Characterizing temperate rocky shores from the perspective of an early juvenile snail: the main threats to survival of newly hatched Nucella emarginata

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.

Section: Introductionmentioning

confidence: 87%

An ecological transition during juvenile life in a marine snail

Gosselin¹

1997

“…Protection from predators: The effectiveness of these rnicrohabitats as shelters from hermit crabs Pagurus spp, and shore crabs Hemigrapsus nudus, the main predators of hatchlings (Gosselin & Chia 1995), was examined in the laboratory. Each plate was placed in a cage slightly larger than the plate itself (modified food containers, 9.5 X 9.5 X 6 cm, with 610 pm mesh screening).…”

Section: Methodsmentioning

confidence: 99%

“…The distribution of early juvenile N. emarginata in the field has not been determined, but hatchlings of an Atlantic specles, Nucella lapillus, have been observed on the underside of rocks (Moore 1938) and in empty barnacle shells, but not on open rock surfaces (Feare 1970), suggesting a non-random distribution. Although newly hatched N , emarginata are most vulnerable to desiccation and predation by decapod crustaceans (Gosselin & Chia 1995) and are unable to grow on energy reserves remaining from the e g g capsule (Gosselin & Chia 1994), it is not known whether the provision of shelter from mortality factors or the distribution of prey are important determinants of the distribution of early juveniles.…”

Section: Introductionmentioning

confidence: 99%

Distribution and dispersal of early juvenile snails:effectiveness of intertidal microhabitats as refuges and food sources

Gosselin¹,

Chia²

1995

In Barkley Sound, British Columbia, Canada, newly hatched Nucella emarginata, a direct developing prosobranch gastropod, are almost exclusively located within 3 structurally complex microhabitats: the filamentous algae Cladophora columbiana, clusters of mussels Mytilus spp., and dense assemblages of the barnacle Semibalanus cariosus. When exposed to desiccation or predators for 4 to 5 h, mortality of hatchlings located in these microhabitats (1.7 to 36% mortality) was considerably lower than for individuals on open surfaces (99 to 100%). Also, food (prey species) in C. columbiana, mussel clusters, and S. cariosus microhab~tats was more abundant but of similar energetic value to that on open rock surfaces. The microhabitats used by early juvenile N. emarginata thus provide the double advantage of a considerably reduced risk of mortality and abundant prey. The means by which hatchlings disperse after emerging from their egg capsules were established by laboratory observations and by deployment of collectors in the field. Hatchlings do not actively initiate dispersal by drifting in the water column. Crawling is the usual means of travelling from the capsule to protective microhabitats, with hatchling crawling speed averaging only 3.7 mm min-' on smooth rock surfaces in the laboratory. The abundance and distribution of microhabitats that protect early juveniles could therefore be important determinants of the local abundance and distribution of N. emarginata populations. The use of protective microhabitats may be the key to survival through the vulnerable early juvenile period in many benthic marine organisms.

Section: Introductionmentioning

confidence: 99%

“…Food limitation, especially in the beginning of benthic life, is also a critical factor that can influence the growth and survival of juveniles (Gallardo et al 2004b, Moran & Manahan 2004. For juvenile intertidal organisms, however, vulnerability also includes other physical factors that do not occur in most terrestrial and freshwater habitats, such as wave exposure, desiccation, and temperature fluctuations, which often result in mortality and affect the distributional limits of the species (Gosselin & Chia 1995a,b, Helmuth et al 2002.Several studies of invertebrates with larval stages have shown that larger sizes are often correlated with better performance in terms of feeding rate, duration of planktonic period, settlement rate, growth rate, and survival (Phillips 2002, Marshall & Keough 2004, 2009). In contrast, for direct developers that lack a planktonic larval stage, maternal provisioning to the embryos at the time of spawning is the primary source of nutrition until the offspring enter juvenile life (Spight 1976, Rivest 1983.…”

mentioning

confidence: 99%

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

Carrasco¹,

Phillips²,

Pérez‐Matus³

2012

Offspring size variation can have pervasive ecological and evolutionary implications for both offspring and mother, affecting an organism's performance throughout its life. Using 2 marine intertidal whelk species Cominella virgata and C. maculosa as model organisms, we examined how different maternal environments and contrasting hatchling size influence juvenile performance. The average size of field-collected hatchlings greatly differed between the species and at different scales of variation (i.e. among sites). Species-specific differences in hatching size were reflected in juvenile performance. Overall, C. virgata with larger hatchlings (~3 mm), exhibited faster growth rates and higher survival than the smaller C. maculosa (~1.5 mm). Desiccation treatment did not affect the performance of fed juveniles; however, large hatchlings had higher growth rates than small conspecifics for both species. Starved hatchlings of both species performed more poorly than fed ones; however, species-specific and size differences were less significant for the evaluated traits, suggesting a non-size-related allocation of resources and similar resource utilization during starvation conditions (i.e. within species). As has been described for many taxa, large offspring often perform better than small conspecifics; however, because this performance is likely context-dependent, understanding the importance of different scales of variation is crucial for determining when variation in size is an advantage or a disadvantage in terms of an organism's performance. KEY WORDS: Progeny size · Reproductive strategies · Environmental variation · Phenotypic plasticity · Offspring size-fitness · Cominella Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 459: [73][74][75][76][77][78][79][80][81][82][83] 2012 to either non-adaptive stochastic variation in provisioning or to a maternal bet-hedging strategy in unpredictable environments (see Kamel et al. 2010).The ability of mothers to anticipate the environment that their offspring will experience may therefore mediate variation in offspring size. When mothers are able to predict their offspring's environment, the expectation is that plasticity in mean offspring size will be favored ('anticipatory' maternal effects;Marshall & Uller 2007). Conversely, when mothers are unable to predict the environment, the expected outcome is that increases in the variation of offspring size will ensure that some offspring will be optimal for the environment (Crean & Marshall 2009). Regardless of the strategy, the division of finite reproductive resources should ultimately result in an optimal equilibrium between the offspring fitness and the maximization of the parental fitness, and therefore, simple models have typically suggested that as the relationship between progeny size and progeny fitness changes, the optimal size of progeny is also expected to change as environmental conditions vary (Fox 2000, Walker et al. 2003. Examples provided by Allen et al. (...