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The greater amberjack Seriola dumerili is a new aquaculture fish that may display reproductive dysfunctions. During extensive follicular atresia, which is a common reproductive dysfunction in females during vitellogenesis, part of the reabsorbed yolk returns to the liver to be metabolized and recycled. Melanomacrophage centres (MMCs) are aggregates of macrophage‐like cells that play a role in the destruction, detoxification and recycling of endogenous and exogenous materials, and have been associated with systemic stress. Wild and captive‐reared greater amberjack were sampled in the Mediterranean Sea during two different phases of the reproductive cycle. The liver of reproductively dysfunctional captive‐reared females sampled during the spawning season showed a high density of both MMCs and apoptotic cells. A weak liver anti‐cytochrome P450 monooxygenase 1A immunoreactivity was observed, suggesting that the examined fish were not exposed to environmental pollutants. We propose that the observed increase in MMCs and apoptosis in captive‐reared fish was related to the hepatic overload associated to the metabolism of yolk proteins reabsorbed during extensive follicular atresia. Since follicular atresia is a frequent physiological and pathological event in teleosts, we suggest that the reproductive state should be always assessed when MMCs are used as markers of exposure to stress or pollutants. [ABSTRACT FROM AUTHOR]

The age of sexual maturity of the Atlantic bluefin tuna (Thunnus thynnus; ABFT) is a reference point for stock assessment and management. The International Commission for the Conservation of Atlantic Tunas (ICCAT) recognizes a western and an eastern Atlantic ABFT stock, based on the assumptions of separate, exclusive spawning grounds, i.e., the northern Gulf of Mexico and the Mediterranean Sea, with different ages of sexual maturity, 8–12 years vs 3–5 years, respectively. Multiple line of evidences indicate that spawning is not restricted to the Gulf of Mexico and the Mediterranean Sea, and reconsideration of historical documents, as well as results from recent studies, indicate that sexual maturation schedules of the two proposed stocks are similar (3–5 years). The present review of classical and recent literature suggests that ABFT have more complex reproductive behavior than previously considered: on eastern spawning grounds 50% of ABFT females reproduce at 3 years of age and 100% are sexually mature at 5 years of age. In the western management area, younger adults (age ≥ 5 years) and some larger adults apparently spawn in the northwest Atlantic Ocean across the Slope and Caribbean Seas, whereas the Gulf of Mexico spawners are mostly large adults (age ≥ 8 years). [ABSTRACT FROM AUTHOR]

The greater amberjack Seriola dumerili is an excellent candidate for the Mediterranean aquaculture, due to its large body size and high growth rate, as well as its high flesh quality and commercial value worldwide. For its successful incorporation in the aquaculture industry, an in-depth understanding of the reproductive function of the species under rearing conditions is necessary, since completion of oogenesis in captivity is currently a bottleneck for the commercial production of the species. Liver and ovary samples from wild and captive-reared greater amberjack females were collected at three different phases of the reproductive cycle: early gametogenesis (EARLY, late April-early May), advanced gametogenesis (ADVANCED, late May-early June) and spawning (SPAWNING, late June-July). The cDNAs of three vitellogenins (VtgA, VtgB and VtgC) were partially sequenced and a qRT-PCR for their expression was used to compare ovarian maturity stage and liver vitellogenin transcript levels between wild and captive-reared individuals. An extensive atresia of late vitellogenic follicles, which prevented any further oocyte development and spawning was observed in captive-reared individuals during the ADVANCED phase. The expression levels of the three vitellogenins, as well as the amount of yolk globules in vitellogenic oocytes, did not differ significantly between captive-reared and wild females, indicating that the observed oogenesis impairment in greater amberjack reared in captivity was not related to an insufficient liver synthesis or a reduced oocyte uptake of vitellogenin. [ABSTRACT FROM AUTHOR]

The article focuses on a study of male germ cell proliferation and apoptosis of captive-reared Atlantic bluefin tuna (ABFT) thunnus thynnus during its reproductive cycle. Topics discussed include increase of germ cell apoptosis when spermatogenesis occurred from April to May, temporal overlapping between spermatogenesis in wild and captive ABFT, and gonadotropins and steroid hormones in mammals as a survival factor that prevents germ cell apoptosis.