Long-term feeding restriction in prepubertal male sea bass (Dicentrarchus labrax L.) increases the number of apoptotic cells in the testis and affects the onset of puberty and certain reproductive parameters

• Long-term feed restriction fails to impair reproduction in male sea bass.
• Feed restriction reduces growth and delays gonadal development.
• Apoptotic bodies increases in the testes of fish under feed restriction.
• Feed restriction reduces sperm concentration but increases volume and motility.

In sea bass (Dicentrarchus labrax), the onset of puberty under intensive farming conditions is likely related to the availability of food. Therefore, a close connection between feed intake, lipid storage and onset of reproduction can be established. This study reports the effects of long-term feed restriction on the reproductive performance of male sea bass entering their first breeding season. A control group (C) was fed to apparent satiety, while experimental groups were restricted to 1/4 (1/4 C) or 1/8 (1/8 C) of the ration administered to the control group. It was determined that restricted feed regimes influenced the weight, length, growth rate and gonadosomatic index (GSI) of the fish. Specifically, the 1/8 C group showed lower GSI values than the control animals. In the experimental animals, the histological analysis revealed a moderate delay in testes development and a larger number of apoptotic bodies at onset of gametogenesis. The plasma level profiles of 11-ketotestosterone (11-KT) were comparable among the groups. Additionally, certain sperm parameters, including sperm count, motility and expressible milt volume, were evaluated throughout the reproductive season, and long-term fasting was found to affect sperm volume and counts, curvilinear velocity (VCL), average path velocity (VAP) and percentage of static and medium motility sperm of sea bass sperm. However, puberty was not suppressed; at most, gonadal development was reduced and progression of gonadal stages delayed as well as the duration of the production of sperm. Unexpectedly, some characteristics of their motility experienced a significant increase.