ABSTRACT
With the increase in breeding density of Exopalaemon carinicauda, appendage breakage may occur, which seriously affects survival and economic benefits. To study the limb regeneration process of E. carinicauda, we induced autotomy of the pereopods. After a period of time, wound swelling disappeared, the pigment gradually accumulated, and a tawny film subsequently formed in the wound. The healing period of the wound occurred 24 h after autotomy, and the blastema formation stage occurred 48 h after autotomy. After 4 days of cutting, the limb buds began to differentiate, grow, and expand rapidly, and this process lasted approximately 15 days. Microscopic observations revealed significant changes in the type and number of associated cells including outer epithelial cells, granulocytes, embryonic cells, columnar epidermal cells, elongated cells, and blastoma cells, during the process from limb fracture to regeneration. A comparative transcriptome analysis identified 1415 genes differentially expressed between the J0h (0 h post autotomy) and J18h (18 h post autotomy), and 3952 and 4366 differentially expressed genes for J0 and J14d (14 days post autotomy) and J18h and J14d, respectively. Some of these genes may be related to muscle growth or molting, as indicated by the presence of troponin C, chitinase, actin, innexin, and cathepsin L. As a functional gene involved in epidermal formation, the mRNA expression level of the innexin inx2 in the pereopod of E. carinicauda changed significantly in the experimental groups (p < 0.05). The results of this study contribute to existing knowledge of regeneration mechanisms in crustaceans.
ABSTRACT
Left-right asymmetry is an essential feature in bilateral animals. The mechanism underlying the left-right asymmetrical organ morphogenesis is a central question in developmental biology. Studies in vertebrates show that left-right asymmetry formation needs three essential steps: the initial left-right symmetry breaking, the left-right asymmetrical gene expression, and the left-right asymmetrical organ morphogenesis. Many vertebrates use cilia to produce directional fluid flow to break symmetry during embryonic development, asymmetric Nodal-Pitx2 signaling to pattern the left-right asymmetry, and Pitx2 and other genes to control the morphogenesis of asymmetrical organs. In invertebrates, there are left-right mechanisms independent of cilia and even others more different from that of vertebrates. In this review, we summarize the major steps and relevant molecular mechanisms of left-right asymmetric development in vertebrates and invertebrates, aiming to provide a reference for the understanding of the origin and evolution of the left-right developmental mechanism.
