Association between shell morphology of micro-land snails (genusPlectostoma) and their predator’s predatory behaviour (original) (raw)
Related papers
PeerJ, 2014
Predator-prey interactions are among the main ecological interactions that shape the diversity of biological form. In many cases, the evolution of the mollusc shell form is presumably driven by predation. However, the adaptive significance of several uncommon, yet striking, shell traits of land snails are still poorly known. These include the distorted coiled "tuba" and the protruded radial ribs that can be found in micro-landsnails of the genus Plectostoma. Here, we experimentally tested whether these shell traits may act as defensive adaptations against predators. We characterised and quantified the possible anti-predation behaviour and shell traits of Plectostoma snails both in terms of their properties and efficiencies in defending against the Atopos slug predatory strategies, namely, shell-apertural entry and shell-drilling. The results showed that Atopos slugs would first attack the snail by shell-apertural entry, and, should this fail, shift to the energetically mor...
Tuning in to multiple predators: conflicting demands for shell morphology in a freshwater snail
Freshwater Biology, 2008
1. We examined the response to chemical cues from fish and crayfish, two predators with contrasting feeding modes, and their single and combined effect on shell morphology in the freshwater snail Radix balthica. 2. Snails were subjected to four treatments: tench (Tinca tinca), signal crayfish (Pacifastacus leniusculus), a combination of tench and signal crayfish and no predators (control). Shell shape, crushing resistance and shell thickness were quantified. We also analysed whether shape or shell thickness contributes most to crushing resistance. 3. Chemical cues from the fish induced a rounder shell shape in R. balthica, a thicker shell and a higher crushing resistance, whereas crayfish chemical cues had no effect on shell morphology, shell thickness or crushing resistance. Shell shape contributed more to crushing resistance than shell thickness. 4. The combined predator treatment showed an intermediate response between the fish and crayfish treatments. Shell roundness was reduced compared with the fish treatment, but the reduced crushing resistance that comes with a less rounded shell was compensated by an increased investment in extra shell material, exceeding that of the fish treatment. 5. Our study extends previous studies of multipredator effects on phenotypically plastic freshwater snails by showing that the snails are able to fine-tune different elements of morphology to counter predator-specific foraging modes.
Marine Ecology Progress …, 2008
Prey with versatile predators need diverse defenses. Such an example of a versatile predator is the voracious European green crab Carcinus maenas. Green crabs prey on snails by either crushing shells or, when shells are too tough to break, by extracting flesh through the shell opening (aperture). Among populations in the northwest Atlantic, the claw size of green crabs (an indicator of crushing strength) co-varies with shell mass of the intertidal snail Littorina obtusata (mass is an indicator of a shell's crushing resistance); thus shell-crushing predation appears to be an important part of the predator-prey interaction. We report that aperture occlusion and soft tissue withdrawal depth (two shell-entry defenses) of L. obtusata snails co-vary with their shell mass (an anti-crushing trait) among populations. When snails were fed directly to green crabs in the laboratory, populations with smaller shell openings and deeper withdrawal depths were less frequently killed by shell-entry attacks, and these same populations, with more massive shells, were also better at resisting shellcrushing attacks. Results provide compelling evidence that greater shell mass, a smaller shell opening, and deeper withdrawal depth are adaptive traits for snails faced with green crab predators. Furthermore, results suggest that American L. obtusata responded to the introduction of green crabs by escalating both anti-crushing and anti-entry defenses.
