Ontogeny of respiratory function in crustaceans exhibiting either direct or indirect development

<jats:title>Abstract</jats:title><jats:p>Dialysed haemolymph from the planktonic larvae of the Norwegian lobster <jats:italic>Nephrops norvegicus</jats:italic> possessed a lower O<jats:sub>2</jats:sub> affinity than the benthic adult stage at equivalent pH. This difference could be correlated with the ability to maintain O<jats:sub>2</jats:sub> uptake during progressive hypoxia; adult individuals showed better developed regulation than the larvae. The intrinsic O<jats:sub>2</jats:sub> affinity of both larval and adult haemocyanin (Hc) could be modified by preexposure to chronic hypoxia. In contrast, there were no significant differences noted in either Hc O<jats:sub>2</jats:sub> affinity or the ability to regulate O<jats:sub>2</jats:sub> uptake during progressive hypoxia between newly hatched and adult individuals of the direct developing amphipod <jats:italic>Echinogammarus pirloti</jats:italic>. Unlike the case in <jats:italic>N. norvegicus</jats:italic> preexposure to chronic hypoxia did not result in any change in respiratory performance at the level of the whole animal or in intrinsic Hc O<jats:sub>2</jats:sub> affinity. The changes (or absence of them) in these aspects of the respiratory biology of the two species examined are discussed in the context of their ecological requirements. © 1995 Wiley‐Liss, Inc.</jats:p>