Tolerance limits of early live history stages and their relevance for the biodiversity and biogeography of reptant decapod crustaceans

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Reptant decapod crustaceans are almost absent in Antarctic waters. One reason could be that reptant decapoda mainly exhibit planktotrophic (feeding) larvae. Taxa with planktotrophic larvae always show a clear decrease toward high latitudes. King crabs (Lithodidae), which have recently been found in sub-Antarctic and Antarctic waters, mainly show lecithotrophy (non-feeding) with abbreviated larval phases and might be able to recolonize Antarctic waters. Lecithotrophic larvae might be more tolerant to cold waters in comparison to planktotrophic larvae.In order to test the hypotheses of thermal tolerance of crab larvae, the following working hypothesis using reptant decapod species as a model group are proposed:1. Thermal tolerance windows of lecithotrophic larvae, measured from the cellular to the organismic level, are broader compared to planktotrophic larvae. This favours species with lecithotrophic larvae at extreme low and high temperatures.2. Compared to planktotrophic larvae lecithotrophic larvae show a minimization of baseline energy costs at maximized developmental time but reduced scopes for activity, which reflects trade-offs between maintenance costs, development and activity of lecithotrophic versus planktotrophic larvae. The goal is to unravel the relevance of developmental modes (lecithotrophic versus planktotrophic) and larval thermal tolerance for the biodiversity and biogeography of reptant decapod crustaceans exhibiting predominately planktotrophic larvae.