In vitro follicle culture shows that progestagens are the maturation-inducing hormones (MIH) and possible regulators of the ovulation-mediating hormone PGE2 in female Eurasian perch Perca fluviatilis

Abstract

In European aquaculture, Eurasian perch, Perca fluviatilis L., is perceived as one of the most highly valuable freshwater fish species and a strong candidate for the development of freshwater aquaculture. In the pursuit of improving the quality of reproduction in this domesticated species, investigating the hormones mediating the final oocyte maturation (FOM) is therefore indispensable. But, the exact nature of the maturation-inducing hormone (MIH) in Eurasian perch is unknown. To further validate the existence of a maturation-inducing activity behind potential hormonal candidates in this species, we in vitro tested a group of nine hormones: cortisol (Co), 11-deoxycortisol (11-D), corticosterone (coS), 11-deoxycorticosterone (DOC), 17α,20βdihydroxy-4-pregnen-3-one (DHP) and 17α,20β,21 trihydroxy-4-pregnen-3-one (THP), prostaglandin E 2 (PGE2), estradiol-17β (E2) and testosterone (T), in their ability to trigger FOM advancement and the production of sex steroids potentially involved in FOM. Using mature female perch, two in vitro experiments were conducted with oocytes at the start of the FOM. The follicles were incubated for 62 h in Cortland media with and without human chorionic gonadotropin (hCG). By the end of the incubation, only DHP and THP triggered the full advancement in FOM even at low doses with the effect of DHP being in vivo validated. However, the de novo productions of E2 and DHP were not shown to be regulated by either of the MIH candidates. Progestagens are hence more credible candidates as MIH than corticosteroids in Eurasian perch. Our in vitro study also revealed that both PGE2 and DHP are strongly associated with ovulation and that PGE2 might have slightly contributed to such DHP activity.

Effect of thermal management on vitellogenesis and maturation in indoor-reared pikeperch (Sander lucioperca)

“…Besides the significantly faster FOM and higher ovulation of fish subjected to the incremental increase in spawning temperature after stimulation, these fish had significantly higher DHP levels in the blood at the time of injection. This finding is of particular https://doi.org/10.17221/136/2023-CJAS importance since recent studies have suggested DHP to be a potent maturation induction steroid (MIS) in Eurasian perch (Perca fluviatilis), another species common to the percids family (El Mohajer et al 2021). This is, for that reason, intriguing as there were thus far three studies showing that the temperature most commonly applied for pikeperch spawning of 12 °C is applicable as the lowest temperature for the spawning induction (Hermelink et al 2013;Milla et al 2021).…”

Maturation Inducing Hormones in teleosts: Are progestogens always the first to be nominated?

“…Baek and Lee, 2019) raised the possibility that PGs effects on FOM induction are mediated through the production of the progestogens DHP and THP. Conversely, in Eurasian perch, DHP induced the in vitro production of PGE2 in maturing follicles which highlight the strong bilateral link between DHP and prostaglandins (El Mohajer et al, 2021). Otherwise, given the capacity of PGs to be effective at low doses (from 1 to 10 ng/ml) in vitro in other studies (Sorbera et al, 2001;Joy and Singh, 2013), we cannot rule out any direct effect of PGs on FOM induction, primarily because the circulating levels of PGs in the plasma of fish in the peri-ovulation stage are within the ranges of the mentioned effective doses, at least in goldfish and brook trout (Cetta and Goetz, 1982;Sorensen et al, 2018).…”

“…Another corticosteroid, DOC, also induces oocytes to mature at 5000 ng/ml in catfish (Goswami and Sundararaj 1974) and provokes GVBD at 100 ng/ml in yellow perch (Goetz and Bergman 1978). However, recent in vitro assays conducted at the beginning of FOM in wild or captive Eurasian perch have revealed that the DHP productions are decreased by DOC and that DOC is not capable to induce GVBD at physiological doses (Mandiki et al 2017;El Mohajer et al 2021), which seems to be quite contradictory to the maturation-inducing activity of DOC recorded for yellow perch, a species phylogenetically close to Eurasian perch. This contradiction raises the question of whether variations exist among close species in the identities of corticosteroids such as DOC as either putative MIHs or inhibitors of FOM.…”

“…In all cases, this descriptive approach may complement an experimental approach that involves administration of the hormone followed by evaluation of its effects on FOM induction. The different methods of MIH administration may range between the injection of the MIH into the muscles or peritoneal cavity of the fish and the direct administration of the hormone into the water containing the fish (El Mohajer et al, 2021;Tokumoto et al, 2011). However, direct hormonal injection imposes risks of unresponsiveness to treatment or injuries to the fish which can affect the success of confirming the MIH identity.…”