Predation on Mosquito Larvae by Mesocyclops thermocyclopoides (Copepoda: Cyclopoida) in the Presence of Alternate Prey

The cyclopoid copepod Mesocyclops thermocyclopoides, a dominant invertebrate predator in many shallow ponds and temporary water bodies in northern India, feeds on cladocerans, rotifers, ciliates and when present, on mosquito larvae also. We studied in the laboratory the prey consumption rates of the copepod on first and fourth instar larvae of two species of mosquito (Anopheles stephensi and Culex quinquefasciatus) in relation to their density. We also studied its prey selectivity with mosquito larvae in the presence of an alternate prey (the cladocerans‐either Moina macrocopa or Ceriodaphnia cornuta) in different proportions. With either mosquito species, the copepod actively selected Instar‐I larvae, avoiding the Instar‐IV larvae, and with either instar, selected Anopheles stephensi over Culex quinquefasciatus. When prey choice included the cladoceran as an alternate prey, the copepod selected the cladoceran only when the other prey was Instar‐IV mosquito larvae. Our results point to the potential and promise of M. thermocyclopoides as a biological agent for controlling larval populations of vectorially important mosquito species.     

A simple method for maintaining a laboratory supply of limnetic cyclopoid copepods

The following method is used for maintaining a laboratory supply of freshwater cyclopoid copepods with intervening diapause phase. Animals are collected with a core sampler from the upper sediment surface just after initiation of diapause, i.e. during early summer for summer resting species and mid autumn for winter resting species. The method makes it possible at all times of the year to keep a variety of cyclopoid copepod species ready for experimental work. The following widespread species have been used: Mesocyclops leuckarti, Thermocyclops oithonoides, Diacyclops bicuspidatus, Cyclops vicinus, C. strenuus and C. abyssorum. Probably all cyclopoid copepods with a diapause phase could be stored according to the present method.     

Changes in the abundance and composition of cyclopoid copepods following fish manipulation in eutrophic Lake Væng, Denmark

1. The seasonal cycle of cyclopoid copepods during and following an approximately 50% reduction in planktivorous fish biomass was studied in shallow, eutrophic Lake Vaeng, Denmark, from 1986 to 1990. 2. The dominant cyclopoid copepods changed from Cyclops vicinus and Mesacyclops leuckarti during 1986–1989 to M. leuckarti and Megacyclops viridis in 1990. The abundance of cyclopoid copepods gradually increased from 1986 to 1988–89, decreased in autumn 1989 and markedly decreased in 1990. 3. The increase in the abundance of cyclopoid copepods from 1986 to 1988 is attributed mainly to the reduction in fish predation pressure, there being no concomitant increase in edible phytoplankton. The appearance of M. viridis in 1990, and the general decrease in cyclopoid copepod density in autumn 1989 and in 1990, are attributed to the appearance of submerged macrophytes. 4. Temperature, predation and availability of edible phytoplankton appear to determine whether C. vicinus or M. leuckarti dominates the cyclopoid copepod population of eutrophic Lake Væng.     

Acidity versus habitat structure as regulators of littoral microcrustacean assemblages

1. Emergence traps were set overnight on the sediment surface to sample the littoral microcrustaceans of 22 Canadian Shield lakes that ranged in pH from 4.56 to 6.92. Traps were randomly allocated in quintuplicate in both wave‐washed sandy habitats where pipewort (Eriocaulon septangulare) was the dominant macrophyte (termed pipewort habitats), and more protected habitats dominated by floating‐leaved macrophytes (termed floating‐leaved habitats). 2. In total, 50 cladoceran and 22 copepod species were found, with 16–45 species in each lake. Lakes that had never acidified exhibited a more diverse fauna than lakes that had acidified. 3. There were only minor differences between the numbers of species found in floating‐leaved versus pipewort habitats except for one lake. Non‐chydorid cladoceran, chydorids and copepods constituted 45%, 26% and 29% of the total number of individuals, respectively. 4. Based on presence/absence, dominance scores and frequency of occurrences of species, the microcrustacean faunal composition was similar in the two habitats. A detrended correspondence analysis confirmed that there was no separation between the two main types of habitat, and that pH was the parameter most strongly correlated with the dominant microcrustacean compositional gradient among lakes.     

