Embryonic development and morphological characteristics of larvae and juveniles of the tomato grouper (Cephalopholis sonnerati)

The tomato grouper (Cephalopholis sonnerati) is a valuable economic fish species in the South China Sea and is highly sought after by consumers. Investigating the morphometrics and physiology of early life stages (embryos, larvae, juveniles) is essential for understanding fish early life history and advancing aquaculture success. This study conducted detailed observation and research on the embryonic development of fertilized eggs and the morphological characteristics of larvae and juveniles of C. sonnerati through microscopic observation. The fertilized eggs of C. sonnerati are floating, transparent and spherical, undergoing development through six major stages that are further subdivided into 24 distinct phases. 3days post hatching (dph) larvae switch to exogenous nutrition with the disappearance of their yolk sac. Meanwhile, their tissues and organs begin to differentiate, and the second dorsal fin spine and the first pelvic fin spine appear. These are signs for late larvae. When the late larvae develop to 24 dph, the absolute lengths of the second dorsal fin spine and the pelvic fin spine have reached the maximum value of the larval and juvenile stage. At the same time, their fin rays are formed, and the larvae metamorphose into juveniles. In the juvenile stage, the growth rate accelerates, and the differentiation of tissue and organ morphology becomes more complete. This study is the first to report the morphological characteristics and developmental patterns of the embryos, larvae and juveniles of C. sonnerati, providing a theoretical basis for the large-scale breeding of C. sonnerati.