Biology subjects

Ramos-Judez, S.

Publications and source records attributed to Ramos-Judez, S..

4 recordsLinked to original sources

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↗

bioRxiv2021

Feeding habits and the influence of pellet diameter on the feeding responses of the flathead grey mullet (Mugil cephalus) in captivity

The feeding habits and effect of the diameter of pelleted feeds on the feeding responses of wild juvenile and adult flathead grey mullet (Mugil cephalus) in captivity were examined. Optimal pellet size for feeding was defined according to the behavioural responses and ingestion of pellets with different diameters (2, 4, 6, 8 mm) that were dropped into the tank in a random sequence. Larger pellets (6 and 8 mm) were more attractive (lower reaction time, high percentage of capture), but the small to medium-sized pellets (2 and 4 mm) were consumed the most. The optimal size was the 2- and 4- mm pellet diameter for juvenile individuals (365.50 {+/-} 36.90 g; 28.8 {+/-} 0.84 cm) and the 4-mm diameter pellet for adults (937.49 {+/-} 146.54 g; 40 {+/-} 1.12 cm). The preferred feeding area of adult mullet was also studied to estimate preference in relation to pellet characteristics such as floating or sink. Two pellet types, floating or sinking, were offered simultaneously in the water column: at the surface, mid-water column and bottom of the tank. The flathead grey mullet had a preference to feed in the mid-water column and the bottom of the tanks indicating that sinking or slow-sinking pellets would be the optimal feed type in relation to mullet feeding behaviour.

animal behavior and cognition↗

bioRxiv2020

Low sperm to egg ratio required for successful in vitro fertilisation in a pair-spawning teleost, Senegalese sole (Solea senegalensis)

Cultured Senegalese sole (Solea senegalensis) breeders fail to spawn fertilised eggs and this bottleneck could be solved with the implementation of large-scale in vitro fertilisation protocols. However, low production of poor-quality sperm has frustrated the development of in vitro fertilisation protocols. Cultured females were induced to ovulate with a 5 {micro}g kg-1 single injection of gonadotropin releasing hormone agonist (GnRHa) and good quality eggs (82.6 {+/-} 9.2% fertilisation) were stripped 41:57 {+/-} 1:46 h after the injection. Sperm was collected from cultured males, diluted in modified Leibovitz and used fresh to fertilise the eggs. A non-linear regression, an exponential rise to a maximum (R = 0.93, P < 0.0001) described the number of motile spermatozoa required to fertilise a viable egg and 1617 motile spermatozoa were sufficient to fertilise 99 {+/-} 12% ({+/-} 95% CI) of viable eggs. Similar, spermatozoa egg-1 ratios of 592 {+/-} 611 motile spermatozoa egg-1 were used in large-scale in vitro fertilisations with 190,512 {+/-} 38,471 eggs. The sperm from a single male (145 {+/-} 50 {micro}L or 8.0 {+/-} 6.8 x 108 spermatozoa) was used to fertilise the eggs. The mean hatching rate of the large-scale in vitro fertilisations was 70 {+/-} 14 % to provide 131,540 {+/-} 34,448 larvae per fertilisation. When unfertilised eggs were stored at room temperature the percentage of viable eggs decreased gradually and indicated the sooner eggs were fertilised after stripping the higher the viability of the eggs. The collection of sperm directly into a syringe containing modified Leibovitz significantly increased the percentage of motile spermatozoa (33.4 {+/-} 12.2 %) compared to dilution in modified Leibovitz immediately after collection (6.6 {+/-} 4.9 %). Senegalese sole have a pair-spawning reproductive behaviour characterised by external gamete fertilisation in close proximity with no sperm competition. The low spermatozoa egg-1 ratio required for maximum fertilisation was consistent with this reproductive behaviour and strategy. The provision of a large-scale in vitro fertilisation protocol (200 {micro}L of sperm per 100 mL of eggs) will enable the industry to operate sustainably and implement breeding programs to improve production.

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↗