Search Results (72)

The Levantine Basin is the first region of the Mediterranean Sea to be impacted by climate warming and the arrival of non-indigenous species (NIS) via the Suez Canal. Although Levantine zooplankton has been studied previously, recent datasets capable of detecting the occurrence of new taxa, or shifts in community composition, especially in the easternmost part of the basin, are lacking. The present study provides updated information on zooplankton composition from Tyre (South Lebanon). In this study, the occurrence of two copepod families (Canuellidae, Longipediidae) and the first regional record of Facetotecta (Y-nauplii) are reported for the first time in the Levantine Basin. Additionally, although six Calanoida species were recorded as new to the Lebanese fauna, none can be attributed to Lessepsian NIS. Full article

The intestinal microbiota of fish is predominantly composed of prokaryotic microorganisms, with research historically focused on bacteria. In contrast, the role of microeukaryotic organisms in the fish gut remains largely unexplored. This review synthesizes current knowledge on the diversity, ecology, and potential functions of intestinal microeukaryotes, particularly fungi and protozoans, in teleost fish. Fungi, especially Ascomycota and Basidiomycota phyla members, are consistently identified across species and may contribute to digestion, immune modulation, and microbial homeostasis. Protists, though often viewed as pathogens, also exhibit potential commensal or immunoregulatory roles, including the modulation of bacterial communities through grazing. Other eukaryotic taxa, including metazoan parasites, microalgae, and zooplankton, are commonly found as transient or diet-derived members of the gut ecosystem. While many of these organisms remain poorly characterized, emerging evidence suggests they may play essential roles in host physiology and microbial balance. The review highlights the need for improved detection methodologies, functional studies using gnotobiotic and in vitro models, and multi-kingdom approaches to uncover fish gut microeukaryotes’ ecological and biotechnological potential. Full article

Antipredator defenses of bloom-forming cyanobacteria species maximize their fitness but can reduce carbon and energy transfer efficiency to higher trophic levels, making them a key regulator of plankton communities in eutrophic waters. We investigated the grazing responses of the tropical cladoceran Moina micrura to different strains of the cyanobacteria Microcystis aeruginosa and Planktothrix isothrix, using a good food source (green algae Mono-raphidium capricornutum) as a control. Both Microcystis strains grow as unicellular and are microcystins producers; however, this cyanotoxin was not detected on the filamentous Planktothrix strains. M. micrura ingested all cyanobacteria at reduced rates compared to single diets with Monoraphidium. In mixed diets, food type had a significant effect on grazing responses, which differed interspecifically. Planktothrix was more grazed than Microcystis strains. Feeding selectivity on Monoraphidium was negatively affected by the increase of cyanobacteria in the diet. We observed varied responses across treatments, ranging from feeding inhibition to different degrees of tolerance toward cyanobacteria, particularly in non-microcystin-producing species. We also highlight the selectivity of small tropical cladocerans, a pattern that is not yet well documented. These findings emphasize that studies incorporating phyto- and zooplankton with a history of coexistence can provide more meaningful insights into natural ecosystem dynamics. Full article

Understanding the motion behaviors of animals is crucial for unraveling the mechanisms underlying ethology across various domains, such as movement patterns, food detection, and defense strategies. In this study, we devised a simplified method enabling the movement of small animals to be tracked conveniently using high-resolution smartphone videos and freely available tracking software. Employing a laboratory video setup, we traced the swimming trajectory of the small copepod zooplankton Eodiaptomus japonicus, which has a body size of approximately 1 mm. From the tracked position data, we analyzed key motion parameters, including swimming distance, speed, and jump frequency. The results of our video analysis showed that adult female E. japonicus exhibited an average swimming speed of 9.8 mm s⁻¹, displaying a predominant cruising pattern with speeds of around 5.0 mm s⁻¹, punctuated by sporadic jumps, showcasing maximum instantaneous speeds reaching a remarkable 190.1 mm s⁻¹. Our successful tracking of the high-speed swimming copepod not only sheds light on its locomotion dynamics but also underscores the potential to refine this method to study the motion trajectories of diverse animal species. Full article

