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La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.The mandibles, first and second maxillae, and maxillipeds of Boeckella major, B. pseudochelae, and Hemiboeckella searli from temporary pools of the upper River Murray catchment were dissected off and examined by light microscopy for features associated with carnivorous feeding. In B. major adaptations for carnivory are enlarged ventral mandibular teeth, strong falciform medial setae on the second maxillae, falciform endopodal setae on the maxilliped, large body size and large mouthpart size in relation to body size. Its mandibular edge index is 772, in the upper omnivore range. B. major is predicted to be an omnivore with strong carnivorous tendencies and able to handle large prey items. Carnivorous features in H. searli are enlarged ventral mandibular teeth, a mandibular edge index of 1395, and strong unguiform and falciform setae on the second maxillae. It is predicted to be an omnivore with moderate carnivorous tendencies, but unable to handle prey as large as can B. major. In B. pseudochelae the only adaptations for carnivory are an edge index of 1080 and falciform setae on the maxilliped. It is predicted to be an omnivore with herbivorous tendencies. Examination of gut contents confirmed these predictions. B. major guts contained 19 animal taxa, mainly planktonic cladocerans, copepods and rotifers, H. searli 12 taxa, mainly copepods and rotifers, and B. pseudochelae 8 taxa, mainly rotifers. All had consumed algae. We suggest that predation by B. major may be an important factor affecting community structure in fishless Australian temporary pools.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Small ephemeral pools in the Murray-Darling basin, Australia, that dry annually lack fish and are dominated by microfauna. Community size structures and species diversity are very variable and many ponds contain one or more of the large calanoid copepods, Boeckella major, Boeckella pseudochelae and Hemiboeckella searli. Gut content analysis showed that these species were omnivores with B, major being the most carnivorous and B. pseudochelae the least. B. major guts contained 21 animal taxa (cladocerans, calanoid and cyclopoid copepodids, nauplii and rotifers), H. searli contained 15 taxa (calanoid, cyclopoid and harpacticoid copepods, nauplii and rotifers) and B. pseudochelae 8 taxa (small cladocerans, nauplii and rotifers). Mean numbers of animals per gut differed significantly between the large calanoids and in B. major, B. pseudochelae and H. searli were, respectively, 2.9, 0.6 and 0.2. In B. major "Rotifers" were positively selected, "Copepodites" and "Others" neutrally selected and "Cladocera" and "Nauplii" negatively preferred. In H. searli "Copepodites", "Nauplii" and "Rotifers" were neutrally selected, and "Others" negatively preferred. B. pseudochelae showed negative preference for "Cladocera", "Nauplii" and "Others", and "Rotifers" were neutrally selected. At sites containing B. major, species diversity was significantly reduced and community size structure (measured as mean and median log-length, % of sizes >500 mu m) was significantly larger than it was at sites lacking large calanoids or with only B. pseudochelae and H. searli. It is hypothesised that predation by B. major may be an important force structuring the communities of these habitats.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.

Copepods are present in numerous aquatic environments, playing key roles in food webs, and are thought to be useful indicators of environmental change. Boeckella is a calanoid copepod genus distributed mainly in the Southern Hemisphere, with 14 species reported at higher southern latitudes in South America and Antarctica. We present an updated database of these 14 species of Boeckella generated from a combination of three sources: 1) new field sampling data, 2) published records, and 3) Global Biodiversity Information Facility (GBIF), to provide a comprehensive description of the geographic distribution of the genus south of latitude 40°S in southern South America and the three main terrestrial biogeographic regions of Antarctica. The database includes 380 records, 62 from field sampling, 278 from the literature and 40 from GBIF. Southern South America, including the Falkland/Malvinas Islands, had the highest species richness and number of records (14 and 297, respectively), followed by the sub-Antarctic islands (5 and 34), South Orkney Islands (2 and 14), South Shetland Islands (1 and 23), Antarctic Peninsula (1 and 10) and finally continental Antarctica (1 and 2). Boeckellapoppei Mrázek, 1901 is the only representative of the genus, and more widely the only terrestrial/freshwater invertebrate, currently reported from all three main biogeographic regions in Antarctica (sub-Antarctic islands, maritime and continental Antarctic). Future development of molecular systematic studies in this group should contribute to assessing the correspondence between morphological taxonomy and molecular evolutionary radiation.

We investigated evolutionary relationships and biogeographical patterns within the genus Boeckella to evaluate (1) whether its current widespread distribution in the Southern Hemisphere is due to recent long-distance dispersal or long-term diversification; and (2) the age and origin of sub-Antarctic and Antarctic Boeckella species, with particular focus on the most widely distributed species: Boeckella poppei.

