Temporal and spatial habitat preferences and biotic interactions between mosquito larvae and antagonistic crustaceans in the field

Investigations on natural antagonists of mosquito larvae found that micro‐crustaceans (e.g., Cladocera) control mosquito populations under experimental conditions. However, their relevance for mosquito control under field situations remains widely unclear because important information about habitat preferences and time of occurrence of crustaceans and mosquito larvae are still missing. In order to fill this knowledge gap, a field study was undertaken in different wetland areas of Saxony, Germany, in different habitats (i.e., grassland, forest, and reed‐covered wetlands). We found negative interactions between larvae of Ae. vexans and predatory Cyclopoida (Crustacean: Copepoda), which both were dominant during the first two weeks of hydroperiod, at ponds located at grassland habitats. Larvae of Cx. pipiens were spatially associated with competing Cladocera, but they colonized ponds more rapidly. Populations of Cladocera established from the third week of hydroperiod and prevented Cx. pipiens colonization thereafter. Ostracoda were highly abundant during the whole hydroperiod, but their presence was restricted to habitats of reed‐covered wetland at one geographical area. Mosquito larvae hardly occurred at those ponds. In general, we found that ponds at the reed‐covered wetlands provided better conditions for the initial development of crustaceans and hence, mosquito larval colonization was strongly inhibited. Grassland habitat, in contrast, favored early development of mosquito larvae. This study showed that micro‐crustaceans are relevant for mosquito management but their impact on mosquito larvae varies between species and depends on environmental conditions.     

How many species of Cladocera are there?

An estimation of the number of taxa within families, genera and local faunas of Cladocera reveals that only c. 129 species (17% of all known species) may be considered as sufficiently well described (valid species), and c. 146 as rather well described (fair species) but needing further study using modern methods of investigation. The status of all other species is vague. The families Chydoridae, Daphniidae and Sididae and genera Diaphanosoma, Daphnia, (including Daphniopsis), Megafenestra, Scapholeberis, Eurycercus, Chydorus, Ephemeroporus and Pleuroxus have been comparatively studied best. The largest number of valid species is known from Europe, North America, Australia and South America, and the smallest number from Africa. Presence of large number of vague species of Cladocera negatively affects faunistic, zoogeographic, and ecological studies of continental waters.Dedicated to the memory of Professor D. J. Frey     

The Cladocera of Sri Lanka (Ceylon), with remarks on some species

The freshwater Cladocera of Sri Lanka has been revised based on the study of over 700 zooplankton samples collected from all habitat types during 1965–1980. The cladoceran fauna is represented by six families; members of the families Polyphemidae, Leptodoridae and Holopedidae are absent. The common temperate genus Daphnia is rare.Sixty-two species have been recorded from Sri Lanka. Of these, five are new records. Remarks on a few species are given with illustrations. The distribution of Cladocera in different types of habitats is discussed. The greatest species diversity was found in ponds. The Sri Lankan fauna is numerically and in species diversity typical of tropical cladoceran fauna. It resembles the southern Indian fauna very closely except for the absence in Sri Lanka of the genera Acroperus and Camptocercus.     

Zooplankton dynamic of Lake Prespa (Macedonia)

The composition and temporal abundance patterns of zooplankton community in Lake Prespa pelagic zone were studied throughout an annual cycle (October 2008–September 2009). Eighteen species (10 Rotifera, 5 Cladocera, 2 Copepoda, 1 Mollusca) were evidenced. It includes Arctodiaptomus steindachneri, an endemic calanoid of the Western Balkans. The zooplankton density varied during the investigated period and certain seasonal successions in temporal transpositions of their maximal development were noticed. The total zooplankton density was much higher in spring and summer period. The representatives of subclass Copepoda were dominant during the whole year. The dominant species was A. steindachneri. At the second place (with exception of the winter period) were the Cladocera representatives. The dominant species was Daphnia cucullata. At the third and fourth place were rotifers and larval form of Dreissena polymorpha, respectively. The quantitative presence of the Copepoda representatives was significantly lower in terms of the previous investigations. The Cladocera quantity reached high values during this period, particularly in summer. Such altering in the quantitative ratio between Copepoda and Cladocera in favor of the Cladocera, especially high quantitative presence of D. cucullata, typical for eutrophic lakes, imply of significant changes in zooplankton community and changes of the water quality in Lake Prespa pelagial.     

