ABSTRACT. This study aimed to assess the impact of microalgal concentrations in diets on the settlement and metamorphosis stages of pediveliger larvae and spat of Crassostrea gigas oysters. Diets containing microalgal concentrations of 8, 12, and 16×104 cells mL-1 were administered for seven days during the larval settlement phase of pediveliger larvae. In the metamorphosis and postlarval cultivation phases, diets with microalgal concentrations of 8, 16, 24, and 32×104 cells mL-1 and a control group without food were tested for 14 and 21 days, respectively. Growth, yield, and survival were assessed every seven days. The diet comprised 30% Isochrysis galbana and 70% Chaetoceros muelleri microalgae. In the metamorphosis phase, the results revealed no significant differences in larval metamorphosis rate and survival across the tested diets. The concentrations exhibited similar survival in the spat with an initial average shell height of 0.657 ± 0.05 mm, with a significant difference only in growth. In the spat with an initial average shell height of 0.830 ± 0.12 mm, no differences in survival were observed among the tested concentrations. We concluded that diets of 12 and 16×104 cells mL-1 provide high rates of larval metamorphosis and spat yield during the larval settlement and metamorphosis phases. During the spat cultivation phases, diets of 32 and 24×104 cells mL-1 could optimize the cultivation time and yield of C. gigas spat in the laboratory. However, when considering survival alone, no advantage was found in providing a diet with a microalgal concentration above 8×104 cells mL-1 across all C. gigas oyster cultivation phases.

Abstract The reproductive cycle is an essential aspect of oyster farming. Understanding the period of each sexual stage aids in planning oyster harvest, seed collection with artificial collectors, and reproductive season for hatchery seed production. In this sense, this work evaluated the reproductive cycle of Crassostrea gasar oysters cultivated in three important oyster farming locations in the Estuarine Complex of Paranaguá, Rasa Island, Medeiros, and Ponta Oeste (Mel Island), with monthly oyster sampling in each sampling site. Temperature and salinity were recorded in loco at each sampling time. In the laboratory, oysters were identified and measured; tissue samples were collected for molecular identification of species; and histology was conducted for reproductive cycle analysis. Histological examination of the gonadal tissue was performed with slides stained with Harris hematoxylin and eosin. Salinity and temperature data showed no differences between the three sampling sites during the studied period. Molecular analysis showed that the oysters sampled were C. gasar (100%). Histological analysis showed intense spawning of C. gasar in December and February (26.72 °C) and June (20 °C). There was a resting stage in both males and females during winter. Some oysters (n = 21) were parasitized by Bucephalus sp., and it was impossible to determine oyster sex. harvest collectors production sense Paranaguá Island Medeiros Mel , Island) site time laboratory measured species eosin C 100%. 100 100% . (100%) 26.72 2672 26 72 (26.7 °C 20 (2 °C. winter n 21 sp sp. sex 10 (100% 26.7 267 2 7 (26. ( 1 (100 26. (26 (10 (1

ABSTRACT. As an alternative to the use of cytochalasin B (CB), 6-dimethylamino-purine (6-DMAP) and thermal shock (heat shock by increasing the temperature from 25 to 36ºC) could be used to induce tetraploidy in Pacific oyster (Crassostrea gigas) diploids. Induction was performed by applying shocks after elimination of the first polar corpuscle at the end of meiosis I. Ploidy rates were verified using flow cytometry. Tetraploid larvae were obtained using all inductor (6-DMAP, thermal shock and CB) treatments. No difference in the efficiency of tetraploidy induction was noted among 6-DMAP, thermal shock and CB. The number of D-larvae and their yield, determined by calculating the percentage of well-formed D-larvae in relation to the total number of larvae, was similar (p > 0.05) among the evaluated induction methods. We suggest that 6-DMAP and thermal shock should be used in tetraploidy induction protocols, thereby avoiding the use of CB, which is a harmful agent for both humans and the environment.