The aim of this investigation is to address the impact of fluctuations in temperature and ultraviolet radiation (UVR) on three species of South American copepods, Boeckella antiqua, B. gracilis and B. brevicaudata. These copepods are cold stenotherm and occur in high latitude lakes of South America and in mountain lakes in the Andes. The forecast scenarios for climate change in southern South America anticipate raising temperature and UVR levels. These changes may have the potential to impact high altitude and latitude ecosystems, including lakes and their cold adapted biota, such as those in Patagonia. Laboratory experiments, consisting of 10 day and 2 day incubations, were set up to analyse copepod mortality in relation with: (i) temperature, and (ii) the combined effect of temperature (5, 8, 12, 16, 20°C) and UV-B dose (61, 194 and 324 J m−2). The results obtained showed up that temperature is a limiting factor for B. brevicaudata that did not survive above 12°C. B. antiqua and B. gracilis withstood the temperature range although their mortality was higher at 12-16°C. The survivorship of these copepod species to radiation was found to depend on the UV-B dose, resulting in higher mortality at the highest UV-B dose. Overall, at least one Boeckella species showed an acute sensitivity to increasing temperature, and the three species studied proved tolerant to the UV-B experimental exposure. The survivorship patterns observed in Boeckella species reflect clearly their adaptation to high solar radiation exposure and to temperate to cold environmental conditions. Fil: Dieguez, Maria del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiología; Argentina Fil: Garcia, Patricia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiología; Argentina

Valid identification of species of freshwater zooplankton is the first step to understand population structures, abundance, and diversity in the pelagic environment. While some Australian taxa can be easily identified morphologically, e.g.,Calamoecia ampulla(Searle, 1911), most other species of freshwater micrometazoans are difficult to identify without specialised training, resulting in limited and even incorrect identification of the various taxa. The use of DNA barcodes, for species identification and discrimination, has added a new dimension to the traditional phenotypic approach and allows researchers to understand the patterns of genetic variability and to overcome taxonomic difficulties in the identification of the species from different life history stages. We used mitochondrial gene cytochrome coxidase I (COI) to examine the species status of common planktonic microcrustaceans in two South Australian reservoirs. COI analyses indicated that the zooplankton specimens examined from the order Diplostraca and the class Maxillopoda, which were assigned binomial names a priori from the generaBosmina,Boeckella,Chydorus,CalamoeciaandDaphnia, possessed distinct COI sequences and nested cohesively within the genealogy, except for individuals ofCeriodaphniacf.cornutaand aCeriodaphniaspecies complex that formed 4 clusters. These clusters were not explicitly identified morphologically. The present study does improve and contribute to the understanding of the status of taxonomy and biogeography of micro-crustaceans in South Australia. This information is crucial for the application of these species in studies of local and regional environmental change over varying time scales. We recommend the integration of traditional morphology with DNA barcoding-based examination, to facilitate species identification, especially for applied research.

Calanoid copepods of the genus Boeckella and Parabroteas (P. sarsi) are dominant in zooplankton communities of Patagonian lakes and ponds. This study addresses the occurrence of sexual size dimorphism in calanoid copepods of the genus Boeckella and in the monospecific genus Parabroteas occurring in 12 lakes and ponds of Patagonia (Argentina). The morphometric analysis performed showed that in all the species studied the female is larger than the male, although the difference in size among sexes was found to be variable between species. Interestingly, all species showed significant intraspecific stability in their sexual size dimorphism despite potential differences in their environments regarding predation pressure, environmental stability (permanent or temporary waters) and altitude distribution of populations. Finally, we discuss the potential implications of sexual dimorphism in terms of resource use and vulnerability to predation among other environmental forces which may play a role in promoting larger female to male size. Fil: García, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina Fil: Garcia, Patricia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina Fil: Reissig, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentina

The McMurdo Dry Valley lakes of Antarctica constitute some of the harshest and most isolated freshwater environments on Earth which might be expected to limit the biogeographical expansion of many organisms. Despite this, we found that the biodiversity of rotifer zooplankton is the highest ever recorded on the Antarctic mainland. We identified in total nine rotifer taxa, of which six are new to the Antarctic continent, in Lake Hoare, and also the first sub-adult crustacean copepod belonging to the genus Boeckella. A possible explanation for the high biodiversity is that many of the recorded species have arrived in the region in relatively recent times and then established invasive populations, suggesting that their distribution pattern was previously limited only by biogeographical borders. Interestingly, we show that the cosmopolitan rotifer taxa identified are relatively abundant, suggesting that they have established viable populations. Hence, our study suggests that the biogeographical maps have to be redrawn for several species.

