Bioacoustics of Parasesarma plicatum

Remarks . Fabricius used the name Cancer quadratus twice for two different species, once in 1787 and again in 1798. Cancer quadratus Fabricius, 1787 ( type locality Jamaica ), is now known to be a species of Ocypode quadratus (see Manning & Holthuis 1981 ) and is a West African taxon. The name Cancer quadratus Fabricius, 1798 ( type locality East India ), however, was used for a sesarmine crab (now Sesarmidae ), which was eventually transferred to the genus Sesarma (see H. Milne Edwards 1837 ). Latreille (1803) , however, had apparently realised that the same name has been used twice for different species, and in a brief comment “Têt uni, avec les angles antérieurs formant une dent, et des plis derrière; main presque lisses. Ce crustacé est peutêtre un grapse” he proposed a new name, Ocypode plicatum . This is the species now generally referred to as Parasesarma plicatum . Almost all authors cite the author and year for Parasesarma plicatum as “ Latreille, 1806 ” (see Tesch 1917 ; Ng et al. 2008). The name was, however, first used as a valid name by Latreille (1803: 47) with a proper description and also clearly referring to the Cancer quadratus of Fabricius (1798) . Fabricius (1798) briefly described Cancer quadratus from an unspecified number of specimens from somewhere in East India . Four specimens of Cancer quadratus deposited at ZMUC have syntype status. Neil Bruce was kind enough to provide photographs of the dried types in the early 1990s which have since been rehydrated and examined by the second author. As Latreille (1803) merely provided a replacement name for the preoccupied name Cancer quadratus (i.e. Cancer plicatum ), Fabricius' type specimens of Cancer quadratus are thus also the types of C. plicatum . Zimsen (1964) mentions five specimens and old photographs taken of the dried specimens in ZMUC in the 1960s show five specimens. However, the second author was only able to find and examine four of the subsequently rehydrated ZMUC specimens. Comparisons of the extant ZMUC specimens with the ZRC specimens from Tamil Nadu and Mumbai (= Bombay ), India , as well as Phuket, Thailand show that all of them are conspecific. The best ZMUC male specimen (21.0 x 17.0 mm) is here selected as the lectotype (ZMUC 2658) ( Fig. 1 ). The most distinctive external feature of Parasesarma plicatum is that in addition to the two oblique rows of beige-coloured pectinated ridges on the antero-subdistal part of the manus, there are several beige-coloured granules posterior to the ridges ( Figs. 2 A, B, 3E). This feature is visible even in the old material. The G1 of P. plicatum is also very distinctive ( Fig. 4 A–D), the distal part being hook-shaped with a rounded tip. The number of dactylar tubercles on the chela of P. plicatum is relatively constant, varying only from 11 to 14 (all granules counted, including the small proximal and very low distal ones) ( Fig. 3 D, E). The number of these tubercles easily distinguishes P. plicatum from P. affine , which has only eight or nine dactylar granules ( Fig. 6 E). These tubercles are also larger and more prominent in P. a f f i n e , with a prominent ridge at the tip. Furthermore, the G1 of P. plicatum ( Fig. 4 A, B) is relatively more slender than that of P. affine ( Fig. 7 A, B). With regards to the affinities with P. exquisitum alluded to by Dai & Song (1986) , we have compared P. plicatum with photographs of the holotype of P. exquisitum taken for us by N. K. Ng and T. Naruse (see comparative material). While P. exquisitum also has oblique rows of beige-coloured pectinated ridges on the antero-subdistal part of the manus, the number of tubercles on the dorsal surface of dactylus of chelipeds is much larger (17–19). They are clearly different species and not closely related. Several specimens from Iraq are here identified as Parasesarma aff. plicatum . These specimens belong to the same species-group and share many characters with P. plicatum . However, a number of differences indicate that they belong to a different species, and in an independent study, Nardeloo & Schubart (in press) regard the taxon as new. As P. plicatum sensu stricto occurs in the eastern Indian Ocean, the records of this species by Richters (1880:157) from Mauritius , Lenz & Richters (1881: 425) and De Man (1889: 434) from Madagascar , Borradaile (1907: 64) from Seychelles , Stebbing (1910: 321) and Barnard (1950: 127.) from South Africa , Tirmizi & Ghani (1996: 151, fig. 58) and Tirmizi et al. (1986: 28, fig. 11 A) from Pakistan , as well as the record of Sesarma ungulata by A. Milne-Edwards (1868: 71) from Zanzibar , and Sesarma affinis by Krauss (1843: 45) from South Africa , should most probably also be referred to this new species. Most authors use the spelling plicata for this species but as the gender of the genus Sesarma and Parasesarma is neuter, it should correctly be plicatum instead. Geographical distribution . Bombay , Tamil Nadu ( India ), Phuket ( Thailand ), Lombok ( Indonesia ).