Search Results (51)

The role of abiotic factors in the allelopathic interactions between copepods and rotifers is poorly documented. Temperature has a marked effect on the metabolism of zooplankton. Therefore, the release of allelochemicals by copepods and the response of rotifers to them may change as temperatures increase. Here, we tested the effect of two temperatures (20 and 25 °C) on the population growth of Brachionus havanaensis cultured on a conditioned medium (CM) of Arctodiaptomus dorsalis and Eucyclops sp. The CM was obtained daily, separately, for the males and females of both copepod species at a density of 0.1 ind. mL⁻¹ for 24 h prior to experiments. In the controls and CM treatments, higher temperatures had a stimulatory effect on the population growth and the rate of population increase (r) of B. havanaensis. At 25 °C, the CM from the females and males of A. dorsalis caused >30% increase in r, but for the CM from Eucyclops sp., this effect was lower (<21%). At 20 °C, the r in the controls and CM treatments was not significantly different. The morphometry of B. havanaensis varied depending on the treatments. Compared to controls, longer loricae were recorded in the CM of male A. dorsalis at both temperatures. However, in the CM of female calanoids, longer rotifers were observed only at higher temperatures. At 20 °C, the CM from Eucyclops produced smaller loricae. The relationship between the lorica length and width of rotifers showed a linear relation but the slope differed among the treatments. Full article

To achieve the aims of the Convention on Biological Diversity’s 2030 Global Biodiversity Framework, the management of marine areas requires the use of cost- and time- effective monitoring of biodiversity. Marine observation platforms are increasingly used for such monitoring activities. These platforms allow data to be collected from a variety of sensors simultaneously in real-time and in situ, providing the opportunity for both adapting where and when sampling is performed and for using multiple data streams for more comprehensive information to be collected on marine biodiversity. While some recent monitoring activities are following an adaptive sampling approach (in which sampling is adapted to ecological phenomena such as diel vertical migration), most still do not use a data-driven approach (in which multiple data streams are used to inform sampling). In this study, we performed eDNA metabarcoding to monitor the community of copepods found in the high-latitude environment near Trondheim, Norway. We applied an adaptive sampling approach to detect calanoid copepods at seasonally contrasting time points using real-time acoustic sensor data. Acoustic sensor data were used to inform when plankton net samples were collected in a 24 h period, as Calanoid copepods migrate through the water column throughout the day to avoid predation. These results demonstrate how multiple information streams from complimentary monitoring methods can be combined for more robust monitoring of biodiversity by confirming the presence (or absence) of relevant taxa. Full article

Egg-carrying ectothermic planktonic organisms in stressed conditions adapt diverse reproductive trade-off strategies, which are denoted by markers of stress, either in their physiology, morphology or reproductive characteristics. This is the first study documenting the fact that egg packing constraints can provide a novel marker of stress through experimental and field data, attuned by a remarkable bioindicator egg-bearing copepod species, Eurytemora affinis, in diverse physical conditions and transboundary sites through a multigenerational assay. This study propounds a packing pressure index (PP index), which is an efficient tool for demarcating reproductive efforts along with reference lines of packing constraints in bioindicator organisms. The packing pressure index for E. affinis varied across geographical locations, showing distinct north–south variations, along with a strong packing constraint in higher-temperature and -salinity conditions. The novel relationships between morphological and reproductive traits and packing constraints could be standardized. Ensuring the presence of the egg sac membrane and its relationship with varied physicochemical parameters can aid in developing a comprehensive understanding of reproductive strategies in keystone species like E. affinis. Full article

Highly conserved among eukaryotes, the chemical defensome protects organisms against chemical stressors and helps to reestablish the altered homeostatic state. The defensome includes genes such as transporters (e.g., adenosine triphosphate ATP-binding cassette), phase I and phase II detoxification enzymes, and antioxidant enzymes. During their life cycle, planktonic copepods, the most abundant and ubiquitous metazoans on Earth, are exposed to many environmental stressors that impair their survival and fitness. Here, using high-quality publicly available transcriptomic data, defensome genes were searched in copepods belonging to different orders and living in different environments (e.g., Antarctic, Subarctic, Mediterranean). Gene expression responses were investigated in four calanoids exposed to different stresses to identify a common and species-specific detoxification system. Our results confirm that the defensome is highly conserved among copepods but also report differences in the relative contribution of genes among species living in different habitats, suggesting a fitness adaptation to environmental pressures. The genes provided here can be used as biomarkers of chemical defense and can also be tested in other planktonic organisms to assess the “health” of marine organisms, which is useful for understanding environmental adaptations and they can be used to assess changes and make predictions at the population and community levels. Full article

