Leptarma aurifrons (Li, Shih & Ng, 2019 ), 2020

Shahdadi, Adnan, Fratini, Sara & Schubart, Christoph D., 2020, Taxonomic reassessment of Parasesarma (Crustacea: Brachyura: Decapoda: Sesarmidae) based on genetic and morphological comparisons, with the description of a new genus, Zoological Journal of the Linnean Society 190, pp. 1123-1158 : 1149-1152

Parasesarma maipoense (Soh, 1978) Chiromantes maipoensis Hong Kong: Mai Po

Naujan Island

Island

:

Manado: Tioman Bitung

:

Mindoro Sulawesi: Malaysia Sulawesi:

locality

Type

Philippines: Indonesia Peninsular Indonesia:

composition and parvulum paucitorum purpureum tarantula

name

Original

Parasesarma Parasesarma Parasesarma Parasesarma

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) 2018 2009), 2018 2018

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Ng,

Ng Ng & Ng

Rahayu

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Rahayu

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Li (Li

Continued parvulum ( paucitorum purpureum ( tarantula 4 Table. Species Leptarma nov. Leptarma nov. Leptarma nov. Leptarma nov.

of different size (age) from different areas and also a small syntype of P. hasswelli (NHM London; see Table 1). It appears that smaller specimens have asymmetric tubercles, whereas in larger males these tubercles are symmetrically ovate. A possible hypothesis is that this difference is caused by a developmental change through ageing. However, morphological examination of more material of P. hasswelli and genetic comparison can help to address the doubt of conspecificity.

Parasesarma bidens was originally described from Japan by De Haan (1833) and was known to be distributed widely in Korea, Taiwan, the Philippines and along the Chinese coast to the Andaman Sea ( Dai & Yang, 1991). However, Li et al. (2019) described the new species Parasesarma sanguimanus Li, Shih & Ng, 2019 , based on some Taiwanese specimens that were shown to be morphologically and genetically distinct from the Japanese P. bidens and other members of Parasesarma . We here examined a male sample of P. sanguimanus from Bohol Island ( Philippines), indicating an enlarged distribution of this new species beyond its type locality (for the material examined, see Table 1). The specimen from Bohol shares the same haplotype with the Taiwanese paratype in the barcode region of the COX 1 gene (for the GenBank accession numbers, see Table 2).

In his description of P. catenatum, Ortmann (1897) mentioned New Zealand as its collection site, but he was not sure about the exact locality of the material. This species is common in East Africa ( Fratini et al., 2005; Cannicci et al., 2017; Fratini et al., 2019), but there are no records from any other part of the world. We examined some specimens from East Africa and compared them with photographs of the type material (see section: Material examined) and they are identical in general morphology. Therefore, we assume that New Zealand as the collection site for the type must have been a labelling error. This species seems aberrant in chelar morphology in comparison to other Parasesarma species, because it has setae on the palm and dactylus and a wide gap between the fingers when closed ( Emmerson, 2016). However, according to the phylogenetic position in this study and having two rows of transverse pectinated crests on the upper face of the palm and a long eyestalk, P. catenatum is assigned here within the genus Parasesarma .

While describing Parasesarma acis Davie, 1993 (which was later synonymized under P. tripectinis by Rahayu & Ng, 2005), Davie (1993) also redescribed P. erythodactyla based on material collected from eastern Australia (deposited in the Queensland Museum and Museum of Victoria). He considered that the types of Hess’ species ( P. erythodactyla ) are missing (for details about type history and material examined in the study, see Davie, 1993). He also separated the Australian P. erythodactyla from P. acis (now P. tripectinis ) via several morphological characters (e.g. the morphology of G1 and chelar dactylar tubercles; Davie 1993: fig. 1). Our present generic assignment for this species is based on the description and illustration given by Davie (1993) and on the examination of three male specimens collected near Sydney ( Table 1).

Given that no material of P. exquisitum is examined here, its generic assignment is based on the original description and illustrations ( Dai & Song, 1986) and new photographs (see section: Material examined).

In his identification key, Davie (2010) did not distinguish P. indiarum from Parasesarma foresti ( Rahayu & Davie, 2002) , and their type localities are close ( Ambon and Irian Jaya, respectively; De Man, 1902; Rahayu & Davie, 2002; see Table 4). Genetic pairwise comparisons (K2P based on COX 1) also revealed a close affinity between these two species (Shahdadi et al., 2017: table 3; Shahdadi et al., 2018b: table 2). Based on this evidence, they may be considered conspecifics, and their taxonomy needs to be evaluated by examining material from their entire area of distribution, including the type material.

