B-chromosomes and male-biased sex ratio with paternal inheritance in the fairy shrimp Branchipus schaefferi (Crustacea, Anostraca)

This study reports on male-biased sex ratios in west Mediterranean populations of the freshwater anostracan Branchipus schaefferi (Crustacea, Anostraca, Branchipodidae), in contrast to populations elsewhere. Crossing experiments over several generations indicate a clear paternal inheritance of the trait, possibly with a dosage effect. Various mechanisms which may underlie this phenomenon are discussed, the most plausible being the presence of one or more supernumerary ('B') chromosomes--as evidenced by karyological observations--interfering with sex determination and probably having an accumulation mechanism in male individuals.     

Respiration of Streptocephalus dichotomus Baird (Crustacea : Anostraca)

Summary The Rate-temperature (R-T) curve for S. dichotomus tends to reach a peak at 30°C in both sexes in all the weight groups. As the temperature increases above 30°C the metabolic rate decreases considerably.The proportionate weight specific rate of oxygen uptake is the same for all sizes.There is no significance in the relationship between oxygen lethal levels and body weight.This work formed part of the thesis submitted for the award of the Degree of Doctor of Philosophy to the University of Madras, in 1970.     

Nitrogen excretion in Streptocephalus Dichotomus Baird (Crustacea: Anostraca)

Summary The total nitrogen excreted by Streptocephalus dichotomus is 1.5177 mg/g/day for males and 1.3875 mg/g/day for females at 30°C.The main excretory product of S. dichotomus is ammonia (75.3%). The rate of excretion of ammonia increased with increase in temperature up to 30°C and at 33°C it decreased.Analyses of covariance revealed that the F ratios are not significant in the case of rate of total nitrogen excretion between the two sexes at 30°C and in the case of rate of ammonia excretion between the two sexes or when comparison is made within the sexes at the different temperatures between 20° and 30°C.This work formed part of the thesis submitted to the University of Madras for the award of the Degree of Doctor of Philosophy in 1970.     

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.     

Molar surface morphology in Streptocephalus coomansi (Crustacea: Branchiopoda: Anostraca)

Except for the posterio-dorsal margin, the circumference of the molar surface exhibits flagellated processes which become simple at the posterioventral margin. Four topographic regions are distinguished: (A) a posterodorsal region, (B) a peripheral region, (C) a transitional zone, and (D) a central region. The postero-dorsal region of the left mandible has one row of widely spaced, stout, conical teeth, while in the right mandible two rows of slender teeth, which become multi-branched anteriorly, are present. The peripheral molar region stretches between the bordering flagellated processes and the central region and consists of several parallel, dorso-ventral rows of armed teeth. The maximum number of teeth in one dorso-ventral row is higher at the ventral than at the dorsal side and in the left than in the right mandible. In the transitional zone, the number of cusps on each tooth is progressively reduced. The central region, a perforated thickened cuticular plate, extends over the majority of the molar surface. This region is unique among the anostracans studied in this respect and may reflect a different feeding ecology. The strongly diversified molar surface probably allows the species to exploit a wide trophic spectrum. It remains to be tested if these observations may be extrapolated to the entire genus. © 1994 Wiley-Liss, Inc.     

Causes of a non-random pairing by size in the brine shrimp,Artemia salina: (Crustacea: Anostraca)

Summary Brine shrimp (Artemia salina) males and females entered precopula assortatively by size in the laboratory; large males also had a pairing advantage over smaller males. We investigated the causes of such nonrandom pairing to test hypotheses on size-assortative mating.We found precopulatory biases with respect to male size in the absence of direct competition among males (which produces pairing biases in other species). Large males encountered females significantly more often than did small males. Similarly, large females encountered males more often than did small females, but showed less willingness than small females to enter precopula when housed with small males. Consequently, large females took longer than small females to enter precopula with small males. Although large males entered precopula readily with small females, such size-mismatched pairs appeared short-lived.We conclude that non-random pairing by size in A. salina is determined by several factors including: encounter rates between males and females of different sizes, female behavior, and time following initial pair formation. Our results are likely applicable to other species and can help explain variation for selection on size or other traits.     

Hatching and Postembryonic Development of Streptocephalus Dichotomus Baird (Crustacea : Anostraca)

Summary Hatching and postembryonic development of Streptocephalus dichotomus have been studied. Only dried eggs hatched in the laboratory. Hatching is influenced by desiccation and temperature. Drying for 10 or 20 days and temperature of 30° C seem to be favourable for S. dichotomus eggs to hatch. In S. dichotomus immersion in water up to 120 cm depth has no effect on hatching.Fifteen larval stages are involved in postembryonic development and sex differentiation appears at the eighth larval stages and becomes more pronounced in later stages. S. dichotomus takes 28 days to attain its adult structure in the laboratory at room temperature.This work formed part of the thesis submitted to the University of Madras for the award of the Degree of Doctor of Philosophy in 1970.     

On the cavity receptor organ (X-organ or organ of Bellonci) of Artemia salina (Crustacea: Anostraca)

Summary The cavity receptor organ (previously X-organ or organ of Bellonci) of Artemia salina consists of ciliated neurons whose cilia protrude into a cavity beneath the cuticle. The neuronal dendrites penetrate a giant accompanying cell and epidermal cells before entering the cavity. The cavity beneath the cuticle, the ciliated neurons and the connexion with the medulla terminalis justifies a homologization with the frontal filament organ of cirripeds and the third unit of copepods. The term cavity receptor is suggested for this organ. It is hardly homologous with the second unit of copepods and the organs described for many malacostracans under the names of sensory pore X-organ or organ of Bellonci. The latter organs are very similar to the cavity receptor but have an internal cavity formed by glial cells.The cavity receptor organ was previously considered neurosecretory but in the light of the present knowledge it is rather sensory although a double function cannot be denied.This investigation was supported by grants (to R. E.) 2760-3 and 2760-4 from the Swedish Natural Science Research Council. One of us (P. S. L.) was on sabbatical leave from the University of Tasmania.     

