Biology subjects

Gimenez, I.

Publications and source records attributed to Gimenez, I..

4 recordsLinked to original sources

bioRxiv2023

In vivo effect of recombinant FSH and LH administered to meagre (Argyrosomus regius) at the initial stages of sex differentiation.

Recombinant gonadotropins, follicle stimulating (rFSH) and luteinizing hormone (rLH), offer the potential to induce gametogenesis in prepubertal fish. This study aimed to determine the in vivo effect of Argyrosomus regius rFSH (arrFSH) and Argyrosomus regius rLH (arrLH) administered to prepubertal meagre juveniles at the initial stages of sex differentiation. Meagre single-chain recombinant gonadotropins, arrFSH and arrLH were produced with the CHO expression system by Rara Avis Biotec, S. L. Juvenile meagre, 9-months old with mean weight of 222 {+/-} 36 g (mean {+/-} SD) were randomly distributed into seven experimental groups (n = 8 per group) that were treated weekly for three weeks with an acute injection of 6, 12 or 18 g kg-1 of arrFSH (groups, 6-arrFSH, 12-arrFSH and 18-arrFSH) or 6, 12 or 18 g kg-1 of arrLH (groups, 6-arrLH, 12-arrLH and 18-arrLH) or saline solution (Control group). Two more groups (n=8) were set up and treated for 6 weeks, with 12 g kg-1 of arrFSH or saline Control. The fish were held in a 10 m3 tank with natural photoperiod (Feb. - March) and temperature 16.1 {+/-} 0.4{degrees}C. At the start of the experiment (n = 8) and end of the three week experiment all fish were sacrificed and gonads dissected. Gonads were weighed, fixed in Bouins solution and processed for histological analysis. Blood was sampled from all fish at the start and end of the experiment (week 3 and 6) for 17{beta}-estradiol (E2) and 11-ketotestosterone (11-KT) analysis. Juvenile meagre at the start of the experiment were in the initial stages of sexual differentiation, indicated by the presence of the ovarian or testes lumen that was surrounded by undifferentiated embryonic germ stem cells and somatic cells. At the end of the experiment, there was no significant difference in gonadosomatic index (GSI) amongst control (initial and saline treated) and the experimental groups. After three weeks of application of arrFSH, arrLH or saline all fish presented a similar gonadal structure as at the start of the experiment. However, the incidence of isolated developing germ cells (principally spermatogonia, spermatocytes, spermatids, but also perinucleolar stage oocytes) generally increased in arrGTH treated meagre. A mean of 44 % of meagre treated with arrFSH or arrLH presented isolate developing germ cells, mainly male cells. Plasma steroid levels of E2 decreased significantly from the start of the experiments to the end. At the end of the experiment there were no differences in plasma E2 amongst Control fish and rGTH treated fish. Plasma 11-KT showed no change from the start of the experiment to week 3. However, a significant increase was observed in the arrFSH group after six weeks of treatment compared to the start of the experiment and the control group on week 6. The application of arrFSH or arrLH to meagre at the initial stages of sex differentiation did not stimulate steroid production until week six and had a limited, but evident effect on the development of isolated germ cells. The rGTHs, arrFSH or arrLH did not stimulate large developmental changes in undifferentiated gonads. HIGHLIGHTSExogenous recombinant gonadotropins administered to meagre did not advance sexual differentiation. Exogenous recombinant gonadotropins administered to meagre did not affect plasma estradiol. Exogenous recombinant FSH increased the proportion of meagre with isolated male germ cells. Exogenous recombinant FSH increased plasma 11-ketotestosterone in meagre treated for 6 weeks.

physiology↗

bioRxiv2023

Thermal suppression of gametogenesis explains historical collapses in larval recruitment

Projections for population viability under climate change are often made using estimates of thermal lethal thresholds. These estimates vary across life history stages and can be valuable for explaining or forecasting shifts in population viability. However, sublethal temperatures can also depress vital rates and shape fluctuations in the reproductive viability of populations. For example, heatwaves may suppress reproduction, leading to recruitment failure before lethal temperatures are reached. Despite a growing awareness of this issue, tying sublethal effects to observed recruitment failure remains a challenge especially in marine environments. We experimentally show that sublethal suppression of female gametogenesis by marine heatwaves can partially explain historical collapses in urchin recruitment. This response differed by sex but was similar between animals from warmer or cooler regions of their range. Overall, we show sublethal thermal sensitivities of reproduction can narrow the thermal envelope for population viability compared to predictions from lethal limits.

