Percentage Of Abnormal Larvae Research Articles

Seagrass meadows as ocean acidification refugia for sea urchin larvae

Foundation species have been widely documented to provide suitable habitats for other species by ameliorating stressful environmental conditions. Nonetheless, their role in rescuing stress-sensitive species from adverse conditions due to climate change remains often unexplored. Here, we performed a mesocosm experiment to assess whether the seagrass, Posidonia oceanica, through its photosynthetic activity, could mitigate the negative effects of ocean acidification on larval development and growth of the calcifying sea urchin, Paracentrotus lividus. Sea urchin larvae at early and late developmental stages that are generally associated to benthic habitats, were grown in aquaria with or without P. oceanica plants, under ambient or low pH conditions predicted by the end of the century under the worst climate scenario (RCP8.5). The percentage of abnormal larvae and their total body length under different experimental conditions were assessed on early- (i.e., pluteus; 72 h post-fertilization) and final-developmental stages (i.e., echinopluteus; 30 days post-fertilization), respectively. The presence of P. oceanica increased mean daily pH values of ∼0.1 and ∼0.15 units at ambient and low pH conditions, respectively, compared with tanks without plants. When grown at low pH in association with P. oceanica, plutei showed a ∼23 % reduction of malformations and echinoplutei a ∼34 % increase in total body length, respectively, compared with larvae developing in tanks without plants. Our results suggest that P. oceanica, by increasing pH and altering seawater carbonate chemistry through its metabolic activity, could buffer the negative effects of ocean acidification on calcifying organisms and could, thus, represent a tool against climate-driven loss of biodiversity.

Strategies for aquaculture and conservation of Neotropical catfishes based on the production of triploid Pimelodus maculatus

Triploidization is a technique to produce sterile fish on a large scale. In the spotted catfish Pimelodus maculatus, sterile fish serve as a host of germ cell transplantation for subsequent reconstitution of endangered catfish species. This study aimed to establish an efficient protocol for triploidization in P. maculatus using temperature shock. In this study, we tested the efficacy of heat shock treatments (37 °C, 38 °C, and 39 °C) applied at 2 min post-fertilization (mpf) for the duration of 2 min. Intact embryos served as diploid control. Ploidy status was confirmed by flow cytometry, characterization of erythrocytes nuclei, and karyotyping. Developmental stages were verified at cleavage, blastula, gastrula, somite, and hatching stages, as well as the percentages of normal and abnormal larvae. No significant difference was observed between the temperature treatments for percentage of unfertilized oocytes (P = 0.1834), 2-cell stage (P = 0.2348), blastula (P = 0.2972), hatching (P = 0.0668), and abnormal larvae (P = 0.6177). Heat shock decreased the survival at the blastula stage (P = 0.0178), somite (P = 0.0469), and the percentage of abnormal larvae (P = 0.0261). All treatments presented high percentages of triploid individuals, and the highest values were observed for heat shock at 38 °C (96.7 %). Based on the results described above, an efficient protocol for triploidization in P. maculatus was established using heat shock (38 °C) at 2 mpf for 2 min.

Coping with seawater acidification and the emerging contaminant diclofenac at the larval stage: A tale from the clam Ruditapes philippinarum

Seawater acidification could alter the susceptibility of marine organisms to emerging contaminants, such as pharmaceuticals. In this study, the combined effects of seawater acidification and the non-steroidal anti-inflammatory drug diclofenac on survival, growth and oxidative stress-related parameters (catalase activity and lipid peroxidation) in the larvae of the Manila clam Ruditapes philippinarum were investigated for the first time. An experimental flow-through system was set up to carry out a 96-h exposure of clam larvae. Two pH levels (pH 8.0, the control, and pH 7.8, the predicted pH by the end of this century) were tested with and without diclofenac (0.5 μg/L). After 4 days, mortality was dramatically higher under reduced pH, particularly in the presence of diclofenac (62% of the larvae dead). Shell morphology was negatively affected by both acidification and diclofenac from the first day of exposure. The percentage of abnormal larvae was always higher at pH 7.8 than in controls, peaking at 98% in the presence of diclofenac after 96 h. Instead, shell length, shell height or the ratio of these values were only negatively influenced by reduced pH throughout the whole experiment.After 96 h, catalase activity was significantly increased in all larvae kept at pH 7.8, whereas no significant difference in lipid peroxidation was found among the treatments. This study demonstrates a high susceptibility of R. philippinarum larvae to a slight reduction in seawater pH. Furthermore, the results obtained highlight that acidification enhances the sensitivity of clam larvae to environmentally relevant concentrations of diclofenac.

