RESOURCE QUALITY EFFECTS ON DAPHNIA-LONGISPINA OFFSPRING FITNESS

The present study addressed the question: is the fitness Daphnia longispina neonates related to the quality (species) of the resource their mothers consumed? A 2 x 2 factorial design with two maternal and neonate resource types was employed, with Rhodomonas and Microcystis used as high- and low-quality resources, respectively. Neonate fitness was assessed using demographic parameters obtained from a life-table study. The resource type neonates consumed always had a stronger effect on the neonates than did the maternal type. Neonate consumption of Rhodomonas, relative to Microcystis, increased fitness. Its estimated by the instantaneous population growth rate, by 25-28%, while maternal consumption of Rhodomonas increased fitness by 6-8%. Neonate Rhodomonas consumption also reduced the age at reaching the primiparous instar; increased brood size at the primiparous instar and body length immediately after the primiparous instar; increases average clutch size, number of clutches produced, total egg production, and mean body length up to and on age 30 days. Regardless of resource type, maternal Rhodomonas consumption resulted in neonates which reached maturity at an earlier age and had a larger individual size immediately after reaching maturity. The mean clutch size, total egg production. and length up to. and at age 30 days were all significantly affected by maternal diet when neonates consumed Microcystis; however, these variables were not influenced by maternal type when neonates consumed Rhodomonas. This is the first study to document maternally mediated effects of resource quality on the fitness of crustacean zooplankton neonates.