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Developmental changes in the bioenergetics of decapod larvae

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Citation:
Anger, K. (1991): Developmental changes in the bioenergetics of decapod larvae , Memoirs of the Queensland Museum, 31 , pp. 289-308 .
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Abstract:

Developmental changes in bioenergetic traits of larval Decapoda are reviewed, comparing subsequent stages of a moult cycle, larval instars, or different taxa that are considered to represent a phylogenetic sequence. Recent data suggest that some developmental trends in energy partition-ing might be similar on all these levels of comparison. These tendencies imply: decreasing instantaneous growth rates, increas-ing metabolic loss, decreasing net growth efficien-cy, and an increasing dependence on energy reserves accumulated in earlier stages of development. They are interpreted as signs of an increasing degree of lecithotrophy in late stages of a moult cycle, late instars of larval development, or in evolutionary advanced taxa within a phylogenetic sequence, respectively. Biochemical changes suggest a developmental shift in predominant growth mechanisms, from hypertrophy (enlargement of cell size, accumulation of lipid reserves) toward hyperplasy (increase in cell number, protein accumulation). Within a moult cycle, the latter phase becomes in principle independent of external energy supply, when a critical point (the "point of reserve saturation", or "D0 threshold"), has been passed. Such a bioenergetic transition, from a phase of energy accumulation to one of epidermal reconstruction, can occur also between successive instars of development: in hermit crab development, the megalopa reaches metamorphosis exclusively with energy accumulated by preceding instars. This mode of development, termed secondary lecithotrophy, is interpreted as an adaptation to extremely specialized habitat requirements (here: a mollusc shell). In the sequence Caridea-Astacidea-Anomura-Brachyura, there is an increasing trend in the average carbon/nitrogen ratio of larvae. This suggests an evolutionary tendency in the larval development of the Decapoda toward an increasing lipid content and possibly, increasing degrees of secondary lecithotrophy and habitat specialization. It corresponds with decreasing trends in the number and variability (the latter both in relation to number and morphology) of larval instars, and an increasing degree of morphological change during development.

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