Life cycle of Boeckella poppei Mrazek and Branchinecta gaini Daday (King George Island, South Shetlands)

In Lake Wujka, a shallow, polymictic Antarctic lake situated at 15 m from the seashore, several yearly cohorts occur of the copepod Boeckella poppei and one of the fairy shrimp Branchinecta gaini. There is circumstantial evidence that the two species compete for food, and perhaps adult fairy shrimp feed on the nauplii of the copepod. Both species are positively influenced by a measure of salinity. However, when autumn storms massively sweep seawater into the lake, all fairy shrimp are wiped out; no hatching occurs until next spring. In B. poppei, some nauplii and copepodites survive or hatch after the salt flows out of the lake. This is an advantage to the copepod that may balance its coexistence with the shrimp. Its cycle is, however, aborted by the freezing of the lake. In contrast to many other Antarctic lakes, the life cycle of the crustaceans is therefore controlled by salinity rather than freezing.     

The brine shrimp Artemia sp. as alternative prey for rearing the predatory bug Macrolophus caliginosus

The predatory bug Macrolophus caliginosus, which is widely used in greenhouse crops, is limited in its application by its high price. An important factor in the cost is the high price of Ephestia kuehniella eggs, the prey used in their mass rearing. In order to reduce their price, alternatives to moth eggs are currently being investigated. The brine shrimp Artemia sp. is produced in large quantities in saline lakes and is fed as live food source to the larvae of a variety of marine and freshwater organisms. In this study, we tested Artemia sp. as prey for rearing M. caliginosus from two strains. We evaluated developmental and reproduction parameters of the predator when fed nauplii, enriched nauplii with a fatty acid, dry cysts and hydrated cysts, and were compared with those obtained when the predator was fed with E. kuehniella eggs. Nauplii had a significant reduction in survivorship, a delay in development of nymphs and a low reproduction of adults. Nauplii enriched with docosahexaenoic acid (DHA, 22:6n − 3), a common practice for larviculture of some marine fish species, resulted toxic to M. caliginosus nymphs and survival was quite low. On the contrary, either dry or hydrated cysts from the two strains tested of the brine shrimp produced the same nymphal survivorship, nymphal development time and weight and fecundity of adults as those obtained with E. kuehniella eggs. Demographic parameters of the eighth generation of the predator reared with cysts of the two strains, either dry or hydrated, were as good as those of moth eggs. We concluded that Artemia sp. cysts were a good substitution prey for the mass rearing of M. caliginosus.     

Early release of eggs and embryos in a brooding ancient asexual ostracod: brood selection or a gambling strategy to increase fecundity?

Asexual lineages lack the means to purge their genomes of (deleterious) mutations through recombination. Evolutionary theory thus predicts that such lineages will be prone to early extinction. In brooding animals, brood selection might provide a mechanism to counter the accumulation of mutations. Of the three putative ancient asexual animal groups, only the darwinulid ostracods are brooders. Here, we test the incidence of egg and juvenile abortion in a darwinulid species, Penthesilenula brasiliensis, under two temperature treatments. Part of the offspring is released without brooding (close to 30% in one treatment). The majority of these aborted eggs hatches and develops. As it is unlikely that females are such bad judges of offspring quality, either the surviving animals will present deficiencies later on in development (brood selection) or early egg release can be a (bet-hedging) strategy to increase fecundity in favourable conditions.     

The adaptive significance of an environmentally-cued developmental switch in an anuran tadpole

