Leptuca leptodactyla (Rathbun, 1898)

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 leptodactyla (Rathbun, 1898) Figures 9A , 11C, D

Recognition characters.

Carapace semi-cylindrical, width ca. 1.7 times the length; strongly arched and dorsal surface without any pile or other ornaments; lateral margins almost parallel (Fig. 11C ). Front triangular and moderately wide making up 20% to 23% of the front-orbital breadth. Dorso-lateral margins well marked and converging posteriorly; short and single pair of postero-lateral striae clearly visible (Fig. 11C ). Male major claw smooth, manus with dorsal margin lined up with minute tubercles; fingers very slender and long, dactylus ca. 1.7 times the manus length (Fig. 11D ); pollex almost straight and dactyl strongly arched ending in a curved downward tip; very wide gap between fingers. Ambulatory legs with narrow segments and devoid of pile or other ornaments. Male abdomen with 3rd to 6th somites fused (Fig. 9A ). Small crabs: male CW maximum 14.29 mm in a population from Itacuruçá mangrove, Sepetiba Bay, southeastern Brazil ( Bedê et al. 2008).

Biological notes.

One of the most common fiddler crabs in sandy substrate of estuarine intertidal zone, L. leptodactyla reproduces year-round in the population of Ceará state (Bezerra and Matthews-Cascon, 2007), but only in warmer months at the southern coast ( Masunari 2012). During the reproductive period (September-March in Guaratuba Bay, Paraná state), males construct a typical hood by piling up sand beside the burrow entrance where they stay for usual waving ( Masunari 2012). The species shows strong preference for sandy substrate of polyhaline areas ( Masunari 2006), and its young individuals can find shelter in the shadow of cordgrasses (S. Masunari, pers. obs.).

Remarks.

Leptuca leptodactyla may be confused with L. cumulanta at the coast from Pará to Rio de Janeiro states. These two species, however, can be distinguished by features of the male abdomen: the middle somites are fused in the former species (Fig. 9A ), while in L. cumulanta all somites are distinct (Fig. 9B ). Furthermore, L. leptodactyla may also be confused with Leptuca uruguayensis in the sympatric area (from Rio de Janeiro to Santa Catarina state), especially among juvenile specimens. The male major claw of L. uruguayensis , however, is provided with a strong groove parallel to the dorsal margin of the manus (even in juvenile specimens) (Fig. 11B , seta), while in L. leptodactyla this groove is absent (Fig. 11D ).

Figures

Figure 9. Abdomen of male, ventral view. A Leptuca leptodactyla, middle somites fused B Leptuca cumulanta, all somites distinct.

Figure 11. Leptuca uruguayensis. A carapace with a pair of postero-lateral striae, dorsal view B male major claw with dorsal groove (seta), dorso-frontal view. Leptuca leptodactyla C carapace with a pair of postero-lateral striae, dorsal view D male major claw without dorsal groove, dorso-frontal view.