Cyst Hatching Research Articles

Microencapsulation of sunscreen reduces toxicity of its components to A. salina: Biochemical, behavioral and morphological studies

Sunscreens contain several substances that cause damage to species where they are disposed. New formulations have been created to prevent such marine environmental damages. One promising formulation is the microencapsulated sunscreen. The objective of this study was to evaluate the possible safety to marine environment of one microencapsulated sunscreen formulation. The animal model Artemia salina (cists and nauplii) was tested with two sunscreen formulations (microencapsulated and non-microencapsulated) and toxicological, behavioral, morphological parameters as well as biochemical assays (lipoperoxidation and carbonylation tests) were analyzed. Results showed that microencapsulated sunscreen impeded some toxic effects caused by the release of the substances within the microcapsule in the highest concentration, reestablishing the mortality and hatching rates to control levels, while removing the sunscreen microcapsule by adding 1 % DMSO reduced the cyst hatching rate, increasing the nauplii mortality rate and decreased locomotor activity in higher concentrations. Finally, nauplii with 24 hours of life and exposed to sunscreen without the microcapsule showed an increase in mitochondrial activity (assessed at 48 hours after exposure) and presented malformations when exposed to the highest concentration non-microencapsulated concentration (assessed by SEM at 72 hours after exposure), when compared to the control group. These results together allow us to conclude that the microencapsulation process of a sunscreen helps protecting A. salina from the harmful effects of higher concentrations of said sunscreens. However, long-term studies must be carried out as it is not known how long a microencapsulated sunscreen can remain in the environment without causing harmful effects to the marine ecosystem and becoming an ecologically relevant pollutant.

Comparative Microbiome Analysis of Artemia spp. and Potential Role of Microbiotain Cyst Hatching.

Brine shrimp (Artemia spp.) is a significant factor in determining aquaculture production. Since the microbiota of Artemia can colonize the gut in larvae, various microorganisms transmitted from Artemia can affect host larval health. Although the microbiota composition of Artemia would be essential in determining aquaculture productivity, our understanding on microbiome of Artemia is still insufficient. Through our study, we identified the species of Artemia cysts supplied by three different manufacturers (P1, P2, and P3) with investigation of size and hatching efficiency. The species of Artemia from P1 was identified as A. tibetiana, and P2 and P3 was A. franciscana. A. tibetiana hatched from the P1 cysts had the largest body size with the lowest hatching rate. Furthermore, we conducted a comprehensive analysis of the microbiome present in the rearing water and the nauplius whole body from each product. We observed specific microbiota compositions, both beneficial and harmful, depending on the product types and the sample types. Additionally, we found that the microbiota composition in the rearing water was associated with the manufacturing environment, while the compositions in the nauplius whole body were species-specific. Notably, we discovered that an extract containing microbiota from the nauplius sample of P3 increased the hatching rate of A. tibetiana, indicating a positive role in Artemia culture. These findings demonstrate that the microbial communities present in Artemia vary according to the product and/or species, underscoring their significance in aquaculture production.

Mercury chloride toxicity attenuation of the Brine Shrimp Artemia Salina after treatment with Mercurius corrosivus as isotherapic


 Isotherapics prepared from toxic substances have been described as attenuation factors for heavy metal intoxication in aquatic animals. Herein, Artemia salina and mercury chloride were used as a model to identify treatment-related bioresilience. The aim was to describe the effects of Mercurius corrosivus (MC) in different potencies on Artemia salina cyst hatching and on mercury bioavailability. Artemia salina cysts were exposed to 5.0 µg/mL of mercury chloride during the hatching phase. MC 6cH, 30cH, and 200cH were prepared and poured into artificial seawater. Different controls were used (nonchallenged cysts and challenged cysts treated with water, succussed water, and Ethilicum 1cH). Four series of nine experiments were performed for 4 weeks to evaluate the percentage of cyst hatching considering all moon phases. Soluble total mercury (THg) levels and precipitated mercury content were also evaluated. Solvatochromic dyes were used to check for eventual physicochemical markers of MC biological activity. Two-way analysis of variance (ANOVA) with mixed models was used for evaluating the effect of different treatments and the simultaneous influence of the moon phases on the cysts hatching rate, at both observation times (24 and 48 hours). When necessary, outliers were removed, using the Tukey criterion. The level of significance α was set at 5%. Significant delay (p<0.0001) in cyst hatching was observed after treatment with MC 30cH, compared with the controls. An increase in THg concentration in seawater (p<0.0018) and of chlorine/oxygen ratio (p<0.0001) in suspended micro-aggregates was also seen, with possible relation with mercury bioavailability. Specific interaction of MC 30cH with the solvatochromic dye ET33 (p<0.0017) was found. The other observed potencies of Mercurius corrosivus 6 and 200 cH were not significant in relation to the observed groups. The results were postulated as being protective effects of MC 30cH on Artemia salina, by improving its bioresilience.

