Heart ultrastructure in Branchinecta paludosa,Artemia salina,Branchipus schaefferi,and Streptocephalus sp. (Crustacea,Anostraca)

Summary The heart ultrastructure of the anostracan Crustacea Branchinecta paludosa, Artemia salina, Branchipus schaefferi, and Streptocephalus sp. is essentially similar. All lack an endocardium and an epicardium, and the heart wall consists of a single layered myocardium. Only in the posterior end of the heart does the myocardium form a tube. In the remaining, anterior part of the heart, the myocardium forms a trough. The dorsal edges of this trough are firmly attached to the basement membrane of the epidermis, which thus forms the lid of the trough.The Z-bands of the sarcomere are diffuse, and H- and M-bands were not seen. Interior couplings are as a rule found at Z-levels.This work was supported by grants from the Norwegian Research Council for Science and the Humanities     

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.     

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.     

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.     

The life history of Chirocephalus kerkyrensis Pesta (Crustacea: Anostraca) in temporary waters of Circeo National Park (Latium,Italy)

The life cycle of Chirocephalus kerkyrensis, a typicalspecies of the Mediterranean plain forest, was studied in thefield during 1990/91 and 1991/92.Temperature, and its variation, was the major factor affectinglife history. Marked, sudden temperature fluctuations resultedin depressed growth and longevity. Fertility was positivelycorrelated (P<0.001) with female body length. Nodecline in egg production was observed at the end of life, incontrast to other species. Hatching was observed after a longdrought followed by alternating wet and dry phases. Laboratorytests on hatching gave contrasting results and showed thatdrying is not obligatory. Cysts stored in 100% relativehumidity gave higher numbers of nauplii after a shorter timethan dried ones, at all temperatures tested.     

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.     

Genetic characterization of Artemia tibetiana (Crustacea: Anostraca)

The brine shrimp Artemia consists of a number of bisexual species and a large number of parthenogenetic forms, which collectively, inhabit a wide range of hypersaline habitats. A recently described species (A. tibetiana) from a carbonate lake (Lagkor Co) in Tibet at an altitude of 4490 m has been tested with New World (A. franciscana USA, and A. franciscana feral population Vietnam) and Old World species (A. salina, A. urmiana, A. sinica) for cross fertility. These tests show complete infertility between A. tibetiana and A. franciscana . Between A. tibetiana and A. urmiana, A. sinica partial fertility through to F₂ and F₃ generations is evident. Allozyme and RAPD comparison of A. tibetiana with A. franciscana (USA), A. franciscana (Vietnam), A. sinica (Mongolia) and A. urmiana (Iran) show that A. tibetiana is similar to other bisexual species in mean heterozygosity (0.074) but has a somewhat higher proportion of polymorphic loci (40%, similar to that of A. urmiana ). The genetic distance between A. tibetiana and A. franciscana is 0.730, between A. tibetiana and A. urmiana is 0.475 and that between A. tibetiana and A. sinica is 0.114. F_IS estimates for A. tibetiana differ significantly from zero for six loci, mainly because of lack of fit to Hardy-Weinberg expectations. This may suggest that even within the limited area of Lagkor Co there are Genétically distinct populations. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 333–344.     

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.     

Evaluation of the fatty acid profiles of two fairy shrimp species,Branchipus pasai Cottarelli, 1969 and Chirocephalus kerkyrensis Pesta, 1936 (Crustacea,Anostraca) fed different diets

Laboratory cultured fairy shrimps Branchipus pasai and Chirocephalus kerkyrensis, fed on an alga (Selenastrum capricornutum), a yeast (Saccharomyces cerevisiae) and an HUFA enriched yeast (Lansy PZ, produced by Artemia Systems, Gent, Belgium) were evaluated for their fatty acid (FA) profiles and total lipid content in order to obtain information on species differences in food conversion. The results indicate significant qualitative and quantitative differences (P < 0.001) in FA profiles both of feed and of fairy shrimp species. Among the three different diets, an appreciable lipid amount was recorded in the alga, as compared with baker‘s yeast which showed the poorest lipid content. The algal fatty acid profile showed adequate amounts of the EFA 18:2n6, 18:3n3 and20:5n3 (the most meaningful for aquacultural purposes). The enriched yeast was characterised by a considerable total lipid amount and by the presence of all the EFA. The overall amounts of fatty acids in the fairy shrimps correlated well with their levels in the feed(r > 0.9, P <0.001). An exception was noted in then-3 HUFA (highly unsaturated fatty acids) and n-6acids, among the individuals fed on yeast. Highly significant differences (P < 0.001) were also noted between the two fairy shrimp species fed on the same food type. When fed enriched yeast, both B. pasai and C. kerkyrensis profiles roughly reflected diet composition. However, when fed on algae or baker‘s yeast, the two species, though to different extents, exhibited higher EFA levels than those recorded in the food. This seems to support the existence of a partial FA bioconversion capacity in fairy shrimps previously noted in the case of the brine shrimp Artemia. This revised version was published online in August 2006 with corrections to the Cover Date.     