The diet of the invasive ctenophore Mnemiopsis leidyi in the Gulf of Trieste was examined during its peak occurrence in the summer and early-autumn months (July to October) from 2017 to 2019, through the analysis of stomach contents. Altogether 506 specimens were individually caught for the analysis. A total of 3215 prey items were isolated and identified. Copepods emerged as the primary prey (relative abundance 66.7%), followed by cladocerans (7.7%), and bivalve larvae (6%). Notably, specimens of M. leidyi constituted a significant portion of the diet (5.4.%), providing further evidence of cannibalism within this species. Copepods were also the most commonly occurring prey items in the diet of M. leidyi. Most of them were represented by calanoid and cyclopoid nauplii (48.2%), followed by a harpacticoid M. norvegica (28.3%), and calanoids (26.8%). Other frequently occurring taxa were bivalve larvae (19.3%), M. leidyi (18.7%), and cladoceran Penilia avirostris (16.1%). The rate of cannibalism peaked in July, coinciding with a period of limited food availability. Additionally, the study revealed that fish eggs and larvae were infrequently found in the stomachs of M. leidyi. However, the presence of massive aggregations of M. leidyi may impact microzooplankton populations in late summer or autumn, potentially leading to competition with small pelagic fish. 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

Calanoida is a representative oligo-mesotrophic indicator species, frequently used as an index for assessing lake ecosystems’ health. Additionally, they function as trophic intermediates in the food web, connecting primary producers and higher consumers within lake ecosystems’ food chains. However, research cases that present the implications of habitat environment assessments, such as ecosystem structure and water quality, represented by these taxa remain insufficient. In this study, we conducted research across 49 lakes in South Korea, analyzing the occurrence characteristics of Calanoida and examining the correlations between Calanoida abundance and water quality parameters and the morphological-based functional groups of phytoplankton. Calanoida were more frequently observed in lakes characterized by greater size, increased depth, and reduced levels of anthropogenic land use. Furthermore, Calanoida occurrence was more probable in environments characterized by lower electrical conductivity and suspended solids concentrations. Their presence was also associated with conditions where Large mucilaginous phytoplankton (MBFG7), which includes cyanobacteria, and Large filamentous phytoplankton (MBFG3) were prevalent. An analysis of the environmental factors influencing the increase in Calanoida abundance revealed an inverse relationship between their abundance and water quality factors, including nutrient levels. This trend was observed consistently across all genera. Additionally, Calanoida were observed to maintain a high abundance in environments where the presence of the Large mucilaginous phytoplankton group (MBFG7) was relatively high. In contrast, Cyclopoida exhibited varying occurrence characteristics by genus in response to different water quality factors. Based on these results, we suggest that Calanoida, commonly used as an indicator of mesotrophic conditions, can also serve as a valuable indicator for evaluating the functionality of the food web. While Calanoida struggle to inhabit environments characterized by degraded water quality, they demonstrate the ability to adapt and persist in environments containing large, mucilaginous, or filamentous phytoplankton species that are typically challenging for other zooplankton to graze. Full article

Historical plankton samples from the St. Lawrence Great Lakes were subjected to taxon-specific ¹⁵N analysis to test the hypothesis that the changes recorded in zooplankton communities during the 21st Century are related to changes in the trophic positions of large-bodied carnivorous copepods. Daphnia mendotae was used as the reference herbivore for trophic-level comparisons. The results were that Limnocalanus macrurus, Diaptomus (Leptodiaptomus) sicilis as well as the cladoceran Bythotrephes cederstroemi show evidence of elevated carnivory compared to data from the 20th Century. The large diaptomid Diaptomus (Leptodiaptomus) sicilis has a stable isotope signature that is significantly more carnivorous in Lake Superior than in Lakes Michigan and Huron by approximately one-half trophic level. Differences were found in 10 cases out of 15 for Limnocalanus (Huron, Michigan Superior), 6 cases out of 15 for Diaptomus (Huron, Michigan) and in 1 out of 1 for Senecella (Superior). We did not find evidence to support the theory that large-bodied calanoid copepods may have improved their representation in the food webs of the upper Great Lakes by shifting their trophic position downward. Instead, large-bodied Calanoida have increased their trophic positions in parallel with their increased relative abundance. More research is thus needed to explain the driving forces for changing food web dynamics in the Great Lakes. Full article

