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Research Article Open access CC BY 4.0

Intra-Specific Variability in Whorl Growth-Rate among Land Gastropods with Conispirally-Coiled Shells

Jean Béguinot

Annual Research & Review in Biology · pp. 59–69 · Published 14 Dec 2021

10.9734/arrb/2021/v36i1230463

Abstract

For most conispirally-coiled Gastropods with determinate growth, the geometry of spirally-winding whorls is usually constrained by a strong negative correlation between whorl growth rate and the number of whorls reached at adulthood, as originally reported by the late S.J. Gould. Yet, beyond the tight control of shell-shape at the species level – resulting from this constraint – what about the amplitude of the intra-specific variability of whorl growth-rate, partly contributing to the variability of the overall shell-size at the species level? I address the issue by designing and implementing a new, indirect method for routinely evaluating whorl growth-rate, thereby aiming at considerably saving measurement time, and making it possible to easily achieve repeated measurements across samples large enough to reach statistical significance. This approach was applied to a series of eight common land snail species. The amplitude of intra-specific variability in whorl growth, evaluated this way, proves: (i) being markedly different among the eight investigated species (by a factor that can exceed 2x); (ii) being, yet, high enough, in all cases, to require compensating variations in the adult number of whorls, so as to limit the resulting consequences on the amplitude of the intra-specific variability of adult shell-size. Despite those marked differences in the amplitudes of intra-specific variability of whorl growth-rate among species, no significant relationship was observed between intraspecific variability of whorl growth rate and species-specific shell-shape types (discoidal/globular/elongate) and only weak positive relationship was observed with species-specific typical shell sizes. However, a rather strong positive correlation was found, as expected, between the degree of intra-specific variability of the whorl growth-rate and the degree of intra-specific variability of the number of whorls reached at adulthood (with the yet unexplained exception of one among the eight investigated species).

Land snail shell geometry shell-size regulation.

References (10)

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Cited by 2

Damping the Impact of Intraspecific Variability of Whorl Growth-rate on the Range of Intraspecific Variation of Adult Shell-size in Gastropods with Determinate Growth: Evidence of a Finely-tuned Regulating Process

Jean Béguinot · Annual Research & Review in Biology · 2022

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