Sesarmops Serène and Soh, 1970

Li, Jheng-Jhang, Shih, Hsi-Te & Ng, Peter K. L., 2020, Paralbunea dayriti, Zoological Studies 59 (16), pp. 1-32 : 16

Sesarmops Serène and Soh, 1970

Type species: Sesarma impressa H. Milne Edwards, 1837 , by original designation.

Remarks: Serène and Soh (1970: 401) recognised five species in Sesarmops : S. atrorubens ( Hess, 1865) , S. impressus (H. Milne Edwards, 1837) , S. intermedius (De Haan, 1835) , S. mindanaoensis ( Rathbun, 1914) , and S. sinensis (H. Milne Edwards, 1853) . Ng et al. (2008: 224) provisionally added Sesarma weberi (De Man, 1892) (from Flores) to Sesarmops . Sesarmops atrorubens is a poorly known species and was supposedly described from Sydney, Australia, by Hess (1865) and while it has also been reported from Timor, Ambon and Fiji ( Tesch 1917: 131), its taxonomy is still unclear as it has never been described or figured to modern standards. Sesarmops mindanaoensis is also poorly known and was briefly described from one female from Mindanao, Philippines, and has never been figured.

As for the type species, S. impressus (type locality not known), Sesarma similis Hess, 1865 (type locality supposedly Sydney, Australia), and Sesarma frontale A. Milne-Edwards, 1869 (type locality Madagascar), both the latter are currently regarded as junior synonyms (see De Man, 1887: 649; De Man, 1902: 527; Tesch, 1917: 158). We have examined the available types or material of S. atrorubens , S. impressus , S. similis and S. frontale , and the taxonomy of these species is complex and will have to be treated at another time. In summary, however, we have examined the dried type female of S. impressus in the Muséum National d’Histoire naturelle, Paris, France ( MNHN). It is from an unknown location. Sesarmops frontale (A. Milne-Edwards, 1869) was described from Madagascar and we have also examined the type specimens in MNHN and they are identical to the type female of S. impressus . Specimens which have been called “ S. impressus ” from the West Pacific are superficially similar to S. impressus s. str. (presumably also from the Indian Ocean) and S. frontale , but differ in details of the carapace and G1 structures. Their colours in life are also strikingly different, with those from the Indian Ocean possessing cream to yellow carapaces and cream chelae whereas West Pacific material has dark purplish brown to brown carapaces with purple chelae (unpublished data). A preliminary genetic study shows the Indian and Pacific Ocean population represent two non-sister clades ( Table 1; Fig. 22 ) and clearly belong to two species. Until their taxonomy can be properly resolved, they are here treated as one species for the moment, i.e., as Sesarmops impressus s. lato. The authors examined fresh specimens of Sesarmops atrorubens and it is a good species, very different from other Sesarmops species with a very short stout G1 and other characters that argue against its inclusion in in the genus (unpublished data). As suggested by Hess (1865) himself, S. similis is likely to be junior synonym of S. atrorubens as it was only known from a female from the same area the latter was collected. The systematics of S. atrorubens and related species will be dealt with at another occasion by the authors and CD Schubart.

The present paper will only deal with two new species found in the Philippines and Taiwan; both are very distinct from S. atrorubens and S. impressus s. lato. Sesarmops mindanaoensis , however, is figured for the first time so that appropriate comparisons can be made with the new species.

Sesarmops is clearly polyphyletic and some of the species (e.g., S. atrorubens as discussed earlier), certainly do not belong there. Its affinity to Bresedium , as noted earlier, is also in question. Ng et al. (2008: 224) have already commented that S. intermedius and S. sinensis (from China, Taiwan and Japan) did not belong to the same clade as S. impressus and was actually closer to some species of Chiromantes Gistel, 1848 and Pseudosesarma Serène and Soh, 1970 ; S. weberi was probably allied with Labuanium trapezoideum (H. Milne Edwards, 1837) instead. Of the two new species recognised here, S. mora n. sp. is closer to S. impressus s. lato in general features and, while clearly different species, are likely to be congeneric ( Fig. 22 ). Sesarmops mindanaoensis , however, although possessing a generally similar carapace as the other species, has a different thoracic sternum and male pleon, and is unlikely to be a Sesarmops species as indicated by the genetic analysis ( Fig. 22 ). Pending a revision of Sesarmops , however, it is retained here for the moment.

Comparative material: Pseudosesarma edwardsii (De Man, 1887) : 1 male (21.2 × 18.9), 1 female (16.9 × 15.4) (NCHUZOOL 16332), Langkawi, Peninsular Malaysia, coll. J.-J. Li, 19 December 2016 (see also Ng and Schubart 2017, for additional material). Pseudosesarma modestum (De Man, 1902) : holotype male (25.0 × 20.9) ( SMF 1989), Ternate, Moluccas, Indonesia, coll. W. Kükenthal, 26 December 1893 – 11 June 1894. Sesarmops impressus (H. Milne Edwards, 1837) : 2 males (28.5 × 25.0, 23.4 × 27.6), 1 female (30.4 × 25.5) ( ZRC 2009.0896), Mahi, Seychelles, coll. 2009; 1 male (37.6 × 32.1) ( ZRC 2011.0005), station 9, Bassin Mro Oua Ouroveni, Mayotte, Comoros, coll. Tervuren Museum, 11 October 2000; 1 male (23.7 × 21.5) ( ZRC 2015.0344), Bay of Bengal, South Andaman Islands, India, coll. I. Das, 20–30 August 1997; 1 female (36.7 × 34.8) (NCHUZOOL 15870), Gangkou R. estuary, Pingtung, Taiwan, 2 July 2001; 2 males (37.6 × 33.7, 35.4 × 32.3), 1 female (23.0 × 20.7) (NCHUZOOL 15069), lower reaches of Gangkou R. estuary, Pingtung, Taiwan, coll. J.-J. Li, 6 July 2017; 2 females (29.0 × 26.3, 28.9 × 26.8) (NCHUZOOL 15071), lower reaches of Gangkou R. estuary, Pingtung, Taiwan, coll. J.-J. Li, 18 May 2019; 1 male (35.2 × 34.6) (NCHUZOOL 15869), Lanyu, Taitung, Taiwan, 7 April 2002; 1 male (30.3 × 29.6) (NCHUZOOL 15868), Meilun R. estuary, Hualien, Taiwan, 29 July 2014; 2 males (larger 31.6 × 34.7) ( ZRC 2017.0477), Guimaras I., Philippines, coll. J. C. E. Mendoza and L. Ganancial, 1 June 2017; 1 male (29.2 × 29.2) (NCHUZOOL 15871), Camiguin I., Philippines, coll. H.- T. Shih, 30 August 2003; 1 female (10.5 × 9.7) ( ASIZ), Philippines, coll. H.-C. Liu, 15 February 2003.

Figures

Fig. 22. Bayesian inference (BI) tree for species of Sesarmidae, based on combined 16S rDNA and cytochrome c oxidase subunit I (COI) genes. Probability values at nodes represent support values for BI and maximum likelihood (ML). For haplotype names, see table 1.