The limnological features of Lake Boeckella, the main water body of Esperanza/Hope Bay (Antarctic Peninsula), were evaluated over a 16-year period, under a climate change context evidenced by the increasing air temperature trend reported for this region for the last 50 years. We analyzed the physicochemical and phytoplankton data of the lake obtained from 1991 to 2007 during the austral summers. At the beginning of January 2001, a sudden water level drop (~3 m) occurred in Lake Boeckella as a consequence of an extremely high water discharge to the sea. This was triggered by the progressive thawing of the permafrost in the basin of the system. After this disturbance, nutrients, conductivity, chlorophyll a (Chl a) and picoplankton density showed strong peaks. The pre-draining and post-draining periods showed significant differences for most of the limnological variables analyzed. Secchi disk depth significantly decreased throughout the study period, resulting in a thinner euphotic layer. Chrysophyceae and Volvocales dominated the >2 μm phytoplankton fraction in the lake, but from 2004 onwards, other small-sized eukaryotic algae (3–5 μm) also became very abundant. Autotrophic picoplankton showed a significant peak during the summer when the water level decreased. A shift in their composition was observed through the study period: in 1998, picocyanobacteria were numerically dominant; from 2002 onwards, picoeukaryotes increased and became dominant in 2004. This study suggests that climate change may trigger the thawing of the permafrost in the catchments of Maritime Antarctic lakes, leading to catastrophic draining events, which favor natural eutrophication processes.

The zooplankton assemblages in southern Chilean Patagonia are characterized by calanoid dominance and low species number that is observable under oligotrophic status and wide conductivity values, whereas at mesotrophic status the daphnids are dominant with high species number, and finally at hyper-saline environments halophilic species such as Artemia persimilis and/or the calanoid Boeckella poopensis predominate. In the present study data of different lakes and ponds between 45-53° S were analyzed, with the aim to determine potential structures at different sites. For this purpose a null model based in guild structure was applied, considering each guild a different kind of water body (lake, small lake, permanent pond, ephemeral pond, and saline lake). The results revealed in two simulations that guild are structured. These results are similar with other descriptions on the basis of null models that revealed a random pattern of species associations for similar ecosystems due to many species repeated in all or practically all studied sites or similarities of ecological features. Ecological and biogeographical topics were discussed.

Branchinecta brushi is a new species of fairy shrimp described from a pool within the volcanic crater of Cerro Paniri, northern Chile. Its occurrence represents a new altitude record for anostracans (5930 m), and it shares the title for highest altitude occurrence across all of Crustacea with a cladoceran from the same pool, Boeckella palustris. Branchinecta brushi is similar to another Chilean anostracan, B. valchetana. However, B. brushi differs from B. valchetana in the detailed morphology of the male second antennae and gonopods. Male specimens of B. brushi possesses a bulbous, distally spinose medial apophysis on the proximal article of its second antenna as well as short, stout, inwardly curved gonopods. Both sexes are distinguished by very short cercopods. Bringing phylogenetic order to the monogeneric family Branchinectidae will require increased levels of morphological documentation and a better understanding of intra-specific variation. Most crustaceans are not well suited to life at hi...

In small metazoan invertebrates classical taxonomic analyses can be ambiguous due to the limited number of morphological characters available. This difficulty can yield incorrect estimates of species richness or taxa distribution. The Boeckella genus has been described as the dominant taxon of zooplankton assemblages in the Andean biogeographical region. In this genus, taxonomic classification and delimitation of boundaries between species has long been problematic and controversial. Among South American centropagids Boeckella gracilipes has been regarded as one of the most broadly distributed species, its presence having been reported from Ecuador to Tierra del Fuego. However, in the high Andean plateau some centropagid populations identified as Boeckella gracilipes have also been considered as B. gracilipes titicacae or even identified as a different species, namely Boeckella titicacae. In an attempt to resolve the taxonomic status of the Centropagidae family from the high Andean plateau, we combined traditional and multivariate morphological analyses (integral approach) with the molecular phylogenetic approach. The results obtained allow us to conclude that centropagids collected from the high Andean plateau actually represent a different species, B. titicacae, not B. gracilipes. The phylogenetic reconstruction of the South American Centropagidae family indicated that B. gracilipes represents a sister taxon to B. titicacae. The present study stresses the usefulness of integrating alfa-taxonomy with morphometric and molecular approaches in order to resolve species boundaries, to determine geographical distributions and to investigate evolutionary processes.

Aim We tested the hypothesis that construction of lakes and ponds has facilitated both inter- and intracontinental invasions of calanoid copepod species. Location North Island, New Zealand. Methods We sampled both natural and constructed lakes, ponds and reservoirs for calanoid copepods in the North Island, New Zealand. Species records were supplemented by examining historically collected samples and literature review. Distributions of non-indigenous calanoid copepod species were compared between constructed and natural waters. Species distributions of native species were compared with the basement terranes (microplates) of the North Island to determine if they possess ‘natural ranges’, and to assess whether construction of new water bodies had altered these distributions. Results Ten calanoid copepod species have been recorded. At least four, and possibly five, of these species are non-indigenous and were restricted to constructed water bodies. Occurrences in constructed water bodies were not restricted to dammed valleys, but also included ponds constructed on farms, ornamental ponds, disused quarries and retired mines. Four Boeckella species had distributions in natural waters closely related to the North Island basement terranes, and therefore possess ‘natural ranges’ on the island. One species, Boeckella propinqua, was found in natural lakes over a small geographical range only, but has spread with construction of new water bodies to now be widely distributed over the island. Main conclusions Construction of lakes and ponds has facilitated the invasion of calanoid copepod species at both inter- and intracontinental scales. Our findings suggest that resident native calanoid copepod species may reduce the risk of invasion to natural water bodies, as similar-sized species are commonly unable to co-occur. Spread of the non-indigenous representatives from constructed into natural waters is inevitable, with established populations providing local propagule supplies for regular introductions.