Increasing dominance of small zooplankton with toxic cyanobacteria

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Littoral microcrustacea in Lake 302S in the Experimental Lakes Area of Canada: acidification and recovery

• 1 The littoral microcrustacean community (Cladocera and Copepoda) was examined from 1989 to 1991 in a lake experimentally acidified to pH 4.5, and from 1992 to 1997 during the early stages of pH recovery.
• 2 Cladoceran abundance declined significantly from 1989 to 1991 (pH 4.5), but species richness did not change. Acantholeberis curvirostris, Simocephalus serrulatus, Latona spp. (Latona setifera, L. parviremis), and all species of chydorid Cladocera declined markedly in abundance while at pH 4.5. The abundance of cyclopoid copepods was low and Ceriodaphnia and calanoid copepods were absent.
• 3 Recovery of the community was subsequently monitored as pH was incrementally changed to a target pH 5.1 in 1992 and 1993, and to 5.8 in 1994–97. Species richness remained unchanged. Chydorid cladocerans remained at low abundance in 1992, and only Chydorus cf. brevilabris increased substantially from 1993 to 1996. Non‐chydorid Cladocera increased in abundance in 1992, declined again in 1993, then gradually increased (mainly due to Ophryoxus gracilis) in 1994–96. All species declined in 1997 as minnows recolonized the lake. The calanoid copepod Leptodiaptomus minutus was present in low numbers in 1997.
• 4 The microcrustacean community in the littoral zone of Lake 302S has not yet shown consistent signs of recovery from acidification.

     

太湖梅梁湾大型控藻围栏对浮游甲壳动物群落结构的影响

2005年对太湖梅梁湾大型鲢、鳙控藻围栏内外浮游甲壳动物群落结构的季节变化进行了监测.结果表明:围栏内外的环境因子、浮游植物生物量、浮游甲壳动物种类组成无显著差异.但鲢、鳙放养对浮游甲壳动物的生物量产生了较大的影响,围栏内浮游甲壳动物的总生物量和枝角类的生物量显著低于围栏外.总体上,枝角类各种类的生物量受鲢、鳙放养的影响程度大于桡足类的种类.太湖梅梁湾浮游甲壳动物的季节演替明显,大部分种类只是季节性出现.冬季和春季以溞(Daphnia sp.)和近邻剑水蚤(Cyclops vicnus)等大型种类为主,夏季和秋季以象鼻溞(Bosmina sp.)、角突网纹溞(Ceriodaphnia cornuta)和中华窄腹剑水蚤(Limnoithona sinensis)等小型种类为主.典范对应分析表明,透明度、温度和浮游植物的生物量是影响浮游甲壳动物季节变化的主要因素.     

Crustacean zooplankton species richness and associations in reservoirs and ponds of Aguascalientes State, Mexico

We report the species of crustacean zooplankton found in 19 resevoirs and ponds that were sampled at on at least two occasions in Aguascalientes State, Mexico, at a latitude of about 21°30 North Latitude. We collected a total of 33 cladoceran taxa, 15 calanoid and cyclopoid copepods, an Ergasilus copepod, 2 anostracans, one notostracan species and an amphipod. All these taxa had previously been reported in Mexico. As in more temperate areas, there was a significant correlation between the species richness and lake size. The species-area relationship for Aguascalientes was indistinguishable from that of more northerly lakes. The two most common associations of zooplankton species were (1) those small species that occurred with fish: Daphnia parvula, Diaphanosoma birgei, Leptodiaptomus siciloides, Mastigodiaptomus albuquerquensis, and Thermocyclops inversus, and (2) the large Daphnia schodleri that occurred with the predator Notonecta, in the absence of fish. With minor variations, these two associations also occur throughout temperate North America.     

Selective feeding of Arctodiaptomus salinus (Copepoda, Calanoida) on co-occurring sibling rotifer species

1. Using two‐ and three‐dimensional video recordings, we examined the steps involved in predation that lead to the differential vulnerability of three sympatric rotifer sibling species (Brachionus plicatilis, B. ibericus and B. rotundiformis) to a co‐occurring, predatory, calanoid copepod (Arctodiaptomus salinus). 2. Brachionus rotundiformis, the smallest prey tested, was the most vulnerable with the highest encounter rate, probability of attack, capture and ingestion, and the lowest handling time. 3. Comparison of our results with those of a previous study shows that A. salinus is a more efficient predator than a co‐occurring cyclopoid copepod (Diacyclops bicuspidatus odessanus) feeding on these same rotifer species. However, despite its higher capture rates, A. salinus seems to be less selective than D. b. odessanus based on attack distances and prey handling times. 4. The differential vulnerability to both calanoid and cyclopoid copepod predation can help explain the coexistence and seasonal succession of these co‐occurring rotifer species.     