Summary This study investigated the proximate basis of bimodally-distributed, environmentally-induced variation that occurs in natural populations of spade-foot toad tadpoles (Scaphiopus multiplicatus). Most individuals in most populations occur as a small, slowly-developing omnivore morph. In some of these same populations, a varying number of individuals occur as a large, rapidly-developing carnivore morph (Pfennig 1989). Censuses of 37 different natural ponds revealed that the frequency of the faster-developing carnivore morph correlated significantly positively with fairy shrimp density (their chief prey) and pond drying rate. By simultaneously varying two diet components and pond drying regime in artificial pools I found that only fairy shrimp density significantly affected the proportion of carnivores. Separate experiments established that the extent to which tadpoles developed the carnivore morphology correlated with shrimp density, and that morph determination depended on the ingestion of shrimp, not simply their presence. If a critical number of shrimp were ingested, the tadpole developed into a carnivore; if not, the tadpole developed by default into an omnivore. Thus a single cue — shrimp ingestion — triggers alternative ontogenetic trajectories. Using shrimp density to induce morph differentiation enables tadpoles to respond to their environment adaptively as shrimp are most abundant in highly ephemeral ponds, where the faster developing carnivores are favored.     

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.     

Cis-and all-trans-canthaxanthin levels in fairy shrimps

The carotenoid composition of cysts of seven species of fairy shrimps (Anostraca) was studied using high-performance liquid chromatography. Canthaxanthin was detected as the major pigment, but an important and often predominant fraction of it occurred in the cis-configuration, which is consistent with previous findings in Artemia cysts. Cis-canthaxanthin rapidly disappeared in nauplii of Thamnocephalus platyurus through conversion to all-trans-canthaxanthin and was preferably localized in the abdominal section carrying the genital segment of females, unlike in mature male animals. In contrast, the intense orange-red colour of the thoracopods and the cercopods in both sexes was only due to all-trans-canthaxanthin.     

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.     

Qualitative and quantitative changes in the carotenoids during development of the brine shrimp Artemia

In order to study the biological fate of all-trans- and cis-canthaxanthin in the brine shrimp Artemia, a quantitative method was developed for the determination of both carotenoids and their metabolic precursors in encysted embryos (cysts), nauplii, whole animals, organs, and subcellular fractions. This method is based on nonaqueous reversed-phase chromatography, two new exhaustive extraction procedures, and the determination of proteins in the extracted residue. Hydration of Artemia cysts caused a reversible conversion of part of the all-trans- to cis-canthaxanthin. During further pre-emergence embryonic development, there was little change in the levels of both isomers. After hatching of cysts, cis-canthaxanthin was progressively isomerized to the all-trans form, while the total (all-trans + cis) canthaxanthin to protein ratio tended to remain constant. Cis-canthaxanthin rapidly became undetectable in animals fed on algae and reappeared in females at an advanced stage of the reproductive cycle. All-trans-canthaxanthin remained present during the whole Artemia life cycle in addition to its metabolic precursors echinenone and beta-carotene. The carotenoid distribution in organs and subcellular fractions indicated high affinity of cis-canthaxanthin for the female reproductive system, oocytes in general, and yolk in particular. A role for cis-canthaxanthin is suggested at an early developmental stage, i.e., in cysts, before hatching.     

Palatability and fatality of the dinoflagellate <Emphasis Type="Italic">Prorocentrum lima</Emphasis> to <Emphasis Type="Italic">Artemia salina</Emphasis>

Prorocentrum lima is a toxic alga that produces both intra-cellular and extra-cellular toxins, including okadaic acid (OA) and dinophysistoxins (DTXs). Nauplii of the brine shrimp Artemia salina were exposed to both the cell and cell-free culture medium of P. lima in order to test the hypotheses that the extra-cellular medium is toxic to brine shrimp and that the P. lima cell is palatable but fatal to it. Artemia cysts incubated in the cell-free medium hatched, but mortalities were recorded for nauplii that hatched in, and metanuaplii exposed to, test solutions (autoclaved filtered seawater + cell-free medium) that contained at least 50% of the cell-free medium. Animals exposed to cells of P. lima readily fed on the cells. Some, especially among the Day 1 nauplii, ingested only one cell before dying, while others ingested more than one cell, up to six cells in the case of Day 3 nauplii, before dying. Day 3 nauplii were readily and heavily impacted by the P. lima cells. Survival analysis was used to evaluate survivorship of Day 1 to Day 3 nauplii exposed to cells of P. lima. Estimates were made of tD50s for the different age groups. Comparisons of the tD50s showed that the tD50s for Day 1 and Day 2 nauplii did not vary significantly, but they each varied significantly from the tD50 for the Day 3 nauplii. The possible ecological implications of the findings are discussed.     

