Bioacoustics of Orisarma

Remarks . The major differences between Orisarma and Chiromantes s. str. have been discussed under the latter genus. In addition to Chiromantes dehaani (H. Milne Edwards, 1853 ) and C. neglectus ( De Man, 1887 ) , two species of Sesarmops and one species of Pseudosesarma also need to be placed in Orisarma . As Serène & Soh (1970) had suspected (see Introduction), Sesarmops intermedius (De Haan, 1835) and S. sinensis (H. Milne Edwards, 1853 ) are more closely related to each other and to species of Orisarma . Surprisingly, we also find that all the morphological characters of the small species, Pseudosesarma patshuni Soh, 1978 , also agree with Sesarmops intermedius and S. sinensis , including the form of the thoracic sternum, male chela with a low median longitudinal ridge, relatively wide male pleons, proportionately long ambulatory legs, structure of their G1s ( Figs. 1G, H , 3F , 5H, I , 9H , 12K–O ) and even in the structure of the vulvae ( Fig. 43D ). The closest genus to Orisarma may be Manarma , new genus , which consists of two species, M. moeschii ( De Man, 1892 ) and M. johorensis ( Tweedie, 1940 ) . These two species, as already highlighted by Serène & Soh (1970) , are characterised by their shiny carapaces, narrow thoracic sterna, narrow male pleons, and form of their G1s (cf. Figs. 24C, D , 26A, B , 29B, C , 33A, B, D, E , 58 ). The remaining species of Sesarmops Serène & Soh, 1970 ( type species Sesarma impressa H. Milne Edwards, 1837 ), have more trapezoidal carapaces and a relatively stout G1 with a very long chitinous distal process. One species still in Sesarmops , S. weberi ( De Man, 1902 ) , does not belong to this genus on account of its short G1 and a male chelipedal dactylar finger that has a row of stridulatory granules on the dorsal margin (see Ng et al., 2008a: 224 ; Naruse & Ng, 2020 ). Ng et al. (2008a) suggested the species was close to Labuanium trapezoideum (H. Milne Edwards, 1837) but Naruse & Ng (2020) showed otherwise. The systematic position of this species should be dealt with when Sesarmops is completely revised.