Temporal dynamics and relationship between climate,limnological variables and zooplankton composition in climate-sensitive Lake Bosumtwi,Ghana

The community composition and the factors affecting seasonal and interannual dynamics of zooplankton in Lake Bosumtwi were studied biweekly at a central index station during 2005 and 2006. The lake zooplankton community was species poor. Mesocyclops bosumtwii was numerically superior seasonally and interannually and was endemic to the lake. Minor constituents included Moina micrura, six rotifer species (except for Hexarthra intermedia) and Chaoborus ceratopogones larvae. Low variance of cyanobacteria-dominated phytoplankton biomass underlined stable zooplankton community structure. Emergence of rare species of rotifers occurred seasonally. The climatic signature on the lake’s stratification and mixing regime was strongly influenced by atmospheric temperature, but weakly by wind strength, because of sheltering of the lake by high crater walls. Increasing mixing depth entrained high TP concentrations from below the thermocline seasonally, but reflected poorly in the phytoplankton biomass behaviour. Total zooplankton abundance did not differ seasonally, but varied markedly from year to year in its timing and magnitude. Herbivores were squeezed between food limitation and high predation pressure from Chaoborus all year round. The low fish planktivory (high fishing pressure) on Chaoborus may create a trophic bottleneck restricting energy transfer efficiency from zooplankton to fish.     

Comparison of the predation rate of freshwater cyclopoid copepod species on larvae of the mosquito Culex pipiens

The predation rates of six copepod species: Acanthocyclops robustus G.O. Sars, Eucyclops neumani Pesta, Macrocyclops albidus Jurine, Mesocyclops longisetus Thibaud, Metacyclops grandis Kiefer and Metacyclops mendocinus Wierzejski (Copepoda: Cyclopidae) on mosquito larvae, Culex pipiens Linnaeus (Diptera: Culicidae) were assessed. Experiments consisted of 24-h incubations of one copepod and 10 larvae without extra food at 16 degrees C and 26 degrees C. Nine replicates were considered for each species and temperature. Predation rates (larvae per copepod per day) were: M. mendocinus (1.8), M. grandis (3.1), E. neumani (3.8), A. robustus (3.8), Ma. albidus (6.1) and Me. longisetus (7.0). There was a significant effect of both species and temperature on predation: all species experienced higher predation at 26 degrees C than at 16 degrees C, except for A. robustus whose predation rate was similar at both temperatures. These observations are consistent with previous results that point to Macrocyclops and Mesocyclops genera as important larval predators and suggest the need for field trials to evaluate the response of Ma. albidus and Me. longisetus under natural conditions in Uruguay.     

用刘氏中剑水蚤防治蚊幼虫(英文)

本研究在室内评价了在济宁采集的捕食性刘氏中剑水蚤单用及与球形芽孢杆菌(B.s.)或苏云金杆菌以色列变种(B.t.i.)合用对蚊幼虫的控制效果。在室内,刘氏中剑水蚤对白蚊伊蚊Ⅰ龄幼虫的捕食效果好于对中华按蚊和淡色库蚊幼虫的效果。蚊笼模拟试验表明,刘氏中剑水蚤可分别于9、10和7周内消灭淡色库蚊、中华按蚊和白蚊伊蚊的幼虫种群。该剑水蚤增长速率快,大量培养经济易行。现场试验证明,刘氏中剑水蚤虽可在蚊虫孳生地存活时间长于蚊虫季节,但单用该剑水蚤不能象化学杀虫剂一样快速完全地控制三种蚊虫。刘氏中剑水蚤与B.s.或B.t.i.合用,应用刘氏中剑水蚤的长持效和生物杀虫剂的速效,取得了高效、持久的防治效果。因此二者合用可用于蚊虫防治并可作为蚊虫综合防治的一个组成部分。     

Dynamics of a subtropical plankton community,with emphasis on the copepod Mesocyclops edax

The zooplankton community of a subtropical, eutrophic lake was studied over an annual cycle. Mesocyclops edax, the numerically dominant crustacean, exhibited a stationary age distribution for most of the year (July–March). Per capita growth rates (r) of M. edax approximated zero throughout most of the study, indicating a close correspondence between birth and death rates. High death rates in the spring and summer probably were due to intense predation, since physiological mortality was low and predators were abundant. Multiple regression analyses indicated that much of the variation in M. edax birth rates could be explained by abundance of their animal prey. Other plankton in this lake exhibited considerable seasonality, but not to the marked degree characteristic of temperate populations. The number of zooplankton species was low and cladocerans were scarce, as is characteristic of many eutrophic Florida Lakes.     

Demographic responses of adult Mesocyclops thermocyclopoides (Copepoda, Cyclopoida) to different plant and animal diets

