Minuca rapax (Smith, 1870)

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

Minuca rapax (Smith, 1870) Figures 7A , 8A, B

Recognition characters.

Carapace pentagonal moderately arched and provided with small and scarce tubercles in the antero-lateral corner (Fig. 8A ); some individuals have pile on H-form depression. Dorso-lateral margins well marked and strongly convergent posteriorly (more pronounced in males); major and minor pairs of postero-lateral striae clearly visible (Fig. 8A ). Front triangular and very wide making up 30% to 36% of the front-orbital breadth. Male major claw with manus covered with tubercles and provided with strong groove dorsally; fingers thick and slightly flattened; dactyl ca. 1.5 times longer than manus; pollex and dactyl strongly curved forming a large gap (Fig. 8B ). Pile limited the dorsal surface of carpus and manus in the first three ambulatory legs; these legs with enlarged merus (especially the 2nd and 3rd), dorsal margin convex and dorsal surface with striated ornaments; last leg without piles and merus more than two times wider the respective carpus in their maximum breadth (Fig. 7A , seta). Male abdominal segments never fused. Medium-sized crabs, male CW up to 28.3 mm and female up to 27.3 mm in a population from Itamambuca mangrove, Ubatuba, southeastern Brazil ( Castiglioni and Negreiros-Fransozo 2004).

Biological notes.

The species reproduces year-round in the populations from northern and southeastern Brazil ( Koch et al. 2005, Castiglioni and Negreiros-Fransozo 2006; Costa and Soares-Gomes 2009). It prefers mesohaline to euhaline areas but it can be found in a wide range of salinities, from oligohaline to euhaline; the preferred substrate is firm sandy to silty clay with humus or clayed silt ( Thurman et al. 2013).

Remarks.

Morphologically very similar to M. burgersi and M. mordax . Minuca rapax can be distinguished from M. mordax in not having a pile around the entire surface of manus of 1st to 3rd ambulatory legs. The distinction between M. rapax and M. burgersi , however, requires an extra attention: both species have piles limited to the dorsal surface of carpus and manus of 1st to 3rd ambulatory legs. The easiest way to distinguish these two species is to compare the last ambulatory leg: while M. rapax has a wide merus with convex dorsal margin (Fig. 7A ), that of M. burgersi is narrow and its margins are almost parallel (Fig. 7B ).

Figures

Figure 7. Last ambulatory legs, posterior view. A Minuca rapax, wide merus (seta). B Minuca burgersi, narrow merus (seta).

Figure 8. Minuca rapax. A carapace with two pairs of postero-lateral striae, dorsal view B male major claw, frontal view. Minuca burgersi C Carapace with two pairs of postero-lateral striae, dorsal view D male major claw, frontal view.