SHELL STRENGTH OF COLOUR MORPHS OF THE MANGROVE SNAIL <i>LITTORARIA PALLESCENS</i>

Cook, L. M.; Kenyon, Georgina

doi:10.1093/mollus/59.1.29

Cited by 14 publications

(13 citation statements)

References 18 publications

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“…This suggests that F s scales roughly with one-third power of shell mass, or simply, shell length (or thickness), in so far as the ratio of shell weight to tissue weight remains constant; this is in conformity with some empirical studies (Currey & Hughes, 1982;Cook, Currey & Sarsam, 1986;Cook & Kenyon, 1993;Lowell et al, 1994). For example, a mollusc with a shell length of 30 mm will have a 10 times stronger shell than an individual with a 3 mm-long shell.…”

Section: Discussionsupporting

confidence: 82%

A comparative study of morphometry in shell‐bearing molluscs

2000

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A comparative study was conducted on the ontogenetic variation in morphometry of a total of 29 shellbearing molluscan species occurring on an intertidal stony shore in south-western Japan. The relationships between shell size and total weight and between shell size and¯esh weight were all highly signi®cant on logarithmic scales with the slopes having values of about three. The arcsine-transformed proportion of shell weight out of total weight varied among and within different morphological/taxonomic groups, ranging from 58.6% in Acanthochiton de®lippi to 76.4% in Nerita albicilla. The allometry of shell weight was analysed by regressing the arcsine transformed values of the proportion of shell weight against total weight in each species. The slope (b) of the regression varied substantially among different taxa, with all three possible cases, i.e. b > 0, b & 0 and b < 0, being observed. Thus, depending on molluscan species, the proportion of shell mass either (1) increases, (2) does not change, or (3) decreases with increasing body mass. Variation in the value of b was to some extent explained by the proportion of shell mass of young individuals of each species; species with relatively high proportions of shell mass in small individuals tended to have low b. Interspeci®cally, it was shown that shell mass scaled in proportion to body mass for this assemblage of 29 species. Consideration was given to the theoretical background of variation in shell morphometry, with particular reference to the shell as a defence structure.

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Section: Discussionsupporting

confidence: 82%

A comparative study of morphometry in shell‐bearing molluscs

2000

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“…nemoralis strongly depended on shell thickness, which was also suggested for C . nemoralis by Jordaens et al (2006) as well as for other gastropods, such as Littorina pallescens (Cook and Kenyon 1993) and Cerion sp. (Quensen and Woodruff 1997).…”

Section: Discussionmentioning

confidence: 97%

“…Sheppard 1951; Allen and Weale 2005; Surmacki et al 2013), other features of its shell, such as thickness and strength, which are potentially important for predators are very poorly recognised (Jordaens et al 2006). Moreover, there is some evidence that the dark pigmentation may strengthen the shell (Cook and Kenyon 1993). Therefore, it would be important to understand not only the effects of shell colour on crypsis but also on a direct resistance to predation.…”

Section: Introductionmentioning

confidence: 99%

Differential shell strength of Cepaea nemoralis colour morphs—implications for their anti-predator defence

Rosin

Kobak

Lesicki

et al. 2013

Naturwissenschaften

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One of the most spectacular evolutionary forces is predation, evidenced to stimulate polymorphism in many prey species. Shell colour polymorphism of the land snail Cepaea nemoralis is a well-known model in evolutionary research. Nevertheless, the knowledge on the ecological causes driving its evolution remains incomplete and proximal factors shaping predatory pressure on C. nemoralis morphs are unknown. We evaluated shell crushing resistance and thickness, constituting crucial snail anti-predator defences in two shell areas (the apex and labium) of eight C. nemoralis morphotypes differing in shell colour and banding pattern. A GLM showed a significant effect of shell colour, banding pattern and shell thickness on shell strength. Pink shells were stronger than yellow ones, and banded forms had stronger shells than unbanded snails. The labium (usually attacked by mice) was generally thicker and more resistant than the apex (usually crushed by birds). Thicker shells were more resistant to crushing, and the rate of shell strength increase per unit of shell thickness was greater in pink and banded individuals compared to yellow and unbanded ones. Yellow and unbanded morphs have been found to be preferred by mice in the previous studies, which suggests that shell strength may be an important trait used in prey selection by these shell-crushing predators. The differences in potential anti-predator defences among snail morphs, found in the present study, justify future research on direct effect of C. nemoralis morphs shell strength on predator selectivity.

