The filtration apparatus of Anostraca (Crustacea): species-specific setulation in the genus Streptocephalus

The structure of the setae, setules, spines and spinules on the limbs of males and females of Streptocephalus torvicornis, S. rubricaudatus and S. proboscideus are described, based on scanning electron micrographs. The data disclose significant variation among the three species in fine structure of the setules and inter-setular distance. The variation may be related to different trophic specialisations, facilitating the sympatric occurrence of congeneric species.     

Observations on temperature optimum,cyst production,and survival of Streptocephalus proboscideus (Frauenfeld, 1873) (Crustacea: Anostraca), fed different diets

Somatic growth in S. proboscideus, fed Chlorella vulgaris increased with temperature reaching a plateau after about 8 to 11 days at between 26 and 31 °C. Survival was best below 29 °C. Fertility (the number of cysts produced per female) and survival, tested at 27 °C, demonstrated some variability as a function of the composition of four different diets. However, large variances and few replicates make exact evaluation impossible.It was found that S. proboscideus can successfully be cultured, using a variety of food sources. Only pure Spirulina platensis gave unsatisfactory results in terms of low cyst production and high mortality. Filamentous blue-green algae, because of their possible toxicity, should preferably be excluded from formulated diets.     

Streptocephalus caljoni n.sp. (Crustacea: Anostraca) from Burundi and analysis of its limb structure

Streptocephalus caljoni n. sp. from Burundi is described. It is related to Streptocephalus trifidus, but differs from it and other Streptocephalus in the cheliform hand of the male antenna II. We also analyse the morphology of the setae on the endo- and exopodite of the fifth trunk limb, using light- and scanning electron microscopy. This analysis reveals additional differences between the two related species, and is a useful tool in the study of the taxonomy of the Anostraca.     

Structural differences between the cyst walls of Streptocephalus dichotomus (Baird), S. torvicornis (Waga), and Thamnocephalus platyurus (Packard) (Crustacea: Anostraca), and a comparison with other genera and species

The surface topography and layering of the cyst wall of the fairy shrimps Streptocephalus dichotomus, S. torvicornis and Thamnocephalus platyurus are described, based on scanning electron micrographs. Cyst walls are not invariably bilayered, but may be composed of up to four layers. They are species-specific in all taxa so far studied. Cyst wall structure within single cysts may differ according to the topographical location on the cyst.     

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.     

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.     

Observations on the biology of the rare Branchipus visnyai Kertesz 1956 (Crustacea, Anostraca) from Monti Reatini (Latim, central Italy)

Branchipus visnyai is presently known from only one location, in Italy, on Monte Catabio (central Appennine, Latium, 1590 m a.s.l). It lives in a large astatic pond and in a small temporary pool close to the pond. Typically two generations appear in the pond (in spring after snowmelt and in autumn after dilution by rainfall), unless an exceptionally dry season occurs. Yet, due to shallowness and small size, filling and duration of the pool is erratic and depends on the annual amount of snow and rainfall. Consequently, B. visnyai does not always appear in the pool.Field studies suggest that either a rise in temperature or a drop in conductivity may trigger cyst hatching in the two biotopes. Also, the species exhibits a high tolerance to change in environmental factors like water temperature. Hatching occurs within a range of 10–22 °C, adults survive at temperatures from 1 to 27 °C. The optimum seems to correspond to 10–20 °C.     

Biogeography and ecology of Anostraca (Crustacea) in middle Paroo catchment of the Australian arid-zone

Fourteen species of Branchinella and one each of Parartemia, Streptocephalus (Parastreptocephalus) and an undescribed branchipodid genus occur in a limited area (2000 km²) of the Paroo in northwestern New South Wales and southwestern Queensland. Syntopic coexistence was common (55% of collections) but to a large degree species interactions are minimized by habitat factors of turbidity, salinity and length of the wet phase in decreasing order of importance, and by a species factor of relative size. Discrete habitats such as claypans had a similar species composition each time they filled, but creek pools and other connected sites had variable species composition over time. The high biodiversity is explained by the presence of many distinct types of wetlands, each with their own characteristic anostracans.     

On the presence of the genus Branchinecta Verrill, 1869 (Crustacea,Anostraca) in Yugoslavia

The genus Branchinecta Verrill, 1869 is represented in Yugoslavia by two species: Branchinecta ferox (Milne-Edwards, 1840) and Branchinecta orientalis G.O. Sars, 1901. The first species was collected in the steppe-like province of Banat, Pannonian Lowland, and in the lowland around the Skadar Lake, Montenegro, the second only in the province of Banat.On the basis of rich material of both species, a detailed study of the most essential morphological characters has been carried out and comparisons have been made with data in the literature. In B. ferox, significant morphological deviations are not found, whereas, in B. orientalis, essential features are clearly ascertained which were previously unknown or were not stated with sufficient precision. B. ferox is known to appear in small, temporary, natronsoda water rainpools, while B. orientalis has been found in a large temporary inundation pool with a high content of natronsoda and salt in the water.     

