João Carlos Shimada Borges

The impact of rising sea temperature on innate immune parameters in the tropical subtidal sea urchin Lytechinus variegatus and the intertidal sea urchin Echinometra lucunter

Ocean temperatures are rising throughout the world, making it necessary to evaluate the impact of these temperature changes on sea urchins, which are well-known bioindicators. This study evaluated the effect of an increase in temperature on the immune response of the subtidal Lytechinus variegatus and the intertidal Echinometra lucunter sea urchins. Both species were exposed to 20 (control), 25 and 30 °C temperatures for 24 h, 2, 7 and 14 days. Counting of coelomocytes and assays on the phagocytic response, adhesion and spreading of coelomocytes were performed. Red and colorless sphere cells were considered biomarkers for heat stress. Moreover, a significant decrease in the phagocytic indices and a decrease in both cell adhesion and cell spreading were observed at 25 and 30 °C for L. variegatus. For E. lucunter, the only alteration observed was for the cell proportions. This report shows how different species of sea urchins respond immunologically to rising temperatures.

Germicide capacity of macrophages (MØ) in the Antarctic fish Notothenia coriiceps (Richardson, 1844) at 0°C

The germicide capability of the macrophage (MØ) of the Antarctic fish Notothenia coriiceps is demonstrated using fluorescence microscopy for the first time. The MØs were able to kill microorganisms by intracellular mechanism and this killing can be stimulated by oyster-derived glycogen. Although the phagocytosis index is lower than in temperate water fish species, this work demonstrates that non-specific defence mechanism plays an important role in the polar environment. There are some studies on inflammation in N. coriiceps [Silva et al. (1998) Polar Biol 20:206–212], parasite–host relation [Silva et al. (1999) Polar Biol 22:417–424] and phagocytosis [Silva et al. (2002) J Fish Biol 60:466–478]. These previous studies have shown that the MØ were able to identify biotic and abiotic factors. However, it can be of interest to study the activity of MØ in microorganism killing, and this work adds new insights of this fundamental process under Antarctic temperatures.

Histopathological and genotoxic effects of pollution on Nile Tilapia (Oreochromis niloticus, Linnaeus, 1758) in the Billings Reservoir (Brazil)

Abstract The Billings Reservoir shows eutrophic waters due to the large amount of sewage, and consequently, the fish can be a problem for public health. Thus, this project aimed to analyze the histological gills and liver of Nile tilapia to verify morphological changes caused by environment, and the frequency of micronuclei was done, to observe the response to genotoxic activity. We observed histological alterations in gills and livers of Nile Tilapia classified as mild to severe, and the presence of micronucleus. The results enable better environmental monitoring and quality control of this species.

Ocean acidification affects parameters of immune response and extracellular pH in tropical sea urchins Lytechinus variegatus and Echinometra luccunter

The rising concentration of atmospheric CO2 by anthropogenic activities is changing the chemistry of the oceans, resulting in a decreased pH. Several studies have shown that the decrease in pH can affect calcification rates and reproduction of marine invertebrates, but little attention has been drawn to their immune response. Thus this study evaluated in two adult tropical sea urchin species, Lytechinus variegatus and Echinometra lucunter, the effects of ocean acidification over a period of 24h and 5days, on parameters of the immune response, the extracellular acid base balance, and the ability to recover these parameters. For this reason, the phagocytic capacity (PC), the phagocytic index (PI), the capacity of cell adhesion, cell spreading, cell spreading area of phagocytic amebocytes in vitro, and the coelomic fluid pH were analyzed in animals exposed to a pH of 8.0 (control group), 7.6 and 7.3. Experimental pHs were predicted by IPCC for the future of the two species. Furthermore, a recovery test was conducted to verify whether animals have the ability to restore these physiological parameters after being re-exposed to control conditions. Both species presented a significant decrease in PC, in the pH of coelomic fluid and in the cell spreading area. Besides that, Echinometra lucunter showed a significant decrease in cell spreading and significant differences in coelomocyte proportions. The recovery test showed that the PC of both species increased, also being below the control values. Even so, they were still significantly higher than those exposed to acidified seawater, indicating that with the re-establishment of the pH value the phagocytic capacity of cells tends to restore control conditions. These results demonstrate that the immune system and the coelomic fluid pH of these animals can be affected by ocean acidification. However, the effects of a short-term exposure can be reversible if the natural values ​​are re-established. Thus, the effects of ocean acidification could lead to consequences for pathogen resistance and survival of these sea urchin species.

Histological organization of intestinal villi in the crocodilian caiman yacare (Daudin, 1802) during dietary lipid absorption

Intestinal villi of Caiman yacare form longitudinal folds instead of the finger-like projections of most birds and mammals. Moreover, they lack Crypts of Lieberkühn and the lamina epithelialis organization is dynamic, changing from pseudostratified to simple columnar epithelium after feeding. Because of these differences, we sought to verify whether intestinal villi of the crocodilian Caiman yacare are functionally compartmentalized along their length similarly to the finger-like villi that harbors Crypt of Lieberkühn. For this, Caiman yacare were force-fed soybean oil, the intestinal mucosa was harvested and analyzed under light microscopy after lipid staining or immunohistochemistry for the proliferative marker PCNA. Functional compartmentalization was assessed by evaluating differences in lipid absorption along intestinal villi base-to-tip axis, by localizing the proliferative enterocytes and by verifying whether such cells were capable of absorbing lipids. Histological morphometric analyses of the extent of enterocyte hypertrophy caused by lipid inclusions and the contribution of such inclusions to histological remodeling from pseudostratified to simple columnar epithelium were also evaluated. Although lacking Crypts of Lieberkühn, enterocytes present at villi base were PCNA positive and devoid of the great amount of lipid inclusions observed in the other intestinal villi domains, in a similar pattern to finger-like villi. Enterocytes doubled their volume because of lipid inclusions, and in spite of such enterocyte hypertrophy, lamina epithelialis continued to be pseudostratified within lateral sides, whereas villi tip were organized in a simple columnar epithelium.