Ctenocheloides, Arthur Anker, 2010

Arthur Anker, 2010, Ctenocheloides attenboroughi n. gen., n. sp. (Crustacea: Decapoda: Axiidea: Ctenochelidae), a new ghost shrimp with pectinate claw fingers from Madagascar, Journal of Natural History 44 (29), pp. 1789-1805 : 1790-1792

Genus Ctenocheloides n. gen.

Diagnosis

Carapace with moderately developed dorsal oval; cardiac prominence present; cervical groove clearly delimited; linea thalassinica running complete length of the carapace. Frontal margin of carapace rounded, without rostral spine and median ridge. First abdominal somite weakly sclerotised, without anterolateral lobes; third to fifth abdominal somites with dense setal rows. Eyestalks somewhat flattened dorsally; corneas relatively well pigmented, dorsal, subterminal. Antennular peduncle shorter and not stouter than antennal peduncle; antennal scale well developed, subacute distally. Scaphognathite of maxilla without long seta on posterior lobe. Second maxilliped without exopod, with rudimentary epipod. Third maxilliped without exopod; ischiomerus pediform; merus with large spine mesially; propodus and dactylus slender. Chelipeds weakly unequal in size and asymmetrical in shape. Major cheliped with ischium armed with teeth on ventral margin; merus with small tooth; carpus short, unarmed; palm ovoid in cross-section, mostly smooth; fingers slender, slightly longer than palm, pectinate. Minor cheliped generally similar to major cheliped, with shorter fingers. Second pereiopod cheliform. Third pereiopod with subrectangular propodus, latter with strong distal spiniform seta on ventral margin. First female pleopod uniramous. Second male pleopod unknown. Second female pleopod biramous, with appendix interna. Third to fifth female pleopods foliaceous, with stubby, projecting appendices internae. Uropodal exopod ovate, without distinct lateral incision, fringed with row of strong spine-like setae.

Type species

Ctenocheloides attenboroughi n. gen., n. sp., by monotypy and original designation.

Species included

Only the type species.

Etymology

The name of the new genus indicates its close affinities to the genus Ctenocheles (the Latin suffix -oides derived from the Greek eidos=εIδος for form, likeness, appearance, resemblance); gender is masculine.

Distribution

South-western Indian Ocean ( Madagascar).

Remarks

Ctenocheloides n. gen. shares numerous morphological features with Ctenocheles , one of the most important being the general shape of the major cheliped, with its elongate, pectinate fingers. Other features that these two genera have in common are the more or less strongly pectinate fingers of the minor cheliped; the very similar second to fifth pereiopods and mouthparts; and the general shape of the abdomen and telson. However, Ctenocheloides n. gen. is readily distinguishable from Ctenocheles in several important aspects. In Ctenocheloides n. gen., the frontal margin of the carapace is broadly convex, without an anteriorly projecting rostral spine ( Figure 1 A), whereas in all species of Ctenocheles , the rostral spine is well developed ( Poore and Griffin 1979; Rodrigues 1978) and sometimes toothed dorsally ( Le Loeuff and Intès 1974; Matsuzawa and Hayashi 1997; Sakai 1999). Furthermore, in Ctenocheloides n. gen., the corneas are relatively well developed ( Figure 1 A, B); this is not the case in Ctenocheles , in which the corneas are small and poorly pigmented ( Rodrigues 1978; Sakai 1999). The fingers–palm ratio of the major cheliped is significantly lower in Ctenocheloides n. gen. (∼1.2), compared with Ctenocheles (>2; Holthuis 1967; Sakai 1999), except for C. collini (1.4; Ward 1945; Poore and Griffin 1979). Generally, the major cheliped fingers of Ctenocheloides n. gen. are more slender and weaker compared with those of Ctenocheles . In addition, the major chela palm of Ctenocheloides n. gen. appears to be more swollen and the longest and strongest teeth on the finger cutting edges are not as pronounced as those of Ctenocheles . Most species of Ctenocheles have a lateral incision on the uropodal exopod ( Le Loeuff and Intès 1974; Manning and Felder 1991; Rodrigues 1978; Sakai 1999); this incision is lacking in the new genus. The development of the dorsal oval may also be used to distinguish these two genera: in Ctenocheloides n. gen., the gastric region is somewhat elevated compared with the cardiac region; in Ctenocheles , the gastric and cardiac regions are at about the same level.

Ctenocheloides n. gen. may be separated from all other genera currently placed in the family Ctenochelidae ( Manning and Felder 1991; Poore 1994; De Grave et al. 2009) or Gourretiidae (sensu Sakai 2006) by the pectinate cheliped fingers, and from most of them by the absence of a rostral spine.

Figures

Figure 1. Ctenocheloides attenboroughi n. gen. n. sp., holotype, female from Nosy-Bé, Madagascar (FLMNH UF Arthropoda 13902). (A) Frontal region, dorsal view; (B) frontal region, lateral view; (C) antenna, detail of basicerite and scaphocerite; (D) carapace and some frontal structures (eyestalks, epistome), lateral view; (E) carapace, dorsal view; (F) ventral (sternal) view of cephalothorax and first abdominal segment; (G) detail of first abdominal somite, lateral (left) view.