Journal of Experimental Marine Biology and Ecology, 2005
Inducible defenses are important in the life strategies of many taxa. In some species of marine gastropods, water-borne chemical cues from potential predators induce defensive changes in shell form and differences in growth rate. We examined such phenotypic plasticity in the direct-developing snail, Littorina subrotundata (Carpenter, 1864). Among experimental field populations of L. subrotundata exposed to differing intensities of predation by the purple shore crab, Hemigrapsus nudus (Dana, 1851), snails collected from predation-intense environments often had more massive shells than closely related snails from adjacent environments where predation was negligible. Snails collected from both environments were raised in tanks containing cages of H. nudus that were feeding on conspecific snails and compared to a control group raised in the absence of this stimulus. Most snails developed significantly more massive shells in the presence of the crabs suggesting that adaptive phenotypic plasticity may account for some of the variation we observed in the field. In one case, snails from a predation-intense environment did not exhibit a statistically significant amount of plasticity, but instead grew a more massive shell irrespective of the laboratory stimulus. We interpret this as evidence for a genetic difference in the plasticity of shell form among experimental populations, caused by intense selection by H. nudus. There was no statistical difference in the growth rates of snails among treatments.
Journal of Animal Ecology, 2012
1. Studies examining the integration of constitutive and inducible aspects of multivariate defensive phenotypes are rare. 2. I asked whether marine snails (Nucella lamellosa) from habitats with and without abundant predatory crabs differed in constitutive and inducible aspects of defensive shell morphology. 3. I examined multivariate shell shape development of snails from each habitat in the presence and absence of waterborne cues from feeding crabs (Cancer productus). I also examined the influence of constitutive and inducible shell morphology on resistance to crushing. 4. Regardless of the presence of crabs, snails from high-risk (HR) habitats developed rotund, short-spired shells, while snails from low-risk habitats developed elongate shells, tall-spired shells, indicating among-habitat divergence in constitutive shell shape. Moreover, allometry analyses indicated that constitutive developmental patterns underlying this variation also differed between habitats. However, snails from HR habitats showed greater plasticity for apertural lip thickness and apertural area in the presence of crab cues, indicating among-habitat variation in defence inducibility. 5. Both shell shape and apertural lip thickness contributed to shell strength suggesting that constitutive shell shape development and inducible lip thickening have evolved jointly to form an effective defence in habitats where predation risk is high.
Ecology, 2004
Many organisms have evolved morphological and behavioral traits that reduce their susceptibility to predation. However, few studies have explicitly investigated the relationships between defensive traits and susceptibility. Here we demonstrate a negative correlation between morphological defenses and behavioral avoidance across several species of marine gastropod that is linked to vulnerability to crab predation. Snails that had relatively taller shell spires (high aspect ratio) showed greater responsiveness when exposed to predation cues than did species with disc-like shells (low aspect ratio). Our results suggest that the snail species most vulnerable to predation compensated by showing the highest levels of behavioral avoidance, and hence may be at a disadvantage in competition with less vulnerable species. This has important implications because the behavioral response of herbivorous gastropods to predation cues may play a central role in structuring rocky intertidal communities through trait-mediated indirect effects.
Adaptive responses and invasion: the role of plasticity and evolution in snail shell morphology
Ecology and evolution, 2013
Invasive species often exhibit either evolved or plastic adaptations in response to spatially varying environmental conditions. We investigated whether evolved or plastic adaptation was driving variation in shell morphology among invasive populations of the New Zealand mud snail (Potamopyrgus antipodarum) in the western United States. We found that invasive populations exhibit considerable shell shape variation and inhabit a variety of flow velocity habitats. We investigated the importance of evolution and plasticity by examining variation in shell morphological traits 1) between the parental and F1 generations for each population and 2) among populations of the first lab generation (F1) in a common garden, full-sib design using Canonical Variate Analyses (CVA). We compared the F1 generation to the parental lineages and found significant differences in overall shell shape indicating a plastic response. However, when examining differences among the F1 populations, we found that they ...
