Leydigia (Neoleydigia) acanthocercoides (Fischer, 1854)

Kotov, Alexey A., 2009, A revision of Leydigia Kurz, 1875 (Anomopoda, Cladocera, Branchiopoda), and subgeneric differentiation within the genus, Zootaxa 2082 (1), pp. 1-84 : 48

Leydigia (Neoleydigia) acanthocercoides species group

Diagnosis. Sufficient characters. (1) only two large distal setae and a single small lateral seta on exopodite III; (2) setules in lateral fascicles on labral keel long, numerous; (3) setules in the middle of posterior margin of valve shorter than those near posteriormost seta.

Necessary characters. (4) on anterior margin of labral keel setules long, reaching its apex; (5) tufts of setules present on posterior margin of keel; (6) setules between marginal setae in the middle of ventral margin of valve long.

Taxonomical comments. Kotov et al. (2003b) demonstrated that characters commonly used for the discrimination of species within this group (i. e. 'dots on valves' instead of striation, 'presence' or 'absence' of a basal spine, ocellus size and shape) are inconsistent. Due to this, we cannot check the accuracy of the majority of previous identifications, and I can give comments only on populations from more or less close to the type localities for all described species. Sometimes it is possible to draw conclusions based on examination of type material (e.g. L. laevis Gurney, 1927 ; L. ankammaraoi Prasad, Santa Kumari et Bose, 1985 ).

At this moment, I have only a preliminary view on the differentiation of species within the acanthocercoides -group, because (1) L. acanthocercoides , type species of the subgenus Leydigia (Neoleydigia) , needs to be re-investigated, especially from non-European localities; (2) differences between L. ciliata and L. acanthocercoides , the two most common species from this group in Eurasia, are reported here on the basis of only limited material of the latter; (3) although South American species are well-separated from Afro-Asian species, their determinations have not been confirmed by examination of topotypic material.

Distribution. Members of the acanthocercoides -group are widely distributed on all continents, except Antarctica; this is the most common group of the genus in the tropics and subtropics. Many previous descriptions and records cannot be attributed with certainty and are not cited here.