A theory for the formation of commarginal ribs in mollusc shells by regulative oscillation
TLDR
A mathematical model is presented, showing how a simple regulative system can produce ribs, and implies that commarginal ribs will evolve almost unavoidably in any shelled mollusc group, as long as they are not selectively disadvantageous.Abstract:
The growth processes responsible for commarginal ribs in molluscs (concentric in bivalves, radial in ammonoids) are not yet known, though several different mechanisms have been proposed. The simplest explanation may be that such ribs form as a result of oscillation in a regulatory system involving purely mechanical factors. A mathematical model is presented, showing how a simple regulative system can produce ribs. If true, this hypothesis implies that commarginal ribs will evolve almost unavoidably in any shelled mollusc group, as long as they are not selectively disadvantageous.read more
Citations
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Mechanical basis of morphogenesis and convergent evolution of spiny seashells
TL;DR: A mathematical model for spine morphogenesis is developed based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth, suggesting that convergent evolution of spines can be understood through a generic morphogenetic process.
Journal ArticleDOI
Mechanical growth and morphogenesis of seashells.
TL;DR: It is demonstrated that the elastic response of the mantle during shell deposition provides a natural mechanism for the formation of three-dimensional ornamentation in shells.
Journal ArticleDOI
Models for the morphogenesis of the molluscan shell
Øyvind Hammer,Hugo Bucher +1 more
TL;DR: A new, generalized, free-form apertural growth map model, used to simulate the formation of megastriae in ammonoids, is presented in this paper, illustrating some aspects of the regulation of logarithmic spiral growth.
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Buckman's first law of covariation–a case of proportionality
Øyvind Hammer,Hugo Bucher +1 more
TL;DR: Buckman's first law of covariation as discussed by the authors has escaped several attempts at functional or physiological explanation, and almost collapses to a tautology, when we reword it as follows: size of lateral and ventral ornamentation correlates with size of the aperture (its width and height, respectively).
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Characters in context: molluscan shells and the forces that mold them
TL;DR: The perspective outlined here implies that shells initially occupied a limited morphospace encompassing one or two modules, adaptation as an epifaunal clamping animal, and slow growth (low expansion rates and metabolism), which caused the morphospace to expand both in the number of independent descriptors and in the range of values that each parameter spans.
References
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TL;DR: In this article, the authors introduce the principles of estimation and inference: means and variance, means and variations, and means and variance of estimators and inferors, and the analysis of factorial experiments having repeated measures on the same element.
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Recognition memory for words, sentences, and pictures
TL;DR: This article found that median Ss were able to recognize the old stimuli in 90, 88, or 98% of the test pairs, respectively, in a test set consisting of words, sentences, or pictures.
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Genetic assimilation of an acquired character
TL;DR: The purpose of the present communication is to describe an experiment in which the hypothesis that if an animal is subjected to unusual circumstances to which it can react in an adaptive manner, the development of the adaptive character might itself become so far canalised that it continued to appear even when the conditions returned to the previous norm.
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The Algorithmic Beauty of Sea Shells
TL;DR: The patterns on the shells of tropical sea snails are not only compellingly beautiful but also tell a tale of biological development, which follows laws like those of dune formation or the spread of a flu epidemic.