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The genus Daphnia O.F. Müller, 1776 (Crustacea: Cladocera) still has a confused taxonomy for several objective and subjective reasons. Still there are many taxa with inadequately described morphology, primarily among the subgenus Daphnia (Ctenodaphnia) Dybowski & Grochowski, 1895. We provide a redescription of an Australian endemic taxon Daphnia (Ctenodaphnia) pusilla (Serventy, 1929) according to recent standards of morphological study with special attention to the thoracic limbs. We conclude that main differences between thoracic limbs of the subgenera D. (Ctenodaphnia) and Daphnia s. str. concern the limb I only as it is well-known among the cladocerans of other families. But still only a few species of D. (Ctenodaphnia) have been studied adequately, and efforts to redescribe their morphology need to be continued.

Murray-Darling Freshwater Research CentreMDFRC item.Intra- and interspecific variation in the intersetular distance (i.s.d.) of some southern Australian cladocerans was examined. The seasonal range of i.s.d. inDaphnia carinata adults (2.34±0.07 mm) was 0.17–0.25 µm. I.s.d. increased with increasing body size forD. carinata andD. thomsoni. Variation in i.s.d. between nine adult cladoceran taxa (several of which coexisted) also was examined; significant differences did occur, but the size range was small (0.14 to 0.58 µm). The possibility that intersetular distances are an index of niche separation based upon the capture of different particle sizes is discussed.

Murray-Darling Freshwater Research CentreMDFRC item.The results of four field surveys for Rotifera in Tasmania are summarized. Most new species and records in a 1987 survey were from acid waters (pH < 4.0) of dune lakes on the west coast (42° S). Marked intra- and interhabitat differences in rotifer communities of lakes and ponds were demonstrated by cluster analysis and related to habitat heterogeneity.

Murray-Darling Freshwater Research CentreMDFRC item.The spatial and temporal dynamics of rotifers in the littoral ecotone of Lake Rotomanuka (37° 55 S, 175° 19 E) were studied from February to November 1994. Rotifers were sampled with artificial substrates at two or three weekly intervals from eight sites chosen with respect to macrophyte species distribution from near shore to deeper water. 58 rotifer species were found, a high diversity in comparison to that of New Zealand limnetic communities, which usually have less than ten species. Rotifers had peak abundances in summer within emergent and submerged vegetation, when shallow regions were dry. Lecane bulla (Gosse) and Testudinella parva (Ternetz) generally had the highest numerical densities. Three major temporal groupings of species were distinguished by cluster analysis and canonical correspondence analysis (CCA): summer–autumn (e.g. Lecane hornemanni (Ehrenberg), L. bulla), winter-spring (e.g. Mytilina mucronata (Müller), Trichocerca porcellus (Gosse)), and late autumn to mid spring (e.g. T. parva, Polyarthra vulgaris (Carlin)). Rotifer species composition appeared to depend on seasonal change of water level and the associated shift from heterogeneous to homogenous physical and chemical conditions across the ecotone. Temporal variability in the abundance of zindividual rotifer species was far greater than their spatial variability. CCA indicated that temperature and pH were the factors most strongly associated with temporal variation in abundances of rotifer species. Macrophytes appeared to play the major role in determining spatial distribution, both because of differences in physical structure between species (affecting microhabitat diversity) and by causing variations in physical and chemical conditions (e.g. oxygen and pH) by inhibiting mixing.

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.Density-size distributions of a river zooplankton community were examined about biweekly over a year in the upper tidal freshwater portion of a regulated Australian river, specifically the Hawkesbury-Nepean, Results were compared with those of similar studies in lakes (and reservoirs) to characterize the similarities and differences in the structure and grazing function of river and lake zooplankton communities. The density-size distributions of the river zooplankton community were similar to those of lake plankton communities, in terms of a marked temporal variation in shape and overall bimodal shape. They differed in terms of the truncation of the upper body size and the absence of a significant relationship between the slope (regression coefficient) of a log-linear density-size model and environmental variables. The river zooplankton community appeared to have a high average rate of biomass increase when measured against body-mass class and a low mass-specific grazing rate, compared with those of lake communities. Because of methodological differences between studies, intersystem comparisons of size spectra and grazing rates need cautious interpretations and generalizations.

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

Murray-Darling Freshwater Research CentreMDFRC item.Grazing rates by a zooplankton community were measured in situ by a radiotracer cellmethod at depths of 1 m and 4 m at the upper tidal freshwater portion of a regulated river over a year.The objectives were to evaluate the likely grazing impact on the river phytoplankton community and toproduce predictive models by regressing the measured grazing rates against zooplankton biomass,temperature and food concentrations (represented by chlorophyll a). Grazing attained rates (overallaverage 0.2 day-', range 0.01-0.59 day-', expressed as instantaneous mortality rates of algal cells)comparable to those reported for lentic zooplankton communities. The measured community grazingrates were predictable largely as a function of total biomass or rotifer biomass and surface temperaturefor 1 m depth, and as a function of total biomass or juvenile copepod biomass and surface temperaturefor 4 m depth, with all-positive regression coefficients in the models. Owing to the predominance ofmicrozooplankton in the river, the impact of zooplankton community grazing appears likely to be linkedto a small-size fraction of the phytoplankton community all year. Management strategies for river waterquality may need to take account of possible functional demarcation of grazing by river zooplankton.