Analyses of biosynthesized silver nanoparticles produced from strawberry fruit pomace extracts in terms of biocompatibility, cytotoxicity, antioxidant ability, photodegradation, and in-silico studies

Numerous disciplines, including biology and materials science, are using nanoparticle engineering. Silver nanoparticles (AgNPs) are produced from strawberry pomace extracts using cutting-edge technology. Biosynthesized nanoparticles were examined for their formation, shape, crystallinity, and size at the nanoscale using a variety of spectral techniques, such as UV-vis absorption spectra, X-raypowder diffraction (XRD), scanning, transmission electron microscopy (SEM/TEM), and their associated techniques like energy-dispersive X-ray (EDX or EDS), and selective area electron diffraction (SAED). AgNPs formation was observed by the surface plasmon resonance (SPR) observation at 431 nm, which was caused by the collective oscillation of the silver nanoparticles' free electrons. AgNPs were confirmed by EDX, showing a distribution of elements and having a distinct peak at 3.0 keV. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability of NPs in a nitrogen atmosphere.Spectrophotometry was utilized to investigate the photocatalytic degradation of methyl orange employing biogenic NPs as nanocatalysts. The solution's decolonization revealed that the dye degrades gradually with longer exposure times. Antioxidant capability was evaluated using the stable free radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH). Additionally, testing for biocompatibility and toxicity employing brine shrimps and red blood cells, respectively, revealed remarkable hemocompatibility with RBCs and no observable toxicity to brine shrimps at lower AgNPs concentrations. Additionally, the active amino acids involved in brine shrimp egg hatching were identified using molecular docking of silver nanoparticles against serine protease. Moreover, to look into non-bonding interactions with the amino acids of the enzyme that can inhibit cyst hatching and healthy growth of brine shrimp napuli.

Bioresilience to Mercury Chloride of the Brine Shrimp Artemia Salina after Treatment with Homeopathic Mercurius Corrosivus.

Finding solutions to mitigate the impact of pollution on living systems is a matter of great interest. Homeopathic preparations of toxic substances have been described in the literature as attenuation factors for intoxication. Herein, an experimental study using Artemia salina and mercury chloride was developed as a model to identify aspects related to bioresilience. The aim of the study was to describe the effects of homeopathic Mercurius corrosivus (MC) on Artemia salina cysts hatching and on mercury bioavailability. Artemia salina cysts were exposed to 5.0 µg/mL of mercury chloride during the hatching phase. MC potencies (6cH, 30cH, and 200cH) were prepared in sterile purified water and poured into artificial sea water. Different controls were used (non-challenged cysts and challenged cysts treated with water, succussed water, and Ethilicum 1cH). Four series of nine experiments were performed to evaluate the percentage of cyst hatching. Soluble total mercury (THg) levels and precipitated mercury content were also evaluated. Solvatochromic dyes were used to check for eventual physicochemical markers of MC biological activity. Significant delay (p < 0.0001) in cyst hatching was observed only after treatment with MC 30cH, compared with controls. This result was associated with an increase of THg concentration in water (p = 0.0018) and of chlorine/oxygen ratio (p < 0.0001) in suspended micraggregates, suggesting changes in mercury bioavailability. A specific interaction of MC 30cH with the solvatochromic dye ET33 (p = 0.0017) was found. Changes in hatching rate and possible changes in Hg bioavailability are postulated as protective effects of MC 30cH on Artemia salina, by improving its natural bioresilience processes.

Administration of Probiotics Improves the Brine Shrimp Production and Prevents Detrimental Effects of Pathogenic Vibrio Species.

