An overview of the reproductive cycle of cultured specimens of a potential candidate for Mediterranean aquaculture, Umbrina cirrosa

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The shi drum (Umbrina cirrosa), belonging to the Sciaenidae family of fish (Nelson et al., 2016) has attracted attention as it is an excellent diversification species in Mediterranean aquaculture to combat the low prices of the most cultured species due to the appearance of new producing countries in the Mediterranean area. In this manuscript we describe for the first time the reproductive cycle of captive shi drum specimens that are able to spontaneously spawn in captivity. Our data show that spermatogenesis started in one year old shi drum specimens, although the fish were not mature enough to complete the reproductive cycle. Thus, three year old specimens showed multiple spawns with around 65% of the eggs fertilized. In mature males, levels of 11-ketotestosterone (11KT), testosterone (T) and progesterone (P) were detected in serum and gonad, while 17β-estradiol (E2) was only detected in gonad. Testicular levels of E2 and P suggest that these hormones might have a role in spawning and in the subsequent spermatogonial proliferation. In mature females, however, P and E2 were detected in serum and gonad, while T and 11KT were only detected in gonad. The pattern shown by P in the ovary indicates a link between this hormone and ovarian renewal and a delay in vitellogenesis, which would explain why the vitellogenic stage of shi drum is quite short. The level of T and 11KT in the ovary suggests a role in oocyte maturation and spawning. The differences observed between sexes in the prevalence of some infection and the important economic losses produced by some vertically transmitted pathogens; have increase the attention to the interactions between the immune and reproductive systems. In this study we observed differences between sexes in the protease and bactericide activity levels. Thus, this manuscript represents the most complete overview to date of the shi drum reproductive cycle.