1. We studied the effects of food type on adult females of the cyclopoid copepod Mesocyclops thermocyclopoides.
2. The test diets, covering a size range of 5–1250 μm, included a toxic strain of Microcystis aeruginosa , three algae (i.e. Chlorella vulgaris, Scenedesmus acutus and Chlorogonium elongatum ), three ciliates (i.e. Tetrahymena pyriformis, Stylonychia notophora and S. mytilus ), two rotifers (i.e. Brachionus angularis and B. calyciflorus ) and two cladocerans (i.e. Ceriodaphnia cornuta and Moina macrocopa ), and a selected subset of them in a second experiment.
3. Experimental diets were started with the last juvenile instar (C5) and data were collected on the newly moulted adult females. The survival of the copepod was less affected by food type than its reproductive output. Net reproductive rate was significantly higher with animal than with plant food. Algal diets enriched with organic extracts supported higher reproductive rates than unenriched diets of the same algal species. The large and motile alga Chlorogonium gave performances which approached those of ciliate diets.
4. The pre-reproductive period of M. thermocyclopoides was shorter and its post-reproductive period longer with animal than with plant diets, the latter being chiefly caused by a briefer period between clutches.
5. The frequency of infertile clutches increased in later clutches, indicating possible sperm limitation in females which have mated only once.
6. There was a significant, positive correlation between the size of food particles and the lifetime reproductive output of M. thermocyclopoides , with more than an order of magnitude difference in the total fecundity between the largest and the smallest food items.
7. Mesocyclops thermocyclopoides achieved the highest total fecundity with 'mixed' food, and thus, reflected the adaptive value of omnivory for this species.     

Two new species of Mesocyclops from southern China and notes on the genus Mesocyclops in China

Two new Mesocyclops species, M. mariae n. sp. and M. shenzhenensisn. sp., are described from southern China, the former species from Guangxi province, the latter from Guangdong province. Both species have setules on the medial margin of the caudal rami. Compared with each other, there are some conspicuous differences, such as the spinule pattern of the antenna basipodite, the structure of receptaculum seminis, the armature of coxopodite and basipodite of P4 and the armature of the caudal rami. The paper also compares the two new species with their supposedly closest relatives, M. pseudospinosus Dussart & Fernando, 1988, M. leuckarti(Claus, 1857) and M. pehpeiensisHu, 1943. In addition, other species of Mesocyclops in China are discussed and a key to 10 Chinese species of Mesocyclops is provided.     

Zooplankton Distribution Related to Environmental Factors and Phytoplankton in a Shallow Tropical Lake (Lake Guiers,Senegal, West Africa)

The chemical and biological characteristics of Lake Guiers (Senegal) have changed markedly since the impoundment of the Senegal River (Diama and Manantali dams) and subsequent development of irrigated agriculture in the nineteen eighties. On a longitudinal transect of 10 stations (from south to north), the environmental characteristics and the spatial variability of physicochemical variables, phytoplankton and zooplankton communities were studied. Within a marked south‐north gradient, the southern stations were characterized by the highest conductivity and pH and by the lowest values of suspended solids, chlorophyll‐a concentrations and phytoplankton abundance (mainly Chlorophycea, Cyanobacteria and Bacillariophycea). The spatial distribution of zooplankton showed a clear distinction between the southern zone, characterized by the presence of the rotifers Brachionus falcatus and Conochiloides sp., the cladoceran Bosmina longirostris, the cyclopoid Thermocyclops neglectus and the calanoid Pseudodiaptomus hessei. A co‐inertia analysis clearly showed that environmental factors and phytoplankton drives the spatial distribution of zooplankton communities. The comparison of our data with previous studies suggests a marked change in the biological communities since the impoundment of the Senegal River, with rarefaction of P. hessei and proliferation of the cyclopoid Mesocyclops ogunnus. Several hypotheses are discussed to explain these biological changes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mesocyclops dissimilis n. sp. from Lake Biwa,Japan (Copepoda,Cyclopoida)

The status of the Mesocyclops from lake Biwa is reexamined and a new species, Mesocyclops dissimilis n. sp., distinct from M. thermocyclopoides Harada, 1931, is described.     

BIOLOGICAL CONTROL OF MOSQUITO LARVAE WITH MESOCYCLOPS LEUKARTI1)

Abstract  The control efficacy of a predatory copepod, Mesocyclops leukarti , collected in Jining, and its compatibility with Bacillus sphaericus (B.s. ) and B. thuringiensis var. csraefensis H-14 ( B. t. i. ) against mosquito larvae were evaluated in the laboratory and in the field. In the laboratory, M. leukarti showed higher predatory activity toward first instar larvae of Aedes albopictus than toward that of Anopheles sinensis and Culex pipiens pallens. Cage simulation test showed that larvae of Cx. pipiens pallens, An. sinensis and Ae. albopictus could be eliminated within 9, 10 and 7 weeks after interaction with the copepods respectively. M. leukarti population can grow quickly, and its mass production is easy and economic. However, pilot field trials indicated that M. leukarti alone could not eradicate mosquito larvae of the three species rapidly and completely as by chemical insecticides, although they could persist in mosquito breeding habitats longer than the mosquito season. When Mesocyclops was used in combination with B. s. and B. t. i. , higher and sustainable control effects were achieved. So this combination, which achieved the rapid larvicidal and sustainable control effect, was presumed to be practical and could be integrated into mosquito control program.     

The productivity of mesocyclops leuckrarti (Claus) in Lake Kinneret (Israel)

Specific rates of growth (Cw) of Mesocyclops leuckarti, young male and female instars varied between 0.03–0.26 and 0.03–0.17 g_(w.w.)/g_(w.w.)/day respectively at 15° and 22°C, whilst at IV–V copepodid stages females showed a higher Cw values. During 1969–1975 the averages of productivity and monthly P/B ratios were 44 (±23) g_(w.w.) (= 5g_(w.w.)/m²/month) and 3.1 respectively. P/B ratios were highly correlated (r(sup2)=0.98) with temperature changes. Metabolic parameters and P/B ratios were found to be similar to other water bodies in the world indicating an adaptation of M. leuckarti to different conditions.