{"title":"Evolution of egg deposition strategies, exaptations of exuvia, and thanatochresis in tardigrades","authors":"Roberto Guidetti","doi":"10.1007/s13127-024-00642-1","DOIUrl":null,"url":null,"abstract":"<p>The cuticle is the tardigrade exoskeleton that, limiting animal growth, needs to be periodically shed. New cuticles must be formed (within the old ones) before getting rid of the obsolete exoskeletons at the end of moulting process. After ecdysis (the release of the old cuticle), the exuvia has different destinies according to tardigrade evolutionary lines. In the marine tardigrades (Heterotardigrada), the exuvia is lost and useless, while in the other taxa, it acquires interesting uses to be considered exaptations, since the cuticle previously shaped by natural selection for a function (i.e. as exoskeleton) is coopted for new adaptive scopes. These are related to egg deposition, parental care, mating, and diapause. Egg deposition within the exuvia is one of the three different egg deposition strategies developed by tardigrades: smooth eggs can be laid freely or within the exuvia, while ornamented eggs are laid freely. A new scenario for the evolution of such egg deposition strategies is characterised by five schematic steps: smooth eggs laid freely (ancestral state), synchronization of egg maturation with moulting (developed in tardigrade ancestor in sea), use of the exuvia for oviposition (for enhanced mechanical and physiological egg protection), acquisition of egg ornamentation, and ornamented eggs laid freely (related to a risk-spreading strategy). An interesting thanatochresis case related to the release of free eggs in crustaceans exuviae, convergently developed in two distant taxa of eu- and heterotardigrades, is presented and discussed.</p>","PeriodicalId":1,"journal":{"name":"Accounts of Chemical Research","volume":null,"pages":null},"PeriodicalIF":16.4000,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Accounts of Chemical Research","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1007/s13127-024-00642-1","RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The cuticle is the tardigrade exoskeleton that, limiting animal growth, needs to be periodically shed. New cuticles must be formed (within the old ones) before getting rid of the obsolete exoskeletons at the end of moulting process. After ecdysis (the release of the old cuticle), the exuvia has different destinies according to tardigrade evolutionary lines. In the marine tardigrades (Heterotardigrada), the exuvia is lost and useless, while in the other taxa, it acquires interesting uses to be considered exaptations, since the cuticle previously shaped by natural selection for a function (i.e. as exoskeleton) is coopted for new adaptive scopes. These are related to egg deposition, parental care, mating, and diapause. Egg deposition within the exuvia is one of the three different egg deposition strategies developed by tardigrades: smooth eggs can be laid freely or within the exuvia, while ornamented eggs are laid freely. A new scenario for the evolution of such egg deposition strategies is characterised by five schematic steps: smooth eggs laid freely (ancestral state), synchronization of egg maturation with moulting (developed in tardigrade ancestor in sea), use of the exuvia for oviposition (for enhanced mechanical and physiological egg protection), acquisition of egg ornamentation, and ornamented eggs laid freely (related to a risk-spreading strategy). An interesting thanatochresis case related to the release of free eggs in crustaceans exuviae, convergently developed in two distant taxa of eu- and heterotardigrades, is presented and discussed.
期刊介绍:
Accounts of Chemical Research presents short, concise and critical articles offering easy-to-read overviews of basic research and applications in all areas of chemistry and biochemistry. These short reviews focus on research from the author’s own laboratory and are designed to teach the reader about a research project. In addition, Accounts of Chemical Research publishes commentaries that give an informed opinion on a current research problem. Special Issues online are devoted to a single topic of unusual activity and significance.
Accounts of Chemical Research replaces the traditional article abstract with an article "Conspectus." These entries synopsize the research affording the reader a closer look at the content and significance of an article. Through this provision of a more detailed description of the article contents, the Conspectus enhances the article's discoverability by search engines and the exposure for the research.