Search Results (47)

Sulfamethoxazole (SMX), a commonly used sulfonamide antibiotic, poses a threat to aquatic life due to its widespread presence in the environment. This study aims to investigate the specific effects of SMX on the development of marine medaka (Oryzias melastigma) embryos and larvae. Marine medaka embryos were exposed to SMX at concentrations of 0 (solvent control group, SC group), 1 μg/L (low concentration group, L group), 60 μg/L (middle concentration group, M group), and 1000 μg/L (high concentration group, H group). The results indicated that SMX exposure significantly accelerated the heart rate of embryos (p < 0.0001) and shortened the hatching time while also causing anomalies such as reduced pigmentation, smaller eye size, spinal curvature, and yolk sac edema. SMX also led to a decrease in the total length of the larvae. The M group and the H group exhibited a significant increase (p < 0.05) in lipid accumulation in the visceral mass of the larvae. In the L group and the M group, there was a significant increase (p < 0.0001) in the swimming distance of the larvae. At the molecular level, SMX exposure affected the transcript levels of the genes involved in the cardiovascular system (ahrra, arnt2, atp2a1, and cacan1da), antioxidant and inflammatory systems (cat, cox-1, gpx, pparα, pparβ, and pparγ), nervous system (gap43, gfap, α-tubulin), intestinal barrier function (claudin-1), detoxification enzymes (ugt2c1-like), and lipid metabolism (rxraa) in the embryos to larval stage. The microbiome analysis showed that at the phylum level, exposure to SMX resulted in an increase in the abundance of Proteobacteria. Additionally, the abundance of Actinobacteriota significantly increased in the L group (p < 0.05). At the genus level, the abundance of Bifidobacterium significantly increased in the L group (p < 0.05), while the abundance of Vibrio significantly increased in the H group (p < 0.05). The alpha diversity analysis revealed a significant decrease in the Chao1 index in the L and H groups, indicating a reduction in microbial richness. The beta diversity analysis showed differences in the microbial communities of marine medaka larvae among different SMX exposure groups. This study elucidates the negative impacts of SMX on the development of marine medaka embryos and larvae and their microbial composition, providing a scientific basis for assessing the risks of SMX in marine ecosystems. Full article

Early life stages are pivotal to the functioning and resilience of ecological systems, displaying heightened vulnerability to environmental changes and exposure to contaminants. Octocrylene (OC), an organic ultraviolet (UV) filter, and its breakdown product benzophenone (BP) are commonly found in aquatic environments, but their impact on keystone processes determining the success or failure of the early life stages of marine organisms remains underexplored. This study aims to assess the impacts of OC and BP at environmentally realistic concentrations (1, 10, and 100 µg.L⁻¹), over a 24 h exposure period, on larvae of the Pacific oyster (Magallana gigas). A multiparametric approach was employed, examining DNA integrity, embryo–larval development and swimming velocity. The results showed that DNA integrity and swimming velocity were not affected by OC or BP; however, both compounds increased developmental abnormalities in D-shaped larvae in all concentrations tested. Considering the robustness of morphological parameters, often assumed as irreversible, and their critical influence on larvae survival, these findings suggest that environmentally relevant concentrations of OC and BP may threaten the success of oyster larvae, potentially impacting the population’s long-term stability and, ultimately, raising ecological health issues. Full article

The ribbon worms of the closely related species Cephalothrix simula, Cephalothrix cf. simula, and Cephalothrix mokievskii, representing the C. simula species complex, possess high concentrations of tetrodotoxin (TTX) and its analogues in all developmental stages from eggs to adults. It has recently been suggested that the eggs and larvae of these animals can be a source of tetrodotoxins (TTXs) for other aquatic organisms. In the current study, TTXs in mature and post-spawning individuals and in the eggs of C. mokievskii were identified using high-performance liquid chromatography–tandem mass spectrometry. For the first time, the quantity and profile of TTXs that these nemerteans released into the environment during spawning were estimated. We showed that the spawning C. mokievskii females released significant amounts of TTX and 5,6,11-trideoxyTTX with their eggs; these levels were sufficient for the potential toxification of marine bioresources. The issues surrounding the monitoring of TTXs in commercial marine animals, and collecting at the sites of the spawning of nemerteans from the C. simula species complex, are discussed. Full article

