Planktonic availability, molt stage and settlement of blue crab postlarvae

Abstract

We quantified (1) spatio-temporal variation in molt stage (developmental state) of blue crab Callinectes sapidus megalopae (postlarvae), and (2) the relationship between planktonic availability, molt stage and settlement of megalopae during peak settlement in Chesapeake Bay, USA. Settlement was significantly correlated with the planktonic availability of megalopae. Developmental state of megalopae also appeared influential in settlement because (1) blue crab megalopae displayed quantifiable changes in molt stage; (2) molt stage of megalopae varied on a temporal scale of days to 1 mo or more, and a spatial scale of kilometers, apparently reflecting the physiological progression through the molt cycle by megalopae pulsing through settlement habitats; and (3) molt stage of megalopae advanced in collections from the plankton, on artificial settlement habitats, and in the benthos, indicating the approach to settlement, metamorphosis and a benthic existence. In addition, settlement was not necessarily obligatory untd sometime in late premolt, as many megalopae collected in the plankton were in late premolt. Hence, megalopae have the time in which to exercise some degree of habitat selection. Our findings show that settlement of a benthic invertebrate is regulated partly by the planktonic availability of postlarvae, and that these postlarvae progress through a predictable series of changes in developmental state as they invade settlement habitats. Thus, a quantitative measure of postlarval developmental state appears useful in relating planktonic availability of postlarvae to natural settlement patterns. Similar alterations in developmental state occur in the larval and postlarval stages of marine fish and a wide range of invertebrate taxa, indicating the potentially broad applicability of quantitative measures of developmental state in studies of settlement.

Relationship of habitat and spatial scale with physiological state and settlement of blue crab posttarvae in Chesapeake Bay

“…Our results agreed with those of Lipcius et al (1990), who found variation in developmental state of megalopae on smaller spatial and temporal scales. This study further advances the idea that changes in physiological state coincide with the timing of megalopal reinvasion and settlement.…”

Delayed metamorphosis of a tropical reef fish (Acanthurus triostegus):a field experiment

“…The paucity of evidence for demersal fishes contrasts with an extensive body of invertebrate literature, for which delays in settlement are well documented and experimentally examined (e.g. Richmond 1985, Lipcius et al 1990, Pechenik 1990, Pechenik et al 1993, Davis 1994, Harvey 1996, Stoner et al 1996. The present study is the first to experimentally examine in the field the capacity of a fish species to delay metamorphosis.…”

“…Morphological criteria have been used to determine the generality in the occurrence of delayed metamorphosis in the field for marine invertebrates with some success (e.g. Emlet 1986, Fenaux & Pedrotti 1988, Lipcius et al 1990. Similarly, Holmes et al (1994) successfully used specific minima of length and weight in spring to predict which lampreys (Petromyzontiformes) would metamorphose the following summer.…”

Tide and wind control of megalopal supply to estuarine crab populations on the Portuguese west coast

“…In crab megalopae competence depends on the physiological stage of the larvae . Several studies indicate a progression of the intermoult stage of crab megalopae as they approach settlement habitats (Metcalf & Lipcius 1992, Morgan et al 1996, Zeng et al 1997, Moksnes & Wennhagen 2001, and differences in intermoult stage can sometimes be found within estuaries (Lipcius et al 1990). It is possible that the delay between supply and settlement in the Mira Estuary could be due to supply from a pool of megalopae in an earlier stage of development (Hasek & Rabalais 2001).…”