This study investigates the mechanisms of zooplankton community assembly and their relationship to environmental factors in high-latitude arid regions. We conducted seasonal sampling at four reservoirs in the upper Tarim River Basin from 2023 to 2024: Shangyou Reservoir (SY), Shengli Reservoir (SL), Duolang Reservoir (DL) and Xinjingzi Reservoir (XJZ). The zooplankton community was categorized into five functional groups based on the predominant species, with small crustacean filter feeders (SCF) in all reservoirs except XJZ, where a seasonal shift between rotifer collectors (RC) in the wet season and SCF in the dry season was observed. Pearson correlation and canonical correspondence analysis (CCA) revealed that interspecific competition, pH, conductivity (COND), and salinity (SALIN) were the main determinants of zooplankton community composition. Significant correlations (p < 0.05) were detected among functional groups RC (rotifers carnivora), RF (rotifers filter feeders), SCF (small copepods and claocera filter feeders), and MCC (middle copepods and claocera carnivora). Environmental factors showed significant spatial heterogeneity, while zooplankton biomass was positively correlated with pH and COND. Cluster similarity analyses indicated complex interactions between 29 zooplankton species, with RF identified as an important positive predictor for larger groups. The network of co-occurrences showed predominantly positive relationships, emphasizing the mutual facilitation between the species. Our results suggest that interspecific interactions have stronger effects on community structuring than environmental factors, with mutual facilitation emerging as an important survival strategy. This study provides important insights into the dynamics of zooplankton communities in dry reservoirs and establishes a framework for understanding ecological patterns and assembly mechanisms under drought conditions. Full article

This study presents the first species-level assessment of zooplankton communities within a designated Special Area of Conservation (SAC, ES7020122) in the coastal waters of an oceanic island in the Atlantic Ocean, conducted in a previously under-sampled protected coastal region. Copepods emerged as the predominant taxa, offering key insights into early-stage community structure and potential indicators of ecological dynamics in marine ecosystems. Zooplankton biomass and abundance were primarily driven by organisms in the 200–500 µm size fraction, with spatial variation observed across latitudinal transects. A total of 44 copepods species were identified, including dominant genera (Oncaea, Oithona, and Clausocalanus) characteristic of subtropical Atlantic ecosystems. Several indicator species (e.g., Candacia ethiopica and Oncaea scottodicarloi) showed spatial patterns. While no direct impacts from the recent 2021 volcanic eruption were detected, the dominance of opportunistic copepods and the observed diversity suggest a potential adaptive response and resilience of the pelagic community to periodic geological disturbances. These results provide a valuable ecological baseline for future long-term monitoring under the Marine Strategy Framework Directive and underscore the importance of copepods as indicators of coastal ecosystem structure and variability. Full article

The present dataset served to evaluate the plankton community composition and abundance in Nuevo Gulf (42°42′ S, 64°30′ W), a World Heritage Site in Argentinian Patagonia and part of the Valdés Biosphere Reserve. It reports zooplankton abundance (>300 µm) and phytoplankton concentration (10–200 μm) during the spring and summer seasons from 2019 to 2021. Special attention was given to the taxonomic classification of zooplankton, leading to the first identification of jellyfish species within the Gulf and the detection of an unreported copepod for the area (Drepanopus forcipatus). Samples were collected at two depths—a surface and a deeper layer—to assess vertical distribution patterns of plankton communities and explore potential environmental drivers influencing their variability. This dataset provides a valuable baseline for future studies analyzing temporal variations in the Gulf’s plankton communities. Moreover, it encourages the local scientific community to contribute data and promote open access to marine biodiversity records in the region. Full article

Deep temperate lakes are increasingly reported to suffer consequences of climate warming, affecting thermal stratification and plankton seasonality. Long-term studies offer a unique opportunity for detecting changes in the zooplankton taxa composition related to climate change. Sampling zooplankton organisms alongside abiotic variables, such as water column temperature, enables the linking of changes in plankton communities with variations in the stratification regime. This provides evidence of direct and indirect warming effects. Our study in Lake Maggiore investigated variations in the population density and persistence of Diaphanosoma brachyurum, a thermophile species that is a member of the original zooplankton community of the lake, along with the increase in water temperature and the duration of the thermal stratification during the period 2013–2023. Our results highlighted an increase in the abundance and persistence of Diaphanosoma during the study period, along with an increase in the mean water temperature of the layer 0–10 m and of the length of the thermal stratification. Such changes, affecting the population dynamics of predators and competitors and their food sources (i.e., small algae), might lead to a rearrangement of the structure of the pelagic food chain. Full article

