Macrothrix Triserialis Research Articles

Toxicity and Hazards of Biodegradable and Non-Biodegradable Sunscreens to Aquatic Life of Quintana Roo, Mexico

Sunscreens have spread widely into aquatic systems over the last 18 years in Quintana Roo, Mexico. This contamination is caused by intensive use as a result of leisure activities, as sunbathers apply the substances intensively (up to 83.75% of tourists and locals). Moreover, 25% of the compounds are mainly released into the water through topical products washing off. On average, 300,000 tourists arrive every week in Quintana Roo, increasing the contamination. In addition, there are no recent studies on sunscreen toxicity and the hazards this represents for the native zooplankton of Quintana Roo. In order to assess their adverse effects, acute toxicity was assessed for nine sunscreens (five non-biodegradable and four biodegradable) in four zooplankton species (Brachionus cf ibericus, Cypridopsis vidua, Diaphanocypris meridana, and Macrothrix triserialis). In total, 21 LC50 values were obtained, which are the baseline values for estimating risk and for determining the expected maximum permissible concentration. Our data on toxicity to freshwater species compared to marine species indicate that freshwater species are more sensitive than marine species. In conclusion, biodegradable sunscreen posed a moderate risk, and non-biodegradable posed a high risk. Our outcomes suggested that the maximum permissible concentrations for the contamination of sunscreens were 8.00E-05 g/L for non-biodegradable and 1.60E-04 g/L for biodegradable sunscreens.

Turbidity effects on feeding by larvae of the endemic Ambystoma mexicanum and the introduced Oreochromis niloticus in Lake Xochimilco, Mexico

We tested the effects of turbidity on the prey consumption by larvae of an endemic predator (Ambystoma mexicanum) and an introduced predator (Oreochromis niloticus). Prey visibility is influenced by turbidity due to organic (algae, detritus) or inorganic (sediment) matter. We hypothesized that the axolotl would be more adversely influenced by high turbidity as compared to Tilapia, resulting in a decrease in the population of the former under natural conditions. In order to test this, we conducted prey preference experiments and tested the reactive distance of both predators at different turbidity levels. Prey species used were the cladocerans Alona glabra, Moina macrocopa, Macrothrix triserialis and Simocephalus vetulus and the ostracod Heterocypris incongruens. In both, clear and turbid waters, the fish consumed about 17.5% and 2.5%, respectively, more prey. The axolotl had a greater preference for H. incongruens and M. triserialis, and the fish for S. vetulus and M. triserialis. These results indicate that turbidity decreases the visual ability during the larval stages of A. mexicanum which in turn influences its capacity to compete against the invasive fish. Implications of these results on conservation efforts for the highly endangered Ambystoma mexicanum are discussed.

Effect of the allelochemicals from the macrophyte Egeria densa on the competitive interactions of pelagic and littoral cladocerans

ABSTRACTMacrophytes release allelochemicals, which affect pelagic cladocerans such as Daphnia. Using population growth experiments, we analysed the effects of allelochemicals from the macrophyte Egeria densa on the interaction between Daphnia mendotae and three littoral cladocerans (Diaphanosoma birgei, Macrothrix triserialis and Simocephalus mixtus). We found that allelochemicals from E. densa increased the abundance of all the tested cladocerans in spite of the presence of a competitor. This effect was stronger (nearly three to four times higher than in controls) for D. birgei and M. triserialis in the absence of D. mendotae. Independent of the presence of allelochemicals, S. mixtus, but not D. birgei and M. triserialis, reduced the abundance of D. mendotae as compared to controls. The rate of population increase (r) per day was significantly elevated due to the presence of Egeria’s allelochemicals (from 0.07–0.16 d−1 without allelochemicals against 0.12–0.24 d−1 with allelochemicals). In our competition experiments, the rates of population increase of the cladocerans were lower than those in single-species cultures when cultured in the absence of allelochemicals. However, in the presence of allelochemicals this trend was not consistent. Thus, the positive effects of Egeria’s allelochemicals over the cladoceran populations may enhance the grazing pressure on phytoplankton.