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.     

Review of the biogeography of the genus Artemia (Crustacea, Anostraca)

In this study, we report on the known Artemia habitats worldwide. Recent literature information is incorporated about the taxonomic status of the various populations studied. The genus is composed of di-, tri-, tetra- and pentaploid parthenogenetic populations and of the following bisexual species: A. franciscana franciscana , A. franciscana monica , A. franciscana sp., A. persimilis , A. salina , A. urmiana , A. sinica and A. sp. from Kazakhstan. The problems of characterizing new brine shrimp populations are discussed. In view of the great importance of Artemia as part of the live food chain for the culture of fish and shellfish larvae and the present cyst shortage from the market, the need for commercial exploitation and development of new Artemia sources is now, more than ever, necessary.     

A Possible Extra-Ovarian Site for Synthesis of Lipovitellin During Vitellogenesis in Artemia sp. (Crustacea; Anostraca)

Summary

Lipovitellin samples, extracted from yolk platelets of cysts, were applied to SDS-PAGE. A female specific antiserum was raised against the high molecular weight apoprotein lipovitellin alpha-1 (LV-α1) of the lipovitellin complex. This anti-LV-α1 was used in the peroxidase-anti-peroxidase staining method with frontal paraffin sections (of 4μm) of whole embedded Artemia. Females were studied during a complete vitellogenic cycle. The presence of exogenous yolk precursors in the fat storage cells of the thoracopods of female Artemia was demonstrated. The amount of the female specific yolk polypeptides and the number of positively stained cells changes during the vitellogenic cycle. In vitro experiments with ³⁵S-radiolabelled methionine show the synthesis of lipovitellin-like substances in the fat storage cells of vitellogenic females.     

Some notes on the ecology of a GermanBranchipus schaefferi population (Crustacea: Anostraca)

Habitat preference, seasonal occurrence, starvation resistance, hatching eggs ofBranchipus schaefferi, and effects of predation onB. schaefferi were studied.Branchipus was only present in turbid, unvegetated ponds and absent in ponds which contain higher aquatic vegetation and theSpirogyra sp. The first individuals ofB. schaefferi appeared in April when water temperature was 10 °C and the last adults in November at a water temperature of 3.5 °C. Up to 6 reproducing generations were observed during this period. Abundance ofB. schaefferi was higher in temporary ponds than in permanent ponds. Sex ratio was close to unity for most of the year. Body size ofB. schaefferi males and females was significantly positively correlated with pond volume. Without foodB. schaefferi could survive for 1.5 to 2 days at 20 °C and 4 to 5 days at 10 °C. Hatching success of eggs decreased when eggs were dried for 7 months. Freezing of eggs had no effect on hatching success. From] the predators tested,Chaoborus sp. larvae clearly selected smallB. schaefferi; one consumed approximately 6Branchipus d–1 at a density of 6 to 12 prey 1–1. The other predators, dragonfly larvae, and larvae and adults ofTriturus alpestris selected alternative prey types, for exampleTubifex sp. and ostracods.     

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 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.     

Uptake of lead,cadmium and zinc by the fairy shrimp,Branchinecta longiantenna (Crustacea: Anostraca)

Individuals of the fairy shrimp, Branchinecta longiantenna, were subjected to 5 concentrations (0.1 to 15 mg l^–1) of Pb in diluted habitat water at 13 °C. Lead concentrations (mg kg^–1 wet weight) in the animals were determined at 2-day intervals by digestion in nitric acid followed by atomic absorption analysis. The shrimp were also subjected to 0.1 mg l^–1 media of Cd and Zn, separately.Uptake rates by the fairy shrimp for the three metal ions at 0.1 mg l^–1 were: 0.111, 0.0885, and 0.0460 mg kg^–1 day^–1 for Zn, Pb, and Cd, respectively. After 2 days in 1.0 mg l^–1 Cd or Zn, the animals expired; but they surviced for 8 days in a 10 mg l^–1 Pb medium and for 2 days in 25 mg l^–1 Pb. Lead uptake demonstrated a linear dependence on the Pb concentration in the media.Shrimp survived at much higher tissue accumulations of Pb compared to Zn and Cd. Estimated lethal doses were 20, 1.2–2.4, and 0.4–1.4 mg kg^–1 wet weight for Pb, Zn, and Cd, respectively. Pb was found to be at much lower concentration than Cd or Zn in the natural pond water but between Cd and Zn levels in the sediment. Thus Cd and Zn probably present a greater threat to B. longiantenna than Pb, although Pb may be in higher concentration in the environment.Contribution 47, Laboratory of Ecology, The Claremont Colleges, Claremont, CA 91711, USA. Send reprint requests to Clyde Eriksen.     

Branchipus cortesi n. sp.: a new anostracan from western Spain (Crustacea,Branchiopoda)

Branchipus cortesi, n. sp. (Anostraca, Branchipodidae) is characterized by the broadly enlarged distal segments of male antenna 2, and a combination of morphological features concerning thoracic limbs, abdominal segments and egg morphology. The species occurs in temporary fresh water bodies in flatlands with temperate Mediterranean climate; it is distributed in the south-western part of Spain. Our study includes a morphological analysis using optical and scanning electronic microscopes. Questions about ecology and distribution of the new species are also discussed.     

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.