Effects of multiple climate change stressors: ocean acidification interacts with warming, hyposalinity, and low food supply on the larvae of the brooding flat oyster Ostrea angasi

Ocean acidification, rising temperatures, and increased intensity of rain events are occurring due to climate change. Individually, each of these stressors has the potential to influence the growth and survival of many marine organisms, particularly during early development. Together the interactive and multiple impacts of elevated pCO2, temperature, and salinity may be exacerbated by a lack of food. Life history traits are important in determining the response of organisms to climate change. Larvae that develop within a brood chamber, such as the flat oyster, Ostrea angasi, may be pre-exposed to living a higher CO2 environment. This study determined the pH of the fluid surrounding the gills of adult oysters where larvae are brooded and investigated the interactive effects of the multiple climate-related stressors: ocean acidification, warming, hyposalinity, and reduced food availability, on development of O. angasi larvae. The fluid surrounding the larvae was of pH 7.88 ± 0.04, lower than that of surrounding sea water, and was significantly reduced (to pH 7.46 ± 0.05) when oysters remained closed as occurs in nature during periods of stress caused by low salinity. Elevated pCO2 [853–1194 µatm (pHNBS 7.79)] resulted in larvae being 3 % smaller, but it had no effect on the timing of progression through developmental stages, percentage of abnormalities, or survival of larvae. Exposure to elevated pCO2 together with increased temperature (+4 °C) or reduced salinity (20) had a negative effect on the time to the eyed larval stage and with an increase in the percentage of abnormal larvae. Unexpectedly, larvae did not meet their higher metabolic requirements to survive under elevated pCO2 by eating more. In a sublethal effect of elevated pCO2, larval feeding was impaired. We found that O. angasi larva were relatively resilient to elevated pCO2, a trait that may be due to the acclimatisation of hypercapnic conditions in the brood cavity or because they are released from the brood cavity at an older, possibly less sensitive stage. This result contrasts with the larvae of broadcast spawning oysters which are extremely sensitive to elevated pCO2.

The Effect of Different Ratios of n-6/n-3 Fatty Acids in Broodstock Diets on Egg Quality of Catfish, Clarias batrachus

This experiment was conducted to acquire biochemical information on the quality of catfish eggs in relation to different n-6/n-3 ratios of fatty acids in the broodstock diet. Five experimental diets, which were isonitrogenous and isoenergy, but containing different levels of n-G and n-3 fatty acids (diet A: essential fatty acid (EF A)-deficient diet containing 0.21%n-6 fatty acid, 0.03% n-3 fatty acid; diet B: 0.67%, 2.09%; diet C: 2.24%,0.07%; diet D: 1.85%, 0.56%; and diet E: 0.26%, 1.68%) were used in the experiment. Five-month-old fish were fed the experimental diets for 10 months. Samples of the eggs produced by the respective broodstock were fertilized by the sperms. Samples of eggs during embryogenesis were analyzed for total lipid (TL), polar lipid (PL) and nonpolar lipid (NL) content as well as fatty acid (FA) composition. The hatching rate of the eggs and the percentage of abnormal larvae were determined. Results showed that the lipid content of the eggs decreased from the first hour after fertilization. The lipid content of the EF A-deficient eggs (diet A) and the n-3 fatty acid deficient eggs (diet C) decreased significantly during embryogenesis compared to the lipid content of the eggs from the other diets. Also, in general, the NL of eggs was much lower than PL during embryogenesis. The NL of diet A and diet C eggs was also much lower during embryogenesis compared to the NL of the eggs from the other diets. The n-6 and n-3 fatty acid levels of unfertilized eggs were influenced by the fatty acid level in the broodstock diet. The n-6 and n-3 fatty acids of NL were much lower than those of PL, especially in the organogenesis stage of the larvae. The n-6 and n-3 fatty acids of NL from diets A, B and C were also much lower compared to those of diets D and E. Hatching rates of eggs produced by the broodstock fed diets and D and E were also higher than those fed diets A, B and C.