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“…Mechanical strengths of rey, 1980). Selective thickening of the body whorl or whole shells have been reported for a variety of differaperture, sculpturing and a reduced apical spire can all ent gastropods (Currey, 1979;Vermeij & Currey, 1980;Blundon & Vermeij, 1983;Brandwood, 1985;Lowell, 1985Lowell, , 1986Lowell, , 1987Ash, 1989;Cook & Kenyon, 1993;Lowell et al, 1994). The morphology of thaiidid snail shells from different shores has been shown to vary according to the degree of exposure to wave action (Cooke, 1895;Kitching & Ebling, 1967;Hughes & Elner, 1979) and the strength also differs (Currey & Hughes, 1982); these changes are believed to be responses to selective pressures of desiccation, hydrodynamic drag caused by wave action and predation, especially by the shore crab Carcinus maenas (Crothers, 1985).…”

Section: Introductionmentioning

confidence: 99%

“…However, gene flow would presumably not prevent an inducible response like that seen in Nucella lapillus, the development of which changes in response to the proximity of crabs feeding on conspecific snails (Palmer, 1990). The strengths of different colour morphs of the mangrove snail Littoraria pallescens have been found to differ significantly at some localities but not at others (Cook & Kenyon, 1993).…”

Section: Introductionmentioning

confidence: 99%

Microgeographical variation in shell strength in the flat periwinkles Littorina obtusata and Littorina mariae

Fletcher

1995

Hydrobiologia

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The strength of molluscan shells has been shown to vary in adaptive ways in a number of species and one of the main factors thought to be involved is shell-crushing by predators. A recent study found that the sibling species of flat periwinkle Littorina obtusata and Littorina mariae showed significant differences in the rates at which shell strength increased with shell length in specimens which had been collected from the same location, where the species were sympatric. This paper describes differences between the shells of the two species from a number of localities around Milford Haven in Dyfed, Wales, and local geographical variation in the shells.Littorina mariae, which is normally found at lower tidal levels than L obtusata, matures at a smaller shell length. Both species reinforce the shell as they grow since shell strength, determined as the maximum force applied by a hydraulic tensile testing machine before the shell cracked, is strongly positively allometric; it increases at a rate close to the cube of shell length whilst isometric growth would result in strength increasing in proportion to the square of shell length. Because L. mariae matures earlier and reinforces the shell at a smaller size, the mature shell of L. mariae is substantially stronger on average than that of a similar sized but immature L. obtusata. At maturity the shell strengths of the two species are not very different despite the substantial difference in mean shell length.Strength varies significantly from shore to shore, and with the level of the shore from which the animals were collected. Strength increases down the shore in both species. Shell strength decreases with exposure to wave action in L. mariae but increases with exposure in L. obtusata; there is also substantial shore-to-shore variation which is not explained by exposure.Path analysis was used to explore the relationship between shell strength and other measured shell parameters (mass, length, height, thickness). The best predictor of shell strength in both species is a parameter which is heavily positively loaded on LN (shell mass) and strongly offset by negative loadings on LN (shell length) and LN (shell height). This is logical because for a given shell length a heavier shell will be thicker and stronger, whilst for a given shell mass a bigger shell will be thinner and therefore weaker. Such differential variation of shell mass and shell length explains most of the geographical variation observed in shell strength; shells are stronger in snails collected from one place than from another because, for the same shell length they are heavier or, to put it the other way, because at the same shell mass, they are smaller.

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SHELL STRENGTH OF COLOUR MORPHS OF THE MANGROVE SNAIL LITTORARIA PALLESCENS

Cited by 14 publications

References 18 publications

A comparative study of morphometry in shell‐bearing molluscs

A comparative study of morphometry in shell‐bearing molluscs

Differential shell strength of Cepaea nemoralis colour morphs—implications for their anti-predator defence

Microgeographical variation in shell strength in the flat periwinkles Littorina obtusata and Littorina mariae

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