Summary 1. The prevalence of mycosporine-like amino acids (MAAs) – a group of potential ultraviolet (UV)-photoprotective compounds – was surveyed across 11 species of freshwater copepods from 20 lakes of varying ultraviolet radiation (UVR) transparency in North America, New Zealand and Argentina. Co-occurring cladocerans were also analysed (seven species from 12 lakes). Many of the calanoid copepod populations were red with carotenoid pigmentation, allowing comparison of MAA and carotenoid accumulation as photoprotective strategies. 2. In two Pennsylvania (U.S.A.) lakes, MAA and carotenoid contents were followed during the early spring to mid-summer period of lake warming. A pronounced seasonal pattern of higher carotenoid/low MAA content in spring, shifting to low carotenoid/higher MAA content in summer, was observed in calanoids from the more UV transparent lake. 3. All copepod samples contained MAAs. Visibly red calanoids, especially southern Hemisphere Boeckella, often had moderate to high concentrations (2.5–11 μg MAA mg−1 dw), but low concentrations (0.04–1 μg MAA mg−1 dw) in some N. American red calanoids show that high carotenoid pigmentation (e.g. 5–10 μg carotenoid mg−1 dw) does not necessarily imply high MAA content. 4. No cladoceran sample had more than trace amounts of MAAs (

This study showed first results on the geographical distribution of mixotrophic ciliates of the genus Stentor in the Chilean North Patagonian Lake District. Thirteen deep North Patagonian lakes were sampled during 2004 and 2005, and important ecological parameters as nutrients, light climate, chlorophyll a and all plankton groups were analysed. The data were evaluated using correlation, cluster and discriminant function analyses. In four of 13 lakes, Stentor was an important constituent of the plankton community and contributed significantly to the total zooplankton biomass. It coinhabited lakes with calanoid copepods (Boeckella, Tumeodiaptomus) and small cladocerans (Eubosmina, Ceriodaphnia). Stentor was negatively correlated with cyclopoid copepods and large cladocerans. Cyclopoid copepods were a very good predictor to discriminate between lakes with and without Stentor. It is suggested that cyclopoid copepods have top-down impact on Stentor.

Recent studies have shown the value of complementing standard taxonomy with genetic analyses to reveal cryptic diversity and to aid in the understanding of patterns of evolution. We surveyed variation in the COI mitochondrial gene in members of the three genera of centropagid copepods from the inland waters in Argentina. In general, we found a close association between molecular and morphological systematics in this group. Similar to findings for marine calanoids, genetic distances within Boeckella species were modest ( 11%). Parabroteas is currently monotypic, although we detected cryptic genetic diversity, with two lineages showing 5.5% divergence. In contrast, Karukinka was not a valid genus, apparently representing an interesting and atavistic offshoot of B. poppei, a result reinforcing the value of considering both morphological and molecular evidence. Moreover, we used combined genetic and morphological information, analysed with maximum likelihood methods, to evaluate the common assumption that evolution tends to proceed via the loss of structures in crustaceans. Although analysis of other taxa and character types is required to evaluate fully the reduction hypothesis, our results suggest that structures may be gained readily as well as lost. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 279–292.

Antarctica is the continent with the harshest climate on the Earth. Antarctic lakes, however, usually presents liquid water, at least during part of the year or below the ice cover, especially those from the sub-Antarctic islands and the maritime Antarctic region where climatic conditions are less extreme. Planktonic communities in these lakes are mostly dominated by microorganisms, including bacteria and phototrophic and heterotrophic protists, and by metazooplankton, usually represented by rotifers and calanoid copepods, the latter mainly from the genus Boeckella. Here I report and discuss on studies performed during the last decade that show that there is a potential for top–down control of the structure of the planktonic microbial food web in sub-Antarctic and maritime Antarctic lakes. In some of the studied lakes, the effect of copepod grazing on protozoa, either ciliates or flagellates, depending on size of both the predator and the prey, could promote cascade effects that would be transmitted to the bacterioplankton assemblage.

