Cryptodromia tumida Stimpson, 1858

Mclay, Colin L., 2001, Dynomenidae and Dromiidae (Decapoda, Brachyura) from Guam, Philippine Islands, Tonga and Samoa, Zoosystema 23 (4), pp. 807-856 : 840-842

Cryptodromia tumida Stimpson, 1858

Cryptodromia tumida Stimpson, 1858: 240 ; 1907: 175. — Ives 1891: 218 (list). — Ortmann 1892: 544. — Bouvier 1899: 176 (list). — De Man 1902: 688. — Ihle 1913: 37, text figs 10-17. — Parisi 1915: 104. — Balss 1922: 107 (list). — Buitendijk 1939: 226. — Ward 1941: 1.— Sakai 1965: 8, pl. 3, fig. 3. — Takeda 1973: 79. — Yamaguchi et al. 1987: 6. — McLay 1993: 199 (key). — [Non Montgomery 1931: 413, pl. 29, figs 4, 4a. (= an undescribed species)].

Cryptodromia tumida typica Sakai, 1936: 18 , pl. 7, fig. 1, text fig. 4a-b; 1976: 14, text fig. 4a-c.

Cryptodromia fallax – Ng et al. 2000: 159, fig. 1d [non C. fallax ( Lamarck, 1818) ].

MATERIAL EXAMINED. — Guam. 13°27’N, 144°47’E, Pago Bay, outer reef flat, intertidal at very low tide, 24. V.1986, coll. R. K. Kropp, 1 4.4 × 4.3 mm, 1 9.0 × 8.1 mm (sponge caps) ( GUM 217C) ( ZRC 2000.2113). — Piti Reef, among rocks, 1 m, 30.VII.1993, coll. H. T. Conley, 1 6.8 × 6.1 mm (sponge cap) ( GUM 302) ( ZRC 2000.2114).

Philippine Islands. Sulu Archipelago, Albatross, stn D5139, 5°6.00’N, 121°2.30’E, 6 m, 14.II.1908, 1 4.2 × 3.9 mm (sponge cap) ( USNM 128573). — Stn D5145, 6°4.30’N, 120°59.50’E, 7 m, 15.II.1908, 1 4.4 × 4.0 mm (compound ascidian cap) ( USHM 128572). — Cataingan Bay, shoreline, 19.IV.1908, 1 4.3 × 4.0 m (compound ascidian cap), 1 (ovig.) 7.5 × 6.5 mm (sponge cap) ( USNM).

Taiwan. Kaohsiung County, Yungan, no date, 1 8.0 × 6.8 mm ( TMCD 2810) (originally identified as C. fallax [ Lamarck, 1818] by Ng et al. 2000).

Samoa. Tutuila Island, Pago Pago, 14°16.00’S, 170°43.00’W, no depth, no date, 1 (ovig.) 6.5 × 6.0 mm (sponge cap) ( USNM).

SIZE. — Largest known male 10.3 × 9.0 mm ( Sakai 1936) and largest female 14.0 × 13.0 mm ( Parisi 1915). Smallest ovigerous female, 6.5 × 6.0 mm carried only 17 large eggs diameter 1.0 mm. Another female, 7.5 × 6.5 mm, carried 30 eggs. Evidently, Cryptodromia tumida has a reproductive strategy that involves the production of few large eggs with abbreviated development. Buitendijk (1939) recorded ovigerous females in October, November, March and June from Indonesia.

DEPTH AND HABITAT. — All the specimens reported here came either from intertidal or shallow sites. The maximum depth recorded by Sakai (1965) was 10 m. Sakai (1936) gives the habitat as being rocky or stony shorelines. Crabs are normally covered with a mass of sponge or compound ascidians.

