Influence of temperature on muscle fibre hyperplasia and hypertrophy in larvae of blackspot seabream, Pagellus bogaraveo

The effects of temperature on Pagellus bogaraveo muscle cellularity were investigated, by morphometry, throughout the endogenous feeding stage, testing two rearing temperatures: 14 and 18 °C. The following parameters were estimated in transversal body sections at post-opercular and post-anal body levels: the total cross-sectional muscle area, the total number of fibres and the mean cross-sectional fibre area. At hatching, no significant influence of the temperature was observed on the morphometric parameters measured in the white muscle. At mouth opening, an increase in the number of post-opercular white fibres was promoted by the highest temperature. During embryonic development, the red muscle fibre number in the post-anal part of the larvae increased with higher temperature, but it appears that the difference was no longer present at mouth opening. An increase in the fibre area and in the total cross-sectional area of red muscle at the post-anal level was promoted by a 4 °C increase in the temperature during the vitelline phase. In conclusion, the axial musculature of blackspot seabream embryos/larvae reacted differently to temperature influence according to the body location, strongly supporting the need to look at and account for different body locations when evaluating muscle cellularity in fish, namely in growth/aquaculture-related studies.