Influence of seasonality on the natural modulation of oxidative stress biomarkers in mangrove crab Ucides cordatus (Brachyura, Ucididae)

Influence of environmental patterns on the population structure and secondary production of the fiddler crab Uca maracoani (Latreille) in the Amazon mangroves

Uca maracoani is a fiddler crab found in estuaries along the western Atlantic coast, with a notable preference for euhaline environments. This study aimed to analyze the population structure and dynamics of this species in an estuary on the North Coast of Brazil, specifically in an area of the upper estuary where seasonal rainfall fluctuations result in significant changes in salinity. Monthly crab samples were taken from December 2013 to November 2015, together with measurements of environmental variables, such as water and climate parameters. The population maintains a balanced sex ratio; however, males are generally larger, with lower mortality rates and longer lifespans than females. Reproduction is continuous but mainly takes place in the dry season when salinity levels are higher (above 12‰). Higher crab densities have been observed during the rainy season when, despite lower salinity levels (below 10‰), the conditions for survival (food availability and milder climate) seem to be more favorable. The estimated average annual biomass and production for the population were 2.62 g AFDM m-2 and 5.43 g AFDM m-2 year-1, respectively, characterized by a high turnover rate (P/B = 2.10 year-1). Our results suggest that U. maracoani has thriving populations in the Amazon coast's mangroves, benefiting from the vast muddy intertidal zone and the high organic content delivered by the estuaries.

Microplastics and 17α Ethinylestradiol: How Do Different Aquatic Invertebrates Respond to This Combination of Contaminants?

The synthetic hormone 17α ethinyl estradiol (EE2) is a molecule widely used in female contraceptives and recognized as a contaminant of attention (Watch List) in the European Union due to its high consumption, endocrine effects and occurrence in aquatic environments. Its main source of introduction is domestic sewage where it can be associated with other contaminants such as microplastics (MPs). Due to their characteristics, they can combine with each other and exacerbate their isolated effects on biota. This study evaluated the combined effects of microplastics (MPs) and 17α ethinylestradiol (EE2) on two tropical estuarine invertebrate species: Crassostrea gasar and Ucides cordatus. Polyethylene particles were spiked with EE2 and organisms were exposed to three treatments, categorized into three groups: control group (C), virgin microplastics (MPs), and spiked microplastics with EE2 (MPEs). All treatments were evaluated after 3 and 7 days of exposure. Oysters exhibited changes in phase 2 enzymes and the antioxidant system, oxidative stress in the gills, and reduced lysosomal membrane stability after exposure to MPs and MPEs. Crabs exposed to MPs and MPEs after seven days showed changes in phase 1 enzymes in the gills and changes in phases 1 and 2 enzymes in the hepatopancreas, such as disturbed cellular health. The combined effects of microplastics and EE2 increased the toxicity experienced by organisms, which may trigger effects at higher levels of biological organization, leading to ecological disturbances in tropical coastal ecosystems.

Experimental effects of cadmium on physiological response of Callinectes danae (Crustacea, Portunidae) from environments with different levels of Cd contamination

Cadmium (Cd) can adversely affect aquatic life, altering reproductive and molting processes in crustaceans. The objective of this study was to evaluate the influence of Cd on reproduction and molting in the crab Callinectes danae. Adult females were obtained from environments with different levels of pollution: low (LC), medium (MC), and high contaminated (HC) areas. Animals from LC, MC, and HC areas were exposed to 0, 0.5, and 2 mg L^-1 of CdCl₂ for 3 h. Cd bioaccumulation, oxidative stress (evaluated by antioxidant enzymes activity), and lipid peroxidation (LPX) were analyzed in mature ovaries (stage II), gills, and hepatopancreas. The expression levels of crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) genes were quantified in the eyestalks, while 17β-estradiol (E2) and melatonin concentration were measured in the hemolymph. Cd bioaccumulated mainly in the hepatopancreas and gills, with increased E2, LPX, and antioxidant enzymes in HC compared to the LC region. Decreased CHH and MIH transcripts were observed in the animals from HC regions compared to LC and MC areas. Physiological differences were recorded, especially for bioaccumulation, oxidative stress, and hormone levels, in animals sampled in HC areas compared to LC and MC regions. In conclusion, the physiological damage triggered by Cd could be reduced due to higher levels of melatonin and antioxidant enzymes in HC areas.