The data on hosts of Ellobiopsis in Central Asia waterbodies are nearly non-existent. All research in this direction was conducted in other regions (Europe and Brazil). Parasitological studies were carried out in different seasons in the North and Middle Caspian Sea. Twenty-one taxa were registered in zooplankton, and only dominants of community calanoids Acartia (Acanthacartia) tonsa and Calanipeda aquaedulcis were infected with Ellobiopsis sp. Calanoida C. aquaedulcis was reported for the first time as a host for Ellobiopsis. The number of parasites per host was equal to one. The body length of parasites varied from 0.10 to 0.80 mm. The highest infection degree was recorded in C. aquaedulcis (5.71%), and it varied from 2.61% to 3.35% in Acartia. The individuals in the juvenile developmental stages were infected in Calanipeda, while in Acartia, individuals in all developmental stages were vulnerable to infection. The infected calanids had reduced body lengths. The findings suggest the possible influence of Ellobiopsis sp. on quantitative variables of hosts in the Middle Caspian, especially on biomass, by reducing the body sizes of hosts. However, no effect on the abundance and biomass of the host and the structure of the zooplankton of the North Caspian Sea has been detected. Full article

Grazing by zooplankton can regulate bloom-forming cyanobacteria but can also transfer toxin-producing cells, as well as toxic metabolites, to the food web. While laboratory investigations have provided extensive knowledge on zooplankton and toxic cyanobacteria interactions, information on zooplankton feeding on toxin-producing cyanobacteria in natural water bodies remains scarce. In this study, we quantified Microcystis-specific mcyE synthase genes from the gut contents of various cladoceran and copepod taxa to assess the in situ crustacean community and taxon-specific ingestion of potentially toxic Microcystis in Lake Peipsi, a large eutrophic lake in Estonia, Northern Europe. Microcystis cells with mcyE genes were found in all crustaceans examined. However, some species, such as the cyclopoid copepod Mesocyclops leuckarti, were more efficient in ingesting potentially toxic Microcystis than other co-occurring cladocerans (Daphnia spp., Bosmina spp., Chydorus sphaericus) and copepods (Eudiaptomus gracilis). The amount of toxigenic Microcystis cells grazed by crustacean population changed temporarily, and copepods were the predominant consumers of toxigenic Microcystis during several months of the 5-month study period. Crustacean ingestion of toxigenic Microcystis was not related to Microcystis biomass or mcyE gene copy numbers in the environment but was instead related to the abundance of major crustacean grazers. Our findings emphasize the close interaction between crustacean zooplankton and toxigenic Microcystis, indicating that some species may play a more significant role in linking toxic cells within the food web than others. Full article

The evaluation of nanoplastics bioaccumulation in living organisms is still considered an emerging challenge, especially as global plastic production continues to grow, posing a significant threat to humans, animals, and the environment. The goal of this work is to advance the development of standardized methods for reliable biomonitoring in the future. It is crucial to employ sensitive techniques that can detect and measure nanoplastics effectively, while ensuring minimal impact on the environment. To understand nanoplastics retention by freshwater organisms, phyto- and zooplankton, and mussels were exposed to gold-doped polymeric nanoparticles synthesized in our laboratory. The results demonstrated that measuring gold content using inductively coupled plasma mass spectrometry (ICP-MS), along with confirmation of its presence through electron microscopy in selected exposed samples provides insight into the accumulation and release of nanoplastics by organisms playing a relevant ecological role at the early levels of aquatic food webs. Full article

This study investigated the abundance of zooplankton copepods and ostracods taxonomic groups in fish farms in Rondônia’s Vale do Jamari and Centro-Leste microregions during the rainy and dry seasons. It also analyzed the correlation between zooplanktons abundance and the presence of acanthocephalan parasites. Conducted in 41 fish farms between November 2021 and September 2023, the study included water, zooplankton, and fish samples from 196 Colossoma macropomum. The results showed that 95% of the farms had fish infected with Neoechinorhynchus buttnerae, with varying parasitism levels. Georeferencing revealed higher parasite densities in the municipalities of Ariquemes, Monte Negro, Machadinho do Oeste, and Buritis (Vale do Jamari), as well as Urupá, Ji-Paraná, Ouro Preto do Oeste, and Teixeirópolis (Centro-Leste), with clusters of heat islands in the latter group. Water quality parameters were suitable for raising C. macropomum. The presence of ostracods and copepods could serve as indicators of parasitic infestations, highlighting the importance of monitoring zooplankton and parasite communities. This approach is valuable for detecting changes in artificial ecosystems, such as fish farms, which could lead to significant long-term effects. Full article

