Elephantis, Castelin & Marquet & Klotz, 2013

Castelin, Magalie, Marquet, Gerard & Klotz, Werner, 2013, Elephantis, a new genus for Caridina natalensis Bouvier, 1925 from eastern rivers of Madagascar, Zootaxa 3702 (6), pp. 573-586 : 576

Elephantis gen. nov.

Type species: Caridina natalensis Bouvier, 1925 , by present designation and monotypy.

Diagnosis. Small Caridina -like crustacean; carapace without supraorbital spine, with well-developed antennal spine; third maxilliped ending in a claw-like spine; 9 pairs of gills, podobranch on second maxilliped well developed, well developed (with distal hooks) epipods on third maxilliped and first to fourth pereiopod; third pereiopod moderately strong, merus inflated, propodus sexual dimorphic, with numerous scattered spinules on posterior margin in males, with few spinules arranged in two rows in females; endopod of first pleopod of males broadened distally, appendix interna arising from distal ¼ of endopod; appendix masculina on males second pleopod club-shaped, longer than endopod in adult males, armed with a row of strong spines on inner margin and a bottle-brush like spinulation on distal 1/3, appendix interna arising from about 0.4 times length of appendix masculina.

Remarks. The holotype of C. natalensis was not available for the present study. Indeed the detailed description and drawings of Richard & Clark (2009, fig.7-8) in their work on African Caridina let no doubts on the identity of the present specimen. Caridina natalensis resembles other species of this genus in branchial formula and shape of chelipeds. Some characters of this species, especially the structure of male sexual appendages is clearly different from all other members of Caridina . Since shape of sexual appendages are frequently used as diagnosis criteria in atyid genera ( Kubo, 1938; Chace, 1983; Cai, 2010), a new genus, Elephantis gen. nov. is proposed here for this species.

The conspicuous enlargement of the appendix masculina with appendix interna arising from about 0.4 times length of appendix masculina differs this species from all other members of Caridina . The shape of endopod of first pleopod in males (dilated distally) was used as a distinguishing feature from Caridina when Kubo erected the new genus Neocaridina in 1938 ( Kubo, 1938). The endopod of first pleopod is also dilated in Elephantis but this species could be differentiated from all known members of Neocaridina by bearing long spines on distal margin of this appendage (versus distal margin without long spines and anterior surface of endopod beset with numerous small spinules in Neocaridina ) and appendix interna is arising from distal ¼ of endopod (versus arising from basal part in Neocaridina ). The appendix masculina on male’s second pleopod is kidney- or taper-shaped in Neocaridina and thus clearly different from the enlarged club-shaped structure in Elephantis . The proposed new genus is also different from Caridina and Neocaridina showing robust 3rd perieopods with merus inflated. From most species assigned to these two genera Elephantis could be differentiated by the sexual dimorphism of the propodus of 3rd and 4th pereiopod. The inner margin of propodus of these pereiopods is beset with numerous small spinules in male specimen whereas just two rows of medium-sized spinules are shown on propodus of females. A similar form of sexual dimorphism is shown in members of the Caridina pareparensis species group known from Sulawesi, Indonesia ( Klotz & von Rintelen, 2013). All members of this species group are different from Elephantis showing a stick-like, slender appendix masculina not reaching to distal end of endopod and a non-dilated endopod of male´s first pleopod. The new genus is only represented by one species Elephantis natalensis comb. nov. known from South Africa and Madagascar.

Etymology. Elephantis is a humorous name after an ancient Greek erotical poetess in reference to the enlarged sexual appendages of males. Gender is feminine.