Elamena gordonae Monod, 1956

Almeida, Alexandre Oliveira De, Guerrazzi, Maria Cec Lia & Coelho, Petr Ȏ Nio Alves, 2007, Stomatopod and decapod crustaceans from Camamu Bay, state of Bahia, Brazil, Zootaxa 1553, pp. 1-45 : 29-30

Elamena gordonae Monod, 1956

( Fig. 7 )

Material examined (N=2). 1f, 25/IX/2004, St. 0 5 ( MZUESC #718); 1f, 29/VIII/2004, St. 0 5 ( MZUESC #719). Distribution. Western Atlantic – Brazil (Sergipe). Eastern Atlantic – from Guinea to Sierra Leone. Pacific – Northeast Australia ( Monod 1956; Lucas 1980; Coelho Filho & Coelho 2002).

Ecological notes. Known from few specimens around the world, and very little is known about its ecology. Type material was collected between 30–40 m off the West Africa coast ( Monod 1956). Australian material was collected at 10 fathoms in Queensland ( Lucas 1980). Material from Sergipe, Brazil, was obtained at a depth of 13 m, on hard bottom associated with sponges and hydrocorals ( Coelho Filho & Coelho 2002). Previous records in Bahia. None.

Remarks. The material examined by us was composed of two ovigerous females, which show some morphological variation from to each other. One of the specimens (3.4 x 2.9 mm CL x CW) (MZUESC#719) ( Fig. 7 A) has a general morphology in agreement with the diagnosis provided by Lucas (1980). The dorsal carapace surface is convex, and its shape is very similar to the holotype and paratype carapaces represented by Monod (1956). This author noted the existence of a medial longitudinal ridge in the middle of the carapace, whereas Lucas (1980) mentioned the existence of a faint gastro-cardiac groove in this region. We observed in the above specimen a very indistinct ridge in the middle of the carapace ( Fig. 7 A). A tuft with a few small curved setae is present in the gastric region, at the beginning of the medial longitudinal ridge ( Fig. 7 A). The rostrum is triangular ( Fig. 7 A), bordered by short small curved setae on its entire contour. The margins of both the carapace and the rostrum are marked by a thick carena. The postocular lobes are undeveloped, and one prominent lobe is present in the pterygostomial region. The chelipeds ( Fig. 7 D, E) and walking legs ( Figs. 7 F–J) are slen- der, with small and sparse setae, except on the ventral face of the dactyli, which has a row of setae along its entire length. The dactyli of pereiopods 2–5 are provided with two subterminal teeth ( Figs. 7 F–J). The female abdomen is conspicuous at the posterior end of the carapace in dorsal view, resembling the specimen represented by Lucas (1980) in figure 2B. As observed by the author, the abdomen is slightly broader than the carapace width (3.1: 2.9 mm). The abdominal female segments 1–4 are visible in dorsal view; segments 1 and 2 are very short compared to segments 3–5 and the telson.

The other specimen (3.3 x 2.8 mm CLxCW) (MZUESC#718) ( Figs. 7 B, C) resembles the first one except: the dorsal carapace surface is concave, with the margin of the carapace distinctly higher than the middle of the carapace; and the basis of the rostrum is shorter than that of the other analyzed female and Monod’s (1956) figures 629 and 630, and Lucas' (1980) figure 2B ( Fig. 7 B, C). The anterior region of this specimen is similar in shape to the anterior region of E. umerata Lucas, 1980 , from Australia, especially in the shape of rostrum; but the anterior lateral angles are more prominent in the Australian species. Another difference in relation to the other analyzed female was found in the abdomen. Only the small segments 1–2 are visible in dorsal view, as observed in figure 630 (holotype) provided by Monod (1956). However, Lucas (1980), in personal communication with Dr. Jacques Forest, was informed that the abdomen of the holotype of E. gordonae , deposited at the Muséum National d’Histoire Naturelle, Paris, is like that of the Australian species. In the present individual, the abdomen was firmly attached under the cephalothorax, like a closed chamber, in an opposite situation to what was represented by Lucas (1980) in his figure 2B. These differences in the abdomen, free or attached, are perhaps related to the brooding stage.

The majority of hymenosomatid species occur in tropical and subtropical waters of the Indo-Pacific Ocean. Because of their brief larval development and low fecundity, the false spider crabs are unsuited to disperse over long distances. In fact, they have not dispersed eastward across the Pacific ( Lucas 1980). Although wide distribution is very uncommon in this family, the occurrence of Elamena gordonae in western Atlantic suggests a circum-tropical distribution. Because of its tiny size, the species has possibly escaped being noticed and collected previously.

Figures

FIGURE 7. Elamena gordonae Monod, 1956, from Camamu Bay, Bahia, Brazil. A, D – J, ovigerous female (MZUESC # 719); B, C, ovigerous female (MZUESC # 718). A, B. carapace, dorsal view; C. anterior region with rostrum and eyes, dorsal view; D. left pereiopod 1, dorsal view; E. same, detail of chela; F. right pereiopod 2; G. left pereiopod 3; H. left pereiopod 4; I. right pereiopod 5; J. same, dactyl. Scale bars: A, B, F – I = 1 mm; C – E = 0.5 mm; J = 0.25 mm.