Effects of predation by Hydra (Cnidaria) on cladocerans (Crustacea: Cladocera)

Planktonic cladocerans have evolved different strategies to avoid predation from vertebrates; these include changes in morphology, behavior, physiology, and/or life-history traits. However, littoral cladocerans are better adapted to avoid invertebrate predation particularly from insect larvae by evolving morphological and physiological adaptations. Nevertheless, this has not been proven for some littoral predators such as <em>Hydra</em>. In this study, we provide quantitative data on how <em>Hydra</em> affects its zooplankton prey. We studied the predation behavior on <em>Alona glabra</em>, <em>Ceridodaphnia dubia</em>, <em>Daphnia pulex, Daphnia </em>cf. <em>mendotae, Diaphanosoma birgei, Macrothrix triserialis, Moina macrocopa, Pleuroxus aduncus, Scapholeberis kingi, Simocephalus vetulus, Elaphoidella grandidieri, Brachionus rubens </em>and <em>Euchlanis dilatata</em>. We also tested the indirect effect of allelochemicals from <em>Hydra</em> on the demography of <em>Daphnia </em>cf. <em>mendotae.</em> Littoral cladocerans are specially adapted to resist nematocyst injection and discharge of toxic substances from <em>Hydra</em>. A significant decrease in the population growth rate from 0.21 to 0.125 d<sup>-1</sup> was observed at densities of 2 ind. ml<sup>-1</sup>. The role of carapace thickness as an adaptive strategy of littoral cladocerans against <em>Hydra</em> predation is discussed.

Effect of water quality on the feeding ecology of axolotl Ambystoma mexicanum

Ambystoma mexicanum , a highly endangered species, is endemic to lake Xochimilco (Mexico City, Mexico) which currently is being negatively affected by the introduction of Oreochromis niloticus (Tilapia) and water pollution. During the first weeks of development, when mortality is the highest, Ambystoma mexicanum depends on a diet of zooplankton. The aim of this study was to check whether contamination levels in lake Xochimilco influence zooplankton consumption by similar size classes of A. mexicanum and Oreochromis niloticus . In this study, we analysed changes in the functional responses and prey preference of A. mexicanum and larval Tilapia in two media, one with filtered lake Xochimilco water and another one with reconstituted water. As prey we used cladocerans (Moina macrocopa , Alona glabra , Macrothrix triserialis and Simocephalus vetulus) and ostracods (Heterocypris incongruens) . Zooplankton was offered in 5 different densities, 10, 20, 40, 80, 160 ind./mL. Prey consumption by A. mexicanum varied in relation to the species offered and age of the larvae. From the first week to the eighth week prey consumption by A. mexicanum increased by 57%. Our functional response tests showed that regardless of the prey type, prey consumption by A. mexicanum was lower in the contaminated water from lake Xochimilco. Among the zooplankton offered in the contaminated environment predators preferred smaller and slower moving microcrustaceans such as Alona glabra and Heterocypris incongruens . Furthermore, O. niloticus preferred prey such as Moina macrocopa and Macrothrix triserialis in the contaminated medium and was more voracious than the axolotl. Our results indicate that both water quality of the lake and the presence of the more resistant exotic fish adversely impact the survival of this endangered amphibian.

Demographic characteristics of cladocerans subject to predation by the flatworm Stenostomum leucops

We present data on the population dynamics and life table demography of four common cladoceran taxa Ceriodaphnia dubia, Ceriodaphnia cornuta, Macrothrix triserialis, and Moina macrocopa at varying densities (0.04 and 0.16 ind ml−1) of the predatory flatworm Stenostomum leucops. We also studied the impact of S. leucops on competition between C. dubia, M. triserialis, and M. macrocopa. Experiments, with four replicates for each treatment, were conducted in 200 ml recipients with 50 ml of moderately hard water and the green alga Scenedesmus acutus at a concentration of 0.5 × 106 cells ml−1. We conducted all the experiments with single clones of each taxa. We found that Ceriodaphnia cornuta, regardless of the presence of its beak, was adversely affected to a greater degree than C. dubia due to the presence of the flatworms. Moina macrocopa and Macrothrix triserialis were adversely affected in the competition experiments due to the presence of the flatworms whereas C. dubia was not. The spines of Macrothrix triserialis were not an effective defense against predation by the worms. The population growth rate of Moina macrocopa was significantly higher (0.45 d−1) in the presence of S. leucops infochemicals than in controls (0.3 d−1).

