Streptocephalus Proboscideus Research Articles

Mass culture of fairy shrimp Streptocephalus proboscideus (Crustacea ? Anostraca) and its use in larviculture of the Persian sturgeon, Acipenser persicus

This study was conducted with cysts of Streptocephalus proboscideus obtained from the University of Gent-Belgium. The cysts were hatched in Environmental Protection Agency (EPA) medium. The nauplii were reared at the Sturgeon Research Institute using a pure culture of Scenedesmus obliquus alga supplied at a density of 5 × 103 cell mL−1 that gradually increased to 1 × 104, 5 × 104 and 1 × 105 cell mL−1 with the growth of the nauplii. The nauplii attained sexual maturity and started producing cysts in 8 days and yielded a mean cyst number of 220±40 female−1 brood−1 cysts. These cysts were used in the larviculture of Persian sturgeon, Acipenser persicus (Borodin). Forty-three larvae of Persian sturgeon (mean weight: 15.4±1.1 mg; mean length: 27.1±2.7 mm) with roughly absorbed yolk sacs were stocked in three aquaria and fed S. proboscideus nauplii at 8-h intervals. By the end of the experiment (day 5), the mean weight and length of Persian sturgeon larvae were 51.4±13.3 mg and 20.7±1.4 mm respectively.

Stage-Specific Cannibalism and Spontaneous Cyst Hatching in the Freshwater Fairy Shrimp Streptocephalus Proboscideus Frauenfeld

Freshwater fairy shrimp that live in episodically filled rainpools are obligate bisexual animals that produce drought-resistant, encapsulated embryos called cysts. A fraction of these hatches upon each inundation, a bet-hedging strategy, and the resulting larvae grow in a concerted manner, forming a cohort. Here, we show that in the Sudan fairy shrimp, Streptocephalus proboscideus, about one-third of the cysts hatches shortly after being released from the brood-sac, without intervening period of drought. However, as long as the adult population overshoots a density of about one specimen per litre, the emerging nauplii are cannibalized by their parents. At such a density and above it, fairy shrimp filter the whole pond volume in less than 24h and since it takes about the same amount of time for first-instar nauplii to moult to an immune size, they are all consumed. In addition to being auto-regulatory, this behaviour is adaptive: animals fed their own nauplii on top of an algal diet showed a 30% increase in reproductive output, and an increase in somatic growth rate. This allocation almost quantitatively recouped the loss of inclusive fitness to cannibalism. In contrast, hatching percentages of cysts obtained from animals fed this nauplii-supplement were the same as in algal-fed animals, such that their bet-hedging strategy remains intact and is carried forward to the next generation.

Rice bran as a diet for culturing Streptocephalus proboscideus (Crustacea: Anostraca).

We cultured Streptocephalus proboscideus using rice bran as a food source, and compared its growth, mortality, fertility, and cyst hatching with published data on animals fed other food sources. We also analysed the fatty acid profile of animals and cysts. The performance of rice-bran fed shrimp was indistinguishable from that of shrimp fed most other formulated diets, but there are indications that some previously applied diets were either defective in essential fatty acids, or toxic.

The influence of processing and temperature conditions on hatching of resting eggs of Streptocephalus proboscideus (Crustacea: Branchiopoda: Anostraca)

In large freshwater branchiopods, erratic hatching success of resting eggs is a major obstacle to various applications. Lack of knowledge of the diapause-regulating processes makes control of hatching difficult. In the Sudanese fairy shrimp Streptocephalus proboscideus cysts are considered to include a diapausing and a quiescent fraction. To effect hatching, diapausing cysts have to be activated, while the quiescent portion has to be triggered by suitable environmental conditions. Of several attempts to control hatching with varying production, processing, and incubation conditions, only a few treatments proved consistently successful. Cysts were produced in an indoor culture system under controlled conditions and were harvested, washed, and dried according to defined procedures before processing (if any) and incubation. Hatchability (first-day and cumulative) was consistently higher in chemically decapsulated than in untreated (non-decapsulated) cysts at 25 °C. At a temperature of 28 °C, hatching was comparable in untreated and in decapsulated cysts and was significantly higher than at 25 °C. Pre-treatment with 7.5% NaOCl for 5–10 minutes, resulted in higher hatching than other decapsulation procedures and durations. It is believed that the decapsulation and temperature treatments were only effective in triggering quiescent cysts but did not activate the diapausing fraction.