In this study, we evaluated a consortium of probiotic bacteria as an environmentally-friendly strategy for controlling pathogenic Vibrio species during the brine shrimp incubation period. Probiotic strains were initially selected on basis of (i) their ability to colonize the cyst surfaces, (ii) their absence of cross-inhibitory effects, and (iii) no detrimental effect on cyst hatching. The cysts and nauplius surfaces were immediately colonized after the application of selected probiotic strains, without detrimental effects on survival. Ten probiotic strains were mixed at similar proportions (probiotic consortium) and evaluated at different concentrations into brine shrimp cultures during incubation and early stages of development. Subsequently, these cultures were challenged with Vibrio parahaemolyticus and Vibrio harveyi. The probiotic consortium was effective to reduce the abundance of pathogenic Vibrio species and to prevent the mortality during Vibrio challenges; however, its effect was concentration-dependent and was successful at a starting concentration of 1.8 × 106CFU/ml. Our results suggest that this probiotic consortium offers an alternative to antimicrobial agents routinely used to reduce the incidence and prevalence of pathogenic Vibrio species in brine shrimp production.

Non-target effects of antifouling agents on mortality, hatching success, and acetylcholinesterase activity in the brine shrimp Artemia salina

Many commercial shipping, leisure crafts, and aquaculture facilities employ antifouling agents to control biofouling/biocorrosion by keeping their metallic hulls clear, but most agents have been known to cause negative effects such as pollution in coastal marine ecosystem. In this study, we measured the deleterious effects of three antifouling agents (i.e. tributyltin; TBT, diuron, irgarol 1051) on nauplii mortality, acetylcholinesterase (AChE, EC3.1.1.7) activity, and hatching success of cysts in the brine shrimp Artemia salina. Lethal concentration 50 (LC50) was measured using A. salina nauplii in time-course (i.e. 24, 48, and 72 h) to select proper concentrations for the suite of AChE assays. The 24 h-LC50 toxicities of three antifouling agents ranged for mortality were as follows: TBT 0.208 μg/L, diuron 10261 μg/L, and irgarol 1051 982 μg/L. Selected doses within the LC50 value of each antifouling agent significantly inhibited AChE activity for 24 h, and newly hatched nauplii were more sensitive than 48 h old nauplii. Furthermore, the exposure conditions dose-dependently reduced the hatching rate of A. salina cysts. We conclude that three antifouling agents tested in this study may have a toxic cholinergic effect on nauplii through AChE inhibition, in addition to ecotoxicity on cyst hatching.

Evaluación del efecto tóxico de hongos Basidiomycota en la eclosión de quistes de Artemia franciscana

BackgroundThe consumption of wild mushrooms has increased in recent years. However, not all mushrooms are edible and some of them may cause poisoning. Therefore, their toxicity needs to be studied. Artemia franciscana is a crustacean used in toxicity tests including toxins of fungi. AimsTo determine the percentage of inhibition and mortality produced by extracts of several basidiomycetes on the hatching of A. franciscana cysts. MethodsAqueous extracts were prepared from 15 species of mushrooms collected from Jalisco state, Mexico. Different concentrations of the extracts were assayed in order to test their toxicity. Potassium dichromate and artificial seawater were the positive and negative controls, respectively. The percentages of hatching and mortality of the cysts were evaluated. ResultsInhibition of hatching greater than 80% in all the concentrations tested was found in 13 of the 15 species studied, in contrast to the positive control, which inhibited cyst hatching less than 50% in all cases. The highest percentage of mortality in the cysts was caused by the aqueous extracts of Amanita virosa, Leucopaxillus amarus, and Tylopilus violatinctus, and the lowest by Macrolepiota mastoidea. ConclusionsThe brine shrimp bioassay appeared to be useful in the evaluation of the toxicity of several basidiomycetes, with the exception of Scleroderma texense, a mushroom considered poisonous, which showed no toxicity over A. franciscana.