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.     

Variability of <Emphasis Type="Italic">Artemia salina</Emphasis> cysts from Sabkhet El Adhibet (southeast Tunisia) with special regard to their use in aquaculture

Brine shrimp Artemia (Crustacea, Anostraca) diverge in biometry and nutritional quality. These differences in Artemia characteristics are significant not only from strain to strain but also from one harvest to another within same strain. The main objective of this study was to compare Artemia salina cysts harvested from Sabkhet El Adhibet (southeast Tunisia) on different dates between 2002 and 2007 with special regard to their use in aquaculture, using cysts and naupliar biometrics, protein, carbohydrate, and lipid content. Fatty acid profiles as well as hatching characterisation were also evaluated. Hydrated cysts measures ranged between 258.1 and 263.7 μm, while the freshly hatched nauplii of Artemia measures ranged between 458.1 and 476.1 μm. Lipid contents of the samples ranged from 16.2 to 18.3% of the dry weight. Fatty acid profiles showed that cysts from Sabkhet El Adhibet contain a high quantity of eicosapentaenoic acid (20: 5n-3) with a percentage ranging between 7.8 and 14.3% of the dry weight. The highest hatching efficiency was obtained for decapsulated cysts collected in 2007 (139500 nauplii g⁻¹ of cysts). Cysts treated with hydrogen peroxide had a hatching percentage of 14.49 to 42.99%. The hatching synchronization time for untreated cysts varied between 23.5 to 27.4 h.     

Larval rearing of chub, Leuciscus cephalus (L.), using decapsulated Artemia as direct food

Little is known about the larviculture of the chub, Leuciscus cephalus (L.), an endangered cyprinid species endemic to European flowing waters. The use of decapsulated Artemia cysts as food for chub larviculture was investigated. After 3‐day feeding with the rotifer Brachionus calyciflorus, the larvae were fed on different diets: (i) dried decapsulated Artemia cysts, (ii) Artemia nauplii, (iii) rotifers for seven more days and then Daphnia collected from a pond, and (iv) an artificial diet. After a 24‐day rearing period, the highest survival rate was obtained with the larvae receiving decapsulated Artemia cysts. Feeding of the larvae with an artificial diet resulted in a significantly lower survival rate compared with the other groups. At the end of the experiment, the larvae fed on Artemia nauplii yielded a significantly higher mean length compared with the other groups. Feeding an artificial diet resulted in a significantly lower average weight and mean length gain compared with the other groups.     

Evidence of a store of informational RNA in encysted embryos of Artemia salina

RNA prepared from dormant cysts and developmental stages of the brine shrimp Artemia salina stimulated the incorporation of ¹⁴C-leucine into polypeptide by a cell-free Escherichia coli system. Preparations from cysts were about as active as those from hatching embryos or nauplii. When analysed by density gradient centrifugation the activity of cyst RNA showed a heterodisperse distribution, not quantitatively related to the absorbance profile. These results and evidence from similar experiments with crude ribosome preparations indicated that the contribution of 18S and 28S ribosomal RNA to the template-like activity was fairly limited. The experiments suggest that RNA with latent messenger activity is present in Artemia cysts during the resting stage.     

