Vertebral Malformation in Hatchery-reared Red Sea-bream, Chrysophrys major

Abstract

Two types of anomalies were identified; lordosis and brachyospondylie. Lordotic vertebrae were primarily observed in the transitional region between abdominal and caudal regions of the vertebral column. These vertebrae, however, exhibited no discernible pathological abnormality except for curvature. Retardation of growth of vertebrae in the tail-end was the most conspicuous characteristic observed in lordotic fry, and these vertebrae manifested typical malformation not only in the centra but also in the arches.
Longitudinal constriction (shortening) of vertebrae exhibiting the condition of brachyo-spondylie was characterized by incomplete growth of centra and arches; the occurrence of this condition was restricted almost exclusively to the abdominal vertebrae.
Two conditions of vertebral malformation were distinguished in larval fish growing to a length of 10mm. One configuration (type A) in which vertebrae of the tail-end region exhibited insufficient development was believed to reflect an early stage of lordosis. A second configuration (type B) on th other hand, was regarded as a prodromal symptom of brachyo-spondylie on the basis of the presence of shortened vertebrae in the abdominal region. From these findings, it is presumed that both anomalous types are the result of malformation occurring in the larval stage.