Cladocera (Crustacea: Branchiopoda) of the south-east of the Korean Peninsula, with twenty new records for Korea

We studied the cladocerans from 15 different freshwater bodies in south-east of the Korean Peninsula. Twenty species are first records for Korea, viz. 1. Sida ortiva Korovchinsky, 1979; 2. Pseudosida cf. szalayi (Daday, 1898); 3. Scapholeberis kingi Sars, 1888; 4. Simocephalus congener (Koch, 1841); 5. Moinodaphnia macleayi (King, 1853); 6. Ilyocryptus cuneatus Štifter, 1988; 7. Ilyocryptus cf. raridentatus Smirnov, 1989; 8. Ilyocryptus spinifer Herrick, 1882; 9. Macrothrix pennigera Shen, Sung & Chen, 1961; 10. Macrothrix triserialis Brady, 1886; 11. Bosmina (Sinobosmina) fatalis Burckhardt, 1924; 12. Chydorus irinae Smirnov & Sheveleva, 2010; 13. Disparalona ikarus Kotov & Sinev, 2011; 14. Ephemeroporus cf. barroisi (Richard, 1894); 15. Camptocercus uncinatus Smirnov, 1971; 16. Camptocercus vietnamensis Than, 1980; 17. Kurzia (Rostrokurzia) longirostris (Daday, 1898); 18. Leydigia (Neoleydigia) acanthocercoides (Fischer, 1854); 19. Monospilus daedalus Kotov & Sinev, 2011; 20. Nedorchynchotalona chiangi Kotov & Sinev, 2011. Most of them are illustrated and briefly redescribed from newly collected material. We also provide illustrations of four taxa previously recorded from Korea: Sida crystallina (O.F. Müller, 1776); Macrothrix rosea (Jurine, 1820); Bosmina (Bosmina) longirostris (O. F. Müller, 1776) and Disparalona cf. hamata (Birge, 1879). Among the newly recorded taxa, there are six Far East endemics; five tropicopolitan species for which the Amur basin is the northernmost margin of their distribution; four tropicopolitan species for which Korea is presumed to be the northern most area of their distribution; two Palaearctic taxa for which Korea could be the southern most area of their distribution; two cosmopolitan species which need to be revised; and one species widely distributed in Eastern Asia. Despite significantly increasing the number of known species of cladocerans in Korea, we recognize that further research is needed to complete the picture, and the cosmopolitan taxa need further revision.

Interactions between the rotifer Euchlanis dilatata and the cladocerans Alona glabra and Macrothrix triserialis in relation to diet type

We studied, separately, the effect of the cladocerans Alona glabra and Macrothrix triserialis on the population growth of the rotifer Euchlanis dilatata using three different food types ( Chlorella and Scenedesmus , live or dead, offered on a comparable dry weight basis, 3.16 μg C ml −1 ). Regardless of the presence or absence of competition, E. dilatata cultured using Chlorella (live or dead) showed a higher population growth as compared to Scenedesmus . Compared to heat-killed C. vulgaris , E. dilatata cultured alone and fed on live algae reached higher abundances. Both cladoceran species had an adverse effect on the population growth of Euchlanis , but did not eliminate the rotifers. Of the two cladocerans, M. triserialis had a far more adverse effect on the population densities of E. dilatata as compared to A. glabra . E. dilatata also influenced the population growth of A. glabra and M. triserialis , the former being more adversely affected than the latter. When the egg ratios of E. dilatata were plotted as a function of population density, a significantly inverse relation was obtained only in treatments containing Chlorella but not for other treatments. Statistically the rate of population increase ( r ) per day of E. dilatata was adversely affected by the diet type and the presence of competing species. The interaction of diet type X competition was also significant. For A. glabra , the presence of E. dilatata and the diet type, but not their interaction, significantly influenced the r . On the other hand for M. triserialis , only the diet type was significant. Our results suggest that the competitive outcome between rotifers and cladocerans was dependent on diet type.

Feeding behaviour of larval Ambystoma mexicanum

Abstract The Axolotl, Ambystoma mexicanum, endemic to the freshwater lakes, Xochimilco and Chalco in Mexico City, feeds on zooplankton during its larval stages. We evaluated the functional response over eight weeks of A. mexicanum fed different prey items found in its natural habitat (rotifers: Brachionus havanaensis, B. calyciflorus, B. rubens and Plationus patulus; cladocerans: Moina macrocopa, Macrothrix triserialis, Alona glabra and Simocephalus vetulus; and ostracods: Heterocypris incongruens). Zooplankton consumption by A. mexicanum varied in relation to the prey species and age of the larvae. Unlike oviparous fish larvae which often feed preferentially on rotifers in the first few weeks, A. mexicanum larvae fed more on cladocerans and ostracods. Among the cladocerans offered, larval A. mexicanum consumed higher numbers of M. triserialis and M. macrocopa. Feeding on the largest cladoceran tested, S. vetulus, increased after the fifth week. There was a consistent increase in the number of ostracods Heterocypris incongruens, consumed with age, from 4 to 169 prey per larva over eight weeks. The results are discussed with relation to the importance of zooplankton diet in conservation effort of this endangered species in Lake Xochimilco.

