Petalomera pulchra Miers, 1884

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 : 116-118

Petalomera pulchra Miers, 1884

( Figs. 8 , 9 )

Petalomera pulchra Miers, 1884: 260 , Pl. 27, Fig. A; Ihle, 1913: 48.

Not Petalomera pulchra McLay, 1993: 166 , Fig. 17a–b [= Petalomera longipes Ihle, 1913 ].

Material examined. – Australia: Torres Strait, Prince of Wales Channel , Queensland, ~9ºS 142ºE, 13–17 m: 2 females 17.8 x 17.7,

Remarks. – The name Petalomera longipes has been ignored and not used since it was established by Ihle (1913). However, it is now clear, after a re-examination of the type specimen and other material collected by the Mortensen Expedition that this taxon is valid.

Size. – McLay (1993) gave the size range of P. longipes (as P. pulchra ) as 5.2–20.8 mm for males and 5.5–22.5 mm for females The male specimen from the Philippines, 22.3 x 22.6 mm, increases the maximum size for males and makes the maximum size similar for both sexes.

The present material includes two ovigerous females from the Kei Islands and the Java Sea , near Jakarta: one female (12.9 x 14.4 mm) carried ~ 550 eggs ( ED = 0.6 mm) while and another female (10.1 x 10.4 mm) had ~ 170 eggs ( ED = 0.5 mm). McLay (1993) reported brood sizes for females CW 6.7–19.9 mm ranging from 120–1278 eggs, with a mean egg diameter of ~ 0.7 mm. The new material collected by Mortensen does not alter these values .

Depth. – McLay (1993) gave the range of specimens from New Caledonia and the Chesterfield Islands as 7–86 m. The depth of the present material does not extend the known depth range .

Camouflage. – A female (CW = 8.5 mm) from New Caledonia (CORAIL 2) (see McLay, 1993, as P. pulchra )

15.1 x 15.5 mm (larger female lectotype, here designated, NHM 1882.7 ); North end Albany Passage, North Queensland , Aug.– Sep.1928: 1 female 14.6 x 15.2 mm ( AM-P19486 ) (coll. M. Ward); Black Is., North Langford Reef , Whitsunday Group, Queensland, ~ 20º30'S 149º30'E, Nov.1969: 1 male 15.3 x 15.7 mm, 1 female (ovigerous) 11.8 x 12.0 mm ( AM-P19529 ); NE Montebello Islands , Western Australia, 20º08'S 115º57'E, 80 m, 2 Dec. 1979: 1 male 13.5 x 15.1 mm ( WAM 109-83 , “ Soela ”); ENE Montebello Islands, 20º18'S 116º01'E, 60–64 m, 2 Dec.1979: 1 female 23.1 x 23.3 mm ( WAM 126-83 , “ Soela ”); 53 km NE of Montebello, 80 m, 19º55'S 116º36'E, 58 m, no date: 1 male 11.6 x 12.2 mm ( WAM 62-83 ); NW Shelf, 19º 04.4'S 118º07.3'E, 80 m, 28 Apr.1983: 7 males 3.9 x 4.0, 4.3 x 4.4, 5.3 x 5.5, 6.7 x 6.9, 6.7 x 7.0, 6.8 x 7.0, 7.3 x 7.5 mm, 1 female 4.3 x 4.4 mm, 2 females (ovigerous) 6.7 x 6.9 mm, 7.0 x 7.6 mm ( NTM AS 0283-133, “Soela”) .

Type specimens. – There are two female syntypes, measuring 17.8 x 17.7 mm and 15.1 x 15.5 mm (NHM 1882.7). We here designate the larger female as the lectotype and our description is based primarily on this specimen. Male characters were obtained from a male 15.3 x 15.7 mm (AM-P19529). In the container of Mier’s types are two small vials, one containing gills and the other containing mouthparts and some gills. There is only one abdomen present and it consists of the first four segments only. This seems to belong to the larger lectotype female, 17.8 x 17.7 mm. The mouthparts and gills should thus belong to the other, smaller, female, 15.1 x 15.5 mm, as it has the carapace detached from the body.

Description. – Carapace about as long as wide, slightly convex, sparsely covered with blunt granules except on the hepatic and anterior branchial areas where granules are denser. Short setae cover the carapace surface with a few scattered longer setae which also fringe pereopods. Frontal and cervical grooves evident, branchial groove faintly marked. Crescent shaped branchiocardiac grooves evident, with a central pit, joined by a shallow groove across mid-line. Rostrum tridentate, median tooth deflexed, set on a lower level, much shorter than lateral teeth in dorsal view. Lateral teeth separated by a wide V-shaped sinus, horizontal, directed anteriorly. All teeth minutely serrated.

