Reproductive biology and life cycle of Leydigia louisi mexicana (Anomopoda, Chydoridae), a rare species from freshwater littoral environments

The family Chydoridae comprises a group of organisms that is relevant in an ecological sense, representing more than 40% of the total number of species of Cladocera recorded in Mexico until now. Leydigia louisi mexicana is a chydorid recently described in the "Los Baños" water reservoir (disappeared by now), located on the Central Mexican High Plateau. Scarce information exists on the maintenance and culture of Chydoridae in the laboratory in general, and on the reproductive biology of this species in particular. Therefore, the present work aimed at establishing the adequate conditions for the growth and reproduction of the species in the laboratory as a conservation strategy, considering that the type locality does no longer exist and the current distribution of this species is most restricted in Mexico. To this end, we experimentally studied the life cycle of L. louisi mexicana by developing a culture procedure in which we assessed three factors: food (Pseudokirchneriella subcapitata and Saccharomyces cerevisiae), type of substrate (commercial soil and artificial sediment), and temperature (20 and 25°C). Experiments were performed through individual assessment of reproductive responses, and by life table analysis. The highest longevity (52.70 ± 2.16 d) was observed in organisms fed S. cerevisiae, on artificial sediment, at 20°C. The highest fecundity (22.3 ± 0.86 neonates), the largest number of clutches (14 ± 0.52), and the highest intrinsic rate of population growth (r = 0.19 ± 0.007 d^-1) were recorded in organisms fed with S. cerevisiae, on artificial sediment, at 25°C. The shortest generation time (T = 18.15 ± 0.59 d) was recorded when L. louisi mexicana was fed P. subcapitata, on artificial sediment, at 25°C. The best reproductive responses were obtained when L. louisi mexicana was fed S. cerevisiae, on artificial sediment. The procedure developed provides fundamental biological information, and could be an option for the maintenance and propagation of other chydorids.