Ontogenetic Development Of Gonads And Transcriptome Analysis Of The Peppermint Shrimp,Lysmata Vittata

The peppermint shrimp Lysmata vittata(Caridea:Hippolytidae)is a marine caridean shrimp popular in marine aquarium trade.The species is Known to display the sexual system of protandric simultaneous hermaphrodite(PSH).In this study,based on captive bred specimens,the complete ontogenetic gonadal development of L.vittata was studied both morphologically and histologically,from newly settled juveniles until they reached euhermaphrodite phase.It was found that in all specimens examined,including the newly settled juveniles,possessed ovotestes,which comprised of an anterior ovarian and a posterior testicular part.Based on both morphological(e.g.,size,color and shape)and histological features(e.g.,oogenesis and spermatogenesis),four gonadal developmental stages were defined and described for L.vittata.From Stage ? to ?,the testicular part of the gonad became gradually mature but the ovarian part was still immature,which is defined as the male phase.At the male phase,cincinulli(5-8 hooks)presented at the tips of the appendix interna on the first pair of pleopods while appendices masculinae(AM),in a form of a stick structure with spines,presented at the inner edge of the appendix interna(AI)on the second pair of pleopods.At Stage ?,both the testicular part and the ovarian part were mature and hence defined as euhermaphrodite phase.At the euhermaphrodite phase,most individuals lacked cincinulli and appendices masculinae on therst and second pair of pleopods respectively.This is the first time that complete ontogenetic gonadal and external sexual character development have been described and staged for a species from the genus Lysmata from newly settled juveniles to euhermaphrodite phase.All specimens possessed ovotestis comprising of an anterior ovarian and a posterior testicular part and displayed the the sexual system of PSH.However,it remains unclear what the molecular mechanism of the sex determination and gonadal development is.Massively parallel DNA sequencing technology was used to develop a deep-coverage transcriptomic sequencing of both the male phase and euhermaphrodite phase.This study will provide important information for further research.Through sequencing,a massive amount of data was obtained from the samples.De novo assembly of these clean data produced 59798 unigenes,with an average sequence length of 799.23 bp.Using the Blastx program,15534(25.98%)unique sequences were annotated with Nr database,3410(5.70%)unique sequences were annotated with String database,10899(18.23%)unique sequences were annotated with Swissprot,8554(18.23%)were annotated with KEGG database.After comparing the libraries of the different developmental stages groups,4592 differentially expressed genes were obtained.It was found that a series of important differentially expressed genes that may be involved in sex differentiation and gonadal development,such as IAG,CFSH and GIH,and related pathways such as Wnt and ovarain steroidogenesis,providing important information for further studies on molecular mechanisms.