SEM morphological observations on Artemiopsis stefanssoni Johansen, 1921 (Crustacea, Anostraca)

The morphology of the female ovisac of the fairy shrimp Artemiopsis stefanssoni Johansen, 1921, is analysed by SEM. SEM observations reveal the existence of a genital opening located ventrally, but anterior to the area where the genital pore is normally situated. Ornamented frontal knobs resembling those on the second antennae of males of Artemia were also found in Artemiopsismales, and account for its particular mating behaviour.     

Effect of vertebrate and invertebrate kairomones on the life history of Daphnia magna Straus (Crustacea: Branchiopoda)

The history of selection of Daphnia magna populations living in North African temporary ponds may differ from populations inhabiting permanent ponds. Laboratory experiments were conducted to examine the effect of fish Gambusia holbrooki and invertebrate Notonecta glauca kairomones on the life history traits of the freshwater Cladocera Daphnia magna Straus. With fish kairomones, Daphnia reproduced early and had a significantly smaller size at first reproduction (SFR) and a smaller size of neonates compared to control. In contrast, daphnids reared in water treated with Notonecta glauca had no effect on the age at first reproduction but females were also smaller and produced smaller neonates.     

The life history of Trichoniscus pusillus pusillus (Crustacea: Isopoda)

The methods are given which were used to determine the number of stages in the life history of Trichoniscus pusillus pusillus Brandt, 1833 and the stages are described as far as possible. Not all stadia can be separated on morphological grounds and animals extracted from monthly litter samples were measured and the stadia separated by use of probability paper. This method proved quite successful and confirmed the characterization of the three earlier juvenile stadia on morpholigical grounds and the number of the later juvenile stadia determined from laboratory cultures. There are six juvenile and five adult stadia.     

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.     

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.     

Food,feeding and digestion in streptocephalus dichotomus baird (Crustacea: Anostraca)

Summary Gut analysis of Streptocephalus dichotomus revealed that the main source of food is phytoplankton. S. dichotomus is a non-selective filter feeder, taking in all the food-items carried in the feeding currents and passed through the midventral groove. The feeding currents are produced by the thoracic limbs.Feeding experiments have shown that the time taken for the passage of food is directly proportional to the number of days of starvation. Food intake of males did not significantly differ from that of females when fresh animals were used, as well as animals used after one day of starvation.Fresh males as well as females took in significantly more food than starved animals.The digestive enzymes such as carbohydrases, proteases and lipases are present in the gut. The optimal pH for amylase ranged between, 5.8 to 6.6, for protease 7.4 to 8.0 and for lipase 5.2 to 6.5.This work formed a part of the thesis submitted to the University of Madras, in 1970 for the award of the Degree of Doctor of Philosophy.     

The life history and culturing of Xestoleberis hanaii (Crustacea,Ostracoda)

Xestoleberis hanaii Ishizaki, 1968 is one of the most abundant species on the Japanese coast and can be collected in all seasons from intertidal calcareous algae on rocky shores. Several characteristics make this species a suitable `experimental animal' in the laboratory: (1) adaptability to artificial environments (room temperature, petri dish, artificial seawater, single cultured food-type), (2) high fertility (active copulatory behaviour, egg brooding within the carapace, high egg productivity) and (3) rapid growth rate. Females mate after the final moult (when the reach sexual maturity); oviposition of fertilized eggs takes place over a period of four days after the final moult. Eggs (about 40 in total) are laid a few at a time in the postero-dorsal brood space of the carapace; they hatch in about 9 d as A-7 instars which are then discharged from the brood space within a day or two. Seven moults take place within the next approx. 33 (female) or 39 (male) days to reach adulthood. Adult females live for about 18 weeks and may repeat the reproductive cycle three times; adult males live for about 14 weeks.     

The energy balance of the Australian brine shrimp, Parartemia zietziana (Crustacea : Anostraca)

SUMMARY. Assimilation budgets (i.e. assimilation = respiration + excretion + production) are presented for cohorts of P. zietziana in two salt lakes. Shrimps in Pink Lake had an assimilation rate of 1631.6 kJ m⁻² year ⁻¹, those in Lake Cundare 212.1 kJ m⁻² year⁻¹. In both lakes, respiration accounted for 60–80% of assimilation. Assimilation rates for individuals (derived as assimilation = ingestion minus faecal output) are also given and compared with respiratory rates of individuals. The comparisons indicated that energy was often consumed at a higher rate by respiration than it could be supplied by assimilation. Starvation due to a low assimilation efficiency was suggested as a cause of the consistent mortality, variable growth rate of individuals and unpredictable recruitment which were characteristic of the cohorts of P. zietziana in both lakes. An analysis of mortality showed that the young had the poorest survival, as predicted by a theoretical model of a starving zooplankter and a comparison of the increase with weight of ingestion and respiration. Gross growth efficiency (production: assimilation) was 15–30%, about the same as published data on Anostracans. Net growth efficiency (production : consumption) was 5–12% and generally lower than published values reflecting the difficulty P. zietziana has in balancing its budget.     

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.