Research progress on reproductive biology of important economic shrimps of Palaemonoidea

Abstract

Palaemonoidea is one of the most important economic shrimps in China, belonging to Caridea, Decapoda, Crustacea. Reproductive biology mainly focuses on the information related to species reproduction, especially to shrimp artificial breeding. At present, <italic>Macrobrachium rosenbergii</italic>, <italic>Macrobrachium nipponense</italic> and <italic>Exopalaemon carinicauda</italic> have been comprehensively studied and cultured on a large scale. There are still a large number of species to be explored in Palaemonoidea, such as <italic>Palaemon gravieri</italic>, <italic>Macrobrachium hainanense</italic>, <italic>Exopalaemon modestus</italic> and <italic>Exopalaemon annandalei</italic>, etc. The purpose of this review is to understand the common and unique reproductive habits of species of Palaemonidae, and to compare the differences and similarities of reproductive habits between Penaeidae, Cambarus and Palaemonidae, as the results might provide a scientific basis for the follow-up study of species of Palaemonoidea. We found that shrimps of Palaemonoidea had a long reproductive period, usually from April to October, and there were usually more than one active reproductive period during the reproductive season. They were able to be sexually mature multiple times during the breeding period and participate in reproduction. And they had generally higher sex ratio(usually higher than 1), which ensured the ability of the groups to breed the next generation. In conclusion, the species of Palaemonoidea had strong fecundity. The female reproductive system of species of Palaemonoidea showed no obvious similarity, according to the existing research data. On the contrary, we found that the gonad structure of some species of Palaemonoidea was similar to that of other families. By summarizing and analyzing various viewpoints, we designed a method for the division of embryonic development period, which might be more reasonable and scientific. There were eight stages in the embryonic development of Palaemonoidea shrimp, which were fertilized egg stage, cleavage stage, blastocyst stage, gastrula stage, pre nauplius stage, post nauplius stage, pro zoea stage and intramembranous zoea stage. After eight periods of development, the larvae hatched from the mother. Due to the weak motility and predation ability of early larvae, the residual yolk was the main source of nutrition. Then the movement ability and predation ability of the larvae gradually formed and improved, and they could start to filter and feed on all kinds of algae. The whole development process was affected by many environmental factors, such as temperature, salinity and pH value. In addition, a variety of genes have been found to participate in the reproductive process of species of Palaemonoidea. Among these, genes related to gonadogenesis, sexual differentiation, development of embryo and larvae, molt, immunity process have been reported, and these genes play important roles in reproduction by affecting group sex ratio, survival rate and growth rate of embryo larvae.