{"title":"Overlooked shell features: asymmetrical columellar folds in volutid gastropods","authors":"Geerat J Vermeij","doi":"10.1093/mollus/eyae004","DOIUrl":null,"url":null,"abstract":"Many gastropods have columellar folds, defined as continuous spiral ridges extending from the aperture to the shell interior on the adaxial side of the aperture. Despite their ubiquity, columellar folds have received little phylogenetic or functional study. In the vast majority of cases, columellar folds have a symmetrical profile, with the anterior (abapical) slope similar to the posterior (adapical) slope. Here I draw attention to the highly unusual phenomenon of asymmetry of columellar folds, where the anterior slope is markedly less inclined than the posterior slope of each fold. I have detected this condition in the volutid genera Scaphella Swainson, 1832; Cymbiola Swainson, 1831 and Lyrischapa Aldrich, 1911; as well as in the Palaeocene and Eocene genus Eovasum Douvillé, 1920. Following a review of Lyrischapa and Eovasum, I suggest that these two genera are closely related members of the volutid subfamily Indovolutinae, and that asymmetrical columellar folds have evolved three times in Volutidae. Although their function remains elusive, asymmetrical folds might prevent abapical displacement of the soft parts during rapid extension of the foot or feeding organs.","PeriodicalId":50126,"journal":{"name":"Journal of Molluscan Studies","volume":"28 1","pages":""},"PeriodicalIF":1.9000,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Molluscan Studies","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1093/mollus/eyae004","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MARINE & FRESHWATER BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Many gastropods have columellar folds, defined as continuous spiral ridges extending from the aperture to the shell interior on the adaxial side of the aperture. Despite their ubiquity, columellar folds have received little phylogenetic or functional study. In the vast majority of cases, columellar folds have a symmetrical profile, with the anterior (abapical) slope similar to the posterior (adapical) slope. Here I draw attention to the highly unusual phenomenon of asymmetry of columellar folds, where the anterior slope is markedly less inclined than the posterior slope of each fold. I have detected this condition in the volutid genera Scaphella Swainson, 1832; Cymbiola Swainson, 1831 and Lyrischapa Aldrich, 1911; as well as in the Palaeocene and Eocene genus Eovasum Douvillé, 1920. Following a review of Lyrischapa and Eovasum, I suggest that these two genera are closely related members of the volutid subfamily Indovolutinae, and that asymmetrical columellar folds have evolved three times in Volutidae. Although their function remains elusive, asymmetrical folds might prevent abapical displacement of the soft parts during rapid extension of the foot or feeding organs.
期刊介绍:
The Journal of Molluscan Studies accepts papers on all aspects of the study of molluscs. These include systematics, molecular genetics, palaeontology, ecology, evolution, and physiology. Where the topic is in a specialized field (e.g. parasitology, neurobiology, biochemistry, molecular biology), submissions will still be accepted as long as the mollusc is the principal focus of the study, and not incidental or simply a convenient experimental animal. Papers with a focus on fisheries biology, aquaculture, and control of molluscan pests will be accepted only if they include significant advances in molluscan biology. While systematic papers are encouraged, descriptions of single new taxa will only be considered if they include some ‘added value’, for example in the form of new information on anatomy or distribution, or if they are presented in the context of a systematic revision or phylogenetic analysis of the group.