Supply of competent larvae to the benthic habitat is a major determinant of population dynamics in coastal and estuarine invertebrates with an indirect life cycle. Larval delivery may depend not only on physical transport mechanisms, but also on larval behavior and physiological progress to the competent stage. Yet, the combined analysis of such factors has seldom been attempted. We used time-series analyses to examine tide-and wind-driven mechanisms responsible for the supply of crab megalopae to an estuarine river under a major marine influence in SW Spain, and monitored the vertical distribution of upstream moving megalopae, their net flux and competent state. The species Panopeus africanus (estuarine), Brachynotus sexdentatus (euryhaline) and Nepinnotheres pinnotheres (coastal) comprised 80% of the whole sample, and responded in a similar way to tide and wind forcing. Tidal range was positively correlated to supply, with maxima 0 to 1 d after spring tides, suggesting selective tidal stream transport. Despite being extensively subjected to upwelling, downwind drift under the effect of westerlies, not Ekman transport, explained residual supply variation at our sampling area. Once in the estuary, net flux and competence state matched the expected trends. Net upstream flux increased from B. sexdentatus to P. africanus, favoring transport to a sheltered coastal habitat (N. pinnotheres), or to the upper estuary (P. africanus). Competence state was highest in N. pinnotheres, intermediate in B. sexdentatus and lowest in P. africanus, as expected if larvae respond to cues from adequate benthic habitat. P. africanus megalopae were found close to the bottom, not above, rendering slower upstream transport than anticipated. KEY WORDS: Upwelling · Ekman transport · Downwind drift · Selective tidal stream transport · Larval net flux · Bay of Cádiz Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 410: [125][126][127][128][129][130][131][132][133][134][135][136][137][138][139][140][141] 2010 1988, Palmer et al. 1996) makes dispersal neutral or even disadvantageous (Strathmann et al. 2002). An ontogenetic migration function has been hypothesized to better explain larval offshore exportation (Strathmann et al. 2002). Offshore migration of early life-cycle stages would reduce predation, expose larvae to a more tolerable environmental variability and, occasionally, diminish food competition with benthic suspension feeders in coastal or estuarine areas. Still, the migration back to adult habitats depends on how far the larvae migrate from the parental area, their behavioral capabilities and the water current patterns they are exposed to (Sponaugle et al. 2002).As coastal (Caley et al. 1996, Armsworth 2002) and estuarine (Bilton et al. 2002) benthic populations may often be recruitment-limited, larval supply and settlement success are critical processes for their maintenance (Gaines & Roughgarden 1985, Roughgarden et al. 1988. Understanding the mechanisms responsible for...

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During the mass settlement events of brachyuran crabs, there is a significant chance of density-dependent injury in the megalopae (last larval stage) because cannibalism can occur by larger conspecifics. Laboratory observations revealed that the appendages that are more prone to injury 15 are eyestalks, as well as first (P1) and fifth (P5) pereiopods. The ability of Carcinus maenas megalopae to autotomize these structures and the effect of such injuries in their feeding ability and metamorphosis were investigated. All tested specimens were able to autotomize one or both of their P1 and P5, but not their eyestalks. Megalopae missing a single P1, 20 as well as one or both P5, were able to capture and ingest prey, as well as intact specimens. Megalopae with either P1 and P5 appendages or at least one damaged eyestalk failed to ingest sufficient food to reach the nutritional threshold required for successful metamorphose.