Supraorbital margin, eave-like, concave behind lateral rostral tooth, edge minutely granulated until slight convex projection halfway, thereafter margin without granules, ending at a well marked orbital fissure beneath post orbital corner. Entire orbital margin stands out from frontal margin so that postorbital corner projects prominently. A straight line connecting tip of lateral rostral tooth and edge of postorbital corner, and then extending laterally, is well in advance of first anterolateral tooth. Suborbital margin convex, unarmed, not visible dorsally. Hepatic area, between postorbital corner and beginning of anterolateral margin, with a few large granules, below level of suborbital margin with a well developed granulated, hepatic tubercle that is visible dorsally. Anterolateral margin begins at level of postorbital corner, armed with 2 granulated teeth: first is directed almost anteriorly and second, behind cervical groove, is directed more laterally; carapace margin granulated behind both these teeth. Posterolateral tooth absent. Posterior carapace margin slightly convex, not granulated.

Suborbital area convex, granulated. Epistome triangular, flat, interantennular septum stout, margins granulated, interrupted by a notch midway along each lateral margin, beside first article of antennule. At corner of buccal frame are exhalant channels formed by the epistome corner and carapace margin; channels lie immediately below base of antennae; adjacent to channel 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 and 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 the 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 well developed bilobed exopod. Distomedial corner produced as a curved, blunt lobe on which third article is inserted at an angle. Fourth article, like the third, as long as wide. All antennal articles freely moveable.

Third maxillipeds operculiform, scattered coarse granules, palp exposed, margins of basis unable to meet medially, crista dentata with 10 well developed blunt teeth with 6 or 7 calcareous teeth on outer margin of basis.

Chelipeds well developed. Merus trigonal lower margin granulated, inner surface petaloid, nacreous, fitting closely against subhepatic area of carapace. Outer surface of carpus convex, granulated, 2 strong distal granules and inner margin of upper border with 4 or 5 granules. Outer face of propodus with 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 teeth are on outer border. Edges of fingers armed with 7 or 8 well developed, last 4 distinct teeth interlocking when fingers are closed.

First 2 pairs of legs shorter than chelipeds, meri petaloid. Carpi tend to be flattened, fitting closely against preceding limbs, propodi sub-cylindrical. Dactyli as long as propodi, tips curved, inner margins armed with 4 or 5 short spines of similar sizes.

Last 2 pairs of legs reduced, third pair smallest, only last pair are truly subdorsal in position. Dactylus of third pair strongly hooked, opposed by a single, almost obsolete, propodal spine. Dactylus of fourth pair strongly hooked, opposed by a single small propodal spine, with another very small 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, 0.5 and 0.8, respectively.

Abdomen of 6 free segments, fourth or fifth segments widest in female, surface mostly smooth. 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 absent 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, to receive 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 the second article increases effective length of tube receiving second gonopod. Second gonopod composed of 3 articles: first short, cylindrical, second a shorter flattened and laterally expanded piece, and third a long terminal part that starts out wide and flattened but narrows to horny needle-like part without microscopic structures on surface. Female spermathecal openings are at ends of sternal sutures 7/8 which lie between bases of first walking legs; openings borne on elevations anterior to gonopores on coxae of second walking legs.

Remarks. – All of the material reported by McLay (1993) as Petalomera pulchra should now be referred to P. longipes . The type specimen reported by Ihle (1913) was an ovigerous female measuring 12.5 x 11.5 mm.

The subchelate mechanism in P. pulchra is more poorly developed than in the other three species. The dactylus in P. pulchra is set at almost a right angles to the end of the propodus and even when moved towards the spine, it cannot reach as far as to allow the tip of the dactylus to get anywhere near the propodal spine. There is no propodal extension in congeners.

Size. – Miers (1884) gave the dimensions one of the females as 18 x 19 mm, but our measurements of the largest specimen shows it to be 17.8 x 17.7 mm. The maximum size for males is 15.3 x 15.7 mm and for females 23.1 x 23.3 mm. The smallest ovigerous female known is 6.7 x 6.9 mm. Egg numbers range from 48 (female CW = 6.7 mm) to ~200 (female CW = 11.8 mm) with the egg diameter varying from 0.68–0.74 mm, suggesting that P. pulchra probably has a planktotrophic larval stage.

Depth. – Only four depths have been recorded, giving a range of ~ 15–80 m.

Camouflage. – Not known.

Distribution. – Most specimens have come from northern Australia, as far as ~20ºS on both east and west coasts. Ihle (1913) has reported the only specimen outside Australian waters, from Aru Island (5 ° 28.2'S 134 ° 53.9'W), Moluccas, Indonesia.

Figures

Fig. 8. Petalomera pulchra Miers, 1884 1913: A, B, dorsal views; C, detail ofcarapace tubercles on right anterolateral area.A, lectotype female 17.8 x 17.7 mm (NHM 1882.7); B, C, male 15.3 x 15.7 mm (AM P19529).

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.