BIOGEOGRAPHIC SHELL SHAPE VARIATION INTROPHON GEVERSIANUS(GASTROPODA: MURICIDAE) ALONG THE SOUTHWESTERN ATLANTIC COAST

The volutid gastropod Zidona dufresnei is an important fishery resource from the Southwestern Atlantic Ocean. This species exhibits strong interpopulation differences in life history features, which lead to postulate the existence of two morphotype ('normal' and 'dwarf'). In this study, we combine and compare traditional and geometric morphometrics to capture shell shape variation of Z. dufresnei among three populations from Mar del Plata (37° S) to San Matías Gulf (42° S) to test the hypothesis that the phenotypic variation already described in the life cycle and size is also expressed in the shell shape. Significant differences in the shell morphology among these three populations were detected, mainly associated to the maximum size of individuals and shell shape. The Bahía San Antonio morphotype had shells with higher general roundness and weight compared to San Matías Gulf and Mar del Plata morphotypes, which were not differentiated. Our results support the hypothesis of Lahille (1895) who distinguished the morphotype of Bahía San Antonio ('dwarf' morphotype) as Voluta angulata affinis. The functional significance of the variability found is discussed in terms of the ecological and genetic effects on shape and size.

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A developmentally descriptive method for quantifying shape in gastropod shells

Journal of The Royal Society Interface ◽

10.1098/rsif.2019.0721 ◽

2020 ◽

Vol 17 (163) ◽

pp. 20190721

Author(s):

J. Larsson ◽

A. M. Westram ◽

S. Bengmark ◽

T. Lundh ◽

R. K. Butlin

Keyword(s):

Empirical Studies ◽

Three Dimensional ◽

Shell Shape ◽

Large Set ◽

Littorina Saxatilis ◽

Shape Variation ◽

Gastropod Shell ◽

Geometric Morphometric ◽

Wide Range ◽

Descriptive Method

The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.

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Insights of the life history in the porcellanid crab Petrolisthes armatus (Gibbes, 1850) (Crustacea: Anomura: Porcellanidae) from the Southwestern Atlantic coast

Invertebrate Reproduction & Development ◽

10.1080/07924259.2017.1285818 ◽

2017 ◽

Vol 61 (2) ◽

pp. 78-89 ◽

Cited By ~ 2

Author(s):

Marcelo Antonio Amaro Pinheiro ◽

Marcio Camargo Araujo João ◽

Maria Helena Arruda Leme ◽

Akeme Milena Ferreira Matsunaga ◽

Juliana Priscila Piva Rio ◽

...

Keyword(s):

Life History ◽

Atlantic Coast ◽

Southwestern Atlantic ◽

Petrolisthes Armatus

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Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

Paleobiology ◽

10.1017/pab.2021.32 ◽

2021 ◽

pp. 1-23

Author(s):

Pablo S. Milla Carmona ◽

Dario G. Lazo ◽

Ignacio M. Soto

Keyword(s):

Trajectory Analysis ◽

Sedentary Lifestyle ◽

Shape Change ◽

Shell Shape ◽

Shape Variation ◽

Ontogenetic Changes ◽

Ontogenetic Trajectories ◽

Higher Genus ◽

Gradual Decay

Abstract Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

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Genetic structure and shell shape variation within a rocky shore whelk suggest both diverging and constraining selection with gene flow

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/bly142 ◽

2018 ◽

Author(s):

Michael R Gemmell ◽

Steven A Trewick ◽

James S Crampton ◽

Felix Vaux ◽

Simon F K Hills ◽

...

Keyword(s):

Gene Flow ◽

Genetic Structure ◽

Rocky Shore ◽

Shell Shape ◽

Shape Variation

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An exposure scale for marine shores in western Norway

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315400056903 ◽

1978 ◽

Vol 58 (4) ◽

pp. 975-996 ◽

Cited By ~ 47

Author(s):

D. H. Dalby ◽

E. B. Cowell ◽

W. J. Syratt ◽

J. H. Crothers

Keyword(s):

Species Abundance ◽

Shell Shape ◽

Rocky Shores ◽

Shape Variation ◽

Nucella Lapillus ◽

Extended Form ◽

Independent Evidence ◽

The North ◽

Western Norway ◽

The North Sea

A rocky shore exposure scale, intended primarily for use in the Fensfjord area, Western Norway, has been prepared. This scale is developed from an earlier scale devised by Ballantine for Milford Haven, Wales, making use of species abundance curves along the wave exposure gradient. Independent evidence for the validity of the scale is provided by shell shape variation in Nucella lapillus and by the height of the black lichen zone in the supralittoral fringe. The successive steps in the preparation of the scale are outlined, definitions of the exposure grades are given in tabular form for the restricted set of species analysed numerically and descriptions are provided in an extended form to provide a fuller picture for users of the scale. It is believed that the scale will prove applicable to other rocky shores around the North Sea.