Hatching and nutritional quality of Artemia cysts progressively deteriorates as a function of increased exposure to hydration/dehydration cycles

Nauplii hatching from Artemia cysts are crucial in larviculture nutrition. Artemia cysts may be exposed to repeated hydration/dehydration (H/D) cycles pre-harvesting or during processing and storage. To observe the effect of these cycles on cyst quality, Artemia franciscana cysts were exposed to a comprehensive set of various H/D treatments, differing in the number of cycles (1, 2, or 3) and the duration of the freshwater hydration period (2 or 4 h). Cyst quality was assessed using the criteria of immediate relevance for aquaculture use, such as hatching percentage directly after H/D treatment and after −18 °C storage up to 1 month, longevity of axenically hatched starved nauplii, cyst and naupliar energy content, and (for the most extreme H/D treatment) cyst and naupliar fatty acid and vitamin C content. Repeated H/D cycles resulted in significantly (P < 0.05) decreased cyst hatching, reduced starved naupliar longevity and individual energy content, loss in vitamin C and fatty acid content, and moreover a close correlation between these parameters as a function of progressive H/D treatments. This is of immediate relevance for aquaculture nutrition, as commercial Artemia cysts may have gone through an unknown sequence of H/D cycles in nature or in the processing line, which affects the nutritional quality of the nauplii used in larviculture operations.

Automatic Estimation of Artemia Hatching Rate Using an Object Discrimination Method

Digital image processing is a process to analyze a large volume of information on digital images. In this study, Artemia hatching rate was measured by automatically classifying and counting cysts and larvae based on color imaging data from cyst hatching experiments using an image processing technique. The Artemia hatching rate estimation consists of a series of processes; a step to convert the scanned image data to a binary image data, a process to detect objects and to extract their shape information in the converted image data, an analysis step to choose an optimal discriminant function, and a step to recognize and classify the objects using the function. The function to classify Artemia cysts and larvae is optimally estimated based on the classification performance using the areas and the plan-form factors of the detected objects. The hatching rate using the image data obtained under the different experimental conditions was estimated in the range of 34-48%. It was shown that the maximum difference is about 19.7% and the average root-mean squared difference is about 10.9% as the difference between the results using an automatic counting (this study) and a manual counting were compared. This technique can be applied to biological specimen analysis using similar imaging information.

Life Cycle of the pseudocolonial dinoflagellate Polykrikos kofoidii (Gymnodiniales, Dinoflagellata).

The athecate, pseudocolonial polykrikoid dinoflag-ellates show a greater morphological complexity than many other dinoflagellate cells and contain not only elaborate extrusomes but sulci, cinguli, flagellar pairs, and nuclei in multiple copies. Among polykrikoids, Polykrikos kofoidii is a common species that plays an important role as a grazer of toxic planktonic algae but whose life cycle is poorly known. In this study, the main life cycle stages of P. kofoidii were examined and documented for the first time. The formation of gametes, 2-zooid-1-nucleus stages very different from vegetative cells, was observed and the process of gamete fusion, isogamy, was recorded. Karyogamy followed shortly after completed plasmogamy. A complex reorganization of furrows (cinguli and sulci) and flagella followed zygote formation, resulting in a 4-zooid zygote with one nucleus. The fate of zygotes under different nutritional conditions was also investigated; well-fed zygotes were able to reenter the vegetative cycle via meiotic divisions as indicated by nuclear cyclosis. However, nuclear cyclosis was preceded by a presumably mitotic division of the primary zygote nucleus which by definition would imply that P. kofoidii has a diplohaplontic life cycle. Nuclear cyclosis in germlings hatched from spiny resting cysts indicate that these cysts are of zygote origin (hypnozygotes). Hypnozygote formation, cyst hatching, the morphology of the germling (a 1-zooid cell), and its development into a normal pseudocolony are documented here for the first time. There is evidence that P. kofoidii has a system of complex heterothallism.

Synergistic toxicity of Macondo crude oil and dispersant Corexit 9500A® to the Brachionus plicatilis species complex (Rotifera)

Using the marine rotifer Brachionus plicatilis acute toxicity tests, we estimated the toxicity of Corexit 9500A®, propylene glycol, and Macondo oil. Ratios of 1:10, 1:50 and 1:130 for Corexit 9500A®:Macondo oil mixture represent: maximum exposure concentrations, recommended ratios for deploying Corexit (1:10–1:50), 1:130 the actual dispersant:oil ratio used in the Deep Water Horizon spill. Corexit 9500A® and oil are similar in their toxicity. However, when Corexit 9500A® and oil are mixed, toxicity to B. manjavacas increases up to 52-fold. Extrapolating these results to the oil released by the Macondo well, suggests underestimation of increased toxicity from Corexit application. We found small differences in sensitivity among species of the B. plicatilis species complex, likely reflecting phylogenetic similarity. Just 2.6% of the water-accommodated fraction of oil inhibited rotifer cyst hatching by 50%, an ecologically significant result because rotifer cyst in sediments are critical resources for the recolonization of populations each Spring.

