Sesarmops imperator Ng, Li & Shih 2020

Sesarmops imperator Ng, Li & Shih, 2020

Figs. 4C, 8E, F

? Sesarma impressa, Estampador 1937: 538; 1959: 95. Not Sesarmops impressus (H. Milne Edwards, 1837).

Sesarmops impressum, Manuel et al. 1991: 90. Not Sesarmops impressus (H. Milne Edwards, 1837).

Sesarmops impressus, Li et al. 2020: 17, fig. 18. Not Sesarmops impressus (H. Milne Edwards, 1837).

Sesarmops impressus 2, Li et al. 2020: fig. 22. Not Sesarmops impressus (H. Milne Edwards, 1837).

Sesarmops imperator Ng et al. 2020: 13, figs. 11B, D–F, 12, 13F, 14G–I, 16Q–S, 17F–K.

Material examined. 1 male, 35.8 by 35 mm (ZRC; NJL160712) Brgy. Poblacion, Maigo town, Lanao del Norte prov., coll. N.J. Lagare, 22 Sep. 2016; 3 males, 32.0 by 31.5 mm—34.0 by 32.5 mm (ZRC; NJL180110–12) Brgy. Liguac, Salug town, Zamboanga del Norte prov., coll. N.J. Lagare, 25 Dec. 2018; 3 males, 37.2 by 36.6 mm—42.2 by 41 mm, 3 females, 33.1 by 30.9 mm—36.7 by 34.8 mm (ZRC; JBN170701– 06) Brgy. Sebaca, Rizal town, Zamboanga del Norte prov., coll. J.B. Neri, 20 Nov. 2017; 3 males, 31.2 by 29.8 mm—35.6 by 33.7 mm, 4 females, 28.7 by 27.3 mm—35.3 by 33.3 mm (ZRC; NJL161101–07) Brgy. Pandan, Mambajao town, Camiguin I. prov., coll. N. J. Lagare, 28 & 29 Sep. 2016; 3 males, 24.0 by 22.6 mm—33.0 by 31.0 mm, 1 female, 29.4 by 22.0 mm (ZRC; NJL182306–09), Brgy. Cawag, Samal Island town, Davao del Norte prov., coll. N.J. Lagare, 11 Oct. 2018; 1 male, 25.4 by 22.8 mm (ZRC; EFM180301), Don Marcelino town, Davao Occidental prov., coll. E.F. Mapi-ot, 2018.

Remarks. Sesarma impressa was described by H. Milne Edwards (1837) based on an adult female of unknown provenance (see De Man, 1887). This species has subsequently been widely reported in the Indo-West Pacific region, from the eastern coast of Africa all the way to Samoa (Bouchard et al. 2013). Serene & Soh (1970) established the genus Sesarmops, with Sesarma impressa H. Milne Edwards, 1837, as the type species.

Bouchard et al. (2013: 24) reported Sesarmops impressus from Mayotte Island in the Indian Ocean, and, according to them (citing correspondence with PKL Ng), this widespread species is probably a species-complex, with at least two species occurring in the Indo-West Pacific region. They further opined that the Indian Ocean population is probably the real Sesarmops impressus, citing that the live colouration (yellowish-white carapace and white chelae) (Bouchard et al. 2013: 24, fig. 19) is quite different from that of the Pacific Ocean population (dark brown carapace and deep red chelae; cf. Fig. 4C), and that the G1 morphology is also different (see Cai & Ng 2003). Li et al. (2020: fig. 22) provided molecular evidence of two distinct clades for S. impressus: one consisting of individuals from the western Indian Ocean and the other consisting of individuals from the western Pacific region. Ng et al. (2020) recently revised Sesarmops impressus, using molecular and morphological evidences, effectively restricting this species to the populations in Madagascar, Mayotte, the Comoros, and other adjacent areas in the western Indian Ocean, and recognizing 4 other species (2 new and 2 taken out of synonymy with S. impressus) distributed in the Indo-West Pacific. Of these, Ng et al. (2020) recognized the populations occurring in Taiwan, Indonesia, the Philippines, the Ryukyu Islands (Japan), and Vanuatu as a new species, S. imperator, with the holotype and paratypes selected from the Taiwan population.

The present material from Mindanao were collected among rocks in brackish and freshwater streams a little distance away from the coast (up to 1 km), and they are similar to the published accounts of Pacific “ Sesarmops impressus ” (viz. Sakai 1939; Dai & Yang 1991; Cai & Ng 2003). The G1 morphology (Fig. 8E, F) of the present material is similar to that of the specimens from Halmahera, Indonesia, illustrated by Cai & Ng (2003: fig. 19D, E). They are also identical to the Philippine material of S. imperator figured by Ng et al. (2020: figs. 11B, D–F, 12, 13F, 14G–I, 16Q–S, 17F–K), and collected from various islands in the central Philippines (see Table 1).

Manuel et al. (1991) previously reported this species from Tabaco, Albay, in Luzon I. There is only one other, somewhat dubious, record of this species from the Philippines. Estampador (1937: 538, 1959: 95) reported “ Sesarma impressa ” from “Luzon, Bataan Province, Mariveles, 2,000 ft. above sea level (Bürger)”. While S. imperator has indeed been recorded from highland localities (Ng et al. 2020) and Estampador attributes his record to Bürger, this record is doubtful because there is only one publication by Bürger that deals with sesarmids (i.e. Bürger 1893), and in it Bürger mentions only Palau as a source locality for his specimen of Sesarma impressa.

New Mindanao record.

Published as part of Lagare, Nickel Jean S., Mapi-Ot, Emmarie F., Molina, Ziljih S., Neri, Jemateo B., Nuñeza, Olga M. & Mendoza, Jose Christopher E., 2020, On a collection of freshwater and estuarine crabs (Crustacea: Brachyura) from Mindanao Island, the Philippines, pp. 301-330 in Zootaxa 4868 (3) on pages 312-313, DOI: 10.11646/zootaxa.4868.3.1, http://zenodo.org/record/44…