To protect aquatic organisms in ecosystems, each country and continental union has established guidelines for deriving the water quality standards (WQS) of specific substances. These guidelines mandate the use of acute and chronic toxicity data for fish, which are high-trophic-level organisms. However, due to increasing concerns about animal welfare and experimental ethics, there is a growing need for alternative methods to determine substance toxicity in fish. Fish toxicity tests using early life stages, such as embryos or larvae, have been utilized as alternative methods for adult fish toxicity assays. This review of the WQS guidelines and relevant test protocols confirmed the classification of acute and chronic toxicity in fish assays using different developmental stages. Fish toxicity data derived from exposure periods longer than one week using embryonic- or larval-stage organisms can be considered as indicative of chronic toxicity. There is a high correlation between fish embryo toxicity and adult effects, suggesting that fish embryo toxicity tests with appropriate exposure durations could replace adult fish toxicity tests, addressing experimental animal ethics concerns. Full article

Background: Carotenoids play essential nutritional and physiological roles in aquatic animals. Since aquatic species cannot synthesize carotenoids de novo, they must obtain these compounds from their diet to meet the physiological and adaptive requirements needed in specific aquaculture stages and conditions. Carotenoid supplementation in Artemia represents a promising strategy to enhance pigmentation, health, and growth in aquaculture species, particularly in larvae and other early developmental stages. Methods: In this study, a β-carotene enrichment process was applied to Artemia metanauplii to investigate the biological fate and potential effects of β-carotene. Results: The results indicated significant β-carotene uptake by Artemia, with peak levels observed at 12 h. Alongside β-carotene, two xanthophylls—canthaxanthin and echinenone—were detected in Artemia, each exhibiting distinct patterns during the enrichment and subsequent depletion phases. The transcriptome analysis identified 2705 differentially expressed genes (DEGs), offering valuable insights into gene functions associated with carotenoid absorption, metabolism, and antioxidant mechanisms. The findings suggest that β-carotene enrichment enhances metabolic activity and energy pathways, supporting the physiological functions of Artemia. Notably, unlike other crustaceans, Artemia lack certain enzymes necessary for converting β-carotene into astaxanthin, restricting them to producing keto-carotenoids like canthaxanthin. Furthermore, the study highlights the upregulation of genes encoding lipid transport proteins, such as CD36 and ABC transporters, which may contribute to carotenoid absorption in Artemia. Additional functional insights are provided by the gene BCO2, which regulates pigmentation by preventing excessive carotenoid accumulation, along with ketolase and hydroxylase enzymes in carotenoid metabolic pathways. Conclusions: This research advances our understanding of carotenoid metabolism in crustaceans, with potential implications for aquaculture nutrition and feed formulation. Full article

The highly hazardous chemical ammonia has been proven to be absorbed by nanoparticles, thereby exerting highly toxic effects on aquatic organisms. As a ubiquitous pollutant in aquatic environments, polystyrene nanomicroplastics (PSNPs) have shown strong adsorption capacity due to their large surface area. Therefore, the potential joint effects of ammonia and PSNPs need to be clarified. In this study, zebrafish embryos were exposed to a water solution with ammonia concentrations (0, 0.1, 1, and 10 mg/L) with or without PSNP (100 μg/L) treatment up to 120 hpf. The results showed that combined exposure increased the accumulation of ammonia and obviously reduced the locomotor speed of zebrafish larvae compared with exposure to ammonia alone. Further studies indicated that PSNPs can aggravate ammonia-induced neurotoxicity by altering the cholinergic system, dopaminergic neurons, and the retinal structure in zebrafish larvae. In addition, our results revealed that ammonia caused significant alterations in the expression of genes related to neurodevelopment and retinal development, and PSNPs exacerbated this adverse effect. In conclusion, PSNPs can aggravate ammonia-induced neurotoxicity in the early stage of zebrafish and their associated health risk to aquatic animals should not be underestimated. The main contribution of this article lies in revealing the synergistic neurotoxicity of ammonia and PSNPs in the early stage of zebrafish. Moreover; it emphasizes that the associated health risks to aquatic animals should not be underestimated. Full article