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Shell variations in the gastropod, Monodonta labio, in the North-western Pacific: the important role of temperature in the evolution process

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315419000481 ◽

2019 ◽

Vol 99 (7) ◽

pp. 1591-1599

Author(s):

Dan Zhao ◽

Ling-Feng Kong ◽

Takenori Sasaki ◽

Qi Li

Keyword(s):

Environmental Gradients ◽

Ecological Factors ◽

Local Maximum ◽

Morphological Diversity ◽

Shell Shape ◽

Shape Variation ◽

Genetic Structuring ◽

Morphological Variations ◽

China Sea

AbstractMolluscan shells showing phenotypic variations are ideal models for studying evolution and plasticity. In north-eastern Asia, genetic and morphological diversity of the gastropod, Monodonta labio, were assumed to be influenced by both palaeoclimatic changes and current ecological factors. In this study, we examined spatial variations in shell shape of M. labio using general measurement and geometric morphometric analysis. We also investigated whether shell shape variation is best explained by environmental gradients or by genetic structuring, based on our prior molecular phylogeographic study. Two common morphological forms were observed among Chinese populations and in the adjacent Asian areas. Both the analyses revealed separation patterns in morphological variations of shell shape among the clades and populations. Environmental modelling analysis showed a significant correlation between shape variations and local maximum temperatures of the warmest month, indicating the role of natural selection in the evolution of this species. Data obtained in this study, combined with the cytochrome oxidase subunit I (COI) molecular phylogenetic data from the prior study, showed that morphological variations in M. labio were constrained by both local adaptation and phenotypic plasticity. We hypothesized that geographic separation by the Dongshan Landbridge was the first step towards its diversification, and that the temperature gradient between the East China Sea and South China Sea probably was the selective force driving the divergence of its morphological variations.

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Adaptive divergence in shell morphology in an ongoing gastropod radiation from Lake Malawi

BMC Evolutionary Biology ◽

10.1186/s12862-019-1570-5 ◽

2020 ◽

Vol 20 (1) ◽

Cited By ~ 1

Author(s):

Bert Van Bocxlaer ◽

Claudia M. Ortiz-Sepulveda ◽

Pieter R. Gurdebeke ◽

Xavier Vekemans

Keyword(s):

Common Garden ◽

Shell Morphology ◽

Model Systems ◽

Shell Shape ◽

Adaptive Divergence ◽

Nominal Species ◽

Shape Variation ◽

In The Wild ◽

Evolutionary Radiations ◽

Contrasting Habitats

Abstract Background Ecological speciation is a prominent mechanism of diversification but in many evolutionary radiations, particularly in invertebrates, it remains unclear whether supposedly critical ecological traits drove or facilitated diversification. As a result, we lack accurate knowledge on the drivers of diversification for most evolutionary radiations along the tree of life. Freshwater mollusks present an enigmatic example: Putatively adaptive radiations are being described in various families, typically from long-lived lakes, whereas other taxa represent celebrated model systems in the study of ecophenotypic plasticity. Here we examine determinants of shell-shape variation in three nominal species of an ongoing ampullariid radiation in the Malawi Basin (Lanistes nyassanus, L. solidus and Lanistes sp. (ovum-like)) with a common garden experiment and semi-landmark morphometrics. Results We found significant differences in survival and fecundity among these species in contrasting habitats. Morphological differences observed in the wild persisted in our experiments for L. nyassanus versus L. solidus and L. sp. (ovum-like), but differences between L. solidus and L. sp. (ovum-like) disappeared and re-emerged in the F1 and F2 generations, respectively. These results indicate that plasticity occurred, but that it is not solely responsible for the observed differences. Our experiments provide the first unambiguous evidence for genetic divergence in shell morphology in an ongoing freshwater gastropod radiation in association with marked fitness differences among species under controlled habitat conditions. Conclusions Our results indicate that differences in shell morphology among Lanistes species occupying different habitats have an adaptive value. These results also facilitate an accurate reinterpretation of morphological variation in fossil Lanistes radiations, and thus macroevolutionary dynamics. Finally, our work testifies that the shells of freshwater gastropods may retain signatures of adaptation at low taxonomic levels, beyond representing an evolutionary novelty responsible for much of the diversity and disparity in mollusks altogether.

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