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 die of live algae in the culture of the Sudanese fairy shrimp,Streptocephalus proboscideus. The test population was kept at a density of 50 individuals 1^–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 0.2mg DW animal^–1 h^–1. The microalgaSelenastrum 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 about 2 cm while this ranged between1.4–1.7 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 nitriate 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 ofS. proboscideus in a cost-effective way by making use of agro-industrial waste products.     

On Branchinecta orientalis Sars (Anostraca) in the Himalayas

We report finding the Anostraca, Branchinecta orientalis Sars, 1901, in a temporary lake in the Nepalese Himalayas. The lake, referred to as a non-permanent water collection by Löffler, was sampled in the framework of a research project on lakes in remote areas (Ev-K2-CNR Project), aimed at studying the transport of pollutants on a global scale. The species identified, never reported before for this region, was found only in one water body out of a total of 34 sampled, identified as Lake 70 in the Ev-K2-CNR Cadastre. Resting eggs were present in the sediments. A list of species making up the zooplankton, together with some information on the hydrochemistry and climate of the region, is provided.     

Life history characteristics of Daphnia magna clones differing in phototactic behaviour

In an analysis of a life table experiment involving positively, intermediately and negatively phototactic Daphnia magna clones, life history traits such as the average duration of the adult instar, neonate and adult body size were found to be correlated with phototactic behaviour. The size of the eggs and neonates was positively correlated with adult body size, and with egg development time. Adult body size was positively correlated with the size of the second and subsequent clutches. I argue that the intrinsic positive correlation between offspring size and egg development time is a key factor structuring the differences in life history patterns observed between the positively and intermediately phototactic Daphnia genotypes, and that the two life history patterns are to be considered alternatives suited for different environmental conditions (e.g. habitats with and without strong predation pressure on adults).     

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.     

An analysis of the phototactic behaviour of Daphnia magna clones and their sexual descendants

Daphnia magna clones, isolated from different natural populations, were inbred and crossbred. Some aspects of the heredity of the phototactic behaviour, quantified by an index, were analysed. Heritability in the broad sense was determined for several assemblages of clones through calculation of the clonal repeatability. Heritability sensu strictu was determined by offspring-parent regressions. Frequency distributions of a phototactic index of several inbred and crossbred families are given.The results indicate a significant contribution of additive genetic variance to the total phenotypic variance. Comparison of heritability estimates suggests an important genetic interaction component.Some implications of these results on the variability of vertical migration patterns in natural populations are discussed.     

A contribution to the systematics of the Streptocephalidae (Branchiopoda: Anostraca)

While developing a data base for phylogenetic analysis of the New World streptocephalids we compaired them with species from Africa, Europe, and India. In doing this, we found that the morphology of the peduncle of the distal antennal outgrowth and the biramous ovaries developed in seven North American species can contribute to the systematics of the genus. Thus, our investigation consisted of (1) a review of the external morphology of the antenna, (2) biometry of selected parts of the antenna to obtain informative ratios, (3) a review of the presence or absence of genetal linguiform outgrowths, extension of the non-retractile parts of the penes, and general morphology of the cercopods, (4) a study of the location of the ovaries, and extension of the brood-pouch. On the basis of the results we classifyStreptocephalus into nine species groups. Five subgroups are identified within two of the species groups Several implications of the present approach are discussed.     

First record of the family Thamnocephalidae (Crustacea: Anostraca) from Southeast Asia and description of a new species of Branchinella

During a two-year investigation of freshwater microcrustaceans in Thailand, an undescribed species of fairy shrimp of the genus Branchinella Sayce, 1903 in the family Thamnocephalidae, was discovered. This is the first record of the genus and the family from Southeast Asia and the second anostracan reported from Thailand. The new species, Branchinella thailandensis n. sp. appears to be morphologically intermediate between B. kugenumaensis (Ishikawa, 1895) from Japan and east China, and B. madurai Raj, 1951 from India and Pakistan. B. thailandensis n. sp. was collected from several temporary ponds in 11 provinces of the northeast and the central Thailand, often co-occurring with Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, 2000.     

Sensorimotor transformation from light reception to phototactic behavior inDrosophila larvae (Diptera: Drosophilidae)

In this paper we examine theDrosophila melanogaster larval response to light. We survey the morphology of the larval visual and motor systems in relation to larval locomotory behavior and phototaxis. In addition, this paper proposes a model of sensorimotor transformation and examines the reversal in taxis occurring at theD. melanogaster larval wnadering stage.     

Notes on a fairy shrimp,Eubranchipus uchidai (Kikuchi) (Anostraca), from Japan

The female of Eubranchipus uchidai (Kikucki) is described and compared to several congeneric species. Notes on its habitat are given.     

Distribution and morphological variation of Streptocephalus torvicornis (Waga, 1842) in Northern Africa

The known range of S. torvicornis is extended to areas of the Western and Central Sahara and Sahel. Morphological variation between populations is important, and cannot be accomodated within the known Iberian and Maghrebian subspecific taxa, which appear untenable. A grouping of populations according to drainage basins appears, however, possible. Populations of the Hoggar, Air, and Tibesti waters, draining towards the Soudanian zone, are more closely related than populations from waters draining towards the Atlantic. Tassili-n-ajjer populations from Central Algeria have individual characteristics, and deserve further study.