Effect of zooplankton type and abundance on prey consumption by the fairy shrimp, Streptocephalus proboscideus (Anostraca: Crustacea)

Laboratory cultured Streptocephalus proboscideus (three sizes (mm), viz. 8.44 ± 0.95 (virgin), 14.18 ± 1.49 (adult I) and 19.24 ± 1.52 (adult II)) were offered (separately for males and females) field collected zooplankton (12 prey types) at three levels of abundance (1.0 ml−1, 2.0 ml−1 and 4.1 ind. ml−1 in 30-minute feeding experiments. Gut contents, analyzed for abundance and diversity of prey type, showed that predator size, sex and their interaction had strong effects on prey consumption. Regardless of their size, and of prey density, S. proboscideus females consumed 25–90% more prey than males. Their filtration rates (adult II) were higher (125 ml ind.−1 h.−1) than those of males (30 ml ind.−1 h.−1) too. Rotifers had the highest numerical percentage in the gut, regardless of predator size or sex. Cladocerans were only consumed by adults I and II. Adult II females consumed 28.5–43.3 µg zooplankton dry weight ind.−1 h.−1. Size distribution of B. longirostris in the field and in the gut were closely similar. This study confirms S. proboscideus as a non-selective filter feeder. Since it did not eat jumping rotifers, copepod nauplii and copepodites, it may contribute to structuring its prey communities, because good escapers will be enriched in the medium, while poor escapers will be depleted.

Evaluation of agro-industrial wastes as diets for culture of the fairy shrimpStreptocephalus proboscideus (Frauenfeld, 1873) (Crustacea:Branchiopoda:Anostraca)

Two micronized waste products were evaluated in a closed recirculation system for their suitability to replace a costly diet of live algae in the culture of the Sudanese fairy shrimp, Streptocephalus proboscideus. The test population was kept at a density of 50 individuals l−1 (sex ratio: 1/1). An agricultural waste product (YM20; mixture of pea and corn), and an industrial waste product (POME; Palm Oil Mill Effluent) were fed at two regimes: 0.1 and 0.2 mg DW animal−1 h−1. The microalga Selenastrum capricornutum, used as a reference diet at a density of 2.0±0.82 × 105 cells ml−1, proved adequate in preliminary screening experiments. The effect of the diets and feeding regimes on selected biological variables and water quality were followed by weekly observations and measurements. Results in terms of growth (= increase in length), cyst production, and mortality were more successful when animals were supplied high densities of YM20 than in all other treatments: mean brood size was 155±6 cysts with a maximum of 266. Length after 6 weeks was about 2 cm while this ranged between 1.4–1.7 cm for the other treatments. Weekly mortality rate was comparable under high food conditions. Mortality rate gradually increased from 5% in the first week to 15% in the last week. Water quality, especially nitrite concentration (measured as NO2-N), was slightly better in the dry food fed than in the algae fed cultures. Present results are promising for large-scale culturing of S. proboscideus in a cost-effective way by making use of agro-industrial waste products.

Larviculture of the fairy shrimp,Streptocephalus proboscideus (Crustacea: Anostraca): effect of food concentration and physical and chemical properties of the culture medium

Larviculture of the fairy shrimp,Streptocephalus proboscideus (Crustacea: Anostraca): effect of food concentration and physical and chemical properties of the culture medium

Modelling of human acute toxicity from physicochemical properties and non-vertebrate acute toxicity of the 38 organic chemicals of the MEIC priority list by PLS regression and neural network

Linear and non-linear modelling of human acute toxicity (as human lethal concentrations; HLCs) of the 38 organic chemicals from the 50 priority compounds of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme was investigated. The models obtained were derived either from a set of 23 physicochemical properties of the compounds or from their acute toxicities to five aquatic non-vertebrates together with the physicochemical properties. For the linear type, modelling was performed using a partial least square projection to latent structures (PLS) regression method; for the non-linear models, both PLS regression and neural network were utilized. A neural network using a combination of backpropagation and cascade-correlation algorithms was applied in this study. The results generally reveal a slightly better predictive performance of the models obtained from PLS regression than those obtained from neural networks. However, the model composed of physicochemical properties (PC-model) from the trained neural network using a back propagation algorithm with pruning technique proved superior to that trained with a combination of back propagation and cascade-correlation algorithms after leave-one-out cross-validation. The predictive power of the PC-models, whether linear or non-linear, was comparable with that of the corresponding models consisting of both structural descriptors and the ecotoxicological tests (ECOPC-models), except for the battery (ECOPC-model) from the neural network. The composition of the ‘best’ PLS and neural network models points to the importance of the combination of physicochemical properties reflecting lipophilicity, size, volume, intermolecular binding forces and electronic properties of the molecule. All the aquatic non-vertebrate tests are shown to be essential in explaining human acute toxicity. However, the degree of contribution differed, with the crustacean ( Artemia salina) and the bacterial (Microtox) bioassays being more important to the linear and non-linear PLS models, whereas the crustacean ( Artemia salina and Streptocephalus proboscideus) tests, and the rotifer ( Brachionus calyciflorus) assay were important to the neural network models. The organochlorine (lindane) and bipyridinium (paraquat) pesticides were common outliers in all the models. Moreover, the latter two compounds and the organophosphate (malathion) pesticide were also common outliers in all ECOPC-models. Other types of pesticides, however, fit the models. The predicted HLCs of a number of non-pesticides, including some chlorinated compounds, also deviated from the observed HLCs by more than one order of magnitude.

