Cheramus Spence Bate, 1888

Komai, Tomoyuki, Maenosono, Tadafumi & Fujita, Yoshihisa, 2014, Two new species of ghost shrimp assigned to the genus Cheramus Spence Bate, 1888 (Crustacea: Decapoda: Axiidea: Callianassidae) from the Ryukyu Islands, Japan, Zootaxa 3895 (4), pp. 503-524 : 504-505

Genus Cheramus Spence Bate, 1888

Cheramus Spence Bate, 1888: 30 .— Borradaile 1903: 545 (part).—de Man 1928: 95.— Manning & Felder 1991: 780.— Poore 1994: 101.— Sakai 2011: 363 (part).

Remarks. The taxonomic composition of Cheramus is still in a state of flux. The genus was established by Spence Bate (1888) for Cheramus occidentalis Spence Bate, 1888 , described on the basis of a damaged specimen, lacking chelipeds, from the West Indies. In the same Challenger volume, Spence Bate (1888) described another new species, Callianassa occidentalis , based on a single cheliped taken in the same haul with the type of Cheramus occidentalis . Borradaile (1903) relegated Cheramus to a subgenus of Callianassa Leach, 1914 , thus making Cheramus occidentalis a homonym of Callianassa occidentalis Stimpson, 1856 [= a junior subjective synonym of Neotrypaea californiensis (Dana, 1854) ]. Hence, Borradaile (1903) proposed Callianassa (Cheramus) batei as a replacement name for Cheramus occidentalis . Later, Biffar (1973) concluded that Spence Bate’s (1888) Callianassa occidentalis and Cheramus occidentalis were actually based on the same individual, and proposed the second replacement name, Callianassa profunda , for Spence Bate’s taxon, because the name Callianassa batei Borradaile, 1903 was also preoccupied by a fossil taxon Callianassa batei Woodward, 1868 . Manning & Felder (1991) recognized Cheramus as a valid genus and proposed a new subfamily Cheraminae to accommodate two genera, Cheramus and Scallasis Spence Bate, 1888 . They referred Callianassa profunda Biffar, 1973 [type species; as Cheramus batei ( Borradaile, 1903) ], Callianassa marginata Rathbun, 1901 , Cheramus orientalis Spence Bate, 1888 , and Callianassa oblonga Le Loeuff & Intès, 1974 , to Cheramus . Tudge et al. (2000), who performed a phylogenetic analysis estimating generic relationships within the Callianassidae and Ctenochelidae , supported the recognition of Cheramus , and added seven species to that genus: Callianassa longicauda Sakai, 1967 , C. praedatrix de Man, 1905, C. propinqua de Man, 1905, C. rectangularis Ngoc-Ho, 1991, C. sibogae de Man, 1905, and C. spinophthalma Sakai, 1970 . Sakai (2011) rediagnosed Cheramus , and assigned the following 16 species to it: Callianassa anoploura Sakai, 2002 , C. aqabaensis Dworschak, 2003 , C. contipes Sakai, 2002 , C. lobetobensis de Man, 1905, C. longicauda , C. malaccaensis Sakai, 2002 , C. modesta de Man, 1905, C. nigroculata Sakai, 2002 , C. oblonga , C. parvula Sakai, 1988 , C. praedatrix , C. profunda , C. propinqua , C. spinophthalma , Cheramus orientalis , and Poti gaucho Rodrigues & Manning, 1992 . Sakai (2011) also established a new genus, Cheramoides , for Callianassa marginata , because of the structural difference in the male second pleopod. Komai & Fujiwara (2012) described a new species, Cheramus cavifrons , from Japan. Dworschak (2012) has clarified that Callianassa rectangularis , once synonymized with Callianassa bouvieri Nobili, 1904 by Sakai (1999; 2005), is actually a junior synonym of Paratrypaea maldivensis (Borradaile, 1904) . Sakai & Türkay (2014) transferred Biffarius pacificus Guzmán & Thatje, 2003 to Cheramus .

The status of the subfamily Cheraminae , originally proposed by Manning & Felder (1991), is rather questionable, although Tudge et al. (2000) supported the recognition of this subfamily. Molecular phylogenetic analysis by Felder & Robles (2009) estimated that two species referred to Cheramus are subordinated within a group of species referred to Callianassinae . We follow Felder & Robles (2009) and abandon Cheraminae for the time being.

Possibly diagnostic characters generally shared by species assigned to Cheramus include: rostrum spiniform; eyestalk with cornea being subterminal and lateral; antennular peduncle not much longer or stouter than antennal peduncle; distal margin of merus of third maxilliped not strongly produced; chelipeds unequal and dissimilar, of which the merus of major side lacks a prominent ventral hook, but sometimes with a ventral spine; female second pleopod lacking appendix interna; and third to fifth pleopods relatively narrow, with slender, digitiform appendices internae distinctly projecting beyond mesial margins of endopods. The development of the male first and second pleopods is known for the type species, Cheramus profundus : first pleopod slender, bi-segmented; second pleopod biramous ( Biffar 1973). It should be noted that male characters remain unknown for many species presently referred to Cheramus . Furthermore, Sakai (2011) referred several species similar to the species of Cheramus , for which male characters are unknown, to Trypaea Dana, 1852 , and the classification has been followed by his subsequent works ( Sakai 2010; Sakai & Türkay 2012, 2014; Sakai et al. 2014). Many workers have pointed out that a thorough revision is necessary to diagnose Cheramus and other genera of Callianassinae (e.g., Tudge et al. 2000; Dworschak 2003; Ngoc-Ho 2003, 2014; Poore 2008; Felder & Robles 2009). The generic assignment of the two new species made in this study is also merely provisional, because no male specimens were available.

Nevertheless, we can say that Sakai & Türkay’s (2014) assignment of Biffarius pacificus to Cheramus is highly questionable. Sakai (2011) transferred B. pacificus to Gilvossius Manning & Felder, 1992 , but this action was only based on character of the male second pleopod, which was not properly described by Guzmán & Thatje (2003) (Sakai estimated that the species does not have the male second pleopod). Later, Sakai & Türkay (2014) found that B. pacificus actually has a male second pleopod, and used this evidence to reassign B. pacificus to Cheramus . Furthermore, the authors claimed that the absence of appendices interna and masculina on the male second pleopod is sufficient to differentiate Cheramus from Gilvossius , but this character is common in Callianassinae , and not appropriate in this case. According to the original description by Guzmán & Thatje (2003), Biffarius pacificus is diagnosed by having an obsolescent rostrum and stubby appendices internae on the third to fifth pleopods slightly projecting beyond mesial margins of endopods, being distinct from other species assigned to Cheramus . It seems reasonable to retain the taxon in Biffarius for the time being.