Detection of Taura syndrome virus (TSV) strain differences using selected diagnostic methods: diagnostic implications in penaeid shrimp

Positive results were obtained with nested white spot syndrome virus (WSSV) diagnostic PCR performed on 5 commercial brands of dry-packed Artemia cysts using several WSSV genomic sequence-specific primers. In 2 brands, PCR and nucleotide sequence analysis found C-->T and C-->G point mutations in the pms 146 WSSV amplicon, but in all 5 brands, the nucleotide sequences that were successfully amplified by the rrl, rr2 and tk-tmk gene-specific primer sets were identical to those of Penaeus monodon WSSV. However, despite the inarguable presence of WSSV or WSSV-like template DNA, we were unable to detect WSSV by PCR in hatched nauplii derived from PCR-positive cysts or in P. monodon postlarvae fed Artemia nauplii hatched from such cysts. Most simply, these results suggested that the cysts were externally contaminated with WSSV or WSSV-like template material that was removed during hatching and washing of the nauplii. Given the small sequence variations found, it may also have been a variety of WSSV non-infectious for P. monodon or Artemia and derived from other crustaceans or arthropods in the Artemia environment. However, we could not establish this conclusively and a small possibility remained that the PCR template in these tests was derived from WSSV template present internally in the cysts and derived from infected Artemia adults. However small, this possibility must be vigorously tested, given the impact that a positive outcome could have on the shrimp industry.     

Artemia cysts as an alternative food for the predatory bug Macrolophus pygmaeus

The suitability of cysts of the brine shrimp Artemia sp. as a factitious food for the predator Macrolophus pygmaeus Rambur was investigated. The influence of decapsulation time and hydration of the cysts on the performance of the predator were studied in the absence of plant material. A longer time of decapsulation had a positive influence on the development of the predator. Hydration of cysts had a significant impact on nymphal survival when cysts where non‐decapsulated or poorly decapsulated. An experiment in which nymphs were switched from a diet of hydrated cysts to non‐hydrated cysts showed that in the absence of plant material the relative importance of hydrating the cysts decreased with nymphal age. Especially, the first instar and to a lesser extent the second instar appear to be susceptible to water shortage. Effects of prolonged rearing on development and reproduction on brine shrimp cysts from different origins were tested in the presence of plant material. Rearing M. pygmaeus on Artemia sp. (Jingyu Lake) cysts yielded similar survival, development, adult weight and fecundity in the fourth as in the second generation. In contrast, for Artemia franciscana cysts, an increase in nymphal development was notable. Biochemical analyses showed that total amino acid content and the concentration of the different amino acids did not differ among diets and generations. There were, however, differences in total fatty acid content between the different diets and generations and in the concentration of certain fatty acids, indicating that insects fed brine shrimp cysts may show nutritional deficiencies compared to those reared on a diet of Ephestia kuehniella eggs. Our results indicate that decapsulated brine shrimp cysts are an economically viable alternative food source in at least part of the rearing process for M. pygmaeus.     

Identification of co-occurring Branchinecta fairy shrimp species from encysted embryos using multiplex polymerase chain reaction

Morphological identification of many fairy shrimp species is difficult because distinguishing characters are restricted to adults. We developed two multiplex polymerase chain reaction assays that differentiate among three Branchinecta fairy shrimp with distributional overlap in southern California vernal pools. Two of the species are federally listed as threatened. Molecular identification of Branchinecta from cysts allows for species surveys to be conducted during the dry season, expanding the timeframe for population assessment and providing a less intrusive method of sampling sensitive vernal pool habitats.     

Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae

Feeding dried and vitamin C enriched decapsulated Artemia cysts to African catfish larvae increased their growth rate significantly after 6 days over those fed only freshly decapulated cysts. Groups fed with Artemia nauplii had a significantly higher growth during the experiment, although this difference was not considerably important in practice. Tank colour had no influence on growth. Because of their lower price, the decapsulation of lower quality cysts can be an appropriate feed source in intensive cultures of African catfish larvae.     