Egg banks in hypersaline lakes of the South-East Europe

The cyst banks of 6 coastal hypersaline lakes of South-East Europe have been investigated. The study concerned the bottom sediments of Khersonesskoe and Koyashskoe lakes in the Crimea (Ukraine), Nartë saltworks (Albania), Vecchia Salina at Torre Colimena (Apulia, Italy), Pantano Grande and Pantano Roveto at Vendicari (Sicily, Italy). A total of 19 cyst types were recognised. The cyst banks of lakes were found to be well separated in the representation derived from a statistical multivariate data analysis. For all the lakes examined a comparison was possible between the resting community in sediments (cyst bank) and the active one in the water. The cyst banks contained more species than those recorded over a multi-year sampling effort in the water column. The study of cyst hatching, performed on 5 cyst types under lab conditions, demonstrated that cysts do not hatch under the same conditions. Furthermore, each cyst type shows a wide range of preferential hatching conditions, which allow us to confirm the ecological generalism of salt lake species.

Sublethal zinc exposure has a detrimental effect on reproductive performance but not on the cyst hatching success of Artemia parthenogenetica

The sublethal zinc toxicity to Artemia parthenogenetica as regards the possibility of colonization of zinc polluted salterns by means of cysts has been assessed by a cyst hatching assay and a life table approach. Emergence and hatching at different times as well as the whole hatching profile were taken as end-points for evaluating success of development. Demographic and reproductive parameters calculated according to the Lotka equation were used as an indicator of the chronic toxicity of the population. No adverse effects of waterborne zinc were found on hatching and emergence of cysts of A. parthenogenetica at any of the concentrations tested (0.01 mg/l, 0.1 mg/l, 0.5 mg/l, 1 mg/l, 5 mg/l). Chronic zinc exposure at 0.08 mg/l had detrimental effects on A. parthenogenetica fecundity, as detected by a decrease in the percentage of fertile females, which in turn produces a decrease in r. Chronic toxicity of zinc may be a limiting step for A. parthenogenetica colonization and the establishing of permanent populations in zinc-polluted brine ponds.

The cyst hatching pattern of the Thai Fairy Shrimp, Branchinella thailandensis Sanoamuang, Saengphan &amp; Murugan, 2002 (Anostraca)

We investigated factors influencing the hatching of the fairy shrimp, Branchinella thailandensis in relation to brood order, and also responses of cysts to wet and dry periods. Male-female pairs of B. thailandensis were cultured under static conditions at room temperature and fed ad libitum micro-algae (Chlorella sp.). Deposited cysts of the first, sixth and eleventh broods were monitored for cyst hatching under wet and dry conditions. Cyst hatching was scored daily for 5 days after incubation. Freshly laid cysts, immediately incubated, did not hatch in any of the experimental conditions (wet/dry). On the contrary, undried cysts immersed in their parental medium for 4 weeks showed the highest hatching in all brood treatments (76.67, 94.67, and 99.33% of the first, sixth, and eleventh broods, respectively). The cysts of the first brood hatched less successfully than did those of the sixth and eleventh broods. Cyst hatching mostly took place within 24 hours after incubation. The present study shows that a wet period has a strong influence on the cyst hatching success of B. thailandensis. The cysts require a period of retention in the parental medium for 2-4 weeks to complete their embryonic development before hatching. Hatching of the three representative broods showed a different pattern for each brood. The early broods required a longer wet period than did the late broods. In contrast to the hatching behaviour of many other species, drying is not absolutely essential for cyst hatching of this species.

