Morphology and biometry of two Chinese diploid parthenogenetic Artemia populations with a special emphasis on the gonopods and frontal knobs of rare males

Morphological and biometric characters of rare males and females of two diploid parthenogenetic populations from Gahai Lake (GH) and Chengkou Saltern (CK-par) (China) were surveyed. The characters were compared with those of six bisexual species. The gonopod of rare males consists of a basal portion and a distal portion. The distal portion of the gonopod ends in a fine digitiform apex and is ornamented with numerous spines (distal gonopod spines). The number and height of spines on the posterior surface (posterior spines) are conspicuously larger than spines on the exo-lateral surface (exo-lateral spines). The morphology of distal gonopod spines of rare males is most closely related to Artemia urmiana, but posterior spines are apparently taller in the rare males than in A. urmiana. Frontal knobs of rare males are sub-spherical in lateral view, and sub-elliptic in frontal view. The large diameter against small diameter ratio of the frontal knob of GH is significantly larger than that of CK-par. The number of frontal knob spines in rare males is close to that of Artemia salina, Artemia franciscana and Artemia persimilis, but significantly smaller than that of Artemia sinica, Artemia tibetiana and A. urmiana. The number of solitary spines of GH is significantly smaller than that of CK-par. Discriminant analyses using 13 parameters in females and 24 parameters in males show that GH and CK-par are close to each other but divergent from bisexual species. The analytical result based on male genital parameters is likely to be more coincident with the molecular phylogeny than that based on the non-sex-related parameters.