Gonadal remodeling and hormonal regulation during sex change of juvenile dusky grouper Epinephelus marginatus (Teleostei, Serranidae), an endangered protogynous hermaphrodite fish

Sex change was induced in Epinephelus marginatus juveniles using a nonsteroidal aromatase inhibitor (AI), a synthetic androgen (17α-methyltestosterone; MT), and a combination of both (MT + AI) in a 90-day experiment. A detailed remodeling of the gonads, the plasma level of gonadal steroids, and immunostaining of pituitary follicle-stimulating hormone (FSH), luteinizing hormone (LH), and somatolactin (SL) cells were analyzed. Sex inversion reached the final spermatogenesis stages using MT, while AI triggered spermatogenesis, but reaching only the spermatid stage. Estradiol (E₂) levels did not change in fish treated with AI but decreased throughout the experimental period in animals treated with MT and MT + AI. Testosterone (T) levels increased in animals treated with MT during the first 60 days (and combined with AI in the first 30 days), decreasing in all experimental groups at 90 days, while AI-treated animals had increased plasma 11-ketotestosterone (11-KT) levels after 90 days. In control fish, FSH- and SL-producing cells (ir-FSH and ir-SL) were restricted to pars intermedia (PI) of the adenohypophysis. Pituitary ir-FSH cells were decreased at the end of the experimental period in all treatments compared with the CT animals. LH-producing cells (ir-LH) were present in proximal pars distalis (PPD) and pars intermedia (PI) of adenohypophysis and did not change after the experimental period. The decreased number of ir-FSH cells at the end of the experiment in all treatments could be related to the negative feedback loop triggered by the increase in natural and/or synthetic androgens.

Influence of tropical reservoirs eutrophication on the polyunsaturated fatty acid profile in Astyanax altiparanae (Pisces: Characidae)

The eutrophication increases the quantity of algae that are deficient in highly unsaturated fatty acids (HUFA) n3, as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), altering the bottom-up transfer of the entire food chain. Due to the importance of the fatty acids (FA) in physiological processes related to the main role of the membrane phospholipids (PL) and precursors of eicosanoids, and also the little knowledge about the influence of eutrophication in tropical ecosystems, it is important to understand how anthropogenic changes in the aquatic ecosystem affect the lipid quality, specifically n3 HUFAs. This study aimed to investigate the influence of eutrophication on the FA profile of the hepatic PL, as well as prostaglandin (PG) levels in Astyanax altiparanae females. Fish were collected in reservoirs with different eutrophication degrees: Jundiaí (Ju) reservoir and Embu-Guaçu (EG) branch, considered as mesotrophic points, and Barragem (Ba) and Aracati (Ar), branches from Guarapiranga reservoir, considered as supereutrophic and hypereutrophic points, respectively. The FA profile of the liver PL was analyzed by gas chromatography, and the concentration of liver PGE2 was analyzed using ELISA immunoassay kits. The degree of eutrophication did not alter the PG concentration and produced few modifications in the FA profile of hepatic PL. Fish collected at Ba and EG presented similar FA profiles, both with high percentages of n3 HUFA, especially DHA, in comparison to fish from Ju. However, no change was observed in the n3 HUFA profile of the fish from Ar. These data demonstrated that the FA profile in A. altiparanae seems to be more related to different physiological requirements of n3 HUFA of the species than eutrophication. So, this study contributed to findings on the trophic transfer dynamics in tropical freshwater reservoirs, where a direct effect of eutrophication on the availability of HUFA n3 to animals is not suggested.

Thermal manipulation and GnRHa therapy applied to the reproduction of lambari-do-rabo-amarelo, Astyanax altiparanae females (Characiformes: Characidae) during the non-breeding season

