Comprehensive comparison of four species of Onchidiidae provides insights on morphological and molecular adaptations of invertebrates from shallow seas to wetlands

Abstract

Background.The Onchidiidae family provides ideal species of marine invertebrates for the study of the evolution from seas to wetlands. However, different species of Onchidiidae have rarely been considered in comparative studies.Methods.A total of 40 samples were collected from four species (10 specimens per onchidiid). In addition, we systematically investigated the histological and molecular differences to elucidate the morphological foundations underlying these adaptations.Results.Histological analysis enabled the structural comparison of respiratory organs (gill, lung-sac, dorsal skin) among onchidiids. Transcriptome sequencing of four representative onchidiids was performed to further expound the molecular mechanisms with their respective habitats. Twenty-six Single nucleotide polymorphism (SNP) markers of Onchidium struma presented the DNA polymorphism determining some visible genetic traits. Non-muscle myosin heavy chain II (NMHC II) and myosin heavy chain (MyHC) played an essential role in amphibian developmental processes and are expressed differentially invarious onchidiids and tissues. The species with higher terrestrial ability and higher integrated expression of Os-MHC (NMHC II gene) and MyHC gene illustrated the expression level associated with the evolutionary degree.Conclusions.The present study indicates that different adaptions occurred in four species in various environments.We hope to provide a valuable reference point and a source of inspiration for amphibian investigatorsstudying the morphological characteristics and molecular mechanisms underlying the transition of invertebrates from shallow seas to wetlands. Comprehensive comparison of four species of Onchidiidae provides insights on morphological and molecular adaptations of invertebrates from shallow seas to wetlands Guolv Xu 1,2,3 , Tiezhu Yang 1,2,3 , Dongfeng Wang 1,2,3 , Jie Li 1,2,3 , Xin Liu 1,2,3 , Xin Wu 1,2,3 , Shen Heding 1,2,3 Guolv Xu and Tiezhu Yang aee fiest co-authoes; they conteibuted equally to the woek. Background.The Onchidiidae family peovides ideal species of maeine inveetebeates foe the study of the evolution feom seas to wetlands. Howevee, diffeeent species of Onchidiidae have eaeely been consideeed in compaeative studies. PeerJ PreprintsMethods.A total of 40 samples weee collected feom foue species (10 specimens pee onchidiid). In addition, we systematically investigated the histological and moleculae diffeeences to elucidate the moephological foundations undeelying these adaptations.Results.Histological analysis enabled the steuctueal compaeison of eespieatoey oegans (gill, lungsac, doesal skin) among onchidiids. Teansceiptome sequencing of foue eepeesentative onchidiids was peefoemed to fuethee expound the moleculae mechanisms with theie eespective habitats.Twenty-six Single nucleotide polymoephism (SNP) maekees of Onchidium struma peesented the DNA polymoephism deteemining some visible genetic teaits. Non-muscle myosin heavy chain II (NMHC II) and myosin heavy chain (MyHC) played an essential eole in amphibian ...