Osmoregulatory responses in the neotropical fish species Astyanax lacustris, exposed to single and combined microplastics, polycyclic aromatic hydrocarbons, and their mixture.

Microplastic (MP) pollution poses a significant environmental threat. These MPs can adsorb toxic compounds such as polycyclic aromatic hydrocarbons (PAH), which are highly lipophilic and carcinogenic. To assess the potential effects of virgin MP, PAH, and MP+PAH in association with osmoregulation and energetic substrate, we conducted experiments with the tetra cardinal Astyanax lacustris. The environmentally relevant concentration of MP (10 mg L-1) and 20 % of the LC50-96 h of crude oil for A. lacustris (2.28 µg L-1) were used during the 96-h exposure. Fish were exposed to virgin MP, PAH, MPC (MP loaded with PAH), PAH+MP (PAH and MP in association), and the control without (CT) and with handling (CH). After 96 h, blood was collected for osmoregulatory parameters (plasma osmolality; Na+, K+, Cl-, Mg2+; glycose and lactate); gills for osmoregulatory enzyme activities (Na+, K+ ATPase, H+ ATPase, and carbonic anhydrase); and white muscle samples were used to determine glycogen as an energetic substrate. The low molecular weight PAH was not detected in PAH-loaded MP (MPC) and PAH in combination with MP (PAH+MP). The PAH concentration of the MPC and PAH+MP was similar and low compared to other works. Virgin MP, PAH, MPC, and PAH+MP were able to cause muscle glycogen depletion. The activity of v-type H+ ATPase and plasma Na+ concentrations were lower in PAH with MP (MPC). However, the hydromineral balance (K+, Mg2+, Cl-, and osmolality) was not affected by any treatment. In this sense, we can conclude that the MPC caused osmoregulatory disturbances not seen in the MP associated with PAH (MP+PAH). However, this seems unrelated to the PAH leaking from the MPC or the PAH absorption to the virgin MP once the PAH concentrations from the MPC and PAH+MP were similar.

Evaluation of the toxicity of di-iso-pentyl-phthalate (DiPeP) using the fish Danio rerio as an experimental model.

The presence of phthalates constitutes a risk to the health of aquatic environments and organisms. This work aimed to evaluate the toxic effects of di-iso-pentyl-phthalate (DiPeP) at environmentally relevant concentrations of 5, 25, and 125 µg/L in Danio rerio after subchronic exposure for 14 days. DiPeP altered the antioxidant system in the liver (125 µg/L), intestine (25 µg/L), brain, and gills in all concentrations tested. In animals exposed to 125 µg/L, DNA damage was identified in the gills. In addition, loss of cell boundary of hepatocytes, vascular congestion, necrosis in the liver, and presence of immune cells in the intestinal lumen were observed. Erythrocytic nuclear alterations in the blood occurred in animals exposed to 25 µg/L. DiPeP was quantified in muscle tissue at all exposure concentrations, appearing in a concentration-dependent manner. Contaminants such as DiPeP will still be used for a long time, mainly by industries, being a challenge for industry versus environmental health.

Contamination gradient affects differently carbonic anhydrase activity of mollusks depending on their feeding habits.

Aquatic organisms that inhabit coastal areas are often exposed to several contaminants. It is known that the bioaccumulation of contaminants can be amplified according to the species feeding habits and contaminant properties. As a consequence, species can experience different effects to contaminant exposure even if they inhabit the same area. The present study aimed to investigate the activities of carbonic anhydrase (CA), Ca2+-ATPase, and Mg2+-ATPase in different tissues (soft tissue, mantle, and gill) of three mollusk species (Lottia subrugosa, Stramonita brasiliensis, and Crassostrea brasiliana) with different feeding habits (herbivore, carnivore, and filter-feeder, respectively) which were sampled within a known contamination gradient at Santos Estuarine System (Southeastern Brazil). From the three enzymes tested, only CA was affected by the presence of contaminants within the contamination gradient evaluated. In general, the CA activity from the three species were lower in contaminated sites when compared to the reference site. The contrasting CA activity response observed in S. brasiliensis compared to L. subrugosa and C. brasiliana could be related to the tissue-specificity of this enzyme activity and species feeding habits (filter-feeders can accumulate more contaminants than herbivores and even carnivores). Results indicated that C. brasiliana mantle is the most suitable tissue for the use of CA analysis as a biomarker.

Shell form and enzymatic alterations in Lottia subrugosa (Gastropoda, Lotiidae) transplanted to a contaminated site.

Studies have shown that shell morphology and enzymatic activities in mollusks are affected by contaminants exposure. However, the correlation between enzymatic activities and the biomineralization process are not fully understood. The present study used a transplant bioassay and field sampling to evaluate shell measurements and the activities of carbonic anhydrase, Ca2+-ATPase, and Mg2+-ATPase in Lottia subrugosa sampled in Brazilian sites under different contamination levels. Results showed that, in general, shells from the reference site (Palmas) were more rounded than the ones from the contaminated site (Balsa). Effects in enzymatic activities in specimens from transplant bioassay were attributed to the known high contaminant levels present at Balsa. While the lack of enzymatic activity alterations during field sampling was attributed to physiological adaptation to contaminants exposure. Enzymatic activities were not correlated to shell biometric parameters in field sampling, indicating that these enzymes were not related to shell alterations detected in the present study.