Suitability of five cladoceran species from Mexico for in situ experimentation

Although they are highly suited for site-specific risk assessment, little attention has been given to in situ ecotoxicological experimentation in tropical regions. This study intended to assess the suitability of five freshwater cladocerans from Mexico for in situ experiments. Juveniles of Ceriodaphnia cornuta, Macrothrix triserialis group, Simocephalus vetulus, Diaphanosoma birgei, and Pseudosida cf. ramosa, from two populations, were used to perform seven day laboratory and in situ experiments. Pseudosida cf. ramosa was very sensitive to handling and was discarded from further evaluations. Ceriodaphnia cornuta reproduced significantly more neonates, with smaller coefficients of variation, than M. triserialis and S. vetulus. Also due to its worldwide distribution in the tropics, C. cornuta is suggested to be highly suitable for in situ experiments.

On Macrothrix agsensis Dumont, Silva-Briano & Babu, 2002 (Cladocera: Anomopoda: Macrothricidae), with description of the male and ephippial females, and comments on the distribution of the genus in Mexico

The Macrothrix rosea-triserialis group of species (Cladocera: Macrothricidae) is characterized by (1) a well developed postabdomen heel; (2) rows of strong spines on preanal margin of postabdomen and (3) scraper 5 of limb II with enlarged subapical teeth. Macrothrix agsensis, a member of this group, was recently described from the Mexican Central Plateau based on parthenogenetic females only. It is characterized by five rows of long spines in the female antenna I, and five thick spines on setae 4–5 of endite 2 of limb I. Here we describe its ephippial females and males, as well as development of the latter. The ephippium is strongly chitinized, with a special ornamentation in the form of hexagonal cells. The male is characterized by peculiar groups of long and short spinules in the anterior half of the antenna I, three furrows with spinules on the male copulatory hook on limb I, and a longer seta in the outer distal lobe, armed with bean-like projections. With regard to the known distribution of Macrothrix in Mexico, it is now feasible to consider the existence of four possible endemic species in this region: Macrothrix mexicanus, M. agsensis, M. sierrafriatiensis and M. marthae. All of them, except the last one, are restricted to the Central Plateau. Another species, Macrothrix smirnovi, was described from Mexico and later found in Sacramento (USA). Among the widespread species are Macrothrix elegans and M. spinosa, the former one of the most common macrothricids in the Neotropics. It shows a northern distributional limit at the northwest of Mexico and it is possible to find it from north to south. Macrothrix hirsuticornis, restricted to North America has a southern limit in the north. Macrotrhix spinosa is found from north to south of Mexico, but its distribution range extends to South America. Other old records are doubtful, such as Macrothrix triserialis, M. rosea and M. laticornis, because they seem to be restricted to the old world.

Comparative study of the sensitivities of neonates and adults of selected cladoceran (Cladocera: Crustacea) species to acute toxicity stress

The body size differences between neonates and adults of many cladoceran species are large and this influences their susceptibility to toxicants. In this study we quantified the mortality rates based on acute toxicity tests using 7 species of Cladocera (Alona rectangula,Daphnia laevis, D. pulex, D. similis, Ceriodaphnia dubia, Moina macrocopa and Macrothrix triserialis) subjected to stress from methyl parathion (a pesticide) and mercury (a heavy metal). Among the test species, the body size of D. pulex was the largest while that of A. rectangula was the smallest, for both adults and neonates. Regardless of the toxicant, for a given species, neonates were more sensitive than the adults. For mercury, the 24h LC50 for neonates varied from 5.6 to 16.6 μ g/L while for the adults the range was higher (7.6 to 42.5 μ g/L); the ratio of LC50 of neonates to adults of D. laevis was > 3.5, while it was lowest (1.3) for M. triserialis. For methyl parathion, the range of LC50 for neonates was from 2.5 to 15.6 μ g/L, while for the adults it was from 8.2 to 25.9 μ g/L. The ratio of LC50 of neonate to adults was lowest (about 1.1) for C. dubia but was highest (> 5.5) for Alona rectangula. Our study also showed the need to employ a range of cladoceran species for ecotoxicological tests since no single species was consistently sensitive for stress from heavy metal or pesticide.

