Cryptodromia tuberculata Stimpson, 1858

Mclay, Colin L., 2001, Dynomenidae and Dromiidae (Decapoda, Brachyura) from Guam, Philippine Islands, Tonga and Samoa, Zoosystema 23 (4), pp. 807-856 : 838-840

Cryptodromia tuberculata Stimpson, 1858

Cryptodromia tuberculata Stimpson, 1858: 239 ; 1907: 174, pl. 21, fig. 6. — De Man, 1888a: 401. — Ives 1891: 217 (list). — Cowles 1913: 119. — Ihle 1913: 35. — Balss 1935: 115. — Sakai 1936: 17, text fig. 3, pl. 6, fig. 3; 1976: 13, text fig. 3a, b. — Buitendijk 1939: 225. — McLay 1993: 199 (key).

Cryptodromia tuberculata var. typica – Ihle 1913: 35.

Dromia (Cryptodromia) tuberculata – Estampador 1937: 510.

MATERIAL EXAMINED. — Philippines. Saftan Island, Albatross, tide pools, 8.XI.1908, 1 9.5 × 8.0 mm (sponge cap) ( USNM 128564). — Sitandi Island, no depth, 26.II.1908, 1 5.3 × 4.5 mm (solitary ascidi- an cap) ( USNM 128566). — Maricaban Island, 13°39.00’N, 120°50.00’E, shoreline, 20.I.1908, 1 7.9 × 6.8 mm, 1 6.5 × 6.4 mm, 2 (ovig.) 6.7 × 6.6, 7.0 × 6.7 mm (sponge caps) ( USNM 128565). — Sector G, exact locality not given, MUSORSTOM 2, 128- 143 m, 20.XI.1980, 1 9.2 × 9.0 mm. — Mactan Marine Station, Olango Reef, 11.XII.1980, 1 4.7 × 4.0 mm, 1 (ovig.) 4.4 × 3.9 mm (sponge cap) ( MNHN-B 12732).

SIZE. — The type specimen measured 13.0 × 11.0 mm and is the largest known male. The largest known female, 9.2 × 9.0 mm, is reported herein from the Philippines. The two larger ovigerous females reported above carried 25- 30 eggs, diameter 0.8 mm. The smallest ovigerous female, 4.4 × 3.9 mm carried only 10 eggs, diameter 1.0 mm. C. tuberculata seems to produce small numbers of larger eggs and may well have abbreviated development as found in C. pileifera (see Tan et al. 1986).

DEPTH AND HABITAT. — Most specimens have been collected from intertidal rocky shores and reefs. Commonly found under stones and among boulders in the middle of the littoral zone. The deepest record is 20 m ( Ihle 1913). They always carry pieces of sponge or compound ascidians. Cowles (1913) described how C. tuberculata obtains its sponge camouflage. The chelipeds are used to cut out the cover, that is left partially attached to the sponge, and the crab lifts up the edge and pushes itself backwards under the cover grasping it with the p4 and p5. The crab then carries off its new piece of camouflage.

DISTRIBUTION. — Type locality Kikai-shima, Amami Group, Japan, South China Sea, Philippine Islands, Indonesia and Singapore. Balss (1935) reported Cryptodromia tuberculata from Cossack, near Port Hedland, western Australia. C. tuberculata was first reported from Mindoro and Luzon, Philippines by Estampador (1937).

DESCRIPTION

Carapace wider than long, moderately convex, smooth, covered with a fine tomentum. Branchial grooves faint but branchio-cardiac grooves distinct. Rostrum tridentate, teeth short, blunt, median tooth slightly longer than lateral teeth. Supraorbital eave with blunt tooth, postorbital corner slightly produced. Orbital fissure narrow, infraorbital margin bears strong blunt tooth visible dorsally. Sub-hepatic area with an arched row of tubercles extending from orbital corner to first anterolateral tooth. These tubercles decrease in size posteriorly: first two prominent, nearly as large as anterolateral teeth, and visible dorsally between postorbital corner and first anterolateral tooth. Two or three teeth in transverse row near corner of buccal frame. These tubercles are variable. Anterolateral margin convex, armed with three blunt, sub-equal teeth: first two teeth strong, third smaller and elongated. First anterolateral tooth widely separated from postorbital corner. Posterolateral tooth blunt, following margin convergent, posterior carapace margin straight.