ecology↗

bioRxiv2021

Recombinant Fsh and Lh therapy for spawning induction of previtellogenic and early spermatogenic arrested teleost, the flathead grey mullet (Mugil cephalus)

With the expansion and diversification of global aquaculture, efforts continue to develop new bio-technologies for assisted reproduction in species that present reproductive dysfunctions. Flathead grey mullet (Mugil cephalus) held in intensive conditions in the Mediterranean region, display a severe reproductive dysfunction, where males do not produce fluent milt and females are arrested at previtellogenesis or early stages of vitellogenesis. In the present study, weekly injections of species-specific single-chain recombinant gonadotropins (rGths); follicle stimulating hormone (rFsh) (6 to 12 g kg-1 doses) and luteinizing hormone (rLh) (2.5 to 24 g kg-1 doses) were administered to induce vitellogenesis, from previtellogenesis / early vitellogenesis to the completion of vitellogenic growth in females and enhance spermatogenesis to produce adequate volumes of sperm from non-fluent males. During the experiment, all treated females (n = 21) developed oocytes in late vitellogenesis with 603 {+/-} 8 m diameter and all treated males produced fluent sperm. To induce oocyte maturation, ovulation and spawning, females were treated with either (i) a priming dose of 30 g kg-1 of rLh and a resolving dose of 40 mg kg-1 of progesterone (P4), (ii) priming and resolving doses of 30 g kg-1 of rLh, or (iii) priming and resolving doses of 40 mg kg-1 of P4 given 24:05 {+/-} 0:40 h apart. Females were placed in spawning tanks with rGth treated males that had fluent sperm. Spontaneous spawns of fertilised eggs were obtained after inducing with rLh + P4 or rLh + rLh (priming and resolving injections) with a spawning success of the 85% (8 of 9 females) and 100% (n = 6), respectively. The eggs collected from the tanks presented 64 {+/-} 22% fertilization with embryo development and 57 {+/-} 24 % hatching. The treatment P4 + P4 had a lower ovulation success (50 % - 3 of 6 females) and spawning success (17 %) with no fertilised eggs. Success was independent of the initial gonadal stage of females. In comparison, control females did not show any advance in gonadal development from initial stages and control males did not produce fluent sperm. The present results confirm the possibility of controlling oogenesis from previtellogenesis to the completion of maturation and fertilised tank spawning using exclusively rFsh and rLh in a teleost species.

physiology↗

bioRxiv2020

Providing recombinant gonadotropin-based therapies that induce complete gametogenesis and produce viable larvae from an immature teleost, flathead grey mullet (Mugil cephalus)

Under intensive captive conditions, wild-caught flathead grey mullet (Mugil cephalus) females remained arrested at early gonad development and no sperm could be obtained from males. With the aim to induce and complete oogenesis, induce the release of sperm and obtain fertilized eggs, adult female and male grey mullet were treated with M. cephalus single-chain recombinant gonadotropins (rGths), follicle-stimulating (rFsh) and luteinizing (rLh) hormones. In Experiment 1, fish were treated with a weekly dose of rFsh (15 g kg-1), which in females significantly (P < 0.001) increased plasma concentration of 17{beta}-estradiol and induced vitellogenic oocyte growth up to a maximum mean diameter of 425 {+/-} 19 m after 9 weeks of treatment. In Experiment 2, fish were treated with weekly injections of both rFsh and rLh at different doses (from 2.5 to 12 g kg-1). Oocyte diameter reached 609 {+/-} 5 m, from which final oocyte maturation and ovulation was induced with 30 g kg-1 of rLh and 40 mg kg-1 of progesterone. Good quality sperm (> 75% motile spermatozoa) was obtained from males in both experiments, and in Exp. 2 the addition of rLh induced the production of higher quantities of sperm that were used to fertilise the eggs. Although fertilisation was low (0.4 %), these fertilized eggs with embryo development produced viable larvae (71% hatching rate). This is the first report in a teleost species, to obtain larvae from eggs that were from immature females induced through to maturation with rGths. In comparison, control females remained arrested as immature fish and control males did not produce sperm. The study demonstrated that both rGths are effective to induce the entire process of oogenesis in sexually immature female grey mullet and to obtain flowing sperm from males, adding more data to confirm the roles of the Gths in teleost gametogenesis. This advance provides the bases of a therapy for the use in the aquaculture of teleost of commercial interest or the conservation of endangered species.

physiology↗