Acute exposure to the water-soluble fraction of gasoline (WSFG) affects oxygen consumption, nitrogenous-waste and Mg excretion, and activates anaerobic metabolism in the goldfish Carassius auratus.

Contamination of aquatic environments by petroleum and its products (e.g. gasoline) is a hazard for aquatic organisms as a result of the potential toxicity of monocyclic aromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAH). Our goal was to evaluate the acute effects of the water-soluble fraction of gasoline (WSFG) on nitrogen excretion, osmoregulation, and metabolism of goldfish Carassius auratus. We first chemically characterized the WSFG and then tested its effects on these physiological aspects of C. auratus, in several different exposure scenarios (0, 0.25, 5, 10 and 25% of WSFG). The WSFG contained high concentrations BTEX (toluene 70% and benzene 17%) relative to PAH (<1%), and low levels of several metals (Al, Fe, Zn, Sr). Routine O2 uptake rate (MO2) of goldfish was inhibited by exposure to 5% WSFG, and during post-exposure recovery, MO2 increased in a dose-dependent fashion. Ammonia excretion was not affected by exposure to WSFG, but urea-N excretion increased progressively with the WSFG concentration. The same pattern of dose/response was observed for net Mg2+ loss rates and steadily increasing plasma lactate concentrations. Loss rates of Na+, Ca2+, K+ and Cl-, and plasma concentrations of Mg2+ and urea-N were not significantly altered. We propose that acute exposure to WSFG inhibits aerobic metabolism and activates anaerobic metabolism, breaking down ATP such that bound Mg2+ is liberated and the purine ring component is metabolized to urea-N, both of which are subsequently excreted.

Skin extract from Rhamdia quelen (Siluriformes: Heptapteridae) does not promote stress in conspecifics

Chemical communication is widely used in aquatic environments, where visual or auditory signals may not be always effective. Fish of the superorder Ostariophysi are known to display epidermal cells (club cells) that produce and store alarm substances, which are released to the water when the skin is damaged. Responses to alarm substances range widely, between active searches for refuge to a complete stop in any locomotor activity. In this study a large number of binucleated club cells (average density of 11 cells /5m2) were histologically observed in the skin of the catfish Rhamdia quelen (known as jundia). Skin extract (2, 5, and 10% w/v) applied for 15 minutes to conspecifics elicited increase in swimming activity and in the area visited by the fish inside the tank. However, exposure to the epithelial alarm cue did not evoke any stress response: plasma osmolality, ions (sodium, chloride, magnesium, and potassium), glucose and cortisol remained unchanged. In conclusion, the conspecific alarm cue of the jundia induces behavioral responses but not an acute stress response upon short-term exposure, compatible with its role in fostering physical integrity without representing major stress activation. Considering that in the natural environment such stimuli must quickly disappear due to dilution and that rapid protection responses may be necessary upon the possibility of an approaching predator, a faster mechanism to assure survival may come into play, such as sympathetic nervous system activation. Comunicagco qummica i amplamente utilizada por animais que vivem em ambiente aquatico, onde sinais visuais e auditivos nem sempre sco facilmente identificados. Os Ostariophysi sco conhecidos por apresentarem cilulas club na epiderme, as quais produzem e estocam substbncia de alarme que sco liberadas para o ambiente quando a pele i lesionada. As respostas dos peixes a substbncia de alarme variam entre exploragco ativa por refzgios ati a parada completa de atividade locomotora. Neste estudo, grande nzmero de cilulas club binucleadas (densidade midia de 11 cilulas/5m2) foram histologicamente observadas na epiderme do jundia, Rhamdia quelen. Peixes expostos a extrato de pele de conspecmficos (2, 5, e 10% peso/vol) por 15 minutos apresentaram aumento da atividade locomotora e da area de dispersco. No entanto, essa exposigco nco promoveu nenhuma resposta de estresse - osmolalidade plasmatica, mons (ssdio, cloreto, magnisio e potassio), glicose e cortisol nco sofreram alteragco. Conclummos que a exposigco aguda a extrato de pele de conspecmficos promovem respostas comportamentais de fuga, que essa espicie apresenta grande concentragco de cilulas club, as quais devem estar envolvidas nessas respostas e que a exposigco aguda ao estmmulo nco promoveu respostas bioqummicas indicativas de estresse. Considerando que no ambiente natural tais estmmulos devem desaparecer rapidamente dados a diluigco do meio e que respostas rapidas de protegco devem ser desencadeadas frente ` possibilidade de presenga de predador, vias rapidas de suporte a essas respostas, como sistema nervoso simpatico, por exemplo, devem estar envolvidos.