Ontogenic development of the spine and spinal deformities in larval barramundi (Lates calcarifer) culture

Abstract

Morphological deformities are a significant problem preventing barramundi (Lates calcarifer) aquaculture from achieving optimal production. This study describes the osteological development of the vertebral column and the types and occurrence of spinal deformities during the larval development of L. calcarifer between 2 and 38 days after hatch (DAH). The first structures to appear as cartilage in the development of the spine are the anterior neural spines, anterior haemal spines and pre-caudal centra which are laid down as cartilage in larvae at 2.7 mm or 6 to 8 DAH. Initial cartilage formation of the pre-caudal centra is characterised by a centrally ventrad U-shaped development. Ossification of the spine begins with the neural and haemal spines at 3.3 to 3.6 mm or 8 to 10 DAH proceeded by ossification of the centra at 3.0 to 4.1 mm or 6 to 12 DAH. The process of ossification is complete by 6.0 mm or 14 DAH. Three types of spinal deformities were recorded in larvae with the most common being slight malformations of the centra. One case of lordotic/scoliotic/kyphotic (LSK) syndrome and one gross vertebral malformation were also documented. The first spinal deformities were observed at 20 DAH. The frequency of deformities increased to a maximum of 7.7% of sampled fish at the completion of the study at 38 DAH. The deformities were recorded 6 days after ossification of the spine (20 DAH) implying dysfunctions in bone metabolism.