Contributions to the knowledge of the Cladocera of north-east Thailand

Examination of 200 samples from 93 freshwater habitats in north-eastThailand revealed 60 taxa of Cladocera, of which 31 are new to the Thaifauna. Six species (Disparalona caudata Smirnov; Leydigialaevis Gurney; Leydigiopsis sp.; Macrothrix flabelligeraSmirnov; Macrothrix cf. paulensis Sars; and Pseudosidaramosa Daday) are new to Asia. The majority of the Cladocera recorded arecircumtropical species. Comments and figures are presented on several ofthe new records for Asia and Thailand. This revised version was published online in July 2006 with corrections to the Cover Date.     

The population of Acacia tree species producing gum arabic in the Karamoja region, Uganda

The study aimed at determining the population status of the different Acacia tree species producing gum arabic in the undisturbed, grazed and cultivated habitats in the Karamoja region, Uganda. A total of 135 sample plots each measuring 20 × 20 m² (0.04 ha) with each habitat having 45 plots were selected and established in the seven counties using a simple random sampling technique. The tree species present, their abundances and sizes were recorded. Twelve Acacia species were identified and a total of 5535 recorded in the sampled area. Out of these, five were gum‐producing acacias. Acacia senegal dominated the acacias in all the seven counties and in all habitats of Karamoja with Acacia nilotica (72.3%), Acacia seyal (13.4%), Acacia sieberiana (4%) and Acacia gerrardii (2.6%). Non‐gum‐producing acacias constituted 7.19% of the total abundance. The tree densities increased with increase in tree size in the undisturbed and grazed habitats but decreased in the cultivated habitat. Most Acacia trees were of large size, an indication of old age and poor regeneration that could affect their future population status. It is recommended that further investigations be carried out into the causes of poor regeneration of Acacia species.     

Analysis of the blennioid assemblages associated with different rocky shore habitats in the Ligurian Sea

The differences among blennioid assemblages (families Blenniidae and Tripterygiidae) on different habitats were assessed at two localities of the Ligurian Sea, namely Arenzano and Riva Trigoso. The assemblage composition and species relative density were evaluated visually on four different habitats of diverse wave exposure and substratum orientation (macro‐habitat characteristics): two vertical intertidal and subtidal habitats (exposed and sheltered rockwalls) and two horizontal subtidal habitats (semi‐exposed flat rock and boulders and pebbles). Each habitat was also characterized in relation to micro‐habitat features, such as substratum complexity, heterogeneity and amount of algae cover. Patterns of differences among habitats in assemblage variables and fish density, and the influences of macro‐ and micro‐habitat features on these patterns were studied at small (within localities) and large (across localities) spatial scales. Higher values of species richness (S), diversity and evenness (J) were generally associated with vertical habitats, as a result of a positive correlation with substratum orientation. The presence of an intertidal zone in the rockwall habitats may partially explain the observed differences in assemblage variables between vertical and horizontal habitats. The strength of relationships between S, and J and the other investigated habitat variables (exposure, complexity, heterogeneity and algae cover) varied greatly depending on spatial scale. All these relationships were positive, except for complexity. Significant variation in the assemblage total density among habitats was recorded only at Arenzano, where a larger number of fishes were counted on rockwalls rather than on the horizontal habitats. The positive effect of orientation on fish total density was strictly dependent on spatial scale. Fish total density showed a negative correlation with complexity and a positive correlation with heterogeneity, both relationships being unaffected by spatial scale. The unexpected relationship with complexity was probably due to the fact that, in the most complex habitat (i.e. boulder and pebbles), the potential positive effect of high complexity on fish density might be overcome by the negative influence of other environmental features, such as horizontal orientation and low wave exposure. Complexity and heterogeneity thus seemed good predictors of fish total density, but their role needs to be carefully interpreted. The most marked differences in species composition and relative density were found between rockwalls and the other habitats, mostly due to an unbalanced distribution of some stenoecious species. Variations in species relative density were related to different combinations of both macro‐ and micro‐habitat features, and these relationships usually changed depending on spatial scale.     