Water-level fluctuations can have significant effects on lake biological communities. Thirlmere Lakes are a group of five interconnected lakes located near Sydney. Water levels in Thirlmere Lakes have fluctuated over time, but there has been a recent decline that is of significant concern. In this study, we examined over one year the species composition and richness of zooplankton (Rotifera, Cladocera and Copepoda) and abiotic conditions in Lakes Nerrigorang and Werri Berri, two of the five Thirlmere lakes, with reference to lake water level. We recorded a total of 66 taxa of zooplankton, with the first report of the rotifer Notommata saccigera from Australia, and the first report of the rotifers Keratella javana, Lecane rhytida and Rousseletia corniculata from New South Wales. There was a marked difference in abiotic conditions between the two lakes, with more variable conditions in Lake Nerrigorang. There was a significant positive correlation between zooplankton species richness and lake water level but only for Lake Nerrigorang. Although the two lakes are closely situated and thought to be potentially connected at high water levels, they show distinct ecological characters and the effect of water-level fluctuations on zooplankton species richness seems to differ between the lakes.

The complete mitochondrial genomes of Brachionus manjavacas German strain were 10,721 bp (mitochondrial DNA I) and 12,274 bp (mitochondrial DNA II) in size, while the complete mitochondrial genomes of B. manjavacas Australian strain were 10,889 bp (mitochondrial DNA I) and 12,443 bp (mitochondrial DNA II) in size. Of 12 protein-coding genes (PCGs), 99.6% of amino acid sequences were identical between the two strains. Of 12 PCGs of both B. manjavacas strains, three genes (ND1, ATP6, and ND5) had incomplete stop codon T. Furthermore, ATA was the start codon for ND4, ND5, and CO3 genes, whereas that for other PCGs was ATG in both strains. The base compositions of 12 PCGs in the B. manjavacas strains were similar, indicating that the mitochondrial genome of the two strains was structurally conserved over evolution. The gene structure and its orientation of 12 PGCs of B. manjavacas strains were identical, as shown in other marine Brachionus rotifers and the freshwater Brachionus rotifers, while the freshwater rotifer B. calyciflorus had an additional cytochrome b gene in the mitochondrial DNA I.

Biotic introductions are an ongoing disruption for many ecosystems. For passively dispersed freshwater zooplankton, transcontinental introductions have been common but are poorly studied in the southern hemisphere. Here we assess the hypothesis of recent introduction for populations of the Chydorus sphaericus group (Crustacea: Cladocera) in Australia. We analyzed 254 sequences (63 original sequences) from the cytochrome oxidase I region of mitochondrial DNA of Chydorus sp., which included global representation. Three Australian populations were connected with separate clades in the northern hemisphere, suggesting multiple colonization events for Australia. The timescale of the divergences was consistent with recent (Quaternary) dispersal. As Australian populations are exposed to migrating birds from the northern hemisphere, both avian and anthropogenic sources are candidates for dispersal vectors. We concluded that recent cross-hemisphere dispersal in the Chydorus sphaericus group is more common than previously believed.

The factors leading to reintroduction success are rarely determined in species translocation programmes attempting to prevent extirpations. Examining interactions between translocated fish and ecological aspects will provide information to increase success of future reintroduction efforts. The zooplankton are a key food source for small-bodied fishes; therefore, the examination of prey availability may contribute useful insight. Fish that are ecological specialists may have preference for invertebrates associated with specific habitat conditions. Food availability for ecological specialists also may be influenced by the presence of alien fishes, through competition for prey and habitat exclusion, including invasive Eastern Gambusia (Gambusia holbrooki) which is linked to the decline of numerous small-bodied fishes. The Murray–Darling Basin in south-eastern Australia is a highly regulated floodplain system where native fishes have declined over recent decades, especially ecological specialists adapted to ephemeral wetlands with natural flow regimes. Yarra Pygmy Perch (Nannoperca obscura) is an ecological specialist that was extirpated in 2008 during a prolonged drought. The objective of this study is to examine dietary aspects of reintroduced Yarra Pygmy Perch as related to zooplankton prey availability and the potential for competition with Eastern Gambusia. The study demonstrated that prey was being consumed by Yarra Pygmy Perch within 24 h of release and provides evidence of overlap in diet with cohabiting Eastern Gambusia. The findings provide direction for further study and a new understanding regarding reintroduction ecology of threatened small-bodied wetland fishes to aid species recovery and persistence.