Active and resting stages of zooplankton and its seasonal evolution in a hypersaline temporary pond of the Mediterranean coast (the Vecchia Salina, SE Italy)

SUMMARY: The species composition of zooplankton and its variability were studied with an integrated water-sediment analysis for a period of two years in a hypersaline temporary pond in SE Italy. The basin was affected by extended drought during summer, and even during the wet period the sodium chloride salinity was never below 42.5‰. The zooplankton showed the presence of seasonal species (mainly Anostraca), together with not seasonal, but opportunistic ones (mainly Rotifera, and Ciliophora) with a shorter life cycle. Rotifers (mainly Hexarthra fennica, and Proales similis), and ciliates (Fabrea salina) attained 99-100% of total planktonic organisms in certain periods. Resting stages were extracted from the upper 6 cm of 14 sediment cores collected during a dry period (August 1998). A total of 24 resting morphotypes (cysts) were listed—more than double the number of the active organisms (11) found in the plankton over the two years. The seasonal succession of species was different in the two years studied. This fact, together with the richness of the cyst bank of the sediment, indicates that in each period the water column shows only a portion of the biodiversity, which the sediment contains unexpressed as resting stages. The study of cyst distribution (both horizontal and vertical) in sediments provided complementary suggestions to understand the space-time distribution of the plankton organisms. Laboratory tests showed that hatching of different cysts generally occurred in a wide range of salinity conditions, and was not synchronous. This allowed us to assume that even the cyst hatching rate could be an adaptation to highly variable extreme environments.

Disinfection efficacy on cyst viability of Artemia franciscana (Crustacea), Hexarthra fennica (Rotifera) and Fabrea salina (Ciliophora)

Resting stages (cysts) of Artemia franciscana, Hexarthra fennica and Fabrea salina were exposed for two periods (acute and chronic exposures) to different concentrations of five aquaculture disinfectants (formalin, sodium hypochlorite, potassium permanganate, organic iodine, copper sulphate). The effects of chemical treatments were ranked according to their action on cyst hatching: total inhibition (no cyst hatching), heavy inhibition (significant decrease of cyst hatching), alteration of hatching synchrony, and occurrence of anomalous hatching (death of emerging individuals or birth of malformed organisms). Resting-stage viability was not completely impaired by disinfectant exposures at the ordinary doses used in aquaculture, so that usual treatments are possibly ineffective against the protist and metazoan cysts potentially present in breeding systems. On the other hand, the high resistance shown by cysts suggests the possibility of using these chemicals in live-feed disinfection.

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.

Acute toxicity of storm water associated with de‐icing/anti‐icing activities at Canadian airports

AbstractEnvironment Canada, Transport Canada, and the Airline Transport Association of Canada recently evaluated the use of toxicity bioassays to assist in managing wastewater from aircraft de‐icing at Canadian airports. This study evaluated the effectiveness of a suite of rapid screening bioassays to predict the responses of standard regulatory test organisms to storm water associated with de‐icing at four Canadian airports. Storm water samples were tested using two standard acute lethality bioassays (rainbow trout [Oncorhynchus mykiss],Daphnia magna) and four rapid screening bioassays (Daphnia IQ™, acute Microtox®, Rotoxkit®, Thamnotoxkit®). Environmental samples (runoff water) and concentrated de‐icing/anti‐icing chemicals from the clean‐up vehicles (sweeper trucks) were collected from each airport and tested. Forty percent (n= 10) of the environmental samples were lethal to trout, and 30% were lethal toD. magna. The IQ and Thamnotoxkit test results were comparable to those of the trout and daphnid bioassays, respectively. Disadvantages associated with the IQ and Thamnotoxkit bioassays included the lack of a standardized quality‐assurance/quality‐control program, subjectivity in endpoint measurements, and problems in cyst hatching. The limited number of storm‐related samples did not permit definitive determination for the causality of toxicity. Results suggest that glycol was not predictive of acute lethality, and that other substances likely contributed to toxicity.

Distribución, abundancia y morfometrÍa de Strombus costatus, Turbinella angulata, Busycon contrarium y Pleuroploca gigantea (Mesogasteropoda: Strombidae, Thrbinellidae, Neptuneidae y Fasciolaridae) en Yucatán, México

The use of Artemia salina nauplii as live food has significantly aided culture of commercial fish and shrimps in recent years. However, reported defficiencies in the nutritional value of some strains originated the study of freshwater fairy shrimps as an alternative to Artemia. This study presents cyst biometry for Dendro­cephalus geayi and D. spartaenovae (Anostraca: Thamnocephalidae), and the effects of some physicochemical variables on cyst hatching. The biometric characteristics of D. geayi and D. spartanovae are within the size range of commercial Artemia strains. Favorable conditions to batch D. geayi are 30°C and conductivity near that of distilled water (<5 μmhos). For D. spartaenovae, these conditions are 28 °C and 280 μmhos. A very low salinity such as 1% inhibits hatching in both species.