The distribution and diversity of calanoid copepods were investigated using samples collected from 37 lakes in North-eastern (NE) China in 2019. A total of 10 calanoid copepods belonging to eight genera and three families were identified. Among them, Heterocope soldatovi Rylov, 1922 was recorded for the first time in China. Species from the family Centropagidae were more widespread than those from the families Temoridae and Diaptomidae. Sinocalanus doerrii (Brehm, 1909), previously not recorded in NE China, is now widespread alongside Boeckella triarticulata (Thomson G.M., 1883), and the latter species is also prevalent in that region. Canonical correspondence analysis (CCA) and redundancy analysis (RDA) revealed that calanoid copepods were significantly correlated with total phosphorus (TP), total nitrogen, conductivity, nitrate nitrogen, altitude, and dissolved organic carbon. TP was the most important environmental variable that impacted the distribution of calanoid copepods, including both fresh and saline–alkaline lakes. Integrating historical records, a total of 21 calanoid copepods were distributed in NE China, and we also gave comments on the ecology and distribution of these species. Full article

The use of marine invertebrates in ecotoxicology is important for an integrated approach which takes into consideration physiological responses and chemical levels in environmental matrices. Standard protocols have been developed and organisms belonging to different trophic levels are needed as model organisms to evaluate toxicant bioavailability and assess their impact on marine biota. The calanoid copepod Acartia tonsa is commonly used in ecotoxicology due to its widespread distribution and well-studied biology. However, different strains coming from various geographical areas are available, and possible variations in physiological characteristics raise concerns about the comparability of ecotoxicological results. This study compares the life cycle assessment and sensitivity of Adriatic and Baltic strains of A. tonsa exposed to nickel (Ni²⁺) in standardized acute and semi-chronic tests. Life cycle assessments revealed differences in egg production, egg-hatching success, and naupliar viability between the strains. The acute toxicity test demonstrated the significantly higher sensitivity of Adriatic strain nauplii to Ni²⁺ compared to the Baltic strain, whereas the semi-chronic test showed no significant difference in sensitivity between the strains. These findings suggest that while strain-specific differences exist in different geographical populations, responses to toxicants are not significantly different. Particularly, the semi-chronic assessments with both A. tonsa strains emphasized the robustness of this species as a model organism in ecotoxicology. Full article

The subtropical North Atlantic is a key region for understanding climate impact in the ocean. Plankton studies in this region have been generally framed in biogeographic provinces or focused on latitudinal gradients. In this study, we demonstrate the benefits of using empirically constructed continuous gradients versus the use of average values for biogeographical provinces to characterize plankton assemblages along a longitudinal transect at 24.5° N using an unprecedented array of stations including hydrographic observations, abundance of phytoplankton and zooplankton, and plankton size spectra in the epipelagic layer (0–200 m). In addition, the variability of zooplankton assemblages was analyzed using detailed taxonomic identification at selected stations. We found significant gradients in most hydrographic and plankton variables. The former, including surface temperature and salinity, the depth of the upper mixing layer, and the depth of the chlorophyll maximum, displayed non-linear gradients with maximum or minimum values near the center of the transect. In contrast, most plankton variables showed linear zonal gradients. Phytoplankton, microzooplankton (<100 µm), and the slope and the intercept of the size spectra increased (and Trichodesmium decreased) to the west. Total mesozooplankton (>200 µm) did not show any significant zonal pattern, but the taxonomic assemblages were characterized by a gradual replacement of large Calanoids by small-bodied Cyclopoid copepods from east to west. The use of continuous gradients provides more detailed information on the zonal structure of subtropical plankton than the classical approach using discrete areas. Full article

