Skeletal development and abnormalities of the vertebral column and of the fins in hatchery-reared turbot Scophthalmus maximus

To describe the skeletal development and abnormalities in turbot Scophthalmus maximus, samples were collected every day from hatching to 60 days after hatching (DAH). A whole-mount cartilage and bone-staining technique was used. Vertebral ontogeny started with the formation of anterior haemal arches at 5.1 mm standard length (LS) c. 11 DAH, and was completed by the full attainment of parapophyses at 16.9 mm LS c. 31 DAH. Vertebral centra started to develop at 6.3 mm LS c. 16 DAH and ossification in all centra was visible at 11.0 mm LS c. 25 DAH. The caudal fin appeared at 5.1 mm LS c. 11 DAH and ossification was visible at 20.6 mm LS c. 37 DAH. The onset of dorsal and anal fin elements appeared at 5.8 mm LS c. 15 DAH and 6.3 mm LS c. 16 DAH, respectively. Ossifications of both dorsal fin and anal fin were visible at 20.6 mm LS c. 37 DAH. The pectorals were the only fins present before first feeding, their ossifications were completed at 23.5 mm LS c. 48 DAH. Pelvic fins began forming at 7.2 mm LS c. 19 DAH and calcification of the whole structure was visible at 19.8 mm LS c. 36 DAH. In the present study, 24 types of skeletal abnormalities were observed. About 51% of individuals presented skeletal abnormalities, and the highest occurrence was found in the haemal region of the vertebral column. As for each developmental stage, the most common abnormalities were in the dorsal fin during early metamorphic period (stage 2), vertebral fusion during climax metamorphosis (stage 3) and caudal fin abnormality during both late-metamorphic period (stage 4) and post-metamorphic period (stage 5). Such research will be useful for early detection of skeletal malformations during different growth periods of reared S. maximus.