Petalomera granulata Stimpson, 1858

McLay, Colin L. & Ng, Peter K. L., 2007, Revision Of The Indo-West Pacific Sponge Crabs Of The Genus Petalomera Stimpson, 1858 (Decapoda: Brachyura: Dromiidae), Raffles Bulletin of Zoology 55 (1), pp. 107-120 : 109-112

Petalomera granulata Stimpson, 1858

( Figs. 1–3 )

Petalomera granulata Stimpson, 1858: 240 ; 1907: 179, Pl. 21, Fig. 4 ; Alcock, 1901: 55 (list); Ihle, 1913: 48, 91 (key & list); Gordon, 1931a: 526 (list); Sakai, 1935: 33, Pl. 1, Fig. 2; 1936: 37, Pl. 2,

Not Petalomera granulata Shen, 1932: 3 , Pl. 1, Figs. 9 , 10, text Figs. 1–3 [= Paradromia japonica ( Henderson, 1888) ].

Material examined. – Japan: MORTENSEN EXPEDITION, Misaki , near Osaka, ~ 34º30'N 135º10'E, 46 m, 9 Jun.1914: 1 female 19.7 x 20.6 mm (coll. T. Mortensen) ( ZMC) ; Sagami Bay , ~ 35º30'N 139º20'E, 40–50 m: 1 female 29.2 x 29.7 mm (coll. T. Sakai) (Neotype) ; Tosa Bay , 33º10'N 133º30'E,? 250 m, Apr.1968: 1 male 26.0 x 26.4 mm (coll. K. Sakai) ( SMF) ; Osezaki, Suruga Bay, Izu Peninsula , 10 m, 3 Jun.1994: 1 male 36.1 x 36.8 mm (NSMT-Cr 11639) . Taiwan: near Keelung, ~25ºN 122ºE, Oct.1999: 1 male 36.2 x 37.2 mm, 1 female 26.0 x 26.4 mm ( ASIZ72378 ) ; South Taiwan, Singkang Port , ~24ºN 121º30'E, 8 Aug.1985: 1 female 20.7 x 20.6 mm ( ZRC 1993.7195 ) . China: Spratly Islands , 8º38'N 111º55'E, 60 m, 30 Apr.1993: 1 female 25.7 x 25.9 mm ( ZRC 1999.001 ) ; Nansha Islands , ~11ºN 116ºE, 28 Sep.1994: 1 male 7.9 x 8.4 mm (coll. H. Chen) .

Type specimens. – Stimpson (1858) gave the size of the type male as 8.4 x 9.1 mm and noted that it was obtained from “ Kagoshima (~34ºN 131ºE), “fundo conchose, prof. 20 org - 37 m ” in Japan. This specimen was housed in the Chicago Academy of Sciences, but was almost certainly destroyed by a fire in 1871 ( Stimpson, 1907; Evan, 1967; Deiss & Manning, 1981). Since the type is not extant we designate the following specimen as the neotype of P. granulata : a female, 29.2 x 29.7 mm, Sagami Bay, 40–50 m, SMF. This we believe is necessary to stabilise the taxonomy of the genus as most of the members are superficially similar to each other and P. granulata is the type species of the genus.

Description. – Carapace as long as or longer than wide, strongly convex, covered in large, blunt granules, especially on anterior half of carapace. A coating of short setae, with scattered longer examples, covers spaces between granules; such setae also present on all pereopods. Frontal groove well marked, cervical groove distinct, branchial groove only faintly marked. Crescent shaped branchiocardiac grooves, with a central pit, well marked, joined by a shallow groove across mid-line. Rostrum tridentate, median tooth deflexed, set on a lower level, lateral teeth, separated by a V-shaped sinus, horizontal, directed anteriorly. Median tooth shorter than lateral teeth in dorsal view. All teeth serrated.

Supraorbital margin concave from lateral rostral tooth, edge armed with 4 or 5 sharp granules increasing in size towards well developed supraorbital tooth, this tooth projects strongly from orbital margin, directed anterolaterally; after supraorbital tooth, orbital margin continues as a concave line to the postorbital corner, bearing 7 or 8 sharp granules, with a short orbital fissure. Postorbital corner not produced; straight line connecting tip of lateral rostral tooth and postorbital corner, running along anterior carapace margin. Suborbital margin armed with several sharp granules and a suborbital tooth that is visible dorsally. Hepatic area, between postorbital corner and beginning of anterolateral margin, evenly covered with large granules. Below level of postorbital corner, granules form a tubercle that is visible dorsally. Anterolateral margin granulate, begins at level of postorbital corner, with a granulated swelling, with another similar swelling after cervical groove. No posterolateral tooth present. Posterior carapace margin slightly concave with a row of granules along edge.

Suborbital area convex densely granulated. Epistome triangular, concave, interantennular septum thick, margins bearing 2 or 3 blunt granules. Posterior margin of epistome bears a row of granules; corner of buccal frame with exhalant channels formed by epistome corner and carapace margin; channels lie immediately below base of antennae; adjacent to this opening is a distinct granulated buccal tooth. Epimeral suture distinct. Inhalant channels at base of chelipeds densely setose. Rest of branchiostegal margin fits tightly around bases of pereopods.