Paleolimnological reconstruction of the trophic state in Lake Balaton (Hungary) using Cladocera remains

The sediment of Lake Balaton (Hungary) provides important information about the lake’s history, particularly with regard to eutrophication. In this study, we used fossil pigment analysis and subfossil Cladocera remains preserved in a dated sediment core to identify trophic stages from ~250 bc to present. Dates of the most recent eutrophic events are in good agreement with previously published data. In general, the abundance and diversity of the Cladocera community increased with eutrophication and decreased with oligotrophication. The sediments of Lake Balaton were characterised by Chydoridae remains, of which Alona species were the most abundant. Of these, Alona quadrangularis and Alona affinis accounted for 40 and 20% of the total Cladocera remains, respectively. The trophic state of Lake Balaton varied between mesotrophic and eutrophic regimes. Seven different trophic periods were identified in Lake Balaton on the basis of Sedimentary Pigment Degradation Unit (SPDU) content of the sediment. Eutrophic states were (1) from ~250 to ~30 bc, (3) between ~300 and ~590 ad, (5) between 1834 and 1944 and (7) from the 1960s until present. Mesotrophic states were (2) ~30 bc to ~300 ad, (4) 590–1834, (6) 1944–1960s. Discriminant analysis of the cladoceran data confirmed these historic events, except for the short mesotrophic episode between 1944 and 1960. The first stage of eutrophication of Lake Balaton (~250 to ~30 bc) was characterised by extensive macrophyte vegetation, as indicated by the increasing abundance of vegetation-associated Cladocera species (Eurycercus lamellatus, Sida crystallina, Pleuroxus sp.). Intensification of eutrophication was identified since the 1980s, reflected by a high abundance of Bosmina species. The most significant planktivorous fish of Lake Balaton was the Sabre carp (Pelecus cultratus), and when its number decreased, the abundance of Bosmina species increased. This study shows that Cladocera are responsive to trophic state changes, underlining their importance as a tool for the assessment of lake eutrophication.     

Contributions to the Cladocera fauna from Papua New Guinea

Twenty-eight taxa of the Cladocera are identified in collections from Papua New Guinea, 17 being new records for New Guinea, bringing the total number of Cladocera taxa reported for this region to 39. Most of the taxa are circumtropical. One species (Sarsilatona papuana) is endemic to Papua New Guinea and northern Australia. The species list includes two species that are normally listed as Holarctic:Alonella nana andAlona rustica. Widespread genera such asDaphnia, Pleuroxus, Disparalona, Acroperus were strikingly absent from the Papua New Guinean material.     

The freshwater zooplankton of Central America and the Caribbean

So far mainly sporadic studies have been made on the freshwater zooplankton of this region. We studied material from Costa Rica, Cuba, Bahamas, El Salvador, Haiti and Trinidad and listed unpublished species data from Jamaica. In all 183 species of Rotifera; 104 of Cladocera; 64 Calanoida and Cyclopoida and a few Ostracoda are known from the region which includes Central America, the Caribbean Islands from the Bahamas to Trinidad and the islands off South America and Central America. Records from individual countries are generally low except for Cuban Cladocera and Copepoda. The total number of Copepoda and Cladocera recorded for the whole regions appears to be reasonably comprehensive. Daphnia is rare or absent from the equatorial regions and it is likely that the low species diversity may be due partly to the lack of a range of habitat types.     

Transitions in functional morphology from “large branchiopods” to Cladocera: Video and confocal microscopic studies of Cyclestheria hislopi (Cyclestherida) and Sida crystallina (Cladocera: Ctenopoda)

Great diversity is found in morphology and functionality of arthropod appendages, both along the body axis of individual animals and between different life-cycle stages. Despite many branchiopod crustaceans being well known for displaying a relatively simple arrangement of many serially post-maxillary appendages (trunk limbs), this taxon also shows an often unappreciated large variation in appendage morphology. Diplostracan branchiopods exhibit generally a division of labor into locomotory antennae and feeding/filtratory post-maxillary appendages (trunk limbs). We here study the functionality and morphology of the swimming antennae and feeding appendages in clam shrimps and cladocerans and analyze the findings in an evolutionary context (e.g., possible progenetic origin of Cladocera). We focus on Cyclestheria hislopi (Cyclestherida), sister species to Cladocera and exhibiting many “large” branchiopod characters (e.g., many serially similar appendages), and Sida crystallina (Cladocera, Ctenopoda), which likely exhibits plesiomorphic cladoceran traits (e.g., six pairs of serially similar appendages). We combine (semi-)high-speed recordings of behavior with confocal laser scanning microscopy analyses of musculature to infer functionality and homologies of locomotory and filtratory appendages in the two groups. Our morphological study shows that the musculature in all trunk limbs (irrespective of limb size) of both C. hislopi and S. crystallina comprises overall similar muscle groups in largely corresponding arrangements. Some differences between C. hislopi and S. crystallina, such as fewer trunk limbs and antennal segments in the latter, may reflect a progenetic origin of Cladocera. Other differences seem related to the appearance of a specialized type of swimming and feeding in Cladocera, where the anterior locomotory system (antennae) and the posterior feeding system (trunk limbs) have become fully separated functionally from each other. This separation is likely one explanation for the omnipresence of cladocerans, which have conquered both freshwater and marine free water masses and a number of other habitats.     