Human acute toxicity prediction of the first 50 MEIC chemicals by a battery of ecotoxicological tests and physicochemical properties

Five acute bioassays consisting of three cyst-based tests (with Artemia salina, Streptocephalus proboscideus and Brachionus calyciflorus), the Daphnia magna test and the bacterial luminescence inhibition test ( Photobacterium phosphoreum) are used to determine the acute toxicity of the 50 priority chemicals of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. These tests and five physicochemical properties ( n-octanol-water partition coefficient, molecular weight, melting point, boiling point and density) are evaluated either singly or in combination to predict human acute toxicity. Acute toxicity in humans is expressed both as oral lethal doses (HLD) and as lethal concentrations (HLC) derived from clinical cases. A comparison has also been made between the individual tests and the conventional rodent tests, as well as between rodent tests and the batteries resulting from partial least squares (PLS), with regard to their predictive power for acute toxicity in humans. Results from univariate regression show that the predictive potential of bioassays (both ecotoxicological and rodent tests) is generally superior to that of individual physicochemical properties for HLD. For HLC prediction, however, no consistent trend could be discerned that indicated whether bioassays are better estimators than physicochemical parameters. Generally, the batteries resulting from PLS regression seem to be more predictive than rodent tests or any of the individual tests. Prediction of HLD appears to be dependent on the phylogeny of the test species: cructaceans, for example, appear to be more important components in the test battery than rotifers and bacteria. For HLC prediction, one anostracan and one cladoceran crustacean are considered to be important. When considering both ecotoxicological tests and physicochemical properties, the battery based on the molecular weight and the cladoceran crustacean predicts HLC substantially better than any other combination.

Predatory Filter‐Feeding in Fairy Shrimps: Functional Response of Streptocephalus proboscideus (Crustacea: Anostraca) Fed Anuraeopsis fissa (Rotifera)

AbstractFour size classes of both sexes of laboratory‐cultured Streptocephalus proboscideus (post‐metanauplii 4.7±0.4; juvenile virgins 8.7±0.7; adults I 13.8±0.9, and adults II 22.07±1.1 mm) were fed five concentrations (20 to 320 ml−1) of Anuraeopsis fissa, or six concentrations (20 to 640 ml−1) in adults I and adults II, for 30 minutes. Post‐metanauplii consumed at maximum 66±9 rotifers ind.−1 min.−1 (mean±S.D.) while the largest adult females maximally ingested 347±37 rotifers min.−1.Regardless of predator size and sex, prey consumption was dependent on prey density. Functional response curves either plateaued or declined at 320 prey ml−1 in post‐metanauplii, juveniles and adults I, and at 640 ml−1 in adults II. Females consumed c. 40% more prey than males. On a daily basis, adult II females consumed up to 1.05 mg rotifer dry weight (10% of their own body weight) while post‐metanauplii consumed up to 0.2 mg DW (100% of their body weight). Intermediate stages had intermediate consumption rates. Filtration rates indicated that a fully grown S. proboscideus may filter as much as 2 1 of water per day, suggesting that fairy shrimps, in their natural environment, may often be food‐limited.

Comparative acute toxicity of the first 50 Multicentre Evaluation of In Vitro Cytotoxicity chemicals to aquatic non-vertebrates

The acute toxicity data of the first 50 chemicals of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme is compared for three “cyst-based toxicity tests” (Artoxkit M with Artemia salina, Streptoxkit F with Streptocephalus proboscideus, and Rotoxkit F with Brachionus calyciflorus), and two other tests (the Daphnia magna and the Photobacterium phosphoreum Microtox™ tests) commonly used in ecotoxicology. The difference in sensitivity for the 50 chemicals was as high as 19 orders of magnitude (on a molecular weight basis) between the most and least sensitive species. Generally, a similar toxicity ranking of the 5 test species was found for most of the chemicals and the interspecies correlations were high. Results from Principal Component Analysis (PCA) and cluster analysis indicated that the groupings are not related to a clear and defined chemical structure. However, the loading plot of the first two principal components may aid in selecting the minimum number and type of tests that have to be included in a battery which encompasses a broad spectrum of toxicity levels. Consequently, this study supports the use of a selected battery of tests to evaluate ecotoxicity and suggests its possible importance for screening of biologically-active compounds from natural sources.

