The comparative energetics of branchiopods: Adaptations to volatile environments

Patterns in eco-physiological traits of branchiopods are studied that are functions of underlying Dynamic Energy Budget (DEB) parameters. Most subgroups live in ephemeral waters, leaving them short time to complete their life cycle and survive as ephippia (winter-eggs) or cysts. Others, mainly the waterfleas, live of phytoplankton that show short -lasting blooms, leaving the grazers also little time to complete their life cycle. The waste-to-hurry strategy implies that branchiopods must have a high somatic maintenance to boost growth and reproduction, which is exactly what the 103 branchiopod species show in the Add_my_Pet collection of data on animal energetics and DEB parameter estimates. The consequences for assimilation are discussed. Weight at birth is linked to maximum weight for waterfleas, but not for brine, fairy, clam and tadpole shrimps. Parallels with unrelated taxa suggest that eggs size being independent of adult size is linked to metabolic acceleration. Weight at puberty is proportional to maximum weight for all groups. Maximum weight-specific neonate mass production shows little scatter as function of the allocation fraction of mobilised reserve to soma. This fraction is very high in fairy shrimps and has a broad range in waterfleas. The maximum neonate mass production was found to be proportional to the maximum respiration rate. The life-time cumulated neonate mass production is approximately equal to the maximum weight. The latter two findings for branchiopods are consistent with similar finding for many different taxa. Life span was again found to be inversely proportional to weight-specific respiration, which is remarkable for fairy shrimps: their very short life span is matched by a very high specific respiration. The fairy shrimps turn out to score lower on the supply-demand spectrum than waterfleas. Classic multidimensional scaling, applied to 12 traits of branchiopods, reveal a complete separation of Cladoceromorpha from the other Branchiopoda. The littoral chydorids and pelagic daphnids also came out separated within the Cladoceromorpha. This finding supports the common view that clam shrimps are a paraphyletic group.