Distribution and abundance of Cladocera (Branchiopoda) in the Paraíba do Sul River estuary, Rio de Janeiro, Brazil

To characterize the cladoceran community of the Paraíba do Sul River estuary, located in the district of São João da Barra, Rio de Janeiro, Brazil, cladocerans were collected monthly in nine sampling stations from September 2002 until August 2003. Samples were obtained by subsurface tows using a plankton net with a 30 cm opening mouth and 70 micron mesh size, fitted with a mechanical flowmeter. Environmental parameters such as salinity and temperature were also obtained. Seventeen species of Cladocera were identified: Pseudoevadne tergestina, Penilia avirostris, Macrothrix triserialis, Moina micrura, Simocephalus kerhervei, Simocephalus vetalus, Simocephalus latirostris, Simocephalus serrulatus, Alona rectangula, Alona quadrangularis, Bosmina longirostris, Bosminopsis deitersi, Camptocercus dadayi, Ceriodaphnia richardi, Diaphanosoma fluviatile, Kurzia latissima and Pleuroxus similis. The highest total abundance of Cladocera occurred in April in the marine zone of the estuary. The most abundant species during this period was Penilia avirostris. At the mixing and freshwater zones of the estuary, the most abundant species were Moina micrura, mainly in January; and Simocephalus vetalus and Bosmina longirostris during spring. From this scenario, it can be inferred that the cladoceran community of the Paraíba do Sul River estuary presents characteristics of marine, brackish and freshwater environments. Temperature and salinity seem to limit the occurrence and distribution of cladocerans in the estuary.

Life History Characteristics of Asplanchnopus multiceps (Rotifera) Fed Rotifer and Cladoceran Prey

Members of rotifer family Asplanchnidae are important invertebrate predators in freshwater communities. Although a considerable amount of information exists on species of Asplanchna, relatively less is known about Asplanchnopus. We isolated Asplanchnopus multiceps from the littoral of a small river in the State of Hidalgo in Central Mexico and separated a clone in our cultures. The gut content analysis of some animals collected from the field revealed the presence of cladocerans and rotifers, and therefore we cultured A. multiceps on a food mixture comprising littoral rotifers and cladocerans. We conducted population growth experiments of A. multiceps using six prey types (cladocerans: Macrothrix triserialis, Alona rectangula and Pleuroxus aduncus; rotifers, Brachionus patulus, B. macracanthus and B. urceolaris). The prey species (A. rectangula and B. patulus) on which the highest growth rates were observed were used to test the life-table demographic patterns in A. multiceps. All experiments were conducted in 50 ml containers with 25 ml of the medium and at three food levels (0.5, 1.0 and 2.0 ind. ml−1 for the cladocerans, and 2.0, 4.0 and 8.0 ind. ml−1 for the rotifers) with four replicates at each treatment. The spines of M. triserialis and B. macracanthus were apparently effective deterrents against Asplanchnopus predation since both these diets resulted in low, and sometimes negative, growth rates of the predator. The average lifespan and net reproductive rate of A. multiceps ranged from 3.8 to 8.4 days and 2.6 to 12.2 ind. female−1, respectively, on A. rectangula; and from 5.0 to 9.4 days and 1.6–18.4 ind. female−1, respectively, on B. patulus. The rate of population increase of A. multiceps ranged from 0.1 to 0.8 d−1, depending on the prey type and density. The role of A. multiceps in structuring littoral rotifer and cladoceran communities is discussed.