Lambari-do-rabo-amarelo Astyanax altiparanae in the wild reproduce during spring and summer, but females undergo vitellogenesis throughout the year, including the non-spawning winter period when water temperatures are low. The present study investigated the physiological role of temperature modulation on the hypothalamus-pituitary-gonads axis of lambari during winter, as well as the effects of gonadotropin releasing hormone agonist (GnRHa) therapy. Captive females were exposed to two different temperatures (20 °C and 27 °C) and were injected weekly with GnRHa for 21 days during winter (Control, CTR; Low dose; LD and high dose of GnRHa, HD). At the end of the 21-days period gonadosomatic index (GSI), oocyte stage of development and theoretical fecundity were evaluated, together with plasma levels of 17β-estradiol (E₂). Gene expression of the two pituitary gonadotropins follicle-stimulating hormone (fshβ) and luteinizing hormone (lhβ), as well as hepatic vitellogenin-A (vtgA) expression were also analyzed. At the end of the experimental period, females from the six different experimental conditions were induced to spawn using human chorionic gonadotropin (hCG). Spawning performance parameters and plasma levels of the maturation inducing steroid (MIS) were analyzed. Gene expression of fshβ did not change with temperature manipulation, but females exposed to 27 °C and supplemented with a HD of GnRHa exhibited an increased fshβ gene expression, associated with higher E₂ levels. The higher water temperature alone was able to increase E₂ levels. At both water temperatures GnRHa injections induced a decrease in E₂ levels. GnRHa injected females had a lower vtgA gene expression levels at 20 °C. Even with differences in the gene expression of gonadotropins among the various temperature/GnRHa treatments, GSI and oocyte diameter did not change, but GnRHa enhanced the number of vitellogenic oocytes at 20 °C. The reproductive performance of lambari induced to spawn with hCG was better after the combined treatment with GnRHa and summer temperature.

Entomopathogenic nematodes in pharmaceutical formulations for Rhipicephalus microplus (Acari: Ixodidae) control: In vitro evaluation of compatibility, thermotolerance, and efficiency

This work aimed to investigate candidate biological control agents against the cattle tick Rhipicephalus microplus by studying three entomopathogenic nematodes (EPN) isolates from two species, Heterorhabditis bacteriophora (isolates LPP30 and HP88) and Heterorhabditis baujardi (isolate LPP7). The study comprised the pharmacotechnical development of four test formulations, and their biological evaluation, in three stages: 1) selection of the fittest EPN isolate at 16 ± 1 °C after 120 h of incorporation in the formulations; 2) determination of the effects of temperature and incubation time on the survival of the selected isolate in formulations; 3) evaluation of the in vitro efficacy (infectivity) of the selected EPN formulations and their components against R. microplus females after 72 h exposure. H. baujardi LPP7 presented the highest survival rates in 0.1% carboxymethyl cellulose sodium (CMC) formulations (100% at 25 °C, up to 10 days after incorporation). At the highest tested temperature (34.2 °C), 54% of LPP7 survived for up to 72 h in CMC formulations. The infectivity of LPP7-containing formulation against R. microplus was 99%, reducing oviposition, egg production index and larval hatching. Considering the pressing need for safer acaricide products, incorporation of EPNs in pharmaceutical formulations is presented as a promising approach for the biological control of cattle tick infestations, potentially reducing environmental impact and resistance development associated with chemical acaricides.

Exposure to aluminum, aluminum + manganese and acid pH triggers different antioxidant responses in gills and liver of Astyanax altiparanae (Teleostei: Characiformes: Characidae) males

Exposure to aluminum (Al) and aluminum + manganese (Mn) can trigger an increase in reactive oxygen species (ROS) and modify the activity of oxidative defense enzymes. This study investigated whether exposure to Al and Al + Mn at acid pH for 24 and 96 h causes oxidative stress evidenced by antioxidants and oxidative damage in the gills and liver of sexually mature Astyanax altiparanae males. The fish were subsequently immersed in metal-free water for 24 and 96 h to see whether they recovered from the effects of these metals. Exposure to an acid pH boosted the activity of gill superoxide dismutase (SOD) at 96 h and the fish did not recover when immersed for the same period in water at neutral pH. Exposure to Al increased glutathione (GSH) levels (24 h) in the gills, returning to control levels during the recovery period, showing the efficiency of the antioxidant system in preventing lipid peroxidation of the gills and liver. Mn did not modify the activity of the enzymes studied, but did trigger late hepatic lipid peroxidation during the recovery period. The group exposed to Al + Mn exhibited several alterations, including increased concentration of GSH, as well as higher GPx and GR activity in the gills. Despite the defensive responses triggered by acute exposure, during the recovery period there were alterations in catalase (96 h) and an increase in hepatic metallothionein (24 h), but this did not prevent hepatic lipid peroxidation. Al and Al + Mn produced different effects, and the timing of enzymatic and non-enzymatic antioxidant defenses also differed.