The recent distribution of the Ponto-Caspian calanoid copepod, Eurytemora velox, in Western and Eastern Europe has been well-documented; however, there are no studies on the genetic diversity of the recently discovered Western Siberian species population. To contribute towards filling this gap, genetic diversity and distribution were investigated for E. velox collected in the Urals and Western Siberia of the Russian Federation to compare with the European populations. In this study, 44 specimens were dissected for the morphological studies, and 22 specimens of E. velox from different geographical points were analyzed for mitochondrial cytochrome oxidase I (CO1), nuclear ITS1-ITS2 (nITS) and nuclear ribosomal RNA (18SrRNA) gene fragments. Analysis of the CO1 gene region showed that the studied populations from the Urals and Western Siberia differ significantly from European ones and represent a separate genetic line. However, the nuclear nITS and 18SrRNA genes, as well as the results of morphological analysis, did not show such isolation of the Trans-Ural populations from those in Europe. As in many studies on E. velox, we found atypical structural features of the fifth prosomal leg among females in the Ob Bay. Their share was 36% of the number of studied individuals. The CO1 shows that the divergence of genetic lines occurred approximately in the Middle Pleistocene, and the species itself is Paleogene–Neogene by origin. Based on these data, a different scenario of E. velox distribution or possible refuge survival is discussed. Full article

The roach, Rutilus rutilus (Linnaeus, 1758), is one of the most common fish species in mesotrophic and eutrophic lakes throughout Europe. In the Serbian reservoirs selected for this study, this species accounts for the majority of juvenile fish biomass. The aim of this study was to investigate the diet composition of juvenile roach to assess their niche based on resource availability in five Serbian reservoirs with different trophic statuses. A modified Costello graph and Kohonen artificial neural network (i.e., a self-organizing map, SOM) were employed to examine the feeding habits of 142 specimens of roach caught in five reservoirs. Our results show that juvenile roach use zooplankton, benthic macroinvertebrates, algae and detritus in their diet. In addition, five neuron clusters (A, B, C, D and E) were isolated in the SOM output network. The SOM identifies specimens that share similar feeding patterns and categorizes them onto the same or adjacent neurons, determined by dominant prey. In terms of the number of specimens, cluster B was the most numerous, and the predominant prey of these specimens were Daphnia sp., Bosmina sp. and calanoid and cyclopoid copepods. The cluster with the lowest number of specimens is cluster C, and the specimens in it benefited from Chironomidae and Insecta. Due to the different trophic statuses of the reservoirs selected for this study, knowledge of fish feeding habits is essential for the formulation of effective conservation and management strategies for both the species and the reservoirs. Full article

Ecosystem alterations to Lake Michigan (LM), such as the invasion of dreissenid mussels, have decreased the abundance of phytoplankton and, subsequently, zooplankton, which has implications for Great Lake fisheries. The community composition of zooplankton has also been altered over the past 20 years in LM, shifting the summer dominance from cladoceran to calanoid taxa. However, most of our information on zooplankton community dynamics is from deeper pelagic zones. The nearshore beach (≤1 m) habitat, which serves as a critical nursery for some larvae and juvenile fish, is composed of different zooplankton taxa than deeper zones, but limited data are available for comparison. We conducted a standardized summer sampling campaign to characterize the zooplankton community across 32 beaches in LM. We found the lowest crustacean zooplankton density and biomass on northern LM beaches and a higher zooplankton density and biomass on Greater Green Bay and central LM beaches, which had warmer water temperatures. Smaller-bodied cladocera (mainly Bosmina) and cyclopoid taxa were the most abundant groups on beaches. Our results provide the first comprehensive characterization of zooplankton on beaches in the Great Lakes, with applications for other lake systems. These results may help identify potential “hot spots” of fish recruitment for management. Full article

The increasing atmospheric CO₂ concentrations and warming of marine waters have encouraged experiments on multi-stressor interactions in marine organisms. We conducted a multigenerational experiment to assess reproductive capacities regarding egg production in calanoid copepods Parvocalanus crassirostis and Acartia pacifica under different pH and temperature conditions. The experimental set-up allowed assessing the tandem effect of warming and acidification on the number of eggs produced by healthy copepod pairs under two pH conditions of 8.20 and 7.50 (hard selection) as well as with a gradual reduction of 0.05 pH units at each generation (soft selection). The results are quite interesting, with very diverse performance across temperatures. The number of eggs produced under hard selection was higher at pH 8.20 compared to pH 7.50 for both species, with the maximum number of eggs produced at 24–28 °C, whereas under soft selection, there was no significant difference in the egg production rate at 24–28 °C across generations and there was an improvement in the number of eggs produced at 8–16 °C. The results provide evidence that in a future ocean scenario of lower pH and higher temperature, the two species, and possibly the copepod population at large, might not decrease. Copepod populations might be resilient, and the transcriptomic evidence of adaptation to increased temperature and lower pH is a ray of hope. We believe further studies are needed to provide more robust datasets to underpin the hypothesis of adaptation to climate change. Full article