Understanding patterns and processes in biological diversity is a critical task given current and rapid environmental change. Such knowledge is even more essential when the taxa under consideration are important ecological and evolutionary models. One of these cases is the monogonont rotifer cryptic species complex Brachionus plicatilis, which is by far the most extensively studied group of rotifers, is widely used in aquaculture, and is known to host a large amount of unresolved diversity. Here we collate a dataset of previously available and newly generated sequences of COI and ITS1 for 1273 isolates of the B. plicatilis complex and apply three approaches in DNA taxonomy (i.e. ABGD, PTP, and GMYC) to identify and provide support for the existence of 15 species within the complex. We used these results to explore phylogenetic signal in morphometric and ecological traits, and to understand correlation among the traits using phylogenetic comparative models. Our results support niche conservatism for some traits (e.g. body length) and phylogenetic plasticity for others (e.g. genome size).

We found a Holarctic microcrustacean Daphnia galeata Sars, 1863 (Cladocera: Daphniidae) in the Lower Lakes of South Australia. This taxon was never detected in continental Australia before. Its identity was confirmed by the sequences of mitochondrial COI, 12S and 16S and nuclear 18S and 28S genes. A maximum likelihood tree from a dataset from combining 12S + 16S mitochondrial sequence and a split network of the COI haplotypes are provided, but resolution of both genes is not sufficient to reveal the exact region of the Holarctic from where D. galeata was introduced to Australia; the vector of its invasion also is unknown. We hypothesize that appearance of D. galeata in the Lower Lakes of the Murray River is related to a recent anthropogenic eutrophication of water bodies in this region, keeping in mind that examples of successful invasion of some European lakes by D. galeata after their eutrophication are well-known. We also hypothesize that establishment of this non-indigenous taxon populations in Australia might have a strong negative impact on native lake biota.

From 2001 to 2010, River Murray flows were extremely low because of drought and over allocation. Barrage releases to the Murray Mouth were small and intermittent, with an extended period of closure and no flow from December 2001 to September 2003 and from February 2006 to November 2010. We studied the zooplankton communities in the Murray estuary and Coorong North Lagoon from 2003 to 2008 to identify the distribution and abundance of zooplankters in flow and no-flow periods, to compare zooplankton communities to those in other Australian estuaries and to consider the role of zooplankton in trophodynamics. Most of our samples were taken with a 59 µm net. In September/October, 2003 a barrage release brought freshwater zooplankters into the Murray estuary. By November and December, salinities had risen and only estuarine and hypermarine species were collected. In the spring/summer of 2004/05, salinities ranged from 16 to 88 parts per thousand (ppt) and a limited estuarine/hypermarine community was pr...

Floodplain wetlands in semi-arid regions have intricate channel-floodplain networks with highly variable and unpredictable wet and dry phases related to changes in hydrology and geomorphology. We tested the hypothesis that the presence of different hydro-geomorphic habitats in those systems drives structural and functional differences in aquatic communities. To test this hypothesis, we examined the densities and species composition (structural variables), and primary productivity and respiration (functional variables) of plankton communities, and water chemistry in three spatially explicit channel, floodout and lagoon habitat types inundated by environmental water releases in the Macquarie Marshes, semi-arid Australia. Significant differences were recorded among the community-level structural and functional variables among the three habitats. Greater densities of phytoplankton, zooplankton and planktonic bacteria were observed in a hydrologically isolated floodplain lagoon. The lagoon habitat also had greater primary productivity of phytoplankton and planktonic respiration compared with the channel and floodout. Our results suggest that water release to meet environmental flow requirements can be an important driver of planktonic diversity and functional responses in semi-arid wetland systems by inundating diverse, hydro-geomorphically distinct habitats.

This study assessed the role that floods play in providing lateral connectivity between riverine habitats and floodplains, stimulating productivity and contributing zooplankton from the floodplain to the river channel. The study took place on the Chowilla Floodplain of the River Murray, Australia, and the adjacent River Murray Channel throughout the 2010–2011 floods. We found that a considerable transfer of zooplankton from the floodplain into the river channel occurred. Average zooplankton abundance was higher on the floodplain than the main river channel and increased the zooplankton abundance in the river channel downstream. At the peak of the flood, flows reached ~93 000 megalitres per day (ML d−1), inundating ~67 km2 of floodplain. At the time of this study, up to 6.3 ± 1.6 (SD) tonnes per day of zooplankton (dryweight) was being exported from the Chowilla floodplain. Differences in species assemblages were also observed within the River Murray, which seemed to be caused by the influence of t...

Disruption to a river’s natural flow regime changes its ecological character, which becomes unfavourable for previously adapted biota. The zooplankton particularly are affected, and survival of larval and juvenile fish is largely determined by their availability. Alien fishes can also impact on recruitment in native fishes, sometimes through competition. In this regard, the invasive eastern Gambusia Gambusia holbrooki is linked to the decline of several fish species. It can have a substantial influence in shaping plankton communities, which implies that it competes with native fish that rely on the microfauna. The effects of river regulation and over abstraction of water in the Murray–Darling Basin, south-eastern Australia, were exacerbated by drought from 1997 to 2010. Consequently, the endangered Murray hardyhead Craterocephalus fluviatilis underwent substantial population decline and extirpations. The purpose of this study is to determine if a link exists between zooplankton response to flooding of a drought refuge and the recruitment success of C. fluviatilis in the presence of G. holbrooki. Flooding triggered sharp and substantial increases in the zooplankton and their eggs, which was the sole food of C. fluviatilis. This apparently benefitted the recruitment of C. fluviatilis, and sometimes alleviated diet overlap with G. holbrooki. Conversely, the zooplankton in a nearby non-flooded refuge was low in abundance and diversity, and all fish species were extirpated. The findings indicate that the flooding of drought refugia with relatively small volumes of water can be timed with ecological cues that would otherwise be desynchronized in highly regulated rivers, particularly during drought.