Effect of Aeolosoma sp. (Aphanoneura: Aeolosomatidae) on the Population Dynamics of Selected Cladoceran Species

Although oligochaete worms naturally coexist with cladocerans in many shallow freshwater ponds and lakes, their influence on the latter is not well established. In this work we studied the effect of Aeolosoma sp. on the population growth of Alona rectangula, Ceriodaphnia dubia, Daphnia pulex, Macrothrix triserialis and Moina macrocopa. Population growth studies were conducted at one algal food density (1 × 106cells ml−1 of Chlorella vulgaris). The experimental design was similar for all five cladoceran species, where we used 100 ml capacity transparent jars containing 50 ml of EPA medium with the desired algal density and three replicates for each treatment. The test medium was changed daily and fresh algal food was added. The initial density of each of the cladoceran species in the population growth studies was 0.4 ind ml−1 while that of the worms 1.0 ind ml−1. Following inoculation, we estimated daily the number of cladocerans and the worms for duration of 21 days. Regardless of the presence of worms, Moina macrocopa and Macrothrix triserialis showed rapid population growth while A. rectangula took more than 2 weeks to reach peak abundances. With the exception of M. triserialis, all the other our cladoceran species declined in the presence of Aeolosoma sp. The lowest peak population density (about 1 ind ml−1) was observed for M. triserialisin controls. The remaining species had peak densities of about 3–5 ind ml−1. The rates of population increase per day varied from 0.03 to 0.19 depending on the cladoceran taxa and the treatment. In general we found that pelagic taxa were more adversely affected by the presence of the worms than were the littoral cladocerans.

Food Type Effects on the Population Growth Patterns of Littoral Rotifers and Cladocerans

AbstractLittoral rotifers and cladocerans feed on bacteria, phytoplankton, and detritus. In comparison to planktonic organisms their species diversity is high, yet little is known about their biology. In this study we present data on the functional response of the cladocerans Macrothrix triserialis and Alona rectangula, and the rotifer Brachionus macracanthus to different levels of the alga Chlorella vulgaris. Based on the incipient limiting level, we chose the food concentration and tested the population growth on four types of diets for three cladoceran species — Macrothrix triserialis, Alona rectangula, and Chydorus sphaericus — and three rotifer species — Brachionus macracanthus, Lecane quadridentata, and Platyias quadricornis. We studied growth rates of each of these species on diets of live Chlorella vulgaris, heat‐killed Chlorella vulgaris, baker's yeast (Saccharomyces cerevisiae), and field collected detritus. The incipient limiting level was around 0.9 · 106 cells mL−1 of Chlorella for the tested zooplankton species. The population growth patterns showed that, in general, the cladocerans took 25…50 d to reach their peak population densities, which ranged from 10…75 ind. mL−11. Among the rotifers L. quadridentata and B. macracanthus had equally high growth rates on live and heat‐killed forms of C. vulgaris while P. quadricornis grew best on detritus. The growth rates ranged from 0.03…0.21 d−1. The similarities and differences between littoral and planktonic organisms in relation to food type and availability have been discussed.

Comparative Life Table Demography and Population Growth of Alona rectangula and Macrothrix triserialis (Cladocera: Crustacea) in Relation to Algal (Chlorella vulgaris) Food Density

ABSTRACT We conducted survivorship and population growth studies with two littoral-benthic cladocerans, Alona rectangula and Macrothrix triserialis, littoral-benthic cladocerans, under low and high food levels (0.5×106 and 2.0×106 Chlorella vulgaris cells ml−1). The net reproductive rate ranged from 13 to 15 offspring/female in the case of A. rectangula and between 19 and 27 for M. triserialis. The generation time was also lower (10 d) for A. rectangula but higher (16–18 d) for M. triserialis. Thus, the growth rates of M. triserialis were around 0.25 d−1 while those of A. rectangula around 0.32. The rates of population increase from the population growth experiments were lower than those from the life table demography studies.

The Biogeography of Cladocera (Crustacea) in Tropical Australia

AbstractNinetysix species of Cladocera, comprising 8 Sididae, 50 Chydoridae, 17 Macrothricidae, 5 Moinidae, 2 Bosminidae, and 14 Daphniidae, occur in tropical Australia. Of this number 38% are cosmopolitan including so‐called cosmopolitan species, 13.5% are circumtropical, 13.5% occur as well innear by countries, and 35% are endemic. North Queensland is a major area of speciation. Species richness varies from north to south and from wetter coastal areas to the drier inland. Major factors influencing richness and distribution are the relative proportion of floodplain billabongs in an area, coupled with rainfall reliability. The most common species include Alonella clathratula, Chydorus nr. pubsecens, Macrothrix triserialis, Oxyurella singalensis, Ephemeroporus nr. barroisi, Dadaya macrops, Diaphanosoma sarsi, Ceriodaphnia cornuta, and Dunhevedia crassa.