Biomass allocation patterns in terrestrial, epiphytic and aquatic species of Utricularia (Lentibulariaceae)

Utricularia forms the largest genus of carnivorous plants and is characterized by the possession of typical traps (“bladders”). Total biomass allocation was examined in three aquatic, six terrestrial and one epiphytic species of Utricularia from natural habitats in West Africa and from the Botanical Gardens, Bonn. Total biomass of aquatic species was considerably higher than that of terrestrial or epiphytic species. Epiphytic Utricularia accumulate about 35% of their biomass in green leaves, in contrast to 65% of nearly chlorophylless reproductive structures and traps. Aquatic species allocated more than 85% of their total biomass to stolons, leaves and traps, but only 10–13% to reproductive structures. This is in stark contrast to the allocation patterns of terrestrial bladderworts. These species allocate nearly 90% of their total biomass in reproductive structures, and only about 10% to stolons, leaves and traps. This reduction of photosynthetically active plant tissue strongly suggests that as a consequence of the alternative resource of chemical energy, the carnivorous habit might have partly replaced autotrophy in certain terrestrial Utricularia species, especially in some smaller ones.     

Fatty acid composition of Cladocera and Copepoda from lakes of contrasting temperature

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Freshwater Cladocera (Crustacea, Branchiopoda) in Lake Tonle Sap and its adjacent waters in Cambodia

Sixty species of freshwater Cladocera (Crustacea, Branchiopoda) are recorded from Lake Tonle Sap and its adjacent waters, Cambodia. Four species, Ceriodaphnia laticaudata, Bunops cf. tuberculatus, Leydigia australis, and Chydorus cf. dentifer are newly recorded from Southeast Asia, and occurrence of Macrothrix pholpunthini is secondary confirmed in the world. The present cladoceran fauna is characterized by having rich epiphytic and benthic forms. It can be associated with the shallow and vegetation-rich habitats of the study sites.     

The occurrence and significance of Cladocera (Crustacea) in some streams of Central Indiana,U.S.A.

Although Cladocera are collected often in large rivers, their importance in streams has been under-estimated. This paper summarizes the results of a preliminary study of the benthic Cladocera in the streams of three watersheds in South Central Indiana. Seventeen sites were sampled with respect to species of benthic Cladocera present, their relative abundance, population size, and population dynamics.Cladocera were present in all streams and sites in the three watersheds. Nineteen species were collected: 13 species from the family Chydoridae, 3 Daphniidae, 2 Macrothricidae, and 1 Bosminidae. Just four species — Alona circumfimbriata, Chydorus brevilabris, Pleuroxus denticulatus, and Macrothrix laticornis — made up 68–96% of the numbers at all sites.Density of Cladocera ranged from 3–5200 m^–2 and they reproduced and maintained populations in the streams sampled. Numbers were generally high in October and early November and decreased to near zero in late December and January. The most important factor appearing to affect population sizes was discharge. Numbers at almost all sites decreased significantly after a rainfall increased discharge.A Principal Components and clustering analysis grouped sites with similar physical parameters in a continuum of low to high order. Sites with low numbers of Cladocera were generally shallow, narrow, and had a loose unconsolidated substrate. Sites with high population numbers were generally deep, wide, and had a stable substrate that accumulated detritus.     

