Bermudacaris britayevi Anker, Poddoubtchenko & Marin 2006

Bermudacaris britayevi Anker, Poddoubtchenko & Marin, 2006

(Figs. 1–3)

Material examined. 1 ovigerous female, cl 3.0 mm, FLMNH UF 54550, Mariana Islands, Guam, Apra Harbor, tip of Glass Breakwater, 144.625471–13.45473, reef slope in the outer lagoon, depth 0–18 m (collection depth for the specimen about 10 m), under coral rock, leg. A. Anker, 20 June 2010 [fcn GUOK-0911].

Distribution. Western Pacific: Vietnam (Nha Trang Bay, type locality) and Mariana Islands (Guam).

Description of chelipeds. Chelipeds slightly unequal in size, clearly asymmetrical in shape, especially in proportions of chelae and armature of finger cutting edges (Figs. 1–3). Right (minor) cheliped similar to left (minor) cheliped of holotype (Anker et al. 2006: fig. 3; see also Fig. 2). Left (major) cheliped robust, carried extended with dactylus in ventrolateral position; coxa and basis unarmed; ischium with slender curved spiniform setae on proximodorsal and distodorsal margins (see below); merus stout, about 3.5 times as long as distal width, with deep transverse constriction distodorsally, with row of short stout spiniform setae along ventromesial margin; carpus cup-shaped, with row of short slender spiniform setae on mesioventral surface, in addition to isolated stiff spiniform setae and one very long stiff seta pointing ventrally; chela with palm smooth, subrectangular, compressed laterally; fingers subequal in length, somewhat gaping when closed, about 0.4 length of palm, with strongly crossing fingertips; dactylus in ventrolateral position, strongly curved distally, cutting edge with broad bulge, extending from midlength to about 0.8 of length of dactylus, proximal portion of bulge armed with medium-sized tooth; cutting edge of pollex armed with very stout, protruding tooth, fitting into broad hiatus on opposed margin of dactylus (Fig. 1).

Colouration. The Guam specimen is generally whitish semi-translucent with a pale yellow tinge, but has distinctive bright red markings, i.e. clusters of red chromatophores, in several areas of the body (Figs. 2, 3). The most conspicuous bright red patches are present on the antennular peduncles, third maxillipeds, sixth pleonite and uropodal endopod. Smaller, more diffuse reddish areas can be seen on the carapace and eyestalks. The chelipeds are generally ivory white, with a yellow tinge near the fingers. The ovaries, visible due to the partial translucence of the tegument, are bright orange, which is also the colour of the developing eggs (Fig. 2A).

Ecology. The Guam specimen was collected on a coral reef, on fine sand under a large piece of coral rubble at a depth of about 10 m. In contrast, the holotype was collected with a suction (yabby) pump on an intertidal sand-mud flat close to mangroves and was apparently associated with an unknown burrowing host (Anker et al. 2006). Thus, the ecological plasticity of B. britayevi is rather unusual, although it cannot be excluded that the Guam specimen was also associated with a burrowing animal, since horizontal or oblique burrows are often exposed and partly destroyed by flipping over large, deeply embedded coral rocks.

Remarks. Since one of the chelipeds (the right one) was lacking in the Vietnamese holotype of B. britayevi, the different armature of the left (major) cheliped fingers in the Guam specimen could be interpreted as (1) general instraspecific variability of the chelipeds, i.e., the holotype may have had the right cheliped very similar to the left one, without strong teeth on the cutting edges; or (2) the species being generally characterised by the somewhat unequal and asymmetrical chelipeds, i.e. the holotype may have had lost the right (major) cheliped with strong teeth, very similar to the left (major) one of the Guam specimen. Possibility of sexual dimorphism can be excluded since the holotype and the Guam specimen are both females.

Not taking into the account the robustness of the chela and the finger dentition, the left (major) and right (minor) chelipeds of the Guam specimen are generally very similar between them and also between them and the left (minor) cheliped of the holotype. In all other characters, including the disposition of the spiniform setae on the merus and carpus (Fig. 1A) and the presence of one conspicuous, long, ventrally pointing, slender seta on the carpus (Fig. 1A, C), the chelipeds of the Vietnamese holotype and the Guam specimen are almost identical (cf. Anker et al. 2006: fig. 3). The slender spiniform setae on the ischium of the left (major) cheliped of the Guam specimen (Fig. 1B) were drawn as two indistinct lines on the original pencil drawing and later interpreted as spiniform setae by the author based on their position in the holotype (Anker et al. 2006: fig. 3a, e); in addition, at least one of them can be seen in some photographs of the lateral view of the specimen (A. Anker, pers. obs.). However, their number, length, shape and exact position should be eventually confirmed by re-examination of the specimen.

Another previously unknown feature of B. britayevi is the low number and the relatively large size of eggs (Fig. 2A), suggesting an abbreviated larval development. At least two species in the related genus Automate De Man, 1888 are known to have large to very large eggs, in the latter case indicating a highly abbreviated or semi-direct development (A. Anker, pers. obs.). Therefore, this phenomenon may be not that uncommon among the so-called “lower” alpheids.