The morphological development of juvenile western rock lobster Panulirus cygnus George, 1962 (Decapoda, Palinuridae) reared in the laboratory

Abundant information on the biology and ecology of lobster pueruli and juveniles collected in the wild is now available. However, biological aspects of the morphological development of spiny lobsters has not adequately reported. In this study, the growth of juvenile western rock lobsters, Panulirus cygnus, was observed and some morphological changes in the pueruli and juvenile are described. Low mortality was found for juveniles reared individually to the 10th instar, with a low mortality being observed in cases of water quality deterioration. The growth rate was similar to other reported works. Some individuals reached the 10th instar (average CL 28.24 mm) after 222 d of culture. Juveniles went through three phases of coloration during their early development and a light red-brown color was fixed at the 4th instar. The main morphological changes in carapace and appendages are shown in the transition from puelurus to the first instar. The mouthparts of the puerulus are simple, having only a few diminutive spines distributed over their surface. After the molt to the first instar, the mandibles show calcification with the mandibular palp being setose and segmented. Spines and setae are present on the endopods as well as segmentation of the exopods of the three maxillipeds. The process of calcification and setation takes place gradually at each successive molt. The relative position of the antennular and antennal peduncles changed during the juvenile growth. Secondary sexual characters develop before the 10th juvenile instar. Sex differentiation can be determined from the position of the gonopores on female and male sterna on large specimens of the 3rd instar, and in all the 4th instar specimens. As in other reported palinurids species, the pleopods of females and males showed different development from the 4th instar. Female subchelate dactyls of the 5th pereiopods develop in individuals during the 7th to 10th instars.