Identity of the tree-spider crab, Parasesarma leptosoma (Hilgendorf, 1869 (Decapoda: Brachyura: Sesarmidae), with descriptions of seven new species from the Western Pacific

Abstract

The identity of the tree-spider crab, Parasesarma leptosoma (Hilgendorf, 1869) (family Sesarmidae), which is believed to be widely distributed in the Indo-West Pacific, is reassessed and shown to be a species-complex with nine species, seven of which are here described as new. Parasesarma leptosoma sensu stricto is now restricted to South and East Africa; and P. limbense (Rathbun, 1914) from Sulawesi, which had been regarded as a junior synonym, is here recognized as a valid species. The following species are described as new: P. gecko n. sp. from Vanuatu, Fiji, Guam and Japan; P. macaco n. sp. from Taiwan and the Philippines; P. kui n. sp. from Taiwan; P. parvulum n. sp. from the Philippines; P. gracilipes n. sp. from Indonesian Papua; P. purpureum n. sp. from Malaysia; and P. tarantula n. sp. from Sulawesi, Indonesia. The nine species of the Parasesarma leptosoma species-complex can be separated by the different shapes of their carapaces, the form of the dactylar tubercles on the male chelipeds, proportions of their ambulatory legs and the structure of the male first gonopod.

Taxonomic reassessment ofParasesarma(Crustacea: Brachyura: Decapoda: Sesarmidae) based on genetic and morphological comparisons, with the description of a new genus

“…short vs. long legs. Among the long-legged species, P. leptosoma is arguably the most distinctive (Li et al, 2018). Overall, these and other lines of evidence reported by indicate that the species currently assigned to Parasesarma belong to more than one clade and that their phylogeny and taxonomy need to be re-evaluated.…”

“…Another possibly important feature for the taxonomy of these crabs is the morphology of G1 Li et al, 2018). Li et al (2018) described seven new species of the long-legged Parasesarma with distinct morphological identities, especially regarding the morphology of G1 and chelar dactylar tubercles. However, in the present study these species show close genetic affinity in their mitochondrial DNA sequences.…”

“…These nine species (i.e. P. leptosoma, Li, Rahayu & Ng, 2018) show low genetic divergences in the mitochondrial tree (Fig. 2).…”

“…They mostly inhabit estuarine wetlands, including mangrove swamps (Tan & Ng, 1994;Shahdadi et al, 2018a), where they play an important role in nutrient cycling (Lee, 1998;Guerao et al, 2004;Cannicci et al, 2008;Lee, 2015). The genus was recently redefined and enlarged , because of the additions and redescriptions of several species, and now comprises 71 recognized species (Rahayu & Ng, 2010;Ng et al, 2016;Cannicci et al, 2017;Li et al, 2018Li et al, , 2019Shahdadi et al, 2018aShahdadi et al, , b, 2019aFratini et al, 2019;. This makes it the most species-rich genus of the family Sesarmidae.…”

First confirmed record of the sesarmid crab, Parasesarma bengalense (Davie, 2003) (Decapoda: Brachyura) in Indian waters

“…The sesarmid genus, Parasesarma De Man, 1895, is currently represented by 68 species (Cannicii et al, 2017;Shahdadi and Schubart, 2017;Li et al, 2018;Shahdadi et al, 2018;Fratini et al, 2019). Parasesarma was certainly known from five species in India (Shahdadi and Schubart, 2017;Trivedi and Vachhrajani, 2017;Trivedi et al, 2018): P. asperum (Heller, 1865) [East Coast (Tamil Nadu); Andaman and Nicobar islands], P. bidens (De Haan, 1835) [West Coast except for Gujarat; East Coast; Andaman and Nicobar islands], P. persicum Naderloo and Schubart, 2010 [West Coast (Gujarat)], P. pictum (De Haan, 1835) [West Coast (Kerala); East Coast (Tamil Nadu and West Bengal); Andaman and Nicobar islands], and P. plicatum (Latreille, 1803) [West Coast; East Coast; Andaman and Nicobar islands].…”