The description of a new species of the Neotropical land crab genus Gecarcinus Leach, 1814 (Crustacea, Decapoda, Brachyura, Gecarcinidae)

Abstract

In this contribution a new species of the land crab genus Gecarcinus Leach, 1814, from the Neotropical Pacific coast of South America is described and illustrated. In addition to its unique body color, Gecarcinus nobilii sp. n. is distinguished from congeners by a distinctly wider carapace front and differences in the shape of the infraorbital margin. The new species is not isolated from Gecarcinus populations from the Pacific coast of Central America by an insurmountable geographic barrier. Considering the closure of the Panamanian Isthmus as a calibration point for morphological divergence between the trans-isthmian mainland populations of Gecarcinus, the virtual lack of morphological differentiation (other than color) between them and the distinctness of G. nobilii sp. n. suggests that G. nobilii sp. n. evolved from a common ancestor before the Isthmus closed.

A morphological, phylogenetic and phylogeographic reappraisal of the land crabs Gecarcinus quadratus De Saussure, 1853, and G. lateralis Fréminville in Guérin, 1832 (Decapoda: Gecarcinidae). Are they different species?

“…Additionally, four sequences (two COI, two 16S) of G. lateralis from Costa Rica and two (COI, 16S) from Panama, courtesy of F. Mantelatto (UNESP, Brazil), were included as well as a sequence of G. ruricola from Cuba, obtained from tissue of two pereiopods donated by C. Schubart (Universität Regensburg, Germany). The morphological description of the material examined was based on the terminology proposed by Perger & Wall (2014) for the frontal and orbital structures. Guinot (1979) and Guinot et al (2018) were followed regarding the ventral sternites and sutures that separate each somite.…”

“…Currently, it contains four species. Two occur along the coast of the eastern Pacific: G. quadratus De Saussure, 1853, from the eastern coast of the Gulf of California, Mexico to Peru (Hendrickx 1995;Cuesta et al 2007;Toledano-Carrasco 2019), and G. nobilii Perger & Wall, 2014, in Ecuador and Colombia. The other two inhabit the western Atlantic coast: G. lateralis Fréminville in Guérin, 1832, occurs from Florida, USA to Venezuela (Toledano-Carrasco 2019, and G. ruricola (Linnaeus, 1758) is distributed from Florida, USA, to Nicaragua, including the Caribbean islands (Rathbun 1918;Chace & Hobbs 1969;Perger & Wall 2014). The taxonomic status of G. quadratus has remained questionable, as it has been regarded by some authors as a junior synonym of G. lateralis (Türkay 1973;Perger & Wall 2014).…”

“…Two occur along the coast of the eastern Pacific: G. quadratus De Saussure, 1853, from the eastern coast of the Gulf of California, Mexico to Peru (Hendrickx 1995;Cuesta et al 2007;Toledano-Carrasco 2019), and G. nobilii Perger & Wall, 2014, in Ecuador and Colombia. The other two inhabit the western Atlantic coast: G. lateralis Fréminville in Guérin, 1832, occurs from Florida, USA to Venezuela (Toledano-Carrasco 2019, and G. ruricola (Linnaeus, 1758) is distributed from Florida, USA, to Nicaragua, including the Caribbean islands (Rathbun 1918;Chace & Hobbs 1969;Perger & Wall 2014). The taxonomic status of G. quadratus has remained questionable, as it has been regarded by some authors as a junior synonym of G. lateralis (Türkay 1973;Perger & Wall 2014). Rathbun (1918), Powers (1977), von Prahl & Manjarrés (1984), and Abele & Kim (1986) tried to distinguish both species based on morphological characters that are highly variable within populations, such as the shape of the merus of the third maxilliped, the degree of coverage of maxillipeds with respect to the epistome of the buccal cavity, and the number of longitudinal rows of spines on the dactyli of pereiopods.…”

“…Due to this variable morphology, Türkay (1970) considered G. quadratus as a subspecies of G. lateralis; nevertheless, after reviewing the type specimens, he concluded that they were synonymous. Later, Perger & Wall (2014) followed this idea and erected G. nobilii, including only three species as valid within the genus (G. lateralis, G. ruricola and G. nobilii) and suggesting the need of molecular analyses including different populations of Gecarcinus.…”

Annotated type-catalogue of Brachyura (Crustacea, Decapoda) of the Muséum national d'Histoire naturelle, Paris. Part II. Gecarcinidae and Grapsidae (Thoracotremata, Grapsoidea), with an Appendix of pre-1900 collectors

“…The differences between the measurements by Türkay (63.0 × 81.0 mm) and ours (63.7 × 82.4 mm) are due to the restoration of the lectotype in the 1990s. Hobbs 1969;Türkay 1970Türkay , 1974aBliss et al 1978;Hartnoll 1988;Ng & Guinot 2001;Ng et al 2008;Perger & Wall 2014). Low et al (2013) stated that Guérin (1832 in Guérin 1829-1837) must take precedence.…”