PLASTICITY OF JAW AND SKULL MORPHOLOGY IN THE NEOTROPICAL CICHLIDS GEOPHAGUS BRASILIENSIS AND G. STEINDACHNERI

I examined plasticity of jaw and skull morphology induced by feeding different diets in two species of the neotropical cichlid genus Geophagus. The two species possess different modes of development, which affect the size at which young begin feeding. I hypothesized that the difference in size at first feeding could lead to a difference in the amount of change inducible in the two species. The young of the substrate-spawning species, G. brasiliensis, which begin feeding at a smaller size, were predicted to be more plastic than those of the mouthbrooding species, G. steindachneri. The two diets used to induce differences were brine shrimp nauplii and chironomid larvae. Numerous measures of the jaw and skull differed significantly between groups fed the two diets but the amount of plasticity induced was small and would not present a problem for taxonomists. Contrary to my prediction, both the magnitude and pattern of plasticity induced in the two species was similar. Thus, mode of parental care and the size at which young begin feeding do not affect the degree of plasticity. Fish fed brine shrimp nauplii were longer in oral jaw region, but were shorter and shallower in the area behind the oral jaws. An additional group of G. brasiliensis was fed flake food to compare the results of this study to other studies. The differences in measures between fish fed brine shrimp diets and flake food diets were greater than those between fish fed brine shrimp and chironomid larvae. A possible role of plasticity for enhancing rather than retarding morphological evolution is discussed.     

Inbred strains of brine shrimp derived from Artemia franciscana: lineage, RAPD analysis, life span, reproductive traits and mode, adaptation, and tolerance to salinity changes

Inbred strains of the brine shrimp were developed from dry dormant cysts of wild-type Artemia franciscana produced in the Great Salt Lake, U.S.A. The established strains were named GSL2, 4, and 7. They were raised in 2% natural sea salt solution at 28 degrees C under a long-day condition, and fed on food sold for Artemia. Ovoviviparous offspring (free-swimming nauplii) in each brood derived from full sib (sister x brother) matings were used for succeeding generations. The ordinal number of the filial generation increased at a rate of ten generations per year. The number was over 60, and the lineage was recorded. Random amplified polymorphic DNA (RAPD) analyses of the inbred strains revealed the uniqueness, homogeneity, and genetic similarity among them. Their life span, the time required to become sexually mature, brood size, mode of reproduction, and adaptation and tolerance to salinity changes were investigated. The inbred strains usually released free-swimming nauplii rather than spawning encysted gastrulae (dormant cysts). On the other hand, the opposite results were obtained from wild-type Artemia under the same conditions. Both adults and nauplii of the inbred strains appeared to be less adaptive and less tolerant to salinity changes compared to those of the wild type. The established inbred strains should provide a wider and deeper scope for Artemia biology in particular, and the life sciences in general.     

Performance of WSSV-infected and WSSV-negative Penaeus monodon postlarvae in culture ponds.

In a survey of 27 Penaeus monodon culture ponds stocked with postlarvae (approximately PL10) at medium density (approximately 40 shrimp m(-2)), single-step nested white spot syndrome virus (WSSV) PCR was used to measure the WSSV infection rates in the shrimp populations within 1 mo after stocking. Seven ponds were initially WSSV-free, and the shrimp in 5 of these were harvested successfully. In the ponds (n = 6) where detection rates were higher than 50%, mass mortality occurred during the growth period, and none of these ponds was harvested successfully. In a subsequent study, P. monodon brooders were classified into 3 groups according to their WSSV infection status before and after spawning: brooders that were WSSV-positive before spawning were assigned to group A; spawners that became WSSV-positive only after spawning were assigned to group B; and group C consisted of brooders that were still WSSV-negative after spawning. WSSV screening showed that 75, 44 and 14%, respectively, of group A, B and C brooders produced nauplii that were WSSV-positive. Most (57%; 16/28) of the brooders in group A produced nauplii in which the WSSV prevalence was high (>50%).When a pond was stocked with high-prevalence nauplii from 1 of these group A brooders, an outbreak of white spot syndrome occurred within 3 wk and only approximately 20% of the initial population survived through to harvest (after 174 d). By contrast, 2 other ponds stocked with low-prevalence and WSSV-negative nauplii (derived respectively from 2 brooders in group B), both had much higher survival rates (70 to 80%) and yielded much larger (approximately 3x by weight) total harvests. We conclude that testing the nauplii is an effective and practical screening strategy for commercially cultured P. monodon.