Search Results (4)

Short-term captivity is widely used in experimental studies but may unintentionally alter host-associated microbiomes, potentially confounding biological interpretation of experimental outcomes. Here, we evaluated the effects of 35 days of captivity on the gut microbiome of Fundulus heteroclitus collected from Long Island Sound (Milford, CT, USA) using 16S rRNA gene sequencing. Comparisons between Field Control (FC) and short-term Captive Treatment (CT) groups revealed a marked reduction in microbial diversity under captive conditions. Observed richness decreased approximately five-fold (Field Control: 1026 features; Captive Treatment: 221 features), and Shannon diversity declined from 8.89 to 5.93. Beta diversity analyses based on UniFrac distances demonstrated clear separation between groups, indicating substantial shifts in community composition. Taxonomic profiling revealed reduced community complexity in captive fish, with increased dominance of Proteobacteria and loss of diverse environmental taxa. Predicted enrichment of pathways associated with stress response, altered respiration, and metabolic flexibility in captivity reflects inferred functional potential rather than direct functional activity. Given the use of pooled samples with limited biological replication, these findings should be interpreted as strong community-level patterns rather than population-level inference. Collectively, these results indicate that short-term captivity alters the F. heteroclitus gut microbiome. Full article

Environmental salinity is a critical factor influencing the physiological and metabolic processes of teleosts. Despite its importance, the molecular mechanisms underlying these responses, particularly those involving specific signaling pathways and gene expression regulation, remain poorly understood. To elucidate the role of lipid metabolism in osmotic regulation, the present study investigated the effects of varying salinity levels (2, 20, 40, and 60 ppt) on growth performance and metabolic status, including the biosynthesis of LC-FAs and VLC-FAs, respectively, in neural tissues (brain and eyes), of the euryhaline fish Fundulus heteroclitus over a 62-day period. The findings revealed multiple physiological adaptations to salinity variation, encompassing both molecular and metabolic responses. Salinity had a significant impact on growth performance, with fish exposed to the highest salinity level (60 ppt) exhibiting reduced growth. At this salinity, plasma levels of lipid-related metabolites, i.e., triglycerides and cholesterol, were decreased, whereas both osmolality and cortisol levels increased. Hepatic glucose and lactate levels increased with rising salinity, while glucose and triglyceride concentrations in muscle tissue declined. Additionally, intestinal lipase activity was significantly higher at 60 ppt. Although no significant differences were observed in the total UFAs content of both tissues, in the brain, significant differences were detected in the levels of 16:1n-7, 18:1n-9, 18:2n-6, 20:3n-3, 20:4n-6, and 20:5n-3, whereas in the eye, differences were observed only for 16:1n-7 and 20:5n-3. Gene expression analysis revealed that salinity exerts a regulatory effect on the expression of fads2b and elovl4a in the eye, with up-regulation observed at 60 ppt. In contrast, no significant changes in the expression of fads or elovl genes were detected in the brain. These findings highlight the contribution of non-osmoregulatory organs, such as the brain and eyes, in the osmotic adaptation of teleosts. Collectively, the results suggest that lipid metabolism plays a key regulatory role in the adaptation of F. heteroclitus to salinity fluctuations. Full article

Although there is rising global concern over the environmental, ecological, and human health risks associated with the discharge of leachates from e-waste dumpsites into the aquatic ecosystems, little is known in this research area. Thus, for this study, we first defined the chemistry of the test leachate, followed by assessment of the leachate on the development of a model aquatic organism (Fundulus heteroclitus) used extensively as a bioassay organism in pollution studies. Chemical analyses revealed that levels of phosphate (20.03 mg/L), cadmium (Cd) (0.4 mg/L), lead (Pb) (0.2 mg/L), and chromium (Cr) (0.4 mg/L) were higher than the 2009 US EPA and the 2009 National Environmental Standards and Regulations Enforcement Agency (NESREA) permissible limits. Polycyclic aromatic hydrocarbon (PAH) burdens were dominated mainly by the high molecular weight congeners, specifically the ∑4rings (73 µg/L). Total polychlorinated biphenyls (PCB) levels ranged from 0.00 to 0.40 µg/L with the ∑deca PCBs reaching the highest concentration. For the biological studies, F. heteroclitus embryos (48-h post-fertilization) were divided randomly into groups and exposed to one of six e-waste leachate concentrations (10, 1, 0.1, 0.01, 0.001, 0.0001%). Significant differences (p ≤ 0.05) between treated and control groups were observed in standard and total length, and head size. Further analysis using Duncan’s post-hoc test of multiple comparison also revealed specific differences within and between specific treatment groups. We conclude that e-waste leachate arising from indiscriminate dumping into aquatic ecosystems in Nigeria contains mixtures of toxic constituents that can threaten ecosystem and public health. Full article

This work aims to undertake a preliminary characterization of winter fish assemblages in the salt marsh areas of Guadiana lower estuary (South-East Portugal) and discusses the potential risks of habitat dominance by a non-indigenous species (NIS). To this effect, six field campaigns were carried out in four sampling sites during winter season targeting the collection of fish species. A total of 48 samples were collected. Individuals from seven different taxa (marine and estuarine) were collected, although the assemblage was dominated by two estuarine species—the native Pomatoschistus sp. (goby) and the NIS Fundulus heteroclitus (mummichog). Goby was the most abundant taxa in the majority of salt marsh habitats, except for one specific, marsh pool, where extreme environmental conditions were registered, namely high temperature and salinity. Such conditions may have boosted the intrusion of mummichog in this area. This species is well adapted to a wide range of abiotic factors enabling them to colonize habitats where no predators inhabit. Impacts of mummichog introduction in the Guadiana salt marsh area are still unpredictable since this is the first time they have been recorded in such high density. Nevertheless, in scenarios of increased anthropogenic pressure and, consequently, habitat degradation, there is a potential risk of mummichog spreading to other habitats and therefore competing for space and food resources with native species. Full article