The diversity and distribution of mosquitoes from Sonora, Mexico, was documented through entomologic surveys conducted in the four physiographic regions and sub-regions of Sonora: the Sonoran Plain, the Sierra Madre Occidental, the Northern Mountains and Plains, and the Pacific Coastal Plain. Immature stages were collected from aquatic habitats, while adult mosquitoes were collected using Shannon traps, resting in vegetation, and by human landing collections. Overall, 11,316 specimens, which comprised 493 larvae, 224 larval exuviae, 400 pupal exuviae, 33 pupae, 4552 females, 5607 males, and seven male genitalia, were identified. Two subfamilies: Anophelinae and Culicinae, seven tribes, 10 genera, 23 subgenera, and 56 species are reported below. Of these, one tribe, one genus, five subgenera, and 15 species were recorded for the first time in Sonora. Two species, Aedes deserticola Zavortink and Toxorhynchites septentrionalis (Dyar and Knab), are the first recordings of their kind nationwide. Toxorhynchites septentrionalis was also barcoded with the cytochrome oxidase subunit 1 (COI) gene. The presence of Psorophora columbiae (Dyar and Knab) is confirmed in Mexico. Taxonomic notes, new geographic distribution limits of mosquitoes in Sonora, and information regarding their importance as disease vectors are provided. By adding Ae. deserticola and Tx. septentrionalis and confirming Ps. columbiae in Mexico, there are currently 251 mosquito species in the Country. Full article

Benzodiazepines, a significant group of newly recognised water contaminants, are psychotropic medications prescribed for common anxiety symptoms and sleep disorders. They resist efficient degradation during sewage treatment and endure in aquatic environments. Their presence in aquatic matrices is increasing, particularly after the recent pandemic period, which has led many people to systematically use benzodiazepines to manage anxiety. In previous studies, an important interference of this class of drugs on both the larval and adult stages of some aquatic species has been demonstrated, with effects on behaviour and embryonic development. This study examined the influence of delorazepam, a diazepam metabolite, on Artemia salina development to gain insight into responses in naupliar larvae. Results demonstrated that treatments (1, 5, and 10 µg/L) increase the hatching percentage and induce a desynchronisation in growth. Mortality was only slightly increased (close to 10% at six days post-hatching), but lipid reserve consumption was modified, with the persistence of lipid globules at the advanced naupliar stages. Locomotory activity significantly decreased only at 10 µg/L treatment. No teratogenic effects were observed, though modest damages were noticed in the posterior trunk and eyes, two targets of environmental toxicity. The negative impact of delorazepam on Artemia salina adds to those already reported in other species of invertebrates and vertebrates, which are not yet considered targets of these drugs. This study underscores the need for further research and immediate attention to this class of contaminants and the importance of monitoring their presence during environmental risk assessments. Full article

Conspecific amphibian populations may vary widely in local demography and average body size throughout their geographical range. The environmental drivers of variation may reflect geographical gradients or local habitat quality. Among fire salamander populations (Salamandra salamandra), local demography shows a limited range of variation because high concentrations of skin toxins reduce mortality from predation to a minimum, whereas average adult body size varies significantly over a wide range. This study on four neighboring populations inhabiting the catchments of low-order streams in the upper middle Rhine Valley (Koblenz, Germany) focuses on the identification of local environmental drivers of variation in age and body size. I collected 192 individuals at two localities per stream, measured snout–vent length, clipped a toe for posterior skeletochronological age determination, and released salamanders in situ again. Populations were similar in age distribution. Local habitat quality accounted for a significant proportion of demographic variability, mediated by the impact of landscape-induced mortality risk, including roads and agriculture. Still, the main effect of variation in habitat quality was on adult body size, the result of growth rates of aquatic larvae and terrestrial juveniles. Larvae exposed to non-lethal heavy metal contamination in streams developed into smaller juveniles and adults than clean-water larvae, providing evidence for carry-over effects from one stage to another. The generally small average adult size in the Rhine Valley populations compared to those in other parts of the distribution range indicates the action of a still unidentified environmental driver. Full article

Cyanobacteria are photosynthetic prokaryotes that play an important role in the ecology of aquatic ecosystems. However, they can also produce toxins with negative effects on aquatic organisms, wildlife, livestock, domestic animals, and humans. With the increasing global temperatures, urban parks, renowned for their multifaceted contributions to society, have been largely affected by blooms of toxic cyanobacteria. In this work, the toxicity of two different stages of development of a cyanobacterial bloom from a city park was assessed, evaluating mortality, hatching, development, locomotion (total distance, slow and rapid movements, and path angles) and biochemical parameters (oxidative stress, neurological damage, and tissue damage indicators) in zebrafish embryos/larvae (Danio rerio). Results showed significant effects for the samples with more time of evolution at the developmental level (early hatching for low concentrations (144.90 mg/L), delayed hatching for high concentrations (significant values above 325.90 mg/L), and delayed development at all concentrations), behavioral level (hypoactivity), and biochemical level (cholinesterase (ChE)) activity reduction and interference with the oxidative stress system for both stages of evolution). This work highlights the toxic potential of cyanobacterial blooms in urban environments. In a climate change context where a higher frequency of cyanobacterial proliferation is expected, this topic should be properly addressed by competent entities to avoid deleterious effects on the biodiversity of urban parks and poisoning events of wildlife, pets and people. Full article