A morphological investigation of the Australian cladoceran Alona macracantha Smirnov and Timms, 1983 revealed numerous differences from all other species of the genus and prompted its assignment to Maraura gen. nov. Main diagnostic characters of the new genus include an elongated rostrum, Monospilus‐like postabdomen, long, sinuous basal spine of postabdominal claw, absence of accessory seta of limb I, thickened scrapers 3 and 5 of limb II, and exopodites of limb III–V fused with the main body of the limb. The affinities and taxonomic position of this rare Australian endemic are discussed.

Copepod systematists should be careful not to attribute taxonomic significance to teratological structures. Given that only a minute fraction of copepod populations is subjected to microscopic examination, and that several workers have encountered intersexual individuals, intersexuality is not an extremely rare phenomenon. The fifth legs of an intersexual Boeckella triarticulata, the second to be recorded in the literature, are figured and described in detail. The factor that induces intersexuality does not affect all four rami of the fifth pair of legs uniformly; one ramus may be fully male in character and another almost completely female. Karukinka fueguina Menu-Marque, 2003 is probably based on two intersexual individuals of Boeckella poppei (Mrazek, 1901). Les taxonomistes de copepodes devraient faire attention a ne pas donner une importance taxonomique aux caracteres teratologiques. Etant donne que seule une fraction infime des populations de copepodes est soumise a un examen microscopique, et que plusieurs chercheurs ont trouve des individus intersexues, l'intersexualite n'est pas un phenomene extremement rare. La cinquieme paire de pattes d'une Boeckella triarticulata intersexuee, representant le deuxieme cas cite dans la litterature, est decrite et dessinee en detail. Le facteur qui induit l'intersexualite n'affecte pas de la meme facon les quatre rames de la cinquieme paire de pattes: une rame peut etre typiquement mâle, et une autre presque completement femelle. Il est ainsi probable que Karukinka fueguina Menu-Marque, 2003 ait ete decrite a partir de deux individues intersexues de Boeckella poppei (Mrazek, 1901).

The parthenogenetic female of a new anomopod crustacean, Notothrix halsei gen. n. et sp. n., is described from Lake Angove and found in five other sites in SW Australia. Although macrotrichid-like at first glance, a detailed morphological study including thoracic appendages revealed a set of primitive characters and similarities with primitive families, in particular with the Eurycercidae and Acantholeberidae. Ancestral traits of Notothrix gen. n. comprise: (i) a single large head pore; (ii) second maxilla; (iii) incomplete dorsal merger of valves; (iv) second antenna with a three- and a four-segmented branch; (v) six trunk limbs; (vi) two setae on a sixth endite in the first limb, vs. complete row of posterior setae on the second limb; (vii) large number of setae on exopodites III–V; (viii) well-developed gnathobase V; and (ix) massive postabdomen with wide, telson-like terminus between end-claws that show complex spinulation but no basal spine. Analysis of the complete 18S (SSU) rRNA gene sequence including taxa from all but four anomopod families and using Ctenopoda as an outgroup, confirms our separation of the new taxon, the Nototrichidae fam. n. Although different alignments resulted in different trees, the analyses confirm an isolated position of Notothrix, which has the shortest SSU rRNA gene length known for anomopods. However, the phylogenies derived from a comparison of 18S rRNA gene sequences between families of the order Anomopoda, does not resolve the descent of the various family groups.

We investigated the phylogenetic relationships of Family Asplanchnidae using both morphological and molecular data. The morphological database, comprising 23 characters from 19 taxa (15 Asplanchnidae and 4 outgroups), was compiled from a survey of the literature and our own observations; the molecular data (ITS and V4 region nuclear regions and mitochondrial cox1) was sequenced from specimens that we collected. Our analysis of the morphological data set (maximum parsimony) yielded 12 most-parsimonious trees with a tree length of 27 steps. From this analysis we conclude (1) Asplanchnidae is a monophyletic group as are the three genera comprising it, (2) there is no compelling support for the argument that Asplanchna should be separated into two discrete genera, and (3) there is some support for the proposal that Asplanchnidae and Synchaetidae are sister groups. Our analysis of the molecular data set supports the first two of these conclusions while the sister group of the family varied depending on the gene region analyzed and families and genera included. Current understanding of the phylogeny of Asplanchnidae is hampered by the need for additional informative morphological characters and a lack of molecular data for the genus Harringia and several other members of the Asplanchnidae.

