Morphological development of larvae and juveniles of codlets Bregmaceros atlanticus in the East China Sea

Abstract

The study focuses on the morphology of larval and juvenile codlets, Bregmaceros atlanticus, collected from the East China Sea in May 2001 and September 2002. A total of 47 individuals were collected by using an IKMT, and the range of their body lengths was 2.41-17.18 mm. Specimens can be categorized into two groups: larvae and juvenile. The first group, in which the yolk is completely absorbed, had a body length of 2.41 mm. They had big heads, and large and thick melanophores were sparsely scattered about the head, bottom of the pectoral fins, rear parts of the trunk and ends of the notochords. The specimens had a body length of 2.54 mm and over, and thin and elongated body trunks. Their heads were significantly smaller, including the body depth, and melanophores were coarsely developed all over their bodies. Occipital rays, the first and unique-ray dorsal fin, were observed on individuals of body length greater than 4.01 mm, and the rays grew proportionally with body length, but didn't reach the root of the second dorsal fin. The second group, juveniles, had an body length of 9.82 mm and over, and their fin rays satisfied the completed numbers of rays and vertebrae for adults. Melanophores were densely scattered all over the body, where thick colors were observed on the rear parts of the dorsal and anal fins and front part of the caudal fin.