Leptuca thayeri (Rathbun, 1900)

Masunari, Setuko, Martins, Salise Brandt & Anacleto, Andre Fernando Miyadi, 2020, An illustrated key to the fiddler crabs (Crustacea, Decapoda, Ocypodidae) from the Atlantic coast of Brazil, ZooKeys 943, pp. 1-20 : 1

Leptuca thayeri (Rathbun, 1900) Figure 2C, D

Recognition characters.

Carapace trapezoidal weakly arched and covered with exuberant pile (pubescence easily detached) (Fig. 2C , seta) and strongly converging posteriorly. Dorso-lateral margins well marked and also strongly converging posteriorly; major and minor pairs of postero-lateral striae clearly visible (Fig. 2C ). Front triangular and narrow making up ca. 15% of the front-orbital breadth. Male major claw with manus provided with a strong groove on the dorsal surface; fingers cylindrical and smooth; dactyl almost straight in the proximal two-thirds and curving down toward pollex tip and provided with a short but strong groove on the dorsal surface usually filled with dirt; moderate gap between fingers (Fig. 2D ). Ambulatory legs with wide merus ca. 3.3 times the width of proximal end of carpus; posterior surface of all segments (except dactyl) of ambulatory legs covered by pile. Male abdomen segments not fused. Medium-sized species: male CW measures up to 28.4 mm in the population from Formoso River mangrove, Pernambuco state, northeastern Brazil ( Farias et al. 2014).

Biological notes.

Populations living in the northeastern Brazilian coast reproduce only in the rainy season ( Ceará state) ( Bezerra and Matthews-Cascon 2007) or continuously (Pernambuco state) ( Farias et al. 2014), and those from southeastern Brazil during the warmer months ( São Paulo state) ( Costa et al. 2006). The species prefers typically muddy mangrove substrates in mesohaline areas, and it is the only fiddler crab in Brazil that forms large populations in shaded areas of the mangrove forest in Guaratuba Bay, southern Brazil ( Masunari 2006). Males and females of L. thayeri can construct year-round highly structured chimneys around the entrance of the burrows; among the burrow with chimneys recorded in the mangrove of Guaratuba Bay, 53.3 % contained non-ovigerous females, 37.7 % ovigerous females and only 9.0 % males. Furthermore, the chimneys belonging to males had always a larger diameter and were lower than those of females’ (T.F. Moreto, pers. comm.).

Remarks.

This species is hardly confused with other species of Brazilian fiddler crabs, as it has a very narrow triangular front (see Fig. 2C ). Furthermore, the carapace and the ambulatory legs are heavily covered with pile.

Figures

Figure 2. Uca maracoani. A carapace with bare surface, dorsal view B male major claw with flat fingers, frontal view. Leptuca thayeri C carapace mostly covered with pile (seta) D male major claw with cylindrical fingers, frontal view.