The status of the Australian genus Caridinides Calman, 1926 (Crustacea: Decapoda: Atyidae) with reference to recent phylogenetic studies.

Traditionally four subfamilies have been recognised within Atyidae (Holthuis 1986) based on an expanded version of Bouvier’s (1925) “série” concept, namely Atyinae De Haan, 1849, Caridellinae Holthuis, 1986, Paratyinae Holthuis, 1986, and Typhlatyinae Holthuis, 1986. The distinction between these subfamilies and the assignment of genera to them was based on the relative development of exopods on the pereiopods, the branchial formulae, pigment presence and reduction of eyes, the number of spines on the uropodal diaresis, as well as the shape and proportions of the chelipeds. In recent years, this subfamily division has not been consistently used in primary taxonomic literature (see Richard et al. 2012) and a growing body of phylogenetic studies have cast considerable doubt on their relevance to common ancestry. This phylogenetic work recently culminated in the comprehensive study of von Rintelen et al. (2012), who included 32 genera (out of the 42 then known) in analyses of one mitochondrial (16S) and two nuclear genes (28S, H3). They found no molecular support to continue to recognise subfamilies as phylogenetic realities, and suggested using informal group names for the five deep clades they recovered. On a more inclusive level, the study of von Rintelen et al. (2012) also highlighted considerable levels of nonmonophyly in Caridina as currently defined, which had been alluded to before (Page et al. 2007a). Most importantly, from a traditional systematic point of view, was the fact that 13 genera were recovered as embedded within their Caridina sensu lato clade (their “Caridella-group”), including Atyella Calman, 1906, Caridinides Calman, 1926, Caridinopsis Bouvier, 1912, Caridella Calman, 1906, Edoneus Holthuis, 1978, Limnocaridina Calman, 1899, Marosina Cai & Ng, 2005, Neocaridina Kubo, 1938, Paracaridina Liang, Guo & Tang, 1999, Parisia Holthuis, 1956, Pycneus Holthuis, 1986, Pycnisia Bruce, 1992 and Sinodina Liang & Cai, 1999. Lancaris Cai & Bahir, 2005 is also closely related to this clade, and falls within it in some analyses. All of these genera are morphologically close to Caridina sensu stricto, and are either troglobitic with considerable morphological adaptations (e.g., Edoneus, Marosina, Pycneus) or are considered different at generic level from Caridina on the basis of the same suite of characters used to delineate subfamilies (e.g., Atyella, Caridinides, Paracaridina). This raises important questions as to the delineation of the majority of genera in Atyidae, and suggests a revision of the morphological characters on which these taxa have been traditionally based. The aim of the present contribution is to re-assess the unique, single morphological character that separates the monotypic, Australian genus Caridinides from Caridina. Caridinides was erected by Calman (1926) for a single species, C. wilkinsi Calman, 1926, discovered in the Cape York Peninsula, Queensland, Australia. The generic diagnosis reads: “...resembling Caridina, but having a welldeveloped exopod on the first pair of chelipeds. No supra-orbital spine. Chelipeds of the Caridina-type, carpus of first pair slightly excavated. An arthrobranch at the base of first chelipeds (nine pairs of gills). A number of spines on exopod of uropods...”. Calman himself already pointed out that, except for the presence of the exopod on the first pereiopod, the species was a normal Caridina, which he thought to belong to the Caridina nilotica group. This is perhaps reflected in the etymology of the name he chose, which means “son of Caridina”. He further states that he uses the generic name as a measure of practical convenience and not to indicate that the species may be phylogenetically more primitive than Caridina. Johnson (1961) already raised some doubts whether the presence of an exopod on the first pereiopod alone would be sufficient to maintain Caridinides as distinct, and suggested the species should perhaps be transferred to Caridina. Smith & Williams (1982) elegantly re-described and fully illustrated the species on the basis of extensive material from across