Rômulo Batista Rodrigues

Three Native Species as Possible Control for Limnoperna Fortunei in Net Cage Farming in the Itaipu Reservoir

The golden mussel (Limnoperna fortunei) possesses high fouling potential and has caused damage to various productive sectors. These individuals do not present known natural enemies, but they may be part of the feeding of one or more species of fish, which would help in their control. The main species of fish cultivated in cages in the Itaipu reservoir is pacu (mesopotamicus), and other species have also been evaluated in relation to intensive production viability such as jundiá (Rhamdia quelen) and curimbatá (Prochilodus lineatus). One of the problems faced in the net cages system in the Itaipu reservoir is the inlaying of the golden mussel in the cage’s mesh, making it difficult to handle, requiring more maintenance and reducing the service life of the net cages. This paper aims at evaluate the presence of L. fortunei in the digestive tract of three native species of fish cultivated in cages in the Itaipu reservoir. L. fortunei were present in the gastrointestinal tract of pacus and jundiás, and there was no L. fortunei in curimbatás. It is possible to conclude that for the three species studied, only jundiá and pacu have the capacity to consume and to control the L. fortunei embedded in the mesh of the net cages.

Production of live larvae following in vitro maturation of zebrafish oocytes

This study aimed to assess the effects of carp pituitary extract (CPE), follicle stimulating hormone (FSH) and luteinizing hormone (LH) on zebrafish oocyte maturation and the ability of these mature oocytes to be fertilized and developed until hatching. Stage III follicles were matured in eight treatments: five concentrations of CPE (16, 32, 48, 64 and 80xa0μg/mL), one of FSH (0.5xa0μg/mL), one of LH (0.5xa0μg/mL), or one combination of FSH (0.5xa0μg/mL) and LH (0.5xa0μg/mL). Maturation rates in CPE treatments were 12.8% (16xa0μg/mL), 24.8% (32xa0μg/mL), 27.0% (48xa0μg/mL), 22.7% (64xa0μg/mL) and 9.6% (80xa0μg/mL); in FSH was 15.7% (0.5xa0μg/mL), in LH was 31.8% (0.5xa0μg/mL) and in FSH (0.5xa0μg/mL) combined with LH (0.5xa0μg/mL) it was 50.4%. Inxa0vitro fertilization was performed in all treatments; however, only the treatment combining FSH and LH resulted in fertilized oocytes. After maturation using FSH combined with LH, the cleavage rate was 33.3% and hatching rate of live larvae was 20.0%. These results showed that FSH combined with LH was effective in IVM of zebrafish oocyte.

Valine in diets for Nile tilapia

This study verified the effect of valine on the zootechnical performance, percentage composition and growth of skeletal muscle fibre in fingerlings of Nile tilapia. A total of 270 fish (average initial weight 1.57 ± 0.05 g and total initial length 4.16 ± 0.46 cm) were used, distributed in 18 tanks (250 litres), in a completely randomised design with six treatments and three replications. Six diets (26.81% DP and 3200.00 kcal DE) were formulated with increasing levels of valine (0.82, 0.86, 0.98, 1.04, 1.10 and 1.26% of the diet). The zootechnical performance, percentage composition of the fish, and muscle-fibre distribution were evaluated. There was no effect from the different levels of valine (P>0.05) on zootechnical performance, percentage composition or the frequency distribution of muscle fibre. The addition of 0.82% valine (2.65% crude protein valine) is recommended in the diet of Nile tilapia fingerlings.

Viability assessment of primary growth oocytes following ovarian tissue vitrification of neotropical teleost pacu (Piaractus mesopotamicus)

Vitrification of ovarian tissue containing immature oocytes provides an important tool for protecting the endangered species and genetic diversity in aquatic species. Therefore, the main objective was to assess primary growth (PG) oocytes viability following ovarian tissue vitrification using histological analysis, two staining protocols (trypan blue or fluorescein diacetate combined with propidium iodide) and mitochondrial activity assay (MTT assay). In addition, oocyte histomorphometry was performed to evaluate the morphometric parameters after vitrification and the relationship with the occurrence of damage (nucleus and/or membrane) in PG oocytes. There was no significant difference among the vitrified oocytes using trypan blue dye or FDAxa0+xa0IP staining. Oocyte viability assessed using histological analysis showed that vitrification solution 2.0xa0M Me2SO + 2.5xa0M etilenoglycol +0.5xa0M sucrose (VS3; 66.43xa0±xa04.68%) and 1.5xa0M methanolxa0+xa05.5xa0M Me2SOxa0+xa00.5xa0M sucrose (VS5; 74.14xa0±xa03.71%) had the lowest viability rate. Similar results were observed in MTT assay where VS3 (1.63xa0±xa00.12) and VS5 (1.58xa0±xa00.09) had the lowest averages when compare with VS1 (2.39xa0±xa00.14), VS2 (1.78xa0±xa00.06) and VS4 (2.34xa0±xa00.19) (Pxa0=xa00.0002). In membrane damage evaluation by histology, there was no difference among vitrified oocytes and control. However, the highest percentages of nucleus damage were observed in treatments VS3 (26.00xa0±xa05.55) and VS5 (26.00xa0±xa05.55). Oocyte diameter did not change after vitrification; however, nucleus diameter was significantly higher in control group (49.03xa0±xa01.07). Oocyte viability by histological analysis was positive-correlated to the occurrence of nucleus (r2u202f=u202f0.78) and membrane (r2u202f=u202f0.45) damage after vitrification/warming. The high viability of PG oocytes obtained after ovarian tissue vitrification of Piaractus mesopotamicus suggests that the protocol applied here might be used successfully in other teleost species for food production.

Eugenol as anesthetic for fingerlings of patinga (Piaractus mesopotamicus x Piaractus brachypomus)

The aim of this work was to evaluate eugenol as an anesthetic agent for hybrid patinga. Were used 60 fingerlings with an average weight of 1.08 ± 0.17 g and total length of 3.53 ± 0.15 cm. They were evaluated six different concentrations of eugenol (10, 20, 30, 40, 50, 60 mg L -1 ). The fish were individually exposed to anesthetic to evaluate the anesthetic induction, after the anesthesia procedure, the fish were transferred to aquaria with anesthetic free water, for observation of recovery time. Thereafter, the fish in each treatment were placed in tanks with 30 liters for monitoring the mortality during 72 hours. There was a significant difference (P <0.05) for the induction times and recovery room for different concentrations of eugenol. Mortality was observed in animals above 40 mg L -1 eugenol concentrations. It is concluded that the best concentration for the eugenol anesthesia patinga is 20 mg L -1 showed efficacy for the induction and recovery of anesthesia, without causing mortality.