| Abstract |
The external morphology of the fish is one of the most important traits for the consumer, and very fundamental for selective breeding programs. In rearing conditions, the variation of the external morphology is been associated mainly with morpho-anatomical abnormalities, and with the normal plasticity of the phenotype.
In the present study, the quantitative and qualitative variability of skeletal abnormalities of the gill cover and jaws of larvae under different rearing conditions, was examined. Subsequently there was an attempt to develop scale for the quantification of the deformities. In the second part of the present study, the body shape variance of adult sea breams under different rearing conditions was examined, aiming for a quality scale, with reference to the wild phenotype. The results of the phenotypic variance, both deformities and body shape, are associated with parentage analysis and family structures, in order to estimate the heritabilities of the examined characters.
The frequency of deformities of the gill cover are affected by the rearing conditions. Main deformity was the inside folding or the partial lack of the operculum, whereas when the deformity degree was getting severer, the deformity was accompanied with abnormalities of the branchiostegal rays and suboperculum. The frequency of the deformities of the jaws, was not affected by the rearing conditions, whereas the main feature were deformities of the maxillary and premaxillary bones. In total, seven semi-quantitative scales were produced, two of them describing the external morphology of the examined areas, while the rest described features of the internal anatomy. From the parentage analysis, significant heritability was observed only for the related deformities to the external morphology of the jaws (h2=0.115±0.041). Different heritability measures were observed in selected deformities with main characteristic the lateral displacement of the upper jaw, and secondarily the narrowing of the maxillary. Absence maxillary's narrowing, heritability rate was significant (h2=0.219±0.059), while the opposite happened in the presence of that deformity (h2=0.049±0.032). Probably, the detailed description of the specific deformity was not needed, due to the fact that could upstage other deformities with genetic background.
The analysis of phenotypic variance of adult sea bream, showed that body shape was affected by the rearing conditions. Morphological differences were mainly correlated to the position of the snout, pelvic fins and body height, whereas the comparison with the wild populations, showed that the body shape from the fish reared in cages, looks alike to that of the wild populations. Results of the phenotypic analysis, match with those of the parentage analysis, due to the fact that they had significant heritabilities (between 0.222±0.109 and 0.604±0.129, in relation to the examined character). For the first time the results of the present study are showing the applicability of semi-quantitative scale of deformities in the early ontogenetic stages, which might eliminate the environmental effect from the heritability estimations. As for the body shape in adult sea breams, the results are been discussed, in order to be included in selective breeding programs. In addition to the causative factors which differentiate the body shape between different environments.
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Πηγές φαινοτυπικής διαφοροποίησης σε εκτρεφόμενους πληθυσμούς τσιπούρας : μορφο-ανατομικές παραμορφώσεις, διακυμάνσεις φυσιολογικού φαινοτύπου και διερεύνηση της γενετικής βάσης τους.