DISTRIBUTION. — The type locality of Cryptodromia tumida is Foukow Bay, Amami Ohshima, Japan. Subsequently this species has been recorded from several other Japanese localities. It was first recorded from the Philippines by Ward (1941). C. tumida is also known from Indonesia and now Guam. Montgomery (1931: 413, pl. 29, figs 4, 4a) recorded C. tumida from the Abrolhos Islands, western Australia, but his illustrations suggest that these specimens are not the same as the type specimen and represent an undescribed species. The occurrence of C. tumida in Australian waters remains to be established. C. tumida was not previously known from Taiwan and its inclusion brings the total number of dromiid species to 10. It is the only representative of the genus Cryptodromia recorded from Taiwan and it can be anticipated that other species in this genus will be found (see Ng et al. 2000). Most of the dromiid species known from Taiwan are large crabs, more easily caught by fishermen, and found among the debris landed at fish ports. Shallow water collections should produce several new Cryptodromia records. C. tumida is also added to the fauna of Samoa. Previously, only C. coronata was known from Samoa.

DESCRIPTION

Carapace wider than long, convex, covered by a short tomentum, smooth, rising abruptly behind front, tumid on gastric and hepatic regions. Front broadly rounded, rostrum tridentate, median tooth short, obtuse, deflexed, lateral teeth blunt, more prominent. Supraorbital margin continues back from lateral rostral tooth, interrupted by a stout supraorbital tooth, ending with small postorbital tooth. Orbital fissure present. Infraorbital tooth stout, obscured from above by supraorbital tooth. One strong sub-hepatic tubercle visible dorsally between postorbital corner and first anterolateral tooth, and one smaller tubercle on ridge above pleural suture. Anterolateral margin with three sub-equal, equidistant, small blunt teeth. First anterolateral tooth largest, second tooth may be obsolete. Posterolateral tooth behind distinct branchial groove. Posterolateral margins convergent, posterior margin slightly concave. Sternal sutures 7/8 end apart on small tubercles between bases of p2. Crista dentata 11 or 12 small teeth.

Chelipeds small, sparsely tuberculate. Carpus with two small central and two strong distal tubercles. Outer surface of propodus smooth, or with longitudinal lines of fine granules. Upper surface of propodus has two elongate proximal ridges and a tubercle at base of dactyl. Male fingers gaping touching only at tips. Dactyl has seven or eight small teeth, but fixed finger only has three or four distal teeth. Female fingers compressed, not gaping. Inner propodal surface densely setose.

P2 and p3 slightly shorter than chelipeds, meri robust, carpi with three distal tubercles, propodi armed with terminal tubercle on anterior border. Dactyli of both legs with five or six small spines on inner margin.

P4 and p5 reduced, p4 shortest, p5 sub-dorsal. Dactyli of both legs strongly curved and opposed by long straight propodal spines with another shorter spine on outer propodal margin.

Prominent rounded tubercles at posterolateral corners of third and fourth abdominal segments and a pair of median tubercles on fourth segment. Four less distinct tubercles may also be present on fifth segment. Tubercles maybe obsolete in some specimens and less distinct in females. Uropods well-developed and visible externally. Abdominal locking mechanism consists of uropods fitting in front of rounded flanges on coxa of p2. Male telson wider than long, trapeziform, posterior margin truncate or concave. Female telson wider than long, posterior margin bluntly rounded.

DISCUSSION

Several features of Cryptodromia tumida are variable. Stimpson (1907) stated that in the female type, which is not extant, the anterolateral teeth were small and equal in size, but De Man (1902) noted that the first anterolateral tooth is usually longest and the third tooth shortest. Ihle (1913) stated that the position of the three anterolateral teeth is variable: the teeth may be evenly spaced, or the distance between the first and second may be slightly larger than between the second and third. However, in De Man’s female the distance between the first and second teeth was twice the distance between the second and third. In the type the abdominal tubercles were obsolete. However these tubercles may vary between the sexes. Ihle noted that sometimes there are a pair of less distinct tubercles on the posterior corners of the third as well as on the fourth and fifth abdominal segments. Ihle accepted these variations as being intra-specific, not warranting the designation of additional species or varieties.

