Effect of Water Temperature on Reproductive Tract Condition of Penaeus setiferus Adult Males

Abstract— This study was conducted to determine the effect of water temperature on male reproductive tract degenerative syndrome (MRTDS) and male reproductive system melanization (MRSM) in Penaeus setiferus , and to evaluate the effect of water temperature on spermatophore regeneration time and sperm quality in electrically ejaculated adult males. Variation in sperm quality, gonadosomatic index, and histological changes in the reproductive system were used to assess reproductive tract changes in the first experiment. Sperm quality and regeneration time were measured before and after successive regenerations in the second experiment. Sperm quality was stable when shrimp were held at 26 C for 30 d but was reduced when shrimp were held at 30 C. Reproductive tissues of 20% of the shrimp held at 30 C were melanized to some degree but tissue melanization was found in only 2.5% of the shrimp held at 26 C. Spennatophore regeneration time was also affected by temperature. Average times for first spermatophore regeneration were 192 h at 25 C, 152 h at 30 C, and 144 h at 33 C. Sperm quality of regenerated shrimp was not affected at 25 C but was reduced for regenerated animals held at 33 C. Based on these results, we recommend a water temperature between 25 and 27 C to obtain adequate spermatophore regeneration and to maintain healthy male P. setiferus broodstock for at least 30 d.     

Thermal preference,tolerance, and thermal aerobic scope in clownfish Amphiprion ocellaris (Cuvier, 1830) predict its aquaculture potential across tropical regions

The clownfish Amphiprion ocellaris is widely distributed in the coral reef ecosystems of tropical and subtropical regions of the West Indo Pacific, an area that hosts economically valuable species, and, thus, a suitable candidate for warm water aquaculture. This study determined the preferred temperature, critical threshold limits, represented by critical thermal maximum and critical thermal minimum, thermal window width, and aerobic metabolic scope of A. ocellaris clownfish acclimated to 20, 23, 26, 29, 32, and 35 °C. A positive response (P < 0.05) occurred when the preferred temperature significantly increased with increasing acclimation temperature. The preferred temperature obtained graphically was 30.0 °C. Acclimation temperature significantly affected the thermal tolerance which increased with acclimation temperature. The thermal window calculated for A. ocellaris was 301.5 °C2. The thermal metabolic scope obtained in animals acclimated at the interval from 23 to 32 °C (P > 0.05) had a mean value of 4240.8 mg O2 h−1 kg−1 w.w., revealing that A. ocellaris is a eurythermal species with a range of optimal physiological performance that closely matches the environmental conditions where it can be farmed. Therefore, the highest value of the thermal aerobic scopes corresponded to the intervals of the preferred temperature obtained for A. ocellaris. These results may partially explain their worldwide distribution pattern, as well as their aquaculture potential in tropical regions.     

Growth,mortality and reproductive traits of diploid and triploid Pacific oysters (Crassostrea gigas,THUNBERG, 1793) in Southern Brazil

This work aimed to evaluate the whole weight (g), shell height (mm), mortality (%) and reproductive aspects (condition index and histology) of triploid (3N) Pacific oysters (Crassostrea gigas) cultivated in southern Brazil. To accomplish this, a comparative experiment was performed with a diploid (2N) control group in two cultivation sites on Santa Catarina Island: North Bay (NB) and South Bay (SB). Whole weight, height and cumulative mortality were evaluated monthly for eight months and condition index (CI) for six months. Histological analysis was performed every two weeks for four months to investigate reproductive aspects. At the end of the experiment, whole weight and height were similar for 3N and 2N oysters. However, while more growth in whole weight and height was observed in the initial phase of cultivation in NB, such growth was not detected in SB until intermediate and final grow‐out phase. At harvest, cumulative mortality in 3N oysters was similar that in 2N oysters. The results suggest that diploid and triploid oysters grown in southern Brazil have similar developmental patterns based on whole weight and height, as well as reproductive cycle. In addition, cultivation sites have more influence on growth and mortality than ploidy levels.     

In vivo and in vitro protein digestibility and growth performance of animal and no‐conventional plant ingredients for river prawn Macrobrachium americanum (Caridea: Palaemonidae)

The objectives of this study were to evaluate the effects of non‐traditional plant and animal protein for river prawn M. americanum on in vivo versus in vitro digestibility in addition to growth performance. In this study, ten ingredients were used: coconut meal, jackfruit meal, soybean meal, poultry by‐product meal, squid meal and fish meal. In vivo studies were conducted using the zeolite marker method, whereas in vitro digestibility was determined by the pH‐stat method using river prawn hepatopancreas enzymes. According to the findings, river prawns digest animals more efficiently than plant ingredients, with squid and fish meal showing a tendency of higher values. Fish meal (53.66%), squid meal (48.52%) and jackfruit meal (42.21%) were found to have a digestibility greater than 40% in in vivo and in vitro methods, thus suggesting that they are the best ingredients used in this study. This also validates their inclusion in practical diets. The correlation of digestibility of in vivo and in vitro was low (R² = .6749). The highest daily weight gain was recorded in the diets containing jackfruit, coconut and squid. Given that the potential of no‐conventional plant ingredients available regionally was significantly higher, this underscores the need to conduct further research to validate their inclusion in practical diets.     

Comparison between the intestinal microbiome of healthy fish and fish experimentally infected with Streptococcus agalactiae

Nile tilapia (Oreochromis niloticus) farming is an economic activity that is soaring in the whole world. Septicemia due to Streptococcus agalactiae is the main disease impacting fish farming. The aim of this study was to compare the gut microbiome of healthy animals and animals experimentally infected with S. agalactiae strain 21171A. The microbiome was established with 16S ribosomal DNA next‐generation sequencing (NGS). One hundred Nile tilapias, with an average weight of 35 g, were distributed into two groups. Fifty fish from the challenged group were orally inoculated with 100 μl of a bacterial solution containing 1.98 × 10³ CFU/ml of S. agalactiae strain 21171A, while 50 controls were orally inoculated with sterile saline. After the experiment, 24 fish from the challenged group and 27 fish from the control group were analysed. For both groups, bacteria attached to the mucosa (M) and present in faeces (F) were analysed. The mean of the number of taxa identified in the infected group (M + F) (45.87 ± 30.13) was lower than in the control (M + F) (67.70 ± 21.10) (p < .01). Nineteen bacterial taxa were more abundant in faecal samples from the infected group when compared with the control group (p < .01). Thirty‐nine taxa were associated with mucosa samples from the challenged group when compared to the control samples (p < .01). No OTU was associated with healthy samples. The results demonstrate that the infection with S. agalactiae reduces the variability of the gut microbiota. Moreover, some bacteria proliferate during the infection.