The origins of the freshwater fauna that inhabits Antarctic lakes are poorly known. The species present today could be relict species that have survived Quaternary glaciations on the continent, or Holocene migrants from more temperate regions. One approach to investigating these questions is to study faunal microfossils in lake sediment. This approach was applied to a 293 cm sediment core from Lake Boeckella, located at the northern tip of the Antarctic Peninsula. The microfossils indicated that most of the metazoan species that occur in the lake today have been present since soon after the lake�s formation c. 5.5 ka ago. In particular, the centropagid copepod Boeckella poppei (Mra´zek) has been present throughout the lake�s history, suggesting a local source for this species. The development of biodiversity in the lake with time was in general more consistent with local (Antarctic) rather than distant (South American) sources, though an alternative explanation is that dispersal to Antarctica was more efficient in the mid-Holocene. Evidence of dispersal from extra-continental sites comes from the scattered occurrence throughout the core of Eubosmina chilensis (Daday), a South American species that does not reach the Antarctic or the sub- Antarctic islands at present, and which failed to establish a permanent population in the lake.

Parabroteas sarsi is a predaceous calanoid copepod that inhabits both shallow temporary fishless ponds and deep fish lakes of Patagonia and Antarctica. The aim of this study was to analyse the effect of P. sarsi on the plankton structure of a deep Andean lake (>100 m depth) and the zooplankton vertical distribution in order to asses a possible vertical refuge of the predatory copepod against visual fish predation. We tested the extent to which the trophic cascade effect of this predator propagates through the food web. We carried out a vertical sampling in Lake Rivadavia (Patagonia, Argentina) in order to assess zooplankton distribution. P. sarsi showed a vertical distribution towards deeper layers of the water column both at midday and at night, indicating that the copepod had an effective refuge against visual predation. Additionally, we carried out both field and laboratory experiments with the presence of P. sarsi. The predator was observed to affect significantly the survival of the copepod Boeckella michaelseni both in laboratory and field experiments. On the contrary, rotifers and adults of Daphnia cf. commutata were not substantially affected by the predator. B. michaelseni mouthparts revealed an omnivorous diet; therefore a broad phytoplanktonic size spectrum could be affected by this copepod. However, no cascade effect was observed due to the presence of P. sarsi despite the decrease of B. michaelseni abundance.

Lake Waihola is a shallow, tidal, coastal lake that receives brackish inflows resulting in salinities of up to 4.8‰. We determined the importance of salinity and tidal currents on crustacean zoo‐plankton abundance and distribution in this lake over 2 years. Tidal currents were traced using drogues, and zooplankton was sampled over tidal cycles. Tidal currents reached velocities of 35 cm s–1 closest to the tidal inlet channel. Salinity explained 26% of the variation in the abundance and species composition of the zooplankton assemblage, and accounted for >60% of the species‐environment correlation. Increases in salinity resulted in a change in crustacean dominance from the freshwater calanoid copepod, Boeckella hamata Brehm, and cladoceran, Daphnia carinata King, to the estuarine copepod, Gladioferens pectinatus Brady. The abundance of D. carinata was negatively correlated with chlorophyll a concentrations, although chlorophyll a was not correlated with salinity. Future increases in salinity and t...

Gradients in environmental variables may promote heterogeneity in the distribution, abundance or composition of a zooplankton community. In tidal systems, salinity gradients strongly affect zooplankton communities, while chlorophyll-a is often important in freshwater ecosystems. Lake Waihola, a shallow coastal lake that receives tidal inflows of 0-4.8‰, is dominated by two species of calanoid copepod, Boeckella hamata and Gladioferens pectinatus, and one cladoceran species, Daphnia carinata. Multiple regression and redundancy analyses of environmental variables were used to relate salinity, chlorophyll-a and particulate suspended matter to the dominant crustacean zooplankton taxa. Salinity explained >50 % of the species-environment correlation, and chlorophyll-a was negatively correlated with B. hamata and D. carinata. Increases in salinity resulted in a change in dominance from the predominantly freshwater taxa, B. hamata and D. carinata, to the predominantly estuarine species, G. pectinatus. We predict that increases in salinity associated with reductions in freshwater flow and/or increased tidal inflows in the future may cause significant changes in the zooplankton community structure, and affect trophic interactions in this lake.