The wheatbelt region of Western Australia has been extensively cleared of indigenous vegetation for agriculture and is now severely affected by dryland salinity. Wetlands that were once freshwater are now saline and others are under threat, as are the animals and plants that inhabit them. Rising groundwater is also affecting the many naturally saline playas. To provide a framework for setting conservation priorities in this region a biological survey was undertaken, including sampling of aquatic invertebrates at 230 wetlands. In this paper, we have used data from the survey to summarise occurrence of species in relation to salinity. Total species richness at a wetland showed no response to salinity below 4.1 g l−1 and then declined dramatically as salinity increased. When halophilic species were excluded from consideration, species richness was found to decline from 2.6 g l−1. These patterns are compared to previous studies of richness-salinity relationships. There is some evidence that the freshwater invertebrate fauna of the wheatbelt may be comparatively salt tolerant, with 46% of freshwater species collected at salinities above 3 g l−1 and 17% above 10 g l−1, though these proportions differed between various invertebrate groups. While this tolerance will provide a buffer against the effects of mild salinisation, many species are at risk of regional extinction as salinisation becomes more widespread.

We investigated factors influencing the hatching of the fairy shrimp, Branchinella thailandensis in relation to brood order, and also responses of cysts to wet and dry periods. Male-female pairs of B. thailandensis were cultured under static conditions at room temperature and fed ad libitum micro-algae (Chlorella sp.). Deposited cysts of the first, sixth and eleventh broods were monitored for cyst hatching under wet and dry conditions. Cyst hatching was scored daily for 5 days after incubation. Freshly laid cysts, immediately incubated, did not hatch in any of the experimental conditions (wet/dry). On the contrary, undried cysts immersed in their parental medium for 4 weeks showed the highest hatching in all brood treatments (76.67, 94.67, and 99.33% of the first, sixth, and eleventh broods, respectively). The cysts of the first brood hatched less successfully than did those of the sixth and eleventh broods. Cyst hatching mostly took place within 24 hours after incubation. The present study shows that a wet period has a strong influence on the cyst hatching success of B. thailandensis. The cysts require a period of retention in the parental medium for 2-4 weeks to complete their embryonic development before hatching. Hatching of the three representative broods showed a different pattern for each brood. The early broods required a longer wet period than did the late broods. In contrast to the hatching behaviour of many other species, drying is not absolutely essential for cyst hatching of this species.

Diatom and micro-invertebrate communities were analyzed in 56 lentic wetlands from the wheatbelt of Western Australia. Sixteen water quality parameters were measured at each habitat and were tested as determinants of diatom and micro-invertebrate distribution. Nearly all waters were dominated by Na1+ and Cl1− and over half had low buffering capacity ( 240 mS/cm; some hypersaline habitats had pH values as low as 2.1, but most sites were alkaline.

Summary 1. A long-lived bank of propagules consisting of eggs, seeds and spores is one mechanism that allows aquatic communities to survive drought. A drying (drought) event is, for aquatic organisms in a temporary wetland, a phase from which communities must recover. Such a dry phase is often considered a disturbance but should not be considered adverse or catastrophic for the organisms that have evolved to live in temporarily wet habitats. 2. This paper explores the parallels between the egg bank of zooplankton and the seed bank of aquatic plants as means of survival in temporary wetlands. The resilience of communities in temporary wetland ecosystems is assessed by examining dormancy, hatching, germination, establishment and reproduction of animals and plants from the egg and seed banks of wetlands with a range of wetting and drying regimes. 3. Both the zooplankton and aquatic plants of the temporary wetlands studied rely on their egg and seed banks as a means for surviving drying. These communities recover after the disturbance of drying by means of specific patterns of dormancy, dormancy breakage, hatching, germination, establishment and reproduction. Spatial and temporal patterns of species richness allow resilience through dormancy, as not all species are present at all sites and not all species hatch and germinate at the same time. Multiple generations in the egg and seed bank and complexity of environmental cues for dormancy breakage also contribute to the ecosystem's ability to recover after a drying event. A persistent egg and seed bank allows species-rich communities to hatch, germinate and develop rapidly once dormancy is broken. Rapid establishment of species-rich communities that reproduce rapidly and leave many propagules in the egg and seed bank also facilitates community recovery on flooding of a temporary wetland after a drying event. 4. To maintain the diversity of temporary wetland communities through droughts and floods we need to manage the dry and wet phases of wetlands. To conserve a wide range of wetland types, we need to maintain a variety of hydrological patterns across the landscape.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Bdelloid rotifer research in Australia is reviewed, the current systematic status of the group is summarized. Based on a survey of floodplain and alpine sites in northern Victoria and Tasmania conducted in January-February 1999 we recorded 20 new bdelloid species for Australia. This brings the continental record to 106 species. The description of Philodinavus aussiensis n.sp. is given, with SEM images of its trophi. Trophi of three more bdelloid species are here presented.