Ichthyophthirius multifiliis, a parasitic ciliate, causes “white spot disease” in freshwater fish and poses a significant threat to global freshwater aquaculture. Eliminating the free-swimming theront stage from the aquaculture environment is a critical measure for controlling I. multifiliis infections. The natural predator of I. multifiliis theronts in fish-farming ponds were identified using fluorescent dye-labelled live theronts and quantitative PCR; meanwhile, the zooplankton community composition in the positive ponds of I. multifiliis detected by quantitative PCR were analyzed by eDNA metabarcoding assay. The results revealed predation on theronts by cyclopoid copepods, including Cyclops vicinus, Thermocyclops taihokuensis, Cyclops sp., Thermocyclops sp., Eucyclops sp., and Mesocyclops sp. from the in-situ predation aquatic ecosystem, and among these copepods, C. vicinus was identified as a natural dominant predator of I. multifiliis. This study provides a scientific basis for further exploration and utilization of natural predators to enhance sustainable and environmentally friendly control strategies against I. multifiliis. Full article

Zooplankton such as copepods and krill are currently used to produce marine oil supplements, with the aim of helping consumers achieve the recommended intake of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs). Oils from lower trophic levels differ from fish oil in the distribution of lipids into different classes, and this can influence the bioaccessibility of fatty acids, i.e., the percentage of fatty acids that are released into the intestine in a form that can be absorbed by enterocytes. We evaluated fatty acid release after in vitro digestion in four commercial marine oil supplements containing fish, krill and Calanus finmarchicus oils using two different analytical approaches, TLC-FID and ¹H-NMR spectroscopy. The results clearly indicated that the release of free fatty acids (FFAs) after simulated digestion mainly depends on the oil source and is mainly related to the partitioning of lipids into different classes. In fact, the lowest FFA release was detected in Calanus oils, which contain high amounts of wax esters. The different release of FFAs, which appeared secondarily related to encapsulation, can modulate the absorption and blood concentration of the administered n-3 LC-PUFAs and therefore their efficacy. This may partly explain the inconsistencies in intervention studies using marine oil supplements. Full article

Recently, 7-diethylamino-4-methylcoumarin (DEAMC) has been identified as a potent antiandrogenic compound in the surface water; however, little is known about the antiandrogenic potentials of other synthetic coumarins and their occurrence in the aquatic ecosystem. In this study, for the first time, we observed that 7-dimethylamino-4-methylcoumarin (DAMC) elicited androgen receptor (AR) antagonistic activity with a 50% inhibitory concentration (IC₅₀) of 1.46 µM, which is 14.3 times more potent than that observed for DEAMC (IC₅₀ = 20.92 µM). We further collected abiotic (water and sediment) and biotic (plant, plankton, and fish) samples (n = 208) from a subtropical freshwater ecosystem, the Dongjiang River basin, in southern China, and determined the concentrations of the two coumarins in these samples. Overall, DAMC was the predominant compound found in the sediment, plant, algae, zooplankton, and fish muscle samples, with median concentrations at 0.189, 0.421, 0.832, 0.798, and 0.335 ng/g dry wt. (DW), respectively, although it was not detected in any surface water sample. For DEAMC, the median concentrations observed in the surface water, sediment, plant, algae, zooplankton, and fish muscle samples were 0.105 ng/L, 0.012, 0.051, 0.009, 0.008, and 0.181 ng/g DW, respectively. The bioaccumulation factor (BAF) values of DAMC and DEAMC in the algae, zooplankton, and fish muscle exceeded 5000 L/kg, suggesting that the two coumarins may have significant bioaccumulation potentials in aquatic biota. Additionally, the mean daily intake (EDI) of coumarins through fish consumption was estimated as 0.19 ng/kg BW/day for male toddlers. This is the first field study to illustrate the antiandrogenic potential of DAMC and document the widespread occurrence of the two synthetic coumarins in aquatic ecosystems. Full article