Brachionus Plicatilis Research Articles

Enriching Rotifers with "Premium" Microalgae: Rhodomonas lens.

The nutritional value of the marine cryptophyte Rhodomonas lens for the filter feeder Brachionus plicatilis as well as its biotechnological potential as a source of phycoerythrin (PE) and polyunsaturated fatty acids (PUFA) were evaluated in semi-continuous cultures maintained with different daily renewal rates (RR), from 10% (R10) to 50% (R50) of the total volume. Steady-state cell density decreased from 22 to 7 × 106cellsmL-1 with increasing RR, with the maximum cell productivity, nearly 0.4gL-1day-1, observed with R40. PE cell content attained the highest values with the highest RR (circa 9pgcell-1). All treatments of R. lens maintained under nitrate-saturated conditions (R20-R50) showed a similar high content of PUFAs, > 60% of total fatty acids (FA), with linolenic acid (18:3n-3) and 18:4n-3, representing 12 and 29% of total FA respectively. The PUFA level in the nitrogen-limited R10 cultures was significantly lower (37%). R. lens promoted higher weight gain in the rotifer B. plicatilis than Tisochrysis lutea (T-ISO), a species commonly used for rotifer culture and enrichment. Significant differences were found in the protein content and in the ratio n-3/n-6 fatty acids among rotifers fed with R. lens from different RRs, with higher values being found in those fed with R. lens from higher RRs. The enrichment of the rotifers for short periods of 3h was sufficient to modify the biochemical composition of the rotifers, but it was evidenced as too short for the accumulation of PUFAs, when compared to long-term (24h) enrichment. The rotifers reflected the higher protein and PUFA content of R. lens cultivated with nutrient sufficient microalgae (R40) after only 3h of enrichment. These results demonstrate that semi-continuous culture of R. lens under appropriate conditions can strongly enhance the nutritional value of this species, being reflected in the growth and biochemical composition of the filter feeder, even in short exposure periods.

Ecological genomics of adaptation to unpredictability in experimental rotifer populations

Elucidating the genetic basis of phenotypic variation in response to different environments is key to understanding how populations evolve. Facultatively sexual rotifers can develop adaptive responses to fluctuating environments. In a previous evolution experiment, diapause-related traits changed rapidly in response to two selective regimes (predictable vs unpredictable) in laboratory populations of the rotifer Brachionus plicatilis. Here, we investigate the genomic basis of adaptation to environmental unpredictability in these experimental populations. We identified and genotyped genome-wide polymorphisms in 169 clones from both selective regimes after seven cycles of selection using genotyping by sequencing (GBS). Additionally, we used GBS data from the 270 field clones from which the laboratory populations were established. This GBS dataset was used to identify candidate SNPs under selection. A total of 76 SNPs showed divergent selection, three of which are candidates for being under selection in the particular unpredictable fluctuation pattern studied. Most of the remaining SNPs showed strong signals of adaptation to laboratory conditions. Furthermore, a genotype-phenotype association approach revealed five SNPs associated with two key life-history traits in the adaptation to unpredictability. Our results contribute to elucidating the genomic basis for adaptation to unpredictable environments and lay the groundwork for future evolution studies in rotifers.

Conflicting outcomes of an integrated approach to sediment quality assessment in a Sardinian coastal area subjected to mining activities

Multidisciplinary research was carried out to verify the best approach for a reliable assessment of sediment quality in marine areas affected by strong metal enrichment. The study was carried out on Sulcis-Iglesiente marine coastal areas (Sardinia, Italy), where a long-lasting past mining operation strongly contaminated marine sediments with heavy metals (Cd, Pb and Zn). Surface sediments were analysed for grain size and mineralogical content, total organic carbon, total metal concentrations and sequential extractions. Additionally, ecotoxicological bioassays were performed using Vibrio fischeri (Microtox®) on the solid phase and elutriate, Dunaliella tertiolecta on elutriate and Brachionus plicatilis on elutriate. Analysed sediments were nearly exclusively sand (98.5–100%) with a very low TOC content; their texture and mineralogy indicated a N-S drift affecting the dispersion of mining contributions. The total concentrations of Cd, Pb and Zn, which are positively correlated, exceeded background and Environmental Quality Standards (EQS) values by up to two orders of magnitude, while sequential extractions revealed their high mobility because Cd and Pb were mainly extracted in the first phase (up to 77 and 82%, respectively) and Zn in the second phase (up to 99%). In spite of this, bioassays recorded the absence of toxicity in all the samples. These apparently conflicting results suggest that ecotoxicological tests cannot replace chemical analyses in sediment quality assessments because they could fail to provide reliable information on the bioavailability of contaminants over time.

Effect of recycling the culture medium on biodiversity and population dynamics of bio-contaminants in Spirulina platensis mass culture systems

Spirulina (Arthrospira) is an important microalga that can generate a variety of commercial products. A semi-continuous mode of cultivation is often employed in microalgal cultivation. The traditional view, however, has been that cultures with recycled medium are more likely to be contaminated by microzooplankton, which is regarded as one of the critical problems in mass algal cultivation. In this study, the relationship between the population dynamics of contaminants and the medium conditions was investigated in Spirulina cultures. Spirulina platensis was cultivated in three groups of raceway ponds: one with fresh culture medium, one with medium that had been recycled for a month, and the third with medium recycled for six months. The results showed that totally 13 species of microzooplankton were observed by light microscopy, and 42 operational taxonomic units (OTUs) of prokaryotic contaminants were detected using amplicon sequencing. Out of all the contaminants, Brachionus plicatilis and Euplaesiobystra hypersalinica were observed to be the most harmful species in Spirulina cultures, while Proteobacteria were the most commonly found non-Cyanobacteria OTUs. On the initial day, more species of microzooplankton were introduced to the cultures that had recycled medium (9 species) than to those that had fresh medium (5 species). By the end of the cultivation, the algal biomass in the fresh medium group was the highest (2.8 g L−1), being almost 5 times higher than in the other two groups (around 0.50 g L−1). Our results proved that Spirulina can grow the best with fresh medium and that the more the culture medium is recycled, the stronger the inhibition on the growth of microalgae and microzooplankton. In order to improve large-scale Spirulina production, it is necessary to both subject the recycled medium to appropriate treatment to reduce the presence of harmful predators and to find effective ways to control contaminants.

Comparative study on early digestive enzyme activity and expression in red sea bream (Pagrus major) fed on live feed and micro-diet

The use of live feed to meet larval nutritional requirements has caused a bottleneck in marine fish larviculture whilst the use of micro-diets has had limited success in completely replacing live feeds. In this study, the variations in enzyme activity and its related gene expressions during early ontogenetic development of red sea bream (Pagrus major) were investigated. The experiment included four treatments: (i) using live feed (enriched L-type rotifers of the Brachionus plicatilis sp. complex) until 15 days after hatching (DAH) and gradually switching to Artemia; (ii) using micro-diet only; (iii) co-feeding diet (using both live feed and micro-diet) and, (iv) starvation (no food supplied). This study lasted 40 days and the activity and expression of digestive enzymes (trypsin (try), chymotrypsin (ctrb), pepsin (pep), amylase (amy2α), pancreatic lipase (pl), expression of energy metabolism (ATP synthase (atp), cytochrome-c-oxidase (cox1), cholecystokinin (cck) and growth (insulin like growth factor 1 (igf