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

Replication is usually regarded as an integral part of biological sampling, yet the cost of extensive within-wetland replication prohibits its use in broad-scale monitoring of trends in aquatic invertebrate biodiversity. In this paper, we report results of testing an alternative protocol, whereby only two samples are collected from a wetland per monitoring event and then analysed using ordination to detect any changes in invertebrate biodiversity over time. Simulated data suggested ordination of combined data from the two samples would detect 20% species turnover and be a cost-effective method of monitoring changes in biodiversity, whereas power analyses showed about 10 samples were required to detect 20% change in species richness using ANOVA. Errors will be higher if years with extreme climatic events (e.g. drought), which often have dramatic short-term effects on invertebrate communities, are included in analyses. We also suggest that protocols for monitoring aquatic invertebrate biodiversity should include microinvertebrates. Almost half the species collected from the wetlands in this study were microinvertebrates and their biodiversity was poorly predicted by macroinvertebrate data.

1. The effect of macrophytes on the spatial distribution of littoral rotifers was examined in Lake Rotomanuka, New Zealand (37°55′S, 175°19′E). Total rotifer abundances and those of abundant species, were compared between three macrophyte species, Myriophyllum propinquum, Eleocharis sphacelata and Egeria densa, and spatially across a littoral transect in relation to these species. 2. The abundances of many species, for example Euchlanis dilatata, Lecane closterocerca and L. lunaris, differed significantly between macrophyte species. More planktonic forms, Ascomorpha saltans, Keratella cochlearis and Synchaeta oblonga, however, showed no significant preference for macrophyte species. 3. Differences in rotifer abundances were evident even when different species of macrophyte grew in close proximity to one another, indicating that variations in physical and chemical conditions, which occur in the littoral of Lake Rotomanuka, could be largely discounted for much of the variation between macrophyte species. 4. Variation in rotifers between macrophytes was probably the result of a number of factors, including differences in macrophyte morphology, macrophyte age, epiphytic algal growths and the differential effects of predation by invertebrates and fish between macrophytes. 5. Variability of rotifer abundances spatially across the ecotone was less marked than between macrophyte species. The species of macrophyte occurring, and therefore the community composition and distribution of macrophyte species in the littoral, appears to be a major influence in the spatial structuring of rotifer communities in the littoral region of lakes.

This paper discusses the influence of predation by a planktivorous fish on zooplankton assemblages within experimental billabongs. Results suggest that the presence of a small planktivorous fish in experimental billabongs had only a small influence on the structure of zooplankton assemblages and densities of rotifers. Microcrustacean populations were dominated by juveniles, however there were greater numbers of juveniles when the planktivorous fish were present.

Calanoid copepods from billabongs near Wodonga, Victoria, Australia were found to be infested with a disc-shaped mobiline peritrich ciliate belonging to the genus Trichodina. Biometrical data, including mean body diameter (43.6m), mean adhesive disc diameter (35.9m), mean denticle ring diameter (20.1m), modal denticle number (17), modal number of radial pins per denticle (9), and denticle shape and dimensions, indicate that the species is T. diaptomi Basson & Van As (1991). This is the first record of T. diaptomi from Australasia. Adults of Boeckella fluvialis and B. minuta were infected, but adult Calamoecia lucasi were not. Levels of infestation were higher on B. fluvialis (67.5% of females, 54.5% of males) than B. minuta (47.4% of females, 33.3% of males). Mean numbers of Trichodina per adult B. fluvialis were 7.68 (range 0‐78) for females and 4.06 (range 0‐43) for males, and differed significantly between sexes. Although calanoid copepods were present in the plankton from January to early December 1991, Trichodinainfestations occurred during October and November only, peaking during late November just before the copepods disappeared from the plankton. Whether the infestation was a cause of the copepod decline, developed because the copepods were rendered susceptible to infection by some other cause, or was determined by physical and/or chemical environmental factors is unknown.

The monogonont rotifer Lecane shieli is recorded for the first time from Australia (Bora Channel in the Macquarie Marshes, New South Wales: 30.65872° S /147.53144° E). Until recently, L. shieli was known only from Thailand, where the species was first described. This Australian record of a Thai ‘endemic’ is interesting in considering possible dispersal and biogeographical distribution.

Lake Gregory is a large semi-permanent lake system in arid north-western Australia. Its catchment extends into humid areas and as a result the lake has dried only twice in the last 25 years. Although the system is mostly fresh, parts of it become saline as they dry. We identified aquatic invertebrates and undertook chemical analysis of water samples from several sites at Lake Gregory in 1989, when the main water-body was saline, and in 1991 and 1993, after the system had flooded and was fresh. During the period 1989–1993, salinities varied from 0.1‰ to 82‰, and ionic composition ranged from strong sodium chloride dominance, in saline water and fresh water of the eastern part of the system, to bicarbonate dominance in fresh water of the western area. At least 174 invertebrate species were recorded, including two mollusc species that were never collected live. This species richness is much higher than that recorded from other Australian arid zone lakes, probably owing to long periods of inundation with fresh water. The fauna was dominated by insects (42 per cent of total species richness), crustaceans (27 per cent) and rotifers (22 per cent). Most species (160) were restricted to fresh water; only 12 species were found in saline water. Only one ostracod occurred in saline conditions, although ostracods are a dominant group in Australian saline lakes. Among species restricted to fresh water, the proportion of rotifer and protozoan fauna that occurred in bicarbonate-dominated water was greater than the proportion of insect, crustacean and hydracarine fauna that did so.

