Reproductive Physiology and Molecular Mechanisms Underlying Testicular Development and Spermatogenesis in...

Echinoderms exhibit a wide range of reproductive strategies as adaptations to variable environments. The processes of gonadal development, germ cell differentiation, and spermatogenesis in echinoderms are crucial physiological processes that warrant further in-depth exploration. This review systematically summarizes research from early basic sciences to recent studies on male gonadal development and spermatogenesis, encompassing morphology, histology, physiology, cell biology, developmental biology, and evolutionary biology. We introduce the structural and cellular similarities and differences among model or non-model organisms from five classes of echinoderms to provide insights for future comparative research between higher vertebrates and lower organisms. The regulatory systems involved in echinoderm spermatogenesis are described from various aspects including nutritional supply, environmental factors, neurological influences, endocrinological influences, and hormonal influences. This article aims to elucidate gonadal development and spermatogenesis in echinoderms-organisms at unique evolutionary nodes-providing valuable materials for studying adaptive evolution and developmental biology. Additionally, a comprehensive summary of characterized genes and gene markers associated with testes development and spermatogenesis is provided as useful information for future systematic studies on cell subpopulations. Future studies can focus on molecular changes associated with chromatin remodeling during germ cell development, cellular differentiation, and intercellular communication mediated by receptor-ligand interactions, to further our understanding of biological processes and regulatory networks involved in echinoderm gonadal development and spermatogenesis.