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Ostracods have discontinuous development, marked by ecdyses, and determinate growth. Ontogenetic studies have suggested a pattern of nine postembryonic stages (eight juvenile phases and the adult) for the main freshwater ostracod superfamilies Cypridoidea, Cytheroidea and Darwinuloidea. However, cases of a supposed extra moult in the adult stage have been proposed for some ostracod species, which would amount to 10 postembryonic growth stages. One such example isElpidium bromeliarumMüller, 1880, a cytheroidean that inhabits tank-bromeliads. The present study is aimed at investigating the ontogenetic development ofE. bromeliarumusing width and length measurements, as well as carapace and appendage morphology in order to test the existing hypothesis of an additional growth stage in adults of this species. Our results revealed nine postembryonic growth stages (eight juvenile and the adult), with sexual dimorphism beginning its expression in the last juvenile stage. Thus, the ontogenetic development ofE. bromeliarumagrees with the overall pattern observed for podocopid ostracods and the hypothesis of 10 postembryonic growth stages was not corroborated. We argue that the inability to differentiate juveniles from adults, or different species from one another, may have misled to the assumption of an additional moult inE. bromeliarum. [ABSTRACT FROM AUTHOR]

The phoretic behaviour of ostracods ( Elpidium bromeliarum) andannelids ( Dero superterrenus) that inhabit tank bromeliads was studied. Our previous field observations had shown that bromeliad ostracods can be found attached to the skin of amphibians and reptiles that move among bromeliads, probably allowing the ostracods to colonise new tanks. In this paper, we present the first record of bromeliad annelids found attached to frogs moving among bromeliads in the field. We have also enlarged the database on bromeliad ostracods engaged in phoretic association with terrestrial vertebrates in three locations in southeastern Brazil. In our laboratory experiments bromeliad annelids show a strong significant tendency to climb onto papers that had been in contact with frog skin when compared with control papers, indicating a kind of chemically oriented behaviour. Bromeliad ostracods, on the other hand, attached themselves to treated and untreated papers with same frequency. When brought into contact with various species of frogs and lizards, the bromeliad annelids and ostracods both presented preference to attach themselves to frogs, but the annelids showed a stronger preference to attach to frogs and to avoid attachment to lizards. Another experiment demonstrated that bromeliad annelids are much more prone to dehydration than are ostracods. We suggest that the chemically oriented behaviour presented by bromeliad annelids toward frogs could diminish the risk of death by dehydration during the transport among bromeliads due to the moist characteristic of frog skins. [ABSTRACT FROM AUTHOR]