The Hawkesbury-Nepean River is a regulated coastal river in New South Wales, Australia. Between March 1992 and March 1993, the freshwater portion of the river was inhabited by a taxonomically rich (total: 116 taxa) and dense (annual mean community density: up to 1024 animals l-1) microzooplankton community, comparable to that in some of the large regulated temperate rivers in the Northern Hemisphere. The common zooplankton taxa in the river were similar to those observed in other rivers at the genus or species level, with a characteristic increase in protists ( Vorticella spp.) towards the downstream reaches of the river. Zooplankton community density in the Hawkesbury-Nepean River was, to some degree, predictable from river environmental variables: density was significantly negatively correlated with river flow rate but positively correlated with temperature, turbidity, conductivity, total phosphorus and chlorophyll a. The results of the present study generally conform to the hypothesis of similar structure of zooplankton communities in rivers, relative to that in lakes.

Murray-Darling Freshwater Research CentreMDFRC item.Samples collected from Lake Fryxell, southern Victoria Land, Antarctica in January 1992 and 1994 were analysed for the abundance of bacterioplankton and the diversity and abundance of protistan plankton. At the times of sampling, 14 ciliate species and 10 species of autotrophic flagellate were recorded. The samples contained two species of rotifer (Philodina spp.), which formed the first record of planktonic metazoans in the Dry Valley lakes of this region of Antarctica. Bacterial concentrations ranged between 1.0 and 3.8×108 l-1 in the upper oxic waters increasing to 20×108 l-1 in the anoxic waters. Heterotrophic flagellates decreased in abundance down the oxygenated water column, disappearing completely at 9 m, and ranged between 0.28 and 7.39×105 l-1 in abundance. Autotrophic flagellates were much more abundant exhibiting a number of distinct peaks down the water column (1.89–25.3×108 l-1). The ciliated protozoa were very abundant (up to 7720 l-1) in relation to flagellate and bacterial numbers, typical of oligotrophic lakes world-wide. The distribution of the protistan plankton showed marked zonation, probably in response to the differing salinity and temperature gradients in the water column. Possible trophic interactions are discussed and comparisons with other continental Antarctic lakes made.

A new species of Cladocera, Extremalona timmsi gen. nov., sp. nov., was found in acid saline lakes in the southwest of Western Australia. Extremalona gen. nov. belongs to the Coronatella-branch of Aloninae, but differs from all members of the group by the oval body with small high-set head (tip of rostrum located at half-height of the body), the exopodite III with uniform, well-developed setae 4–6 and male antennule with six lateral and nine terminal aesthetascs, and by numerous other characters. In our opinion, Extremalona gen. nov. is one of the ancestral genera of the Coronatella-branch of Aloninae, sharing numerous common features with the elegans-group of Alona s.l. Our data confirm a high level of endemism in Australian Chydoridae and Cladocera in general.

We present the description of a new species of bdelloid rotifer, Adineta ricciae n. sp., which emerged from dry mud of Ryan’s billabong, Victoria, Australia. Its conspicuous frontal eyes easily diagnose the species; it differs from A. oculata (Milne) by the position of the eyes and its general habitus. The animal came to our attention because it is exceptionally easy to culture, so that the species already is being used in diverse experimental studies utilising bdelloid rotifers as model organisms.

Rotifer emergence from dry billabong sediments was studied from 3 sites on the River Murray floodplain, near Wodonga, northern Victoria, Australia. The sites had different flood histories, ranging from annual to approximately 25-year flooding intervals. Half of each sediment type was sterilized by γ-radiation to contrast the contribution of recruitment from the egg bank with recruitment from passive dispersal. A series of mesocosms was employed to assess differences between treatments, i.e. sediment sterilization and flood history. Analysis by Canonical Correspondence Analysis and Similarity Percentages suggested that some species were passively dispersed. Of the 54 species colonizing after 35 days, four were undescribed, one was a new record to Australia, three species had previously been recorded only from Tasmania and five more were new to the study area. Overall, 22% of species were previously unrecorded from the study area. This suggests that habitat poor mesocosms, may be more successful in locating passively dispersed taxa than examination of natural temporary waters.

The distribution and ecology of planktonic rotifers was investigated in 33 lakes in the North Island, New Zealand, between 1997 and 1999. A total of 79 species of monogonont rotifer were identified, with an average of 21 species per lake, a diversity which is high in comparison with many previous New Zealand studies. Most species recorded were cosmopolitan taxa, and were widespread in their distribution over the North Island. Multivariate analyses (Multi-Dimensional Scaling and Canonical Correspondence Analysis) did not distinguish distinct lake groupings based on rotifer communities, but rather gradients in assemblages, which were most highly associated with lake trophic state. Based on these responses, the development of potential rotifer bioindicator schemes for lake trophic state is described and discussed.