The water lily aphid (Rhopalosiphum nymphaeae) is a highly polyphagous herbivore that causes severe damage to many terrestrial and aquatic plants, especially lotus. Due to environmental concerns about water pollution and other issues caused by chemical control methods, there is an urgent need to develop effective and sustainable control methods. The harlequin ladybird (Harmonia axyridis) is a well-known aphid predator and may pose a potential threat to R. nymphaeae. To study the predation ability of H. axyridis at different developmental stages on R. nymphaeae, we assessed the functional response, attack rate, and search effect of H. axyridis larvae and adults preying on R. nymphaeae. The numerical response of this process was also evaluated under a constant ladybird-to-aphid ratio and constant aphid density conditions, respectively. Our results showed that all predator stages exhibited type II functional responses. The predation rate of individual H. axyridis on R. nymphaeae nymphs significantly increased as prey density increased. In contrast, the search effect of H. axyridis gradually decreased with an increase in prey density. Meanwhile, H. axyridis at different developmental stages possess varying predation abilities; fourth instar and adult H. axyridis were found to be highly efficient predators of R. nymphaeae. H. axyridis adults exhibited the highest predation ability and predation rate, while both the adult and fourth-instar larvae exhibited the highest attack rate. Moreover, fourth-instar larvae exhibited the highest search effect value at initially lower prey densities, although adults surpassed them at higher prey densities. Our results also indicated that H. axyridis exhibited varying degrees of intraspecific interference and self-interference influence as predator density increases. These results strongly support H. axyridis as an effective biocontrol agent for R. nymphaeae. Full article

A suitable feed size has a positive effect on animal feeding. For aquatic larvae, the correct feed size is very important for their growth. This experiment analyzed and compared the effect of different particle sizes of feed for larval stages on the growth performance, whole body composition, and muscle amino acid and fatty acid composition of crayfish. Five larval crayfish diets of different particle sizes, namely < 0.40 mm (Group A, control group), 0.40–0.50 mm (Group B), 0.71–0.85 mm (Group C), 0.90–1.00 mm (Group D) and 1.5 mm (Group E), were fed to 2000 crayfish (initial weight 0.0786 ± 0.0031 g) for 100 d. The results showed that as the particle size increased, final weight, weight gain (WG, p = 0.001) and specific growth rate (SGR, p = 0.000) of the crayfish tended to increase and then leveled off, with the control group being the lowest. The feed conversion ratio (FCR, p = 0.000) showed a decreasing and then equalizing trend with increasing particle size, but there was no significant difference between the groups except the control group. Broken-line regression analysis showed that the critical values for the appropriate particle feed size for crayfish larvae were 0.55 mm and 0.537 mm using SGR and FCR as indicators. Groups B, C and D had the highest crude protein content and were significantly higher than the control group (p = 0.001). Group E had the highest umami amino acid (UAA) and was significantly higher than the control group (p = 0.026). The content of isoleucine (Ile, p = 0.038) and phenylalanine (Phe, p = 0.038) was highest in group C and significantly higher than in the control group. Through principal component analysis, groups C and D were shown to contain leucine (Leu), glutamic (Glu), methionine (Met), valine (Val), histidine (His), Phe, and Ile levels significantly induced. The content of linoleic acid (C18:2n6, p = 0.000), linolenic acid (C18:3n3, p = 0.000), saturated fatty acid (SFA, p = 0.000), monounsaturated fatty acid (MUFA, p = 0.001), polyunsaturated fatty acid (PUFA, p = 0.000) and n-6 PUFA (p = 0.000) in group C was the highest and significantly higher than the control group. Principal component analysis showed that group C significantly induced the levels of C18:2n6, C18:3n3, DHA, EPA, n-3 PUFA and n-6 PUFA in muscle. Therefore, our results suggest that appropriate feed particle size can improve the growth performance and nutrient composition of crayfish. Based on the broken-line regression analysis of SGR and FCR, the critical values of optimal particle size for crayfish are 0.55 mm and 0.537 mm, and when the particle size exceeds these critical values (not more than 1.5 mm commercial feed), growth performance and FCR of the crayfish are no longer changed. Nevertheless, group C has high protein and low lipid content, as well as better nutrition with amino acids and fatty acids. Overall, combined with growth performance and nutrient composition, it is recommended that the particle size of the diet at the larval stage for crayfish is between 0.71 and 0.85 mm. Full article