The process of ozone depletion over the Antarctic continent has resulted in the increase of incident ultravioletB (UVB) radiation, whose effects may be damaging to living organisms. To counteract the negative effects of ultraviolet radiation (UVR), aquatic organisms may display one or more strategies: (1) avoidance (i.e. deep distribution); (2) photoprotection through the use of ‘‘sunscreen’’ compounds, such as mycosporine-like amino acids (MAAs); and (3) enzymatic repair of the damage. The effects of UVR were assessed on four populations of the copepod Boeckella poppei from Antarctic lakes using laboratory and field experiments. The results were related to measurements of DNA enzymatic repair activity and MAA concentration. This is the first study that combines these measurements in zooplankton. Boeckella poppei was highly tolerant to UVR (LD50 5 2.2‐2.78 J cm 22 ). However, measurements of photorecovery (comparison of UVB mortality in the presence and absence of photoreactivating light) and dosage of photolyase activity indicated low rates of enzymatic repair, which may be the result of low temperatures typical of Antarctic lakes. Three different MAAs were identified, both in phytoplankton and copepods: porphyra-334, mycosporine-glycine, and shinorine. The population of B. poppei from Lake Boeckella had the lowest MAA concentration, as well as the lowest tolerance to artificial and natural UVR. These findings support the idea that UV tolerance in this species is related to the accumulation of MAAs. A comparison of the strategies used to cope with potentially damaging levels of UVR by different species of Boeckella indicates a high degree of plasticity in this genus, which has probably been key for its success to colonize a wide range of UV environments.

The nutrient characteristics of aquatic environments at Hope Bay (Antarctica) depend on different factors, penguin enrichment being one of the most important. In this study we surveyed three water bodies of different morphometry and trophic status: Esperanza Lake (oligotrophic), Boeckella Lake (meso-eutrophic), and Pingui Pond (hypereutrophic). This research provides a preliminary characterization of the periphyton colonization on artificial substrata (glass slides) of these water bodies from the end of January to mid-March 2000. Qualitative and quantitative analyses of the algae, chlorophyll a, dry weight, ash-free dry weight, and physical and chemical variables of the lakes were assessed. The Autotrophic Index and the Lakatos system of classification were also applied. All three lakes differed clearly in all the variables considered. The periphyton from Esperanza Lake was first dominated by Bacillariophyceae and subsequently by the chrysophyce Phaeogloea mucosa. P. mucosa was the dominant species at Boeckella Lake and Chlamydomonas subcaudata was dominant at Pingui Pond. Highest mean maximum density values were reached at Pingui Pond, followed by Boeckella and Esperanza Lakes. Highest biomass figures were registered with increasing trophic status. According to the Lakatos index, the periphyton of Esperanza Lake was the least developed and it was mainly organic and heterotrophic; Boeckella Lake showed intermediate development in periphyton mass, which was autotrophic and mainly inorganic whereas Pingui Pond showed the highest development in periphytic mass, and it was mainly autotrophic.

[A new genus is established to accommodate a new species of freshwater centropagid related to the Boeckella clade. Karukinka fueguina n. gen., n. sp., is described on two males from a sample collected from an ephemeral pond in Tierra del Fuego. Diagnostic features of the new taxon are almost exclusively related to the male fifth legs, since females are unknown. The number of characters of these appendages in a plesiomorphic state, the most striking feature of which is the presence of swimming setae on both exopods, makes it unique among the Centropagidae. Otherwise, the characters indicate its close relationship to the ancestor of Boeckella and thus make it the best available living species to be used as an outgroup in phylogenetic studies of the species of this genus. Un nouveau genre est etabli pour une espece nouvelle de Centropagidae des eaux douces apparentee aux Boeckella. Karukinka fueguina n. gen., n. sp., est decrite a partir de deux mâles provenant d'un echantillon recolte dans une mare temporaire de Terre de Feu. Les caracteres diagnostiques de ce nouveau taxon concernent presqu'exclusivement les P5 mâles, les femelles etant inconnues. Le nombre de caracteres en etats plesiomorphes de ces appendices, dont le plus important est la presence de soies natatoires sur les deux exopodites, est unique chez les Centropagidae. D'autre part, les caracteres indiquent sa proche parente avec l'ancetre des Boeckella et en font la meilleure espece vivante disponible pour etre utilisee comme "outgroup" pour les etudes phylogenetiques sur les especes du genre., A new genus is established to accommodate a new species of freshwater centropagid related to the Boeckella clade. Karukinka fueguina n. gen., n. sp., is described on two males from a sample collected from an ephemeral pond in Tierra del Fuego. Diagnostic features of the new taxon are almost exclusively related to the male fifth legs, since females are unknown. The number of characters of these appendages in a plesiomorphic state, the most striking feature of which is the presence of swimming setae on both exopods, makes it unique among the Centropagidae. Otherwise, the characters indicate its close relationship to the ancestor of Boeckella and thus make it the best available living species to be used as an outgroup in phylogenetic studies of the species of this genus. Un nouveau genre est etabli pour une espece nouvelle de Centropagidae des eaux douces apparentee aux Boeckella. Karukinka fueguina n. gen., n. sp., est decrite a partir de deux mâles provenant d'un echantillon recolte dans une mare temporaire de Terre de Feu. Les caracteres diagnostiques de ce nouveau taxon concernent presqu'exclusivement les P5 mâles, les femelles etant inconnues. Le nombre de caracteres en etats plesiomorphes de ces appendices, dont le plus important est la presence de soies natatoires sur les deux exopodites, est unique chez les Centropagidae. D'autre part, les caracteres indiquent sa proche parente avec l'ancetre des Boeckella et en font la meilleure espece vivante disponible pour etre utilisee comme "outgroup" pour les etudes phylogenetiques sur les especes du genre.]