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.Spring surveys of 112 temporary floodplain waters on River Murray tributaries demonstrated a heterogeneous habitat series, with ca. 500 species of microfauna encountered. Rotifers comprised the most diverse group (>250 taxa), however mean diversity was low (10.93 ± 7.5), in part reflecting predation by copepods and macroinvertebrates. Notably, only 10 rotifer species could be considered widespread in the study area. Ephemeral pool microfaunal communities were distinct from those of adjacent permanent billabongs; their community variability is seen as a function of, or response to, habitat heterogeneity. The significance of high species diversity in ephemeral waters is considered in the context of age of the Murray-Darling Basin, which has persisted in its present location since the breakup of Gondwana, >65 MY BP.

Murray-Darling Freshwater Research CentreMDFRC item.Daily plankton collections were taken from a billabong of the River Murray for two weeks prior to inundation in March 1990, and continued for ten days after flooding. Quantitative responses of the plankton community and the component species were analysed against measured environmental variables and between species. Rotifers and copepod nauplii were the predominant net plankton (> 53 µm). Significant negative or positive responses to inundation were detected for most common taxa of 63 rotifer species recorded. A four-fold dilution from intrusion of river water masked rapid population increases. Opportunistic responses to inundation appear to be a survival strategy in the highly unpredictable billabong environment.

Rotifers are obligate aquatic animals that are reputed to have particularly efficient mechanisms to survive extreme, or prolonged periods of drought, in the form of inconspicuously small resting stages, hidden between plant litter and sediment. In order to study this phenomenon, we conducted a hatching experiment on dry sediment from two billabongs in Victoria, Australia, which had been stored under dehydrated conditions for about one year. Here, we report on the diversity of rotifers that hatched during the experiment. A total of 48 species, a majority of which belong to groups of sessile rotifers, were recorded, including several new or interesting taxa. Two new taxa are described: Floscularia wallacei n. spec., and Pentatrocha gigantea n. gen., n. spec., the largest rotifer ever recorded. Ptygura ctenoida Koste & Tobias, 1990 is raised to species rank.

The responses of zooplankton assemblages in arid zone rivers to seasonal changes, flow events, drying and water quality changes are fundamental to our understanding of these unregulated rivers. For three years the zooplankton and littoral microfauna in three rivers in the Lake Eyre Basin were studied. A diverse assemblage was discovered with a total of 398 identifiable taxa being recorded, consisting of 72 protist, 227 rotifer and 93 microcrustacean taxa. Zooplankton diversity was highest in a boom phase during, or in the summer following, a large flood. The rotifer assemblage dominated during, or soon after, periods of flow. However, during the winter and early summer, there was a decline in rotifer taxon richness and abundance accompanied by an increase in microcrustacean taxon richness and abundance. The winter samples occurred during the recession of a large flood and the early summer samples during periods of no flow. These changes suggested the involvement of a strong annual cycle of ecosystem structure evident within the longer term patterns of boom and bust driven by the timing and size of flood events. Multivariate and regression analyses found that salinity was a significant and independent driver of assemblage composition.

A biological survey of wetlands in the Wheatbelt and adjacent coastal areas of south-west Western Australia was undertaken to document the extent and distribution of the region's aquatic invertebrate diversity. Two hundred and thirty samples were collected from 223 wetlands, including freshwater swamps and lakes, salinised wetlands, springs, rivers, artificial wetlands (farm dams and small reservoirs), saline playas and coastal salt lakes between 1997 and 2000. The number of aquatic invertebrates identified from the region has been increased five-fold to almost 1000 species, of which 10% are new and known to date only from the Wheatbelt, and another 7% (mostly rotifers and cladocerans) are recorded in Western Australia for the first time. The survey has provided further evidence of a significant radiation of microcrustaceans in south-west Western Australia. Comparison of the fauna with other regions suggests that saline playas and ephemeral pools on granite outcrop support most of the species likely to be restricted to the Wheatbelt. Most species were collected infrequently, but for many of the least common species the Wheatbelt is likely to be on the periphery of their range. Cluster analysis was used to identify 10 assemblages of species with similar patterns of occurrence. Richness of these assemblages was best predicted by salinity and climate variables, or by physical habitat characteristics (granite outcrop pools, flowing water), although the amount of variation explained by models was variable (R 2 0.36 to 0.79). Fourteen groups of wetlands were recognised from cluster analysis of sites based on community composition. Wetlands of these groups differed primarily in their physical habitat, salinity, degree of secondary salinisation, pH and their occurrence across geographic and climatic gradients. Some assemblages were closely associated with particular wetland groups but others occurred across a range of wetland types. Salinity was identified as the primary influence on the occurrence of aquatic invertebrates in the Wheatbelt, although other variables are important in particular situations. Secondary salinisation dramatically alters composition and richness of freshwater aquatic invertebrate communities, involving gradual replacement of salt sensitive species by a smaller set of salt tolerant and halophilic species as salinity increases. These altered communities are relatively homogeneous compared with those of freshwater or naturally saline wetlands. Communities of naturally saline wetlands are comprised of a heterogeneous array of halophilic species, but these communities and species are also threatened by altered hydrology and chemistry associated with dryland salinity.