An ecological transition during juvenile life in a marine snail

Abstract

Ecological shifts occurring after metamorphosis in benthic marine invertebrates have received much less attention than the more conspicuous transition occurring at metan~orphosis and settlement. It remains unclear whether postmetamorphic shifts occur simultaneously or at different times, and whether the shifts occur over brief, discrete periods or are extended or even continuous through juvenile life. The present study of the muricid gastropod Nucella emarginata exarmnes the ontogeny of \r.ulnerabillty to desiccation, of susceptibll~ty to hatchling predators, of shell coloration, and of distribution among microhabitats as a function of snail size. All the above parameters changed substantially over approximately the same size range. Individuals acquired the ability to survive direct exposure to desiccation for the duration of a low tide over the 3.1-6.5 mm shell length (SL) size range, and also became virtually invulnerable to hatchling predators when they reached 6.5 mm SL. The shift in mortality factors was paralleled by a change in shell colour over the 3-7 mm SL size range, and in distribution over the 3-8 mm SL size range. All shifts were therefore completed by the time individuals reached 8 mm, or by the age of -4 n~o based on growth rates in the laboratory. The coordination of these ecological changes in N. emarglnata over the 3-8 mm SL size range constitutes an ecological transition that partitions postinetamorphic life into 2 penods, early juvenile and late juvenile/adult, each with d~stinct selective environments and corresponding adaptive traits. A similar ontogenetic transition has also been documented in juvenile lobsters, and studies of juveniles of other species reveal that comparable ecological changes are common among benthic marine invertebrates. Interspecific variation is nevertheless expected in the exact nature and timing of the transition, particularly as a result of differences in initial juvenile size, growth rate, adult size, ability to learn, and motility.

Manipulating thermal stress on rocky shores to predict patterns of recruitment of marine invertebrates under a changing climate

“…For marine invertebrate larvae, the transition from the water column to the intertidal zone is usually characterised by high levels of mortality due to increased heat and desiccation stress (Gosselin 1997, Hunt & Scheibling 1997. In the present study, however, we found no effect of our thermal manipulation (i.e.…”

Long-term and trans-life-cycle effects of exposure to ocean acidification in the green sea urchin Strongylocentrotus droebachiensis

“…This increased energy cost is leading to decreased energy availability for later stages and/or during transition processes. Transitions such as gamete production or ontogenetic shifts are energetically expensive (Gosselin 1997). For example, 60 % of the energy stores accumulated by oyster larvae are expended during metamorphosis (Videla et al 1998).…”

Offspring size and maternal environments mediate the early juvenile performance of two congeneric whelks

“…For a range of taxa across a variety of habitats, individuals that start juvenile life with a large size often perform better than smaller conspecifics. This pattern has been shown for gastropods (Spight 1976, Gosselin 1997, Moran & Emlet 2001, mussels (Phillips 2002), barnacles (Thiyagarajan et al 2003), ascidians (Marshall et al , 2006, beetles (Fox 2000, Clark et al 2011, isopods (Tsai & Dai 2001), spiders (Walker et al 2003), fish (Green & McCormick 2005, Fisher et al 2007, and birds (Krist 2011). Therefore, intraspecific variation in offspring size is of fundamental ecological and evolutionary importance (Marshall & Keough 2008).…”