Observations on the zooplankton in the reedbelt area of the Neusiedlersee

Weekly sampling and simultaneous measurements of temperature, pH, and conductivity were made at three stations in the reedbelt, between 1980–82. 20 cladoceran and 14 copepod species were encountered, of whichCyclops vicinus vicinus was found in the lake for the first time. Of the measured environmental features, temperature showed the greatest seasonal changes; pH and conductivity were less variable. There were, both quantitatively and qualitatively, constant differences between the three stations, although they lay close to each other.     

Biogeography of copepods in lakes and ponds of subarctic Québec,Canada

We aimed to determine whether the copepod assemblages in lakes and ponds of northern Québec, Canada, were closer in composition to those found in southern Québec, or to those reported from the subarctic and arctic. Six calanoid and five cyclopoid species were identified from 37 ponds and lakes located in the region between 55° N and 59° N. Species diversity was generally low, ranging from 0 to 4 species per lake. Dominant species were Leptodiaptomus minutus and Acanthocyclops vernalis. The species assemblages showed high affinity with those found in forested regions of southern Québec. Exceptions were Leptodiaptomus tyrrelli, previously only recorded west of Hudson Bay, and Hesperodiaptomus arcticus, hitherto recorded north of 58° N. Relationships between the lakes, species, and environmental variables were explored using multivariate analysis. Lakes situated along the coast and on two offshore islands clustered together and were characterised by higher conductivity and pH than those lakes located further inland. Leptodiaptomus tyrrelli was common in these coastal lakes. Canonical correspondence analysis revealed statistically significant relationships between copepod distributions and conductivity, dissolved organic carbon and pH. These three variables accounted for 70% of the variation in the species' distribution.     

Coexistence with similar life cycles in two species of freshwater copepods (Crustacea)

Two species of freshwater cyclopoid copepods, Cyclops scutifer Sars and Mesocyclops leuckarti (Claus), with different ecological requirements, coexist in three humic ponds near the timberline in boreal forests in south-central Norway. The life cycle in both species is basically regulated by complete depletion of oxygen during the long winter. There is a short period of reproduction in spring followed by a rapid development during summer and autumn to advanced instars, capable of diapause when oxygen depletion starts in early winter. Both species have an exclusive 1-yr cycle.The long winter under anoxic conditions is passed in diapause as large copepodids (late developmental instars) with usually no individuals left in the plankton.Even if co-occurring in the same habitats with similar life cycles, there is a temporal and spatial segregation.     

Life cycles of the two freshwater copepods Cyclops strenuus Fischer and Cyclops insignis Claus (Cyclopoida,Copepoda) in an amphibious floodplain habitat

Life cycles of the freshwater cyclopoids Cyclops strenuus Fischer and Cyclops insignis Claus are described from populations of one permanent and two temporary waters in a floodplain area. The abundance of these two species was studied in detail, with special regard to instars surviving summer drought. Both species coexist in two locations during the flood period in the cold season. Cyclops insignis is strictly univoltine, whereas Cyclops strenuus may produce two generations. Differences in timing of egg production, mortality of juvenile instars at four different temperatures, and survival of resting stages in terrestrial conditions are discussed as possible characteristics facilitating the coexistence of the two species.     

