On the Hepatosomatic Index of Holocephalian Fish

Abstract

The hepatosomatic index (liver weight/body weight × 100, HSI) of holocephalian fish was examined, using two species, ratfish, Hydrolagus colliei, and rabbitfish, Chimaera monstrosa. Compared with HSI in teleostean fishes, the index was remarkably high in these holocephalian fishes. It was 16.96±0.66% in ratfish (14 specimens, body weight: 360–1405 g). In rabbitfish, 52 specimens having wide range of body weight (12.5–1918 g) were available. Therefore, HSI was calculated in fishes divided into the following three groups; A group (31 specimens, 12.5–88 g), B group (5 specimens, 118–168 g), and C group (16 specimens, 222–1918 g). In small fishes of group A, HSI was 4.34±0.19%. However, the liver weight increased conspicuously in the specimens of group B (HSI: 11.06±1.15%), and finally liver weight attained a level of about 16% of body weight in the specimens of group C (HSI: 15.91 ±0.34%). Microscopically the liver tissue of specimens in groups B and C strongly resembles adipose tissue, owing to the tremendous accumulation of fat droplets in hepatic cells. © 1978, The Japanese Society of Fisheries Science. All rights reserved.