The common house mosquito (Culex pipiens) is a native vector for West Nile virus (WNV). Invasive species like the tiger mosquito (Aedes albopictus) and Asian bush mosquito (Aedes japonicus) are rapidly spreading through Europe, posing a major threat as vectors for dengue, chikungunya (CHIKV), and Japanese encephalitis virus (JEV). These mosquitoes share a similar ecological niche as larvae, but the carry-over effects of aquatic larval interactions to the terrestrial adult stage remain largely unknown and their medical relevance requires further investigation. This study examines the context dependency of larval interactions among Aedes albopictus, Aedes japonicus, and Culex pipiens. The survival, development time, growth, and energetic storage were measured in different European populations within density-response (intraspecific) experiments and replacement (interspecific) experiments at 20 °C and 26 °C. Overall, Ae. japonicus was the weakest competitor, while competition between Ae. albopictus and Cx. pipiens varied with temperature. Adults emerging from this larval competition were infected as follows: Culex pipiens with WNV, Ae. albopictus with CHIKV, and Ae. japonicus with JEV. While no JEV infection was observed, mosquitoes experiencing interspecific interactions during their larval stages exhibited higher infection rates and viral RNA titers for CHIKV and WNV. This increased susceptibility to viral infection after larval competition suggests a higher risk of arbovirus transmission in co-occurring populations. Full article

To update the record of mosquito diversity in the state of Morelos, Mexico, mosquito collections were conducted in both physiographical regions of Morelos: the Neo-volcanic Axis and the South Mountain Range. Immature stages were collected from aquatic habitats, while adult mosquitoes were collected using CDC light traps, Shannon traps and approaching/landing on the collecting personnel. All specimens were identified using taxonomic keys and the mitochondrial cytochrome C oxidase subunit 1 (COI). Following Mexico State, this is the second study of mosquito taxonomy of a complete Mexican state using COI barcoding. In Morelos, a total of 58 species of mosquito occurs, of which we report 12 for first time (Aedes vexans, Ae. euplocamus, Ae. vargasi, Psorophora cilipes, Ps. lineata, Culex restrictor, Cx. interrogator, Cx. nigripalpus, Cx. tarsalis, Cx. sandrae, Cx. lactator and Toxorhynchites moctezuma). Morelos now ranks sixth in mosquito diversity among Mexican states. Phylogenetic trees were constructed for 32 species, including Ae. shannoni, which is a new record for GenBank databases. Additionally, we report COI barcode sequences of Culiseta dugesi Dyar and Knab, which is resurrected from the synonymy of Cs. particeps (Adams). Fourth-instar larvae and adult females of Cs. dugesi were redescribed. This brings the number of mosquito species in Mexico to 248. Ecological and distributional notes for the new records, the medical importance of mosquito species in Morelos, and an identification key for larvae and females of the known Culiseta species occurring in Mexico are also included. Full article

Graphene-based nanomaterials are exceptionally attractive for a wide range of applications, raising the likelihood of the release of graphene-containing nanoparticles into aquatic environments. The growing use of these carbon nanomaterials in different industries highlights the crucial need to investigate their environmental impact and evaluate potential risks to living organisms. The current investigation evaluated the nanotoxicity of graphene (nanoflakes) and graphene oxide (GO) nanoparticles on the cardiorespiratory responses (heart rate, gill ventilation frequency), as well as the swimming and nesting behavioral parameters of early stage larvae and juvenile salmonids. Both short-term (96 h) and long-term (23 days) exposure experiments were conducted using two common species: brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). The findings demonstrated notable alterations in fish nesting behavior, swimming performance, and cardiorespiratory functions, indicating the potential toxicity of nanoparticles. This impact was observed at both physiological and whole-organismal levels in salmonids at early stages. Future investigations should explore different types of nanocarbons and their potential enduring effects on fish population structure, considering not only individual survival but also broader aspects of development, including feeding, reproductive, and other social dynamics. Full article