This study investigated the effects of two source carotenoids on the hepatosomatic index (HSI) and the gonadosomatic index (GSI) of the goldfish (Carassius auratus). For this experiment, six diets containing concentrations of 50, 100, and 150 mg carotenoid kg-1 of synthetic astaxanthin and β-carotene were added to a basic carp diet, while one group of fish was fed a control diet (no added carotenoids). Fiberglass tanks were used for the study, which was performed from January to April of 2013. During the breeding period, the hepatosomatic (HSI) and gonadosomatic (GSI) indices were exa- mined monthly, along with the total carotenoid levels in the ovaries and livers of female goldfish broodstock. A significant positive correlation was observed between total carotenoids in both the liver and ovary tissues and GSI after 90 and 120 days of the experiment. The HSI was not affected by the carotenoid-enriched diets. However, the carotenoid-enriched diets resulted in greater accumulation of carotenoids in the gonads. β-carotene-enriched diets (B150) led to greater accumulation of carotenoids in the liver after 90 days. Lastly, we found that diets containing higher levels of astaxanthin and β-carotene improve the GSI in goldfish broodstock.

Este estudio investiga el efecto de dos fuentes de carotenoides sobre el índice hepatosomático (HSI) y el índice gonadosomático (GSI) de la carpa dorada (Carassius auratus). En este experimento, se adicionaron seis dietas conteniendo concentraciones de 50, 100 y 150 mg carotenoide kg-1 de astaxantina sintética y β-caroteno a una dieta de carpa, mientras a otro grupo de peces se le suministró una dieta control (sin carotenoides). Se utilizaron estanques de fibra de vidrio de enero a abril 2013. Durante el periodo experimental, el HSI y el GSI se examinaron mensualmente junto con la concentración de carotenoides totales en ovario e hígado de hembras. Una correlación positiva significativa se encontró entre el total de carotenoides aportados en la dieta y el hígado, ovario y el GSI después de 90 y 120 días de experimento. El HSI no fue afectado por las dietas enriquecidas con carotenoides. Sin embargo, las dietas con carotenoides mostraron un mayor acumulación de carotenoides en las gónadas. La dieta con β-carotenos (B150) presentó una mayor acumulación de carotenoides en el hígado después de 90 días. Finalmente, se encontró que las dietas que contenían el nivel más alto de astaxantina y β-caroteno mejoraron el GSI en los reproductores de carpa dorada.

Este estudo avaliou os efeitos da densidade de larvas, no cultivo em sistema de fluxo contínuo, na recuperação e número de larvas. O primeiro experimento comparou o rendimento de larvas de um sistema de fluxo contínuo (80 larvas mL-1) e um sistema estático (8 larvas mL-1), resultando um rendimento e número de larvas mais elevado, após 23 dias, para o sistema de fluxo contínuo. O segundo experimento comparou duas densidades de larvas (20 e 45 larvas mL-1) em sistema de fluxo contínuo. As densidades afetaram o rendimento após 15 e 23 dias e a quantidade de larvas final nos tempos testados (8, 15 e 23 dias). Após 23 dias de larvicultura, o rendimento foi maior para 20 larvas.mL-1 e o número de larvas para 45 larvas.mL-1. O terceiro experimento também comparou duas densidades larvais (100 e 150 larvas mL-1) em sistema de fluxo contínuo. As densidades de larvas não afetaram o rendimento e o número de larvas para todos os tempos testados (8, 15 e 23 dias). Assim, considerando o número de larvas capazes de assentar, o sistema de fluxo contínuo mostrou-se mais eficiente do que o sistema estático. Porém, em geral, observouse diminuição do rendimento com alta densidade larval no sistema de fluxo contínuo.

This study evaluated the effects of larval densities, cultured in flow-through system, in the yield and quantity of larvae. The first experiment compared the larval yield of a flow-through system (80 larvae mL-1) and a batch system (8 larvae mL-1), which resulted in a higher yield and number of larvae in the flow-through system, after 23 days. The second experiment compared two larval densities (20 and 45 larvae mL-1) in flow-through system. The densities affected the yield after 15 and 23 days and the larvae final quantity after all tested times (8, 15, and 23 days). After 23 days of larviculture, the yield was highest for 20 larvae mL-1 and the larval number for 45 larvae mL-1. The third experiment also compared two larval densities (100 and 150 larvae mL-1) in flow-through system. The larvae densities did not affect the yield and number of larvae for all tested times (8, 15, and 23 days). In general, the yield has reduced at higher larval densities. Therefore, considering the number of suitable larvae for settlement, the flow-through system was more efficient than the static system. However, in general, we observed reduced yield with high larval stocking-density in flow-through system.