Several oil spills due to ruptures in the pipeline oil systems have occurred at the Andean paramo. A sample of this crude oil was mixed with water from a nearby Andean lagoon and the toxicity of the soluble fraction was assessed through lethal and avoidance assays with a locally occurring copepod (Boeckella occidentalis intermedia). The integration of mortality and avoidance aimed at predicting the immediate decline of copepod populations facing an oil leakage. The 24-h median lethal PAH concentration was 42.7 (26.4-91.6) µg L(-1). In the 12-h avoidance assay, 30% avoidance was recorded at the highest PAH concentration (19.4 µg L(-1)). The mortality at this PAH concentration would be of 25% and, thus, the population immediate decline would be of 55%. The inclusion of non-forced exposure testing with the quantification of the avoidance response in environmental risk assessments is, therefore, supported due to underestimation of the lethal assays.

Metazooplankton are potentially important links between classical food chains and pelagic microbial food‐webs of lakes. We determined the short‐term effects of nutrient enrichment and predation on the microbial food‐webs of oligotrophic Lake Manapouri and eutrophic Lake Hayes, New Zealand, in summer, by adding calanoid copepods (Boeckella hamata Brehm) and cladocerans (Daphnia carinata King) to in situ enclosures in the presence and absence of added nutrients (nitrogen, phosphorus). In Lake Manapouri, bacteria and phytoplankton, but not picocyanobacteria, increased in response to nutrients; Daphnia reduced the densities of phytoplankton, bacteria, heterotrophic nanoflagellates (HNF), and ciliates; and Boeckella lowered the densities of HNF and ciliates. In Lake Hayes, the growth of bacteria, HNF, and phytoplankton, including eukaryotic picoautotrophs, was enhanced by enrichment; Daphnia depressed the concentrations of picoautotrophs and HNF, whereas Boeckella decreased the density of ciliates. In...

The ultraviolet (UV) sensitivity of five species of freshwater zooplankton (three Cladocera, two Copepoda) were investigated. The animals were exposed to varying levels of UV‐radiation in a sunshine‐simulator and the UV doses for 10 and 50% mortality (LD10, LD50) were estimated using a dose‐response model. To place these doses in context they were compared with modelled clear‐sky surface UV irradiances in New Zealand. The cladocerans Daphnia carinata and Ceriodaphnia dubia were sensitive to levels of UVB irradiance of LD10 = 18–25 kJ m−2 and LD50 = 35–37 kJ m−2. These sensitivities are consistent with published values for other cladocera. In contrast a third cladoceran, Bosmina meridionalis, exhibited no higher mortality over the full range of the cumulative UVB‐doses used (3–40 kJ m−2) than controls receiving no UV exposure. The copepod Boeckella delicata showed the highest UV‐sensitivity of all organisms tested (LD10 = 7 kJ m−2, LD50 = 33 kJ m−2) whereas for Boeckella triarticulata, which was m...

Through their consumption of protozoa, cladocerans and copepods link classical food chains and microbial food webs in aquatic ecosystems. Published results of studies of the effects of these metazooplankton on protozoa in lakes allow few generalizations to be made. To determine if general patterns exist along a trophic gradient, we measured the effects of cladocerans and calanoid copepods on heterotrophic nano- flagellates (HNF) and ciliates in four lakes that ranged from ultraoligotrophic to eutrophic using the same methodology. Copepods (Boeckella spp.), and to a lesser extent cladocerans (Daphnia, Ceriodaphnia), had significant negative effects on the growth of protozoa, and the rates at which both groups cleared protozoa from the water were higher in nutrient-poor conditions than in nutrient-rich conditions. In two oligotrophic lakes, calanoid copepods ingested HNF at biomass-specific rates that were 2.2 times higher than those of cladocerans. Rates of ciliate ingestion by copepods, relative to cladocerans (top-down effects on the ciliate community), increased with lake productivity from 2.5 times higher in an ultraoligotrophic lake to 9.5 times higher in a mesotrophic lake. Our study shows that copepods are more effective consumers of protozoa than cladocerans, particularly in eutrophic conditions.

