Unravelling spermatogenesis in spotted wolffish: Insights from the ultrastructure of juvenile male testes to the cryopreservation of broodstock sperm.

The aim of this study was to deepen our understanding of the reproductive biology of male spotted wolffish () using two different experimental approaches involving juvenile and mature broodstock fish. The first approach consisted of a detailed histological examination of the testes to identify the onset of gonadal maturation and characterise the spermatogenic stages in two- and three-year-old juvenile specimens. Light microscopy analysis revealed clear differences between the age groups.

Gonadotropin expression, pituitary and plasma levels in the reproductive cycle of wild and captive-reared greater amberjack (Seriola dumerili).

We compared the endocrine status of the pituitary-gonad axis of wild and captive-reared greater amberjack (Seriola dumerili) during the reproductive cycle (April - July), reporting on the expression and release of the two gonadotropins for the first time in the Mediterranean Sea. Ovaries from wild females were characterized histologically as DEVELOPING in early May and SPAWNING capable in late May-July, the latter having a 3 to 4-fold higher gonadosomatic index (GSI). SPAWNING capable wild females exhibited an increase in pituitary follicle stimulating hormone (Fsh) content, plasma testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P), while almost a 10-fold increase was observed in pituitary luteinizing hormone (Lh) content.

Effects of different hormonal treatments on spermatogenesis advancement in hatchery-produced greater amberjack Seriola dumerili (Risso 1810).

In earlier studies, wild-caught greater amberjack Seriola dumerili (Risso, 1810) males reared in sea cages showed gametogenesis impairment and low sperm production and quality. Here, we (a) examined if F1 hatchery-produced males reared in sea cages also exhibit reproductive dysfunctions and (b) evaluated the effects of gonadotropin releasing hormone agonist (GnRHa) administration through injections (GnRHa) or sustained-release implants (GnRHa), and human chorionic gonadotropin (hGC) injections on spermatogenesis/spermiation enhancement. Fish were given a hormone treatment just prior to the spawning season, and were transferred to land-based tanks, according to an established spawning induction protocol.

Timing of puberty in F1-generation hatchery-produced greater amberjack (Seriola dumerili).

We evaluated the onset of puberty of first-generation (F1) hatchery-produced greater amberjack (Seriola dumerili) reared in sea cages for 5 years. Fish were sampled every year in June, at the expected peak of the spawning period in the Mediterranean Sea. No sexual dimorphism in body weight was observed in the study.

Sperm quality of greater amberjack Seriola dumerili throughout the reproductive season and in response to GnRHa treatment with controlled release implants.

A wild-caught stock of greater amberjack Seriola dumerili reared in sea cages in two commercial aquaculture facilities in Greece was administered gonadotropin-releasing hormone agonist (GnRHa), loaded in controlled release implants, and was used in spawning induction experiments throughout the reproductive season. Sperm quality was evaluated using computer-assisted sperm analysis (CASA) before and after GnRHa administration and the extent of the spermiation period was determined. Males were in spermiation throughout the monitoring period from May 30 until July 18, at temperatures between 19 and 24 °C.