Human modifications to estuaries correlate with the morphology and functional roles of coastal fish

Animals can respond to human impacts by favouring different morphological traits or by exploiting different food resources. We quantified the morphology and diet of four functionally different fish species (n = 543 fish) from 13 estuaries with varying degrees of human modification in Queensland, Australia. We found differences in the responses of trophic groups to the environmental conditions of estuaries; principally the extent of seagrass in the estuary, and the amount of shoreline and catchment urbanisation. Here, seagrass and urbanisation extent correlated with the diet and morphology of zooplanktivores and detritivores; thereby indicating that human modifications may modify these species functional roles. Conversely, environmental variables did not correlate with the diet or morphology of zoobenthivores or piscivores thereby indicating that human modifications may have less an effect on these species functional roles. Our findings demonstrate that anthropogenic impacts to coastal ecosystems might extend from the traditionally measured metrics of abundance and diversity.

Biomarkers and occurrences of heavy metals in sediment and the bioaccumulation of metals in crabs (Ucides cordatus) in impacted mangroves on the Amazon coast, Brazil

In this study, we analyzed biomarkers and heavy metals in Ucides cordatus specimens caught in mangrove areas [A1 = reference (low impact area); A2, A3 and A4 = port complex (potentially impacted area)] of the Amazonian northern coast of Brazil. Sediments and crab muscles sampled from the potentially impacted mangroves showed high levels of metals. Additionally, catalase and glutathione S-transferase enzymes in the gills and hepatopancreas of the collected crabs were elevated in crabs from A2, A3 and A4 relative to those from A1. The histological characteristics of the gills and hepatopancreas differed in crabs collected from A2, A3 and A4 compared with those collected from A1. The crabs were larger and heavier in the rainy season in A1 and A3 and heavier in the dry season in A4. Heavy metal analyses of sediments, crab muscles and biological responses indicated that the animals are subjected to stress levels differentiated in the mangroves due to a gradient (A4>A3>A2>A1) of anthropogenic pressure in São Marcos Bay. In conclusion, the analyses of metals in the sediment and in the muscles of crabs, as well as the biochemical biomarker and histological analyses, suggest that crabs from mangroves in the port complex region are subject to pollutants that compromise their health.

Modulation of physiological oxidative stress and antioxidant status by abiotic factors especially salinity in aquatic organisms

Exposure to a variety of environmental factors such as temperature, pH, oxygen and salinity may influence the oxidative status in aquatic organisms. The present review article focuses on the modulation of oxidative stress with reference to the generation of reactive oxygen species (ROS) in aquatic animals from different phyla. The focus of the review article is to explore the plausible mechanisms of physiological changes occurring in aquatic animals due to altered salinity in terms of oxidative stress. Apart from the seasonal variations in salinity, global warming and anthropogenic activities have also been found to influence oxidative health status of aquatic organisms. These effects are discussed with an objective to develop precautionary measures to protect the diversity of aquatic species with sustainable conservation. Comparative analyses among different aquatic species suggest that salinity alone or in combination with other abiotic factors are intricately associated with modulation in oxidative stress in a species-specific manner in aquatic animals. Osmoregulation under salinity stress in relation to energy demand and supply are also discussed. The literature survey of >50 years (1960-2020) indicates that oxidative stress status and comparative analysis of redox modulation have evolved from the analysis of various biotic and/or abiotic factors to the study of cellular signalling pathways in these aquatic organisms.

Biomarcadores enzimáticos e histológicos em brânquias de Ucides cordatus (Linnaeus, 1763) (Crustacea, Brachyura, Ucididae) indicativos de impactos ambientais em uma região portuária do nordeste do Brasil

RESUMO Objetivou-se neste estudo analisar biomarcadores histológicos e bioquímicos em brânquias de U. cordatus indicativos de impactos na Baía de São Marcos. Caranguejos foram coletados em quatro áreas na Baía de São Marcos: A1= Ilha dos Caranguejos (com baixo impacto); A2= Coqueiro, A3= Porto Grande, A4= Cajueiro (áreas potencialmente impactadas). Mediram-se os dados biométricos de cada exemplar de caranguejo. Amostras de brânquias foram submetidas à técnica histológica padrão e homogeneizadas em tampão fosfato, e o sobrenadante foi utilizado para análise das enzimas glutationa-S-transferase (GST) e catalase (CAT). A biometria indicou que os caranguejos de A1 são significativamente (P<0,05) maiores e mais pesados do que os caranguejos das áreas A2, A3 e A4. As alterações branquiais (rompimento das células pilastras, deformação do canal marginal, deslocamento da cutícula e necrose) foram significativamente (P˂0,05) mais frequentes em caranguejos de A2, A3 e A4 do que nos caranguejos de A1. As atividades enzimáticas da GST e CAT nos caranguejos apresentaram diferença significativa (P<0,05) entre as áreas de coletas, com padrão similar ao observado para as alterações branquiais. Os biomarcadores analisados mostraram que os caranguejos estão sob diferentes níveis de impactos (A4>A3>A2>A1) ao longo da Baía de São Marcos.