The phylogeographic study by Silva et al. (2010) showed that Parasesarma guttatum (A. Milne-Edwards, 1869) forms two separate clades in the south and north of Mozambique. Confirming this separation, Fratini et al. (2019) recently split P. guttatum into two pseudocryptic species, of which the newly described P. capensis Fratini, Innocenti & Cannicci, 2019 is endemic to mangrove forests south of the Mozambique Channel. Thus, P. guttatum (whose type specimen, described by Alphonse Milne-Edwards in 1869, was from Zanzibar) is now restricted to populations distributed from the Gulf of Oman ( Naderloo, 2011) and the Red Sea to northern Mozambique ( Fratini et al., 2019).

Four species [ P. calypso , P. ellenae , P. kuekenthali and P. lanchesteri ( Tweedie, 1936) ] were originally described as subspecies of P. calypso (see Table 4), sharing longitudinal lines on the proximal slopes of the chelar dactylar tubercles ( De Man, 1895, 1902; Tweedie, 1936; Pretzmann, 1968). Accordingly, three of them cluster tightly together in our phylogenetic analyses, whereas P. lanchesteri is more distantly related ( Fig. 2). Parasesarma ellenae was the latest described species of this group. Pretzmann (1968) briefly described this species based on a single small male from New Caledonia ( Table 1) and highlighted differences from other members of the P. calypso group. For the present study, we examined the holotype, which turned out to be a juvenile male with undeveloped G1. Here, we also examined an adult male from New Caledonia and two larger males from Vanuatu Island ( Table 1). A separate study will provide a detailed redescription of P. ellenae along with morphological comparisons with other related species.

Parasesarma panguaranense was originally described based on a single female ( Rathbun, 1914), with no further record. In our study, we examined the holotype of this species, but we were not able to study any male specimen or to obtain any sequences from the type locality. Therefore, our generic assignment is based merely on structures such as orbit and eye morphology ( Fig. 11B), which are assumed to be less affected by sexual dimorphism. More specimens from both sexes are necessary to confirm the taxonomy and phylogeny of the species.

Parasesarma rutilimanum was described from Singapore ( Tweedie, 1936), and 1 year later Parasesarma prashadi ( Chopra & Das, 1937) was described from the nearby Mergui Archipelago without a comparison to P. rutilimanum . According to their original descriptions and illustrations, these two species show high morphological similarity in their general appearance (e.g. carapace morphology, ambulatory legs, number of chelar dactylar tubercles and long primary pectinated crest) and might be conspecific. In the present study, we examined a series of material from Phuket ( Thailand), Singapore, Labuan ( Malaysia) and a syntype of P. rutilimanum (from Pulau Senang). It is hard to distinguish the two species morphologically, and therefore in this study species assignments were based on their geography (i.e. specimen from Phuket as P. prashadi ; specimens from Singapore and Labuan as P. rutilimanum ). In this study, we were not able to examine the type of P. prashadi and we did not obtain any DNA sequence from P. rutilimanum . Therefore, a targeted study examining the corresponding type material and additional specimens from their distribution area should address this taxonomic issue.

Parasesarma corallicum and P. sigillatum show close genetic affinity in our mitochondrial analyses ( Fig. 2). Parasesarma sigillatum was synonymized under P. carolinense by Serène (1968) and being treated as such until Ng et al. (2016) clarified the identities of P. carolinense and P. sigillatum and showed that they are separate species. Ng et al. (2016) also presented several morphological diagnoses to separate P. corallicum , P. carolinense and P. sigillatum .

Shahdadi et al. (2017) described P. tuerkayi as a member of the genus Perisesarma in the special volume dedicated to Michael Türkay, because the generic rearrangement by Shahdadi & Schubart (2017) had not yet been published. However, at the end of their paper, Shahdadi et al. (2017: p. 1175) clarified in an addendum that this species would become a member of Parasesarma .

Parasesarma gemmatum was recently described by Li et al. (2019) from Taiwan. A male specimen of this species, collected from Cebu Island ( Philippines), was also examined in the present study, matching all diagnostic characters of the Taiwanese types. Genetically, there is only 1 bp difference between the Cebu specimen and the Taiwanese paratype (i.e. ~0.2% of genetic distance; for the GenBank accession numbers, see Table 2). Although this species is similar to other species of Parasesarma in general carapace and chelar morphology, it differs by having rows of fine granules and no chitinous pectinate crest on the palm ( Li et al., 2019; present study). According to its phylogenetic position in the mitochondrial tree ( Fig. 2; see also Li et al., 2019: fig. 13), this species is well nested within the P. plicatum clade. Therefore, it appears that P. gemmatum could have lost the pectinated crest secondarily. This might also be the case for Guinearma kamermani (De Man, 1883) , a West African sesarmid crab that, in comparison to its congeners [i.e. Guinearma alberti (Rathbun, 1921) and Guinearma huzardi (Desmarest, 1825) ], has lost the oblique pectinated crest ( Shahdadi et al., 2019b).