| Abstract |
The osteological development of the vertebral column and fins in shi drum, Umbrina cirrosa (Linnaeus, 1758), as well as the development of skeletal deformities under different rearing conditions, was studied, in order to gain applicable results for solutions in practical issues concerning the introduction of shi drum in the Mediterranean aquaculture. The osteological development was studied in 170 individuals that were reared under the mesocosm technique, between 2.7 and 30.2 mm total length (TL). The development of the deformities was studied in 821 individuals that were reared under intensive conditions with different stocking density (50 larvae/l και 25 larvae/l) and 231 individuals that were reared under intensive conditions with different feeding protocols (A: weaning at 20 D.A.H (supplying Artemia spp.), B: weaning at 29 D.A.H (supplying Artemia spp.), C: weaning at 29 D.A.H (no supplying Artemia spp.). All the samples were studied after selective staining of the cartilage and bones. Vertebral ontogeny started at 3.4 mm TL and 4.0 mm TL, with the formation of the first cartilaginous neural and haemal spines respectively, and was completed with the full attainment of dorsal ribs (12.5 mm TL). The formation of vertebral centra occurred between 4.1 and 7.4 mm TL. Pectoral supports were the first fin elements that started to develop (3.0 mm TL), followed by those of the caudal fin (3.8 mm TL), of the pelvic fin (3.9 mm TL) and finally by those of the dorsal and anal fin (4.5 mm TL). The caudal fin of shi drum was the first to develop fin rays and attain the full count of lepidotrichia (4.5-6.8 mm TL), but the last to attain the full count of dermatotrichia (6.9-17.5 mm TL).The next fins starting to present rays were the dorsal (5.3 mm TL) and the pectoral fins (5.6 mm TL), while the anal and pelvic fins were the last (5.7 mm TL). Following the caudal lepidotrichia (6.8 mm TL), the dorsal, anal (6.9 mm TL), pelvic (7.4 mm TL) and pectoral fins (9.8 mm TL) were the next with fully completed ray counts. Finally, fin meristics were fully developed with the caudal dermatotrichia. The results of the development of the skeletal deformities showed that stocking density does not affect the type of the developing deformities but affects only the frequency of them. It was also shown that the higher stocking density leads to higher percentage of high severity deformities like fusion, lordosis and saddleback. On the other hand, although the three different feeding protocols showed differences on the frequency of the deformities, this did not prove one of them to be better than the others. Plus, the types of the deformities did not differ between the three protocols. The above results contribute to the early detection of skeletal deformities as well as on the improvement of the quality of the reared shi drum populations.
|
Μελέτη της οντογένεσης του σκελετού και των παραμορφώσεών του στο μυλοκόπι, Umbrina cirrisa (Linnaeus, 1758).
