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Developmental biology of Armases miersii (Grapsidae), a crab breeding in supratidal rock pools. 1. Facultative lecithotrophy of larval stages

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  • Medicine

Abstract

Starvation resistance in the larvae of a grapsid crab, Armases miersii, that breeds in supratidal rock pools in Jamaica was examined by point-of-no-return (PNR) and point-of-reserve- saturation (PRS) experiments. A. miersii shows an abbreviation of larval development (only 3 zoeal stages) and a high degree of lecithotrophy in the zoea I and II stages. In complete absence of food, larval development is possible from hatching to the zoea III stage. The potential for endotrophic development decreases during ontogeny: the zoea I is, in principle, entirely independent of food, without significant effects of starvation on survival; the zoea II shows significantly higher mortality under continued lack of food (since hatching) and delayed development after initial temporary starvation; the zoea III can also develop independently of food, but only if the preceding stages were fed continuously. Hence, no PNR or PRS can be given for individual zoeal stages of this species. Late effects of early feeding or starvation indicate that lecithotrophy in A. miersii is only facultative, i.e. food is not essential in the beginning of larval life, but it will be taken up when available. Conspicuous intraspecific variability in the degree of lecithotrophy was observed in larvae originating from 2 different females. In a hatch with particularly high endotrophic potential (but not in nutritionally more vulnerable larvae), development was significantly faster under starvation. This effect is interpreted as a change in energy partitioning: lack of food may induce a signal for switching from growth (accumulation of exogenous energy) to rapid mobilization of internal reserves (accelerated development, termination of the nutritionally vulnerable planktonic larval phase). Feeding after initial starvation may cause inverse effects, i.e. slower development, replacement of utilized reserves, and accumulation of additional energy for later stages. This switching should occur only in facultatively lecithotrophic larvae that have sufficient internal energy reserves to allow for this opportunistic bioenergetic strategy. Compared with most planktotrophic marine decapod larvae, the zoeal stages of A. miersii show higher starvation resistance and endotrophic potential. These ontogenetic traits are considered adaptations to breeding and larval development in a short-lived, nutritionally unpredictable habitat.

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