Leptuca uruguayensis (Nobili, 1901)

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 uruguayensis (Nobili, 1901) Figure 11A, B

Recognition characters.

Carapace semi-pentagonal strongly arched and dorsal surface without pile or other ornaments (Fig. 11A ). Dorso-lateral margins well marked and converging posteriorly; short and single pair of postero-lateral striae clearly visible (Fig. 11A ). Front triangular and moderately wide making up from 20.0 % to 23.6% of the front-orbital breadth. Manus of male major claw with dorso-lateral surface covered by small tubercles except along the strong submarginal groove, mostly filled with dirt (Fig. 11B , seta); both edges of dorsal margin armed with lined up by tubercles; dactyl moderately long ca. 1.4 times the manus length; pollex almost straight but dactyl strongly arched ending in a curved downward tip, forming a wide gap. Ambulatory legs with narrow segments and without pile. Male abdomen with 4th to 6thsomites fused. Small crabs: males with CW up to 12.0 mm in a population from Itacuruçá mangrove, Sepetiba Bay, southeastern Brazil ( Bedê et al. 2008). Leptuca uruguayensis , however, can attain up to 19.5 mm CW in the population from Solís Grande River, Uruguay ( Masunari et al. 2017).

Biological notes.

The species reproduces year-round in southeastern ( Costa et al. 2006) and southern coast ( Martins and Masunari 2013). It tolerates a wide range of salinities and is recorded in sandy substrates with a high degree of organic matter ( Masunari 2006). In environments where the mangrove forest is absent (such as in the Uruguayan coast), L. uruguayensis occurs in marginal lowlands of rivers that flow into estuaries.

Remarks.

Leptuca uruguayensis can be confused with L. cumulanta and L. leptodactyla in Rio de Janeiro state coast (these species are sympatric) due to the small size attained by these three species. The easiest way to separate them is by observing the male abdominal segments: among these three species only L. cumulanta has all somites distinct (see Fig. 9B ) while the other two species have middle somites fused (Fig. 9A ). On the other hand, L. uruguayensis can be distinguished from L. leptodactyla , by having a deep groove (filled with dirt) on dorsal granulated surface of manus of male major claw (Fig. 11B ); in contrast, L. leptodactyla has the major claw manus with bare surface (Fig. 11D ). Furthermore, the carapace of L. uruguayensis is semi-pentagonal with dorso-lateral margins moderately converging posteriorly (Fig. 11A ), while L. leptodactyla has a cylindrical carapace and dorso-lateral margins weakly converging posteriorly (Fig. 11C ).

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.