First article of antennule longer than wide, sub-rectangular, second article inserted at disto-medial corner, folded laterally across distal end; this article fits tightly against rostral extension that joins interantennular septum. Third article longer than wide, folds posteriorly and along with flagellum, is concealed beneath supraorbital edge. First article of antenna (urinal article) wider than long, beak-shaped medially, not gaping. Second article much longer than wide, distal border bears several small granules and a well developed bilobed exopod. Disto-medial corner produced as a curved, blunt lobe on which third article is inserted at an angle. Fourth article, like third article, as long as wide. All antennal articles freely moveable.

Third maxillipeds operculiform with scattered large blunt granules on outer surface, palp exposed, crista dentata with 10 well developed blunt teeth and 7 or 8 calcareous teeth on outer margin of basis.

Chelipeds well developed, larger in males. Merus trigonal in cross-section, lower margin granulated, inner surface nacreous, expanded as petals, fitting closely against subhepatic areas of carapace. Outer surface of carpus convex, granulated, with 2 strong distal granules and inner margin of upper border with 4 or 5 granules. Outer face of propodus covered in large granules that tend to be arranged in longitudinal rows. Inner margin of upper border crest-like, granulated. Fingers short, down-curved, hollowed out internally, so that cutting teeth are on outer border. Edges of fingers armed with 6 or 7 weakly developed teeth, all of which are touching when fingers are closed.

First 2 pairs of legs shorter than chelipeds, merus of first pair petaloid, merus of second pair, smooth, flattened, but not petaloid. Carpi tend to be flattened, fitting closely against preceding limbs, propodi sub-cylindrical. Outer surfaces of carpi and propodi sparsely granulated. Dactyli as long as propodi, tips curved, inner margins armed with 6 or 7 short spines, all of similar size.

Last 2 pairs of legs reduced, third pair smallest, only last pair truly subdorsal in position. Dactylus of third pair opposed by a single propodal spine about half length of dactylus. Dactylus of fourth pair also opposed by a similar single propodal spine, with another much shorter spine on outer propodal margin at base of dactylus. Ratio of length along dorsal margin (not including spine) to width of propodus for third and fourth legs 1.3 and 1.6, respectively.

Abdomen of 6 free segments, fourth or fifth segments widest in female, surface sparsely covered with granules. Last segment has many fewer granules than others. Uropod plates well developed, visible externally. Female telson much wider than long tip broadly rounded. All segments of male abdomen about same width, sparsely granulated, uropod plates large, visible externally, used to lock abdomen by fitting in front of prominent granulated flanges on coxae of first walking legs; such flanges present but not effective in mature females. Male telson wider than long, tip truncate.

Both male gonopods in situ reach just beyond sternal suture 4/5. First gonopod composed of 2 articles: first article concave ventrally, receiving long extension of vas deferens, second article concave medially, gradually forming a short tube ending in a chitinous tip. Margins of both articles and tip of second article densely setose. Marginal setae of second article increases effective length of tube in receiving second gonopod. Second gonopod with 3 articles: first short, cylindrical, second a shorter flattened and laterally expanded piece, and third is long terminal part that starts out wide, flattened, but quickly narrows to horny needle-like part, without microscopic structures on needle. Female spermathecal openings are at ends of sternal sutures 7/8 which lie between bases of first walking legs; openings on elevations lying close to gonopores on coxae of second walking legs; their diameter about half that of gonopores but not wide enough to receive tip of first male gonopod; only tip of second gonopod narrow enough to enter spermathecal opening.

Remarks. – This is the best known species in the genus and is often encountered in East Asia. See discussion for other species for comparisons with congeners.

Size. – Stimpson (1858) gave the size of the original male type as 8.4 x 9.1 mm. Dai & Yang (1991) had a male 35.2 x 35.6 mm. The largest P. granulata specimen recorded is a male from Suruga Bay, Japan and measured 36.1 x 36.8 mm. The largest known female is the neotype from Sagami Bay, which measures 29.2 x 29.7 mm. Females and males probably grow to about the same size. Petalomera granulata is the largest of the four known species. The only known ovigerous female (carapace width 22.3 mm) was collected by Yamaguchi et al. (1987) in July from the Amakusa Islands, Japan, but the egg size and number was not reported.

Depth. – Stimpson (1858) gave the depth of the type locality of P. granulata , in Kagoshima Bay, as 37m. The depth range given by Sakai (1965) for Sagami Bay is 30- 85 m. All other records fall within this range except for one specimen collected by K. Sakai from Tosa Bay that apparently came from 250 m. This outlier needs to be confirmed by further collections.

Camouflage. – No specimens carrying pieces of camouflage have been collected.

Distribution. – Taiwan, Hong Kong, North China and Japan.

Figures

Fig. 1. Petalomera granulata Stimpson, 1858, male 36.2 x 37.2 mm (ASIZ 72378): A, overall dorsal view; B, right anterolateral margin showing tubercle arrangement; C, frontal view.

Fig. 4. Petalomera indica Alcock, 1900:A, overall view; B, posterior view of left first walking leg. (After Alcock, 1900: Fig 14, 14a).

Fig. 9. Petalomera pulchra Miers, 1884: A, dorsal view of right anterolateral area; B, outer view of left chela; C, propodus and dactylus of right P4; D, propodus and dactylus of right P5. A, C, D, lectotype female 17.8 x 17.7 mm (NHM 1882.7); B, male 15.3 x 15.7 mm (AM P19529). Scale bars – A, B = 2.0 mm; C, D = 1.0 mm.