Embryonic and larval development and fatty-acid profile of Epinephelus marginatus spawned in captivity: tools applied to captive rearing

Development, ontogeny of the digestive system and the fatty-acid (FA) profile, were analysed during development of Epinephelus marginatus. Larvae were analysed 7 and 17 days post fertilization (dpf) to evaluate fatty-acid profile and morphological variables, respectively. Epinephelus marginatus larvae have relatively slow development of digestive structures, but were able to capture, ingest and digest prey by 5 dpf. Eggs were composed of high percentages of polyunsaturated fatty acids (PUFA) in phospholipids. The percentage of n3 PUFAs was higher than n6, especially docosahexaenoic acid (DHA), which exhibited higher levels compared with other marine species during the first 3 days of development, both in terms of phospholipids and triglycerides. The larvae present a high content of docosahexaenoic acid-eicosapentaenoic acid (DHA-EPA) and, during this phase, live food of small size was required (copepods or SS-strain Brachionus rotundiformes), enriched with DHA-EPA. These results may guide future studies on the contribution of FAs required during this stage of the life cycle of E. marginatus, to advance knowledge of the use of these FAs throughout ontogeny and contribute to the culture of this species commercial production or restocking.

Aluminum as an endocrine disruptor in female Nile tilapia (Oreochromis niloticus)

The effects of aluminum on plasma ion, lipid, protein and steroid hormone concentration were evaluated in Oreochromis niloticus broodstock females. Lipid and protein concentrations from the gonads and liver were also measured. Experiments were performed at neutral and acidic water pH. Four groups of fish were tested for 96h: 1) control conditions at neutral water pH; 2) control conditions at acidic water pH (CTR-Ac); 3) aluminum at neutral water pH (Al-N); and 4) aluminum at acidic water pH (Al-Ac). Aluminum and acidic water pH exposure caused no ionoregulatory disturbances. Total lipid concentration increased in the mature gonads and decreased in the liver, suggesting an acceleration of lipid mobilization to the ovaries in animals exposed to aluminum. However, a decreased protein concentration in ovaries was also observed. Exposure of control fish to acidic water pH caused an increased concentration of plasma 17alpha-hydroxyprogesterone. However, females exposed to aluminum at acidic water pH showed a decreased of plasma 17alpha-hydroxyprogesterone and cortisol. No differences in plasma 17beta-estradiol were observed. The physiological mechanisms underlying the disturbances observed are discussed focusing on reproduction. We suggest that aluminum can be considered an endocrine disrupting compound in mature O. niloticus females.

Patterns of oocyte development in natural habitat and captive Salminus hilarii Valenciennes, 1850 (Teleostei: Characidae)

Fecundity and oocyte development in Salminus hilarii female brood stock were analyzed with the aim of investigating the impact of migration impediment on oogenesis. Histological analyses of the ovaries were performed in adult females caught in two different environments--the Tietê River (natural) and captivity--and the gonadossomatic index, oocyte diameter and fecundity determined. Five germ cell development stages (oogonium, perinucleolar, cortical alveoli, vitellogenic, ripe) and two other structures (postovulatory follicles and atretic oocytes) were observed in females caught in the river. Captive animals lacked the ripe oocytes and postovulatory follicles and had a relatively higher number of atretic oocytes. Females in captivity are known to produce larger oocytes, and they release fewer eggs in each spawn (absolute fecundity) when compared with animals that are able to migrate. Our results suggest that the Tietê River is undergoing alterations which are being reflected in the reproductive performance of S. hilarii, mainly due to the presence of atretic oocytes in females caught in the river. The lack of postovulatory follicles and ripe oocytes in captive animals reveals that migratory impediment negatively impacts final oocyte maturation. However, the stage of maturation reached is adequate for ovulation induction with hormone manipulation.

Application of high hydrostatic pressure to eliminate Listeria monocytogenes from fresh pork sausage

Ground pork patties were inoculated separately with 10(9) CFU/g each of three strains of Listeria monocytogenes obtained from the National Animal Disease Center (NADC). Inoculated patties were packaged under vacuum and treated at 414 megapascals (60,000 lb/in2) for up to 60 min by high hydrostatic pressure (HHP). Survivors were determined by surface plating onto modified Oxford agar and trypticase soy agar with yeast extract, as well as by the most probable number method using Listeria enrichment broth. Average D values ranged from 1.89 to 4.17 min, depending on the strain, with the most virulent strain (reported by the NADC) having the highest D value. We tested the usefulness of applying a mild heat treatment at 50 degrees C, simultaneously with HHP, to lower these values. Average D values ranged from 0.37 to 0.63 min, depending on the strain. Thus, a 10-log10 reduction could be achieved even in the most pressure-resistant strain of L. monocytogenes by a 6-min application of heat and HHP. Shelf life studies were also conducted, with spoilage levels reached after 5 days of storage at 4 degrees C for controls versus 28 days for treated samples. Sensory evaluation of uninoculated grilled patties showed that panelists could not distinguish between those treated by heat and HHP and untreated controls (P<0.05). Thus, treatment by HHP in combination with mild heating can be used successfully to produce safer, longer-lasting fresh pork without affecting quality.