However, Sakai (1936) dealt with this variation by recognizing three sub-species: Cryptodromia tumida typica , C. tumida bispinosa , and C. tumida trispinosa . These sub-species were defined largely on the basis of the shape of the telson. In the trispinosa sub-species (male type 11.5 × 10.4 mm) the posterior margin of the telson has three unequal spines, and in the bispinosa sub-species (male type 11.0 × 9.4 mm) it has two closely spaced, long, acute spines. Sakai assumed that, in the typica sub-species (male 10.3 × 9.0 mm and female 11.9 × 9.5 mm), the telson has two blunt posterior projections, separated by a concave margin. The original description of C. tumida by Stimpson (1858) did not include any mention of the shape of the telson and, since the type is not available, it is impossible to establish the relationship of Sakai’s sub-species to the original form.

Ihle (1913) stated that the posterior margin of the telson in the Siboga specimens was bluntly round- ed in females but truncate in males. However, after examining the some of the same specimens, Buitendijk (1939) declared that some of the males from Siboga , station 225, had three spines or lobes on the telson margin, thus indicating that they should belong to the trispinosa sub-species.

Besides the telson, Sakai notes differences in the anterolateral teeth, abdominal tubercles and sternal sutures 7/8 of his sub-species. In C. tumida trispinosa the second anterolateral tooth is not more prominent than the others, the fourth and fifth (sic “fourth to seventh”, but his text fig. 5 shows tubercles on segments four and five) abdominal segments of the male have a very low tubercle on each side. In C. tumida bispinosa the first anterolateral tooth is nearly as large as the sub-hepatic tubercle, the second tooth is small and indistinct, third is not prominent, abdominal tubercles very low and indistinct, sternal sutures 7/8 very broad but without a terminal process. According to Sakai, C. tumida typica has three sub-equal anterolateral teeth (presumably the second tooth can be smaller, although his illustration, pl. 7, fig. 1, shows three similar teeth), abdominal segments four and five have tubercles at the posterolateral corners, and sternal sutures 7/8 end with a terminal process. Clearly, there is some doubt about which of these sub-species may represent the original form, but I have included all three in the above key. The status of these subspecies needs further investigation. Evidently, all three occur in Japanese waters, but apart from the typical form, C. tumida trispinosa is the only one recorded elsewhere, in Indonesian waters.

Genus Cryptodromiopsis Borradaile, 1903 DIAGNOSIS. — Carapace as wide or wider than long, surface smooth, short dense tomentum with longer setae on the fringes, frontal groove separating two low rounded protuberances, branchial and cardiac grooves marked. Rostrum tridentate, supraorbital tooth usually present, postorbital tooth blunt or obtuse, a fissure may or may not be present separating the suborbital margin on which there are usually two unequal teeth. Anterolateral margin begins at orbital level, teeth may or may not be present. Subhepatic region usually smooth, without teeth. Coxae of third maxillipeds closely approximated (or separated by a narrow gap) and inserted in front of tip of sternum, separated from it by a trough. Female sternal sutures 7/8 end together or apart between chelipeds, first or second legs, with or without tubercles. No epipod on cheliped, borders of merus may be dentate, no spine on inner superior margin of carpus, up to four tubercles on superior margin of propodus. Distal margins of carpi and propodi of first two pairs of legs lobe-like, two to five spines on inner margins of dactyli. Third leg shorter than fourth, dactyl opposed by one or two propodal spines with one or two spines on the outer propodal margin. Fourth leg shorter than second, dactyl opposed by one or two propodal spines, one to three spines on the outer propodal margin and usually one spine on the outer margin of the dactyl itself. Abdomen of six free segments. Telson rounded or bluntly tipped. Uropod plates well-developed. Abdominal locking mechanism involves a serrated ridge or tooth on the base of the first leg and uropod plates may or may not be involved. First male gonopod stout, two segmented, usually tipped by a sharp tubercle, densely setose. Second gonopod simple, needle-like, tapering, or shorter and tapering only at tip (modified after McLay 1993).