Journal of Experimental Marine Biology and Ecology, 1999
A predator-deterrence function for the varices of the muricid gastropod Ceratostoma foliatum was tested. In the first set of experiments, snails of five treatment groups were presented over a 10-week period to one of three predators: sunflower stars (Pycnopodia helianthoides Brandt), red rock crabs (Cancer productus Randall), and kelp-greenling fish (Hexagrammus decagrammus Pallas). The five treatment groups were: snails with all varices removed, snails with one only of the right, middle, or left varix removed, and snails with all varices intact. The kelp-greenling fish ate no snails and were discarded from subsequent experiments. Seastars consumed significantly more snails with all varices removed than any of the other treatment groups. Crabs ate significantly more snails with all varices-and right varix-removed compared with the other three groups. Thus, snails with all varices intact were less likely to be eaten by either crab or seastar predators. Scoring the shells of Ceratostoma, but leaving the varices intact had no effect on consumption rates by either seastars or crabs. In a second set of experiments, the smooth-shelled Nucella lamellosa (Gmelin) was presented as a food item along with Ceratostoma with all varices removed and Ceratostoma with all varices intact for an 8-week period. Seastars clearly preferred the smooth-shelled Nucella over the other two groups. In contrast, crabs ate Ceratostoma with all varices removed at a greater rate than control Ceratostoma and Nucella. Energy content of dry flesh of the two snail species was almost identical, suggesting that other factors were involved in governing selection of one prey species over the other. In both sets of experiments, ingestive conditioning learning was not apparent for either the seastars or the crabs. Crabs were videotaped while feeding on Ceratostoma with all, one only, or no varices removed. The videotapes revealed that a combination of chipping the shell around the aperture with the chelipeds, then snapping it in half, was the method most often used to gain access to the soft parts of the shell. However, snails with all varices removed were more often snapped in two without any preliminary chipping, presumably because the lack of varices made them easier to break apart. There was no relationship * Corresponding author. Current address:
Marine Ecology Progress Series, 2007
The shell architecture of the intertidal snail Littorina obtusata (L.) is thought to have undergone an adaptive transition in response to invasion of the Gulf of Maine, NW Atlantic, by the European green crab Carcinus maenas (L.). In order to investigate the hypothesis that this morphological transition affects snail fitness, we conducted predation experiments with snail populations showing morphological differences that are hypothesized to have been caused by, and affect resilience to, green crab predation. Our results are consistent with the adaptive-transition hypothesis, but they reveal more varied predator foraging tactics and prey defensive attributes than previously considered. Crabs killed smaller and less heavily-armored snails by breaking their shell, but killed larger and more heavily-armored individuals using a fairly complex 'shell-entry' tactic, which we refer to as 'winkling'. The snail population which suffered lower mortality from green crab predation apparently obtained protection from crushing by having a thicker, more massive shell, and from winkling by having a smaller aperture. Our study provides evidence that the morphological transition undergone by L. obtusata following the green crab's invasion of the NW Atlantic is adaptive, and raises new questions regarding the phenotypic basis of this recent ecological interaction.
Parallel evolution of passive and active defence in land snails
Scientific Reports, 2016
Predator-prey interactions are major processes promoting phenotypic evolution. However, it remains unclear how predation causes morphological and behavioural diversity in prey species and how it might lead to speciation. Here, we show that substantial divergence in the phenotypic traits of prey species has occurred among closely related land snails as a result of adaptation to predator attacks. This caused the divergence of defensive strategies into two alternatives: passive defence and active defence. Phenotypic traits of the subarctic Karaftohelix land snail have undergone radiation in northeast Asia, and distinctive morphotypes generally coexist in the same regions. In these land snails, we documented two alternative defence behaviours against predation by malacophagous beetles. Furthermore, the behaviours are potentially associated with differences in shell morphology. In addition, molecular phylogenetic analyses indicated that these alternative strategies against predation arose independently on the islands and on the continent suggesting that anti-predator adaptation is a major cause of phenotypic diversity in these snails. Finally, we suggest the potential speciation of Karaftohelix snails as a result of the divergence of defensive strategies into passive and active behaviours and the possibility of species radiation due to anti-predatory adaptations.