Osteological Development of the Red Snapper, Lutjanus Campechanus (Lutjanidae)

Osteological development of a series of 129 red snapper (Lutjanidae: Lutjanus campechanus) larvae, juveniles and adults (2.5 mm NL to 332 mm SL) is described from cleared and stained material. Emphasis is placed upon development of the vertebral column, ribs, fins and their supports, hyoid arch, branchial skeleton, mandibular arch, and opercular series. Cartilaginous neural arches and spines develop from anterior to posterior. Cartilaginous haemal arches and spines develop caudad at the time when neural arches develop dorsad, but haemal parapophyses develop rostrad. Ossification of neural and haemal arches and spines proceeds in the same direction as cartilaginous development. Ossification of centra is approximately in step with neural and haemal arch and spine ossification. Saddle-shaped ossifications on the notochord at the base of the neural and haemal arches are the first signs of centra ossification. Eight pairs of pleural ribs originate from cartilage and then ossify. Eight pairs of epipleural ribs ossify in the tissue of the myosepta. Notochord flexion starts in larvae between 3.9 and 4.8 mm NL. Four cartilaginous hypurals appear before flexion; hypural 5 develops after flexion. The sequence of spine and ray development for fins is as follows: spinous dorsal, pelvic, caudal, soft dorsal and anal, pectoral. Addition of spines and rays is caudad for the spinous, soft dorsal, and anal fins, from lateral to medial for the pelvic, from the midline outward for the caudal, and from dorsal to ventral for the pectoral. Dorsal fin spines are smooth during development, but pelvic spines have serration during parts of the larval and juvenile stages. All bones basic to the percoid caudal skeleton develop without fusion in adults, except the spinous dorsal fin distal radials are fused to the proximal radials. There was no fusion in the pectoral, pelvic, soft dorsal and anal fin support bones. The hyoid arches form initially in cartilage, but branchiostegal rays are of dermal origin. The branchial arches form in cartilage, gillrakers and toothpatches are of dermal origin, and the origin of tooth plates is not clear. Bones of the upper jaw are dermal in origin, whereas the lower jaw originates from cartilage and has endochondral and epichondral ossifications. Meckel's cartilage is retained in the lower jaw in adults. In the opercular series only the preopercular develops spines in larvae. Preopercular spines are added to the interior shelf in juveniles and adults, so that it becomes serrated.