Morphological abnormalities in hatchery-reared horsehead tilefish Branchiostegus japonicas

• Published in: Aquaculture Science Vol. 65; no. 2; pp. 117 - 124
• Main Authors: Toyomura, Kousuke, Mizuta, Atsushi, Matsuura, Mitsuhiro, Nakanishi, Kenji, Aritaki, Masato
• Format: Journal Article
• Language: English; Japanese
• Published: Tsu Japanese Society for Aquaculture Science 2017; Japan Science and Technology Agency
• Subjects: Animal morphology; Branchiostegus; Branchiostegus japonicas; Deformation; Epidermis; Fish; Fish hatcheries; Fish skin; Head; High frequency; Malformations; Marine fishes; Morphological abnormality; Morphology; Operculum; Swim bladder; Twisted head; Vertebra; Vertebrae
• ISSN: 0371-4217; 2185-0194
• DOI: 10.11233/aquaculturesci.65.117

Morphological abnormalities were classified and the skeletal structure of 205 abnormal hatchery-reared horsehead tilefish Branchiostegus japonicas were described in detail to examine the factors affecting five morphological types, including a deformed body, operculum deficit, head depression, deformed mouth, and a deformity of the inter-nostril epidermis. The incidence rates for each abnormal type were 26%, 26%, 23%, 20%, and 5%, respectively. An operculum deficit, head depression, and deformed mouth often occurred together, and the expression of these three abnormal types was conspicuously biased to the left or right side. In addition, left-right asymmetry of these three abnormal types was strongly related to a twisted head. On the other hand, a high frequency of deformation and/or fusion of vertebrae was concentrated in caudal vertebrae, and all fish had an abnormally closed swim bladder. These results strongly suggest that these three abnormalities expressed in the head and deformed body types were caused by a twisted head and a malformed swim bladder, respectively.