Description of the male of Coronatella paulinae (Crustacea, Branchiopoda, Chydoridae) with an identification key for the genus based on the male morphology

Abstract

Cladoceran males are not very frequent in natural populations, since they are only produced in stress situations. Thus, only a few species have had the male morphology described. Nevertheless, whenever data concerning the morphology of males is available, they are used as a tool to resolve taxonomic problems. In this study, the morphology of Coronatella paulinae Sousa, Elmoor-Loureiro and Santos, 2015 (Cladocera: Chydoridae) was described and compared to other species within the genus. Coronatella paulinae shares the diagnostic morphological traits typically attributed to the genus: (1) gonopores opening ventrally, subapically to the postabdominal claw; (2) marginal setulae arranged in groups on the postanal margin; (3) Inner Distal Lobe (IDL) armed with three setae, of which one is the male seta. `The absence of lateral aesthetascs on male antennules might also be an important diagnostic character for the genus, since they are present in other Aloninae groups. Coronatella paulinae males present a unique combination of morphological traits on the postabdomen, which distinguish them from other Coronatella Dybowsky and Grochowski, 1894 species, such as a marked postanal angle and an almost straight basal spine, longer than the mid-length of the postabdominal claw.