Chelipeds strongly tuberculated. Tubercles conical blunt. Outer carpal surface has about three large and ten small tubercles, distal tubercles more prominent. Propodus has 20 to 25 tubercles of variable size, mostly on outer surface. Tubercles on superior propodal border larger, inner surface densely pubescent. Fingers compressed, gaping, tips naked and white. Cutting edges armed with six or seven variable teeth, distal three interlocking.

P2 and p3 shorter than chelipeds, strongly nodular or verrucose. Carpi have longitudinal ridges on superior margins and four or five strong tubercles. Inner margins of dactyli armed with four small spines increasing in size distally.

P4 and p5 reduced, p4 shortest, dactyli opposed by single, short propodal spines with another spine on outer propodal margin of the p5.

Third, fourth and fifth abdominal segments each have four tubercles along posterior margin, two in middle and one at each corner. These tubercles are variable in development between individuals. Telson much wider than long, posterior margin sub-truncate, concave. Uropods well-developed, visible externally, used in abdominal locking mechanism by fitting in front of ridge on coxae of p2. Female sternal sutures 7/8 end wide apart on low rounded tubercles between bases of p2.

DISCUSSION

Stimpson (1858) briefly described Cryptodromia tuberculata based on specimens collected from Japan. The type specimen is not extant. The species was first illustrated by Stimpson (1907: pl. 21, fig. 6) and subsequently by Sakai (1936: pl. 56, fig. 3). Species of Cryptodromia are often distinguished by small differences in the rostrum, anterolateral margin and the abdomen and so these illustrations have largely defined exactly what C. tuberculata looks like. The introduction of two varietal names, by Alcock (1899) and Ihle (1913), complicated the taxonomy of C. tuberculata .

Alcock (1899) referred his 70 specimens from the Andaman Islands to Dromia (Cryptodromia) tuberculata var. pileifera . Although the type specimen of this new variety apparently still exists, in the Indian Museum, its unavailability means that Alcock’s (1901: pl. 2, fig. 7) illustration has assumed special significance.

Ihle (1913) separated his specimens from Indonesia into C. tuberculata var. pileifera and C. tuberculata var. typica and listed the major differences: in the typica variety there are five subhepatic tubercles, arranged in a row, with two being larger, while the pileifera variety has only two large tubercles; typica has three tubercles above the pleural suture but only one tubercle in pileifera . Because he found some specimens with an intermediate numbers of sub-hepatic tubercles, Ihle stated that he considered these two forms to be varieties and not species. Specimens with three larger tubercles were assigned to the typica variety while those with only two tubercles were assigned to pileifera . Buitendijk (1939) also identified both varieties, from the same localities, among the Snellius Expedition material from Indonesia and noted several specimens which had some features of both varieties. Similarly in a collection from Singapore, Buitendijk (1950) noted some C. pileifera specimens which had some features of C. tuberculata . Clearly there is a lot of variation in C. pileifera . Thus the question arises of whether these two varieties of C. tuberculata should be treated as synonyms or as separate species?

Comparison of Sakai’s (1936: pl. 56, fig. 3) illustration of C. tuberculata with Alcock’s (1901: pl. 2, fig. 7) illustration of C. pileifera shows additional differences between these two species: lateral rostral teeth very short and blunt in C. tuberculata (blunt but larger in C. pileifera ); median tooth longer than lateral teeth (median tooth shorter); three sub-hepatic teeth visible dorsally (two teeth, one visible dorsally); branchial groove not evident (groove wellmarked); chelipeds very tuberculate (not so tuberculate); distal margins of articles of p2 and p3 very tuberculate (not tuberculate). I think that all of these differences indicate that C. tuberculata and C. pileifera should be treated as valid species.