Acute toxicity tests with Streptocephalus proboscideus (Crustacea: Branchiopoda: Anostraca): influence of selected environmental conditions

The influence of selected environmental conditions on the acute toxicity of 3 selected chemicals (K 2Cr 2O 7, CuSO 4 and Na pentachlorophenate) to instar II-III larvae of Streptocephalus proboscideus was evaluated. Mortality after a 24-h incubation was used as effect criterion. Factorial experiments were set up resulting to 25 different combinations of temperature and water hardness. The effects of pH of the dilution medium and light regime during toxicant exposure were also assessed. Results (24-h LC50's) from nearly 200 tests revealed that the degree of variation is chemical- and test condition-dependent. Water hardness had the greatest effect on larval sensitivity, showing a significant (p<0.05) negative correlation. A significant effect (p<0.05) on sensitivity was furthermore detected only for the extreme values of temperature (30°C) and pH (6.0) tested. Light conditions during acute exposure caused no change in larval sensitivity.

The Predictive Potential of a Battery of Ecotoxicological Tests for Human Acute Toxicity, as Evaluated with the First 50 MEIC Chemicals

The acute toxicities of the first 50 chemicals (dextropropoxyphene hydrochloride excluded) of the multicentre evaluation of in vitro cytotoxicity (MEIC) programme were determined on four aquatic invertebrates and a bacterial strain (Photobacterium phosphoreum for the Microtox™ test) commonly used in ecotoxicology testing. Three of the aquatic invertebrate tests consisted of cyst-based toxicity tests (Artoxkit M with Artemia salina, Streptoxkit F with Streptocephalus proboscideus, and Rotoxkit F with Brachionus calyciflorus), and the Daphnia magna test. Results of simple linear regression analyses indicated that the rodent tests (rat and/or mouse) were better than the ecotoxicological tests for predicting acute oral lethal doses in man. However, it appears that the batteries of ecotoxicological tests resulting from the partial least squares method appear to be better than the rodent tests for predicting human oral lethal doses.

The influence of solvents on the acute toxicity of some lipophilic chemicals to aquatic invertebrates

Due to the difficulties encountered in dissolving lipophilic substances in aqueous media, solvents are often used in aquatic toxicity tests. Yet, in most cases the potential effect of the solvent is only assessed separately from that of the toxicant. In the present study, water-insoluble chemicals such as diazepam, digoxin, and malathion have been tested either in pure form or in combination with dimethylsulfoxide (DMSO), ethanol, methanol or acetone, for their acute toxicity to several aquatic invertebrates commonly used in ecotoxicology. The three former compounds are included in the first 20 “priority chemicals” of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. The results indicate that the use of solvent carrier gave differences in the acute effect of the three chemicals to 6 test species: the crustaceans Artemia salina, Streptocephalus proboscideus, and Daphnia magna, the rotifers Brachionus plicatilis and Brachionus calyciflorus, and the bacterium Photobacterium phosphoreum. Consequently, the toxicity resulting from the combination of test substance and solvent should be evaluated carefully, and the magnitude of interaction taken into consideration when comparing toxicity data from various sources.

FEEDING IN THE FAIRY SHRIMP STREPTOCEPHALUS PROBOSCIDEUS (FRAUENFELD) (BRANCHIOPODA: ANOSTRACA). II. INFLUENCE OF ENVIRONMENTAL CONDITIONS ON FEEDING RATE

ABSTRACT The relationships of filtration and ingestion rates at different food concentrations were analyzed in individuals of different sizes in the fairy shrimp Streptocephalus proboscideus and ingestion rate determined in relation to sex, animal density, light and darkness, culture medium, and water quality at one food concentration. Maximum ingestion rates of about 1,000,000 cells animal-1 h-1 in adult males (13-14 mm) were measured for food concentrations between 50,000 and 500,000 algal cells (Selenastrum capricornutum) ml-1. At higher food concentrations, ingestion rates dropped. For the largest size class tested (13.7 mm), maximum ingestion rate (about 820,000 cells animal-1 h-1) was more than 10 times higher than in the smallest size class (4.4 mm) and was reached at a lower cell concentration (about 80,000 cells ml-1) than in the smallest animals (about 280,000 cells ml 1). Significant sexual differences in ingestion rates were observed in SRW (P < 0.05) and EEC (P < 0.01) synthetic fresh-water media for the 12-h measurements and in SRW medium for the 3-h experiments (P < 0.05). These results, however, were not confirmed by a third series of 3-h experiments in SRW medium. Significant influences of culture medium on feeding rates were observed in females only. The ingestion rate in darkness (1,435,000 ± 1,118,000 cells animal-1 h-1) was not significantly different from that in light (1,120,000 ± 812,000 cells animal-1 h-1). Increasing the density to more than 10 animals in 500 ml of medium had a negative effect on the feeding rate. High NH3-N and NO2-N concentrations had an inhibitory effect on food uptake; interpolated EC50 values were approximately 4 mg 1-1 and 60 mg 1-1, respectively.

