as the shape of the ocular acicles, left cheliped, telson, and absence of 1st pair of gonopods in males. However, as previously mentioned, they clearly differ by the shape and armature of the right cheliped.

Figures

Fig. 25. Paragiopagurus acutus (De Saint Laurent, 1972), holotype male (SL 5.6 mm), Philippines, USNM 168309: a, shield and cephalic appendages; b, right antennal peduncle, lateral; c, left cheliped, dorsolateral; d, right cheliped; e, chela of same, mesial; f, right 2nd pereopod, lateral; g, dactyl of same, mesial; h, propodus and dactyl of left 4th pereopod, lateral; i, left 2nd pleopod, lateral; j, telson. Scales = 2 mm (a,c-g), and 1 mm (b,h,j).

Fig. 26. Te1sons of Paragiopagurus acutus (De Saint Laurent, 1972). Paratypes, Indonesia, ZMK: a, female (SL 6.8 mm); b, male (SL 8.0 mm). Scale = 1 mm.