Intra-lake heterogeneity of sedimentary cladoceran (Crustacea) assemblages forced by local hydrology

Intra-lake variation of fossil Cladocera (Crustacea) assemblages in 31 surface sediment samples in Lake Pieni-Kauro and River Saavanjoki, eastern Finland, was examined with an objective to identify habitat specificity of Cladocera in relation to local hydrology-related environmental factors. The surface sediment assemblages showed high levels of heterogeneity, mainly as to water depth and lentic–lotic gradients in the lake–river complex. This was evident from the principal component analysis which indicated a major trend from shallow to deep samples and a secondary trend from lentic to lotic samples, and from redundancy analysis (RDA), which recognized water depth and river flow as the most important environmental variables in explaining cladoceran variability within the dataset. According to the RDA and generalized linear models, Daphnia spp., Bosmina (Eubosmina), and Alona quadrangularis showed association with deep water localities, whereas Bosmina longirostris and Alona affinis preferred littoral habitats. Acroperus harpae and Chydorus sphaericus s.l. appeared to favor lotic habitats. The results propose that littoral taxa are primarily deposited postmortem or after molting close to their shallow water habitats, while planktonic cladocerans accumulate principally in deepwater locations. Accordingly, it appears that in heterogeneous basins intra-lake surface sediment samples integrate locally living fauna that is driven by local hydrology-related factors, such as water depth, sediment properties, macrophytes, and river flow and coupling biotic interactions.     

The influence of climatic factors on the distribution of C4 species in Europe

A checklist of the currently-known C4 species which occur in Europe was compiled, and the number of these found in European territories was ascertained. Their contribution to the local floras range from 4.35% in the Azores to 0% in Svalbard. Subsequently, a stepwise multiple regression analysis was used to correlate the relative abundances of four subdivisions of C4 species with climatic variables derived for each territory from meteorological tables. The four subdivisions were: (a) total number of C4 species; (b) number of native C4 species; (c) C4 monocots and (d) C4 dicots. These values were expressed as percentages of either the total flora, (a), or the native flora ((b), (c) and (d)) for the regressions. The abundance of each C4 subdivision was found to be strongly correlated with temperature, and to a lesser extent, negatively with precipitation. Habitat information about the European C4 species was also analysed and it was concluded that their apparent preference for maritime and ruderal habitats indicates some form of competitive advantage of the pathway under saline or disturbed conditions. A small number of European C4 species was identified whose distribution appears to be anomalous with respect to temperature and/or soil moisture content.Nomenclature follows Tutin et al. Flora Europaea.     

Molecular identification of the prey range of the invasive Asian paper wasp

The prey range of the invasive Asian paper wasp, Polistes chinensis antennalis, was studied using molecular diagnostics. Nests of paper wasps were collected from urban residential and salt marsh habitats, larvae were removed and dissected, and DNA in the gut of the paper wasp larvae was amplified and sequenced with cytochrome c oxidase subunit I (COI). Seventy percent of samples (211/299) yielded medium‐to high‐quality sequences, and prey identification was achieved using BLAST searches in BOLD. A total of 42 taxa were identified from 211 samples. Lepidoptera were the majority of prey, with 39 taxa from 91% of samples. Diptera was a relatively small component of prey (three taxa, 19 samples). Conclusive species‐level identification of prey was possible for 67% of samples, and genus‐level identification, for another 12% of samples. The composition of prey taken was different between the two habitats, with 2.5× more native prey species being taken in salt marsh compared with urban habitats. The results greatly extend the prey range of this invasive species. The technique is a more effective and efficient approach than relying on the collection of “prey balls”, or morphological identification of prey, for the study of paper wasps.     

Pelagic cladocera in upper volga water reservoirs

The results of cladoceran crustaceans studies in the pelagial of the Ivankovo and Uglich water reservoirs were generalized. In the period of 1973–1995, both waterbodies were similar in terms of Cladocera species composition and the dominating complex. The list of species composition of pelagic cladocerans has increased since the 1950s. The highest abundance of cladocerans was observed in the Ivankovo water reservoir. Daphnia cucullata G. Sars has been stably dominant in zooplankton summary biomass, while Chydorus sphaericus (O.F. Müller) and Bosmina longirostris (O.F. Müller) prevailed in terms of abundance. Changes in the pelagic cladoceran complex composition is evidence of the waterbodies’ eutrophication. The share of Cladocera in the zooplankton’s total summer biomass was 68 and 53% in the Ivankovski and Shoshinski stretches of the Ivankovo water reservoir, correspondingly, and 60% in the Uglich water reservoir (on average for 1970s–1990s).