Cyst-Based Toxicity Tests. IV. The Potential of Ecotoxicological Tests for the Prediction of Acute Toxicity in Man as Evaluated on the First Ten Chemicals of the MEIC Programme

In the framework of the multicentre evaluation of in vitro cytotoxicity (MEIC) programme, the first ten chemicals of the prescribed list were tested for acute toxicity in four standardised cyst-based aquatic invertebrate tests, consisting of two rotifer species (the estuarine Brachionus plicatilis and the freshwater Brachionus calyciflorus) and two crustacean species (the halophilic anostracan Artemia salina and the freshwater anostracan Streptocephalus proboscideus). Mortality was the test criterion and toxic effects, expressed as 24-hour LC50 values, were correlated with rodent and human acute oral toxicity data. Generally, a good correlation was obtained between any of the invertebrate tests and the rodent data. Likewise, the predictive screening potential of the aquatic invertebrate tests for acute oral toxicity in man was slightly better than the rat test for eight (excluding diazepam and digoxin) and nine (including diazepam, excluding digoxin) of the ten substances. The aquatic test systems, however, appear to be more suitable for compounds soluble in water.

Lipid classes and fatty acid profiles in cryptobiotic cysts of Streptocephalus dichotomus and Streptocephalus proboscideus (crustacea: anostraca)

Polyunsaturated fatty acids (PUFA) are required for growth in lobsters (Casteel & Covey, 1976), prawns (Guary et al., 1976; Kanazawa et al., 1979), marine fish (Owen et al., 1972) and the brine shrimp Artemia (Schauer et al., 1980; Abatzopoulos et al., 1989). Comparable studies on fresh water anostracan species are not available. Studies are available on the fairy shrimp S. dichotomus, dealing with egg shell stabilization, and with the involvement of lipids in accelerating hydration of cysts (Munuswamy & Subramoniam, 1984; Munuswamy, 1987). The present investigation provides an analysis of the fatty acid composition of cysts of the fairy shrimps Streptocephalus dichotomus Baird and Streptocephalus proboscideus (Frauenfeld) with an aim at understanding their functional value.

On predatory tendencies in the feeding ecology of the fairy shrimp Streptocephalus proboscideus (Frauenfeld, 1873) (Crustacea: Anostraca)

The feeding habits of the filter-feeding fairy shrimp Streptocephalus proboscideus are documented experimentally by offering them ciliates, Volvox, rotifers, nematodes and small crustaceans as prey. Escape capabilities (e.g. swimming speed) rather than size or shape were found to determine these animals' vulnerability to predation by the fairy shrimp. Ingestion rates for Volvox increased hyperbolically with size and, at the high temperatures in which they live, fairy shrimps may daily remove the equivalent of their body weight from the environment.

A culture system for fairy shrimps (crustacea, anostraca)

A laboratory system for the semi-automatic culture of fairy shrimps is described and evaluated. The design is directed towards an automation of both the algal food culture and the feeding of the organisms themselves. The fairy shrimps are reared in conical tanks, equipped with a recirculation system consisting of a sand filter. Deposited cysts are collected in a separate compartment, which is easily removed for further processing of the harvest. Streptocephalus proboscideus, a subtropical species, was reared at an initial density of 56 animals/litre. Several physico-chemical and biological variables were monitored at regular intervals and compared to the results derived from a static/renewal system with an initial density of 30 individuals/litre and with discontinuous food supply. The present recirculation system proved to be a reliable technique in maintaining good rearing conditions, assuring low mortality rates (±5% per week) and a high cyst production (±200 cysts per brood cycle) in the experimental fairy shrimp population (sex ratio 1 1 ), opening possibilities for several types of applications in aquaculture and aquatic toxicology. Total production yielded an average of 18 000 cysts per day and per culture unit (volume: 61).