Recovery of zooplankton diversity in a restored Mediterranean temporary marsh in Doñana National Park (SW Spain)

Over 30 years after drainage for agriculture, a 2700 ha temporary marshland was recently restored in Doñana National Park. We describe the recovery of zooplankton communities (copepods, cladocerans and rotifers) in 47 new temporary ponds excavated as part of the restoration project during the first two hydroperiods (April 2006 and 2007), and compare them to those of eight reference sites in the surrounding marshland. Major changes in the species composition and abundance occurred in new ponds between years. While rotifers and cyclopoid copepods dominated in terms of number of individuals in 2006, calanoid copepods and cladocerans were the most abundant groups in 2007. Rotifer species richness was significantly lower in 2007, but there was an increase in Simpson and β-diversity in 2007 owing largely to a dramatic decline in the abundance of Hexarthra cf. fennica (rare in reference sites) from 93% of all rotifer individuals in new ponds in 2006 to only 32% in 2007. In contrast, species richness of copepods and cladocerans was significantly higher in new ponds in 2007, but there were no changes in Simpson diversity. β-Diversity of cladocerans was also significantly higher in 2007. In 2006, the species richness of cladocera and copepods was significantly lower in new ponds than in reference sites, but by 2007 there were no differences in richness or Simpson diversity. Overall, 7 copepod, 13 cladoceran and 26 rotifer taxa were recorded in new ponds, including 80% of taxa recorded in reference sites. These results indicate that zooplankton communities can be rapidly restored in Mediterranean temporary wetlands, at least when large source populations in the surrounding area reduce dispersal limitation. They also illustrate the importance of comparing different metrics of richness and diversity in studies of zooplankton restoration.     

Distribution and ecology of copepods in mountainous regions of the Eastern Alps

Copepod species richness, patterns of distribution and composition of assemblages were evaluated in high-altitude sites in the Eastern Alps. Diverse habitats were sampled in 160 lentic water bodies from different geologic areas, ranging from acid bog ponds to alkaline karst waters and from small temporary puddles to deep lakes. The altitudinal range comprised all mountainous regions from the montane (1290 m a.s.l.) to the alpine (2886 m a.s.l.) zone. Forty-four species were recorded, with the harpacticoids being the richest group. Although most species occupied a wide altitudinal range, some stenotopic mountain forms were restricted to alpine habitats. The most widespread taxa were Acanthocyclops vernalis, Eucyclops serrulatus, Bryocamptus rhaeticus, Arctodiaptomus alpinus and Cyclops abyssorum tatricus. All species found were listed along with notes on their distribution, ecology and patterns of coexistence. There was both a marked change in species composition and a decline in species richness from hardwater habitats in the Limestone Alps to softwater sites in the Central Alps. Copepod taxocoenoses were most diverse in montane limestone lakes and impoverished with increasing altitude. Copepods and sampling sites were ordinated using canonical correspondence analysis (CCA), and copepod assemblages were defined in relation to physical and chemical parameters, habitat type and presence/absence of planktivorous fish. Planktonic species were largely absent from lakes with introduced fish. Although calanoid associations were common, coexisting diaptomids were rare, suggesting a strong interspecific competition between these predominantly filter feeders. Most copepods found are common eurytopic or cold stenothermal, but some exhibit peculiar disjunct patterns of geographical distribution, and others are apparently restricted to the Alps. Some species are discussed in more detail from a zoogeographical point of view. A complete checklist of copepods recorded to date from high-altitude sites in the Eastern Alps is provided.     

Antennule shape and body size of <Emphasis Type="Italic">Bosmina</Emphasis>: key factors determining its vulnerability to predacious Copepoda

Cyclopoid copepods are common in lakes and ponds, and they have a significant predation impact on the communities of the small zooplankton species. To reduce the predation risk, some cladoceran zooplankters develop protuberant (defensive) morphologies in the presence of the copepods. In the case of the small cladoceran Bosmina, they elongate their appendages (antennule and mucrone) and change the antennule morphotype. However, information about the effectiveness of these defensive devices against copepod predation is still insufficient. In our study, to find the compositive effects of these appendages on the vulnerability of Bosmina, we exposed two bosminid species (B. longirostris and B. fatalis) of different body sizes and with appendages of different lengths and shapes to copepod (Mesocyclops) predation. The experiment revealed that the shape of the antennule is a main factor determining the bosminid’s vulnerability to copepod predation and indicated that the protection of the opened ventral carapace must be a key strategy by which Bosmina avoids copepod predation.     