Summary 1 Planktivorous fish were hypothesised to influence the abundance of algal biomass in lakes by changing zooplankton grazing, affecting zooplankton nutrient recycling and by direct recycling of nutrients to phytoplankton. The relative roles of direct fish effects vs. zooplankton grazing were tested in mesocosm experiments by adding to natural communities large grazing zooplankton (Daphnia carinata) and small planktivorous fish (mosquitofish or juveniles of Australian golden perch). 2 The addition of Daphnia to natural communities reduced the numbers of all phytoplankton less than 30 µm in size, but did not affect total biomass of phytoplankton as large Volvox colonies predominated. 3 The addition of Daphnia also reduced the abundance of some small (Moina, Bosmina, Keratella) and large (adult Boeckella) zooplankton, suggesting competitive interactions within zooplankton. 4 The addition of mosquitofish to communities containing Daphnia further reduced the abundance of some small zooplankton (Moina, Keratella), but increased the numbers of Daphnia and adult Boeckella. In spite of the likely increase in grazing due to Daphnia, the abundance of total phytoplankton and dominant alga Volvox did not decline in the presence of mosquitofish but was maintained at a significantly higher level than in control. 5 The addition of juveniles of golden perch to communities containing Daphnia reduced the abundance of small zooplankton (Moina), increased the abundance of large zooplankton (adult Boeckella) but had no significant effect on Daphnia and total phytoplankton abundance. 6 The results of the present study suggest that some planktivorous fish can promote the growth of phytoplankton in a direct way, probably by recycling nutrients, and even in the presence of large grazers. However, the manifestation of the direct effect of fish can vary with fish species.

Boeckella antiqua n. sp. from samples collected in an ephemeral pond on the Patagonian plateau is described and illustrated. Diagnostic features of B. antiqua are almost exclusively related to the male fifth pair of legs, females being almost indistinguishable from those of the closely related B. poppei. The two-segmented, spine-bearing left endopod of the male fifth leg suggests that it may be the basal species in the genus.

The suitability for laboratory culture and comparative sensitivity of three species of New Zealand freshwater copepod (Calamoecia lucasi Brady, Boeckella delicata Percival, and Mesocyclops cf. leuckarti Claus) to pentachlorophenol (PCP) was assessed. Acute bioassays used two life stages (nauplii and adults). Acute 48-h lethality tests were conducted at 22 C with laboratory-cultured animals of all species and at varying temperatures with seasonally collected C. lucasi adults. Mean 48-h median lethal concentration values for nauplii ranged from 52 to 227 {micro}g/L PCP for C. lucasi and B. delicata, respectively, and from 106 to 173 {micro}g/L for adult C. Lucasi and M. Leuckarti, respectively. The survival rate in controls was {ge}95% in acute tests, with the exception of C. lucasi nauplii, in which it was 60%. Mean 48-h median lethal concentration values for seasonally collected C. lucasi adults were significantly higher in summer than in all other seasons. Chronic sublethal tests starting with nauplii

1. The calanoid copepods, Boeckella triarticulata Sars and Boeckella hamata Brehm, are major components of the freshwater zooplankton of New Zealand. It was not known whether these copepods ingest rotifers, nor whether the inclusion of rotifers in their diets might improve their fitness. The present study aimed to identify rotifer taxa which are eaten by each copepod species, and to examine the fitness consequences of the inclusion of one species of rotifer in the diet of B. triarticulata. 2. In feeding experiments using natural rotifer assemblages, both species of copepod ingested the rotifer Anuraeopsis fissa (0.4–4% of daily carbon intake), and B. triarticulata also ingested Polyarthra dolichoptera (6–30% of daily carbon intake) and Keratella cochlearis tecta (1% of daily carbon intake). 3. The contribution of rotifers to the fitness of adult female B. triarticulata was assessed by comparing survival and reproduction among five diets that contained varying densities of algae (Cryptomonas sp.) and/or Polyarthra dolichoptera (4 μg C L−1). Boeckella triarticulata produced fewer clutches on a rotifer-only diet than on a solely algal diet, and addition of rotifers to a threshold algal diet did not affect copepod fitness relative to the solely algal diets. The present results suggest that Polyarthra at 4 μg C L−1 is not a high-quality food for B. triarticulata.

The conceptual model of trophic structure in a typical north temperate lake that underlies attempts at biological manipulation to improve water quality is reviewed in relation to the trophic structure and community composition of planktonic food webs in New Zealand and Australian lakes. New Zealand's relatively simple food webs are characterized by an absence of obligate piscivores and few vertebrate and invertebrate planktivores; manipulation of fish stock to improve water quality has not been attempted. The largest crustacean zooplankton in Australasia, and potentially the most effective grazers of phytoplankton, are Daphnia carinata and calanoid copepods (Boeckella spp.). Their potential capacities to remove algae and colonial cyanobacteria (Microcystis, filamentous forms) from waterways are discussed in relation to colony size and concentration, toxicity, selectivity, and digestibility. The potential of D. carinata to suppress rates of increase in phytoplankton biomass may be lowered by its sensitivity to crowding and starvation, and its susceptibility to predation by fish. Decisions to use biomanipulation as a management tool to improve water quality should be based on the results of a whole lake study and take into consideration relevant obligations to preserve the biodiversity of native species, and curb the spread and dominance of exotic species. Programmes that are based on reductions in biomass of planktivorous fish should be complemented by control of nutrient loads (integrated management).