Seasonal trophic dynamics affect zooplankton community variability

1. The degree to which communities are variable may be affected by the ecological conditions to which they are exposed and can affect their propensity to form alternative states. We examined the influence of two common ecological factors, predation and seasonal successional stage, on the variability in community composition of herbivorous pond plankton. In a highly replicated, two factor, mesocosm experiment we determined whether beta diversity was affected by seasonal successional stage of the community (two levels), by fish predation (presence/absence) or by their interaction. 2. Several significant changes were found in the composition of the rotifer, cladoceran and copepod assemblages. Most cladoceran abundances showed sharp declines in the presence of fish, while some rotifers, as well as their assemblage species richness, responded favourably to fish. The copepod assemblage was composed of omnivorous and carnivorous species, which added invertebrate predation to the experiment and which intensified as the season progressed. Copepods showed responses to fish predation that depended on seasonal successional stage of the initial community, because of changes in their stage structure and edibility as they grew from nauplii to adults. 3. Community variability was consistently high at the end of each month‐long experimental period for both cladoceran and rotifer assemblages, except under two conditions. In the early season treatments, the rotifer assemblages were more consistent (lower beta diversity) in the presence of fish. This was attributed to high population growth rates for rotifers under these ecological conditions because of reduced copepod predation on them through a trophic cascade from fish. Low community variability was also observed in the late season for rotifers when fish were excluded and, as a result, they were exposed to high invertebrate predation from cyclopoid copepods. 4. Results from the early season support theoretical predictions that when community size increases, variability in composition should decline because of an increase in competitive processes over stochastic ones. Late season results suggest that a second mechanism, specialist predation, can also reduce prey community variability. Our study demonstrates that plankton communities may be more predictable under certain trophic web configurations and challenges ecologists to find ways to incorporate such inherent variability into experiments and community theory.     

Species richness of crustacean zooplankton and trophic structure of brackish lagoons in contrasting climate zones: north temperate Denmark and Mediterranean Catalonia (Spain)

We sought to identify environmental factors influencing crustacean zooplankton species richness in brackish lagoons and to elucidate whether crustacean zooplankton species richness and trophic structure of brackish lagoons differ among two regions with contrasting temperatures. We sampled 35 and 42 brackish lagoons (salinity ranging from 0.3 to 55‰) in Mediterranean Catalonia (NE Spain) and northern-temperate Denmark, respectively. No significant differences were found in total crustacean zooplankton species richness or cladoceran richness between the climatic regions. Calanoid richness was higher in Denmark than in Catalonia, while cyclopoid richness was higher in Catalonia. Salinity was the most important variable associated with zooplankton species richness in both regions, richness of total zooplankton species, cladocerans and cyclopoids being negatively related with salinity. In both regions, a shift occurred from dominance of large filter feeding cladoceran species at low salinities to copepods and small cladoceran species at higher salinities. Cladoceran richness increased with increasing total phosphorus, but was not influenced by total nitrogen or chlorophyll-a. Trophic structure in Mediterranean brackish lagoons showed a more pronounced seasonal variation than in north temperate brackish lagoons. Our results imply that the indirect effects of climate warming, such as changes in salinity and hydrology, will have a larger impact on brackish lagoon ecosystems than the increase in temperature per se.     

Life cycles of two limnetic cyclopoid copepods, Cyclops vicinus and Thermocyclops crassus, in two different habitats

The life cycles of Cyclops vicinus and Thermocyclops crassusin two shallow eutrophic habitats, Junsainuma and Naganuma Ponds,Hokkaido, Japan, were investigated. Both ponds exhibited similarseasonal patterns of temperature, oxygen levels and pH duringice-free periods; however, oxygen levels were extremely lowerunder the ice in Naganuma Pond. Cyclops vicinus showed differentlife cycles in the two ponds; in Junsainuma Pond, it reproducedin winter and spring (January-May) and entered diapause duringsummer and autumn (June-October) as copepodite IV stage, whileit reproduced in autumn (October-November) and spring (April-May),and entered diapause in summer (June-September) and winter (Januaryand February) as copepodite V stage in Naganuma Pond. Thermocyclopscrassus entered diapause during winter (December-April) as copepoditeIV and V stages in both ponds, and egg-bearing females appearedonly during the warmseason, from early May to late October,when water temperatures were >10°C. Summer diapause inC.vicinus was suggested to be an adaptation against fish predation,whereas C.vicinus entered winter diapause in Naganuma Pond probablyto avoid low oxygen levels. Thermocyclops crassus entered diapausein both ponds to avoid low water temperature. These resultssuggest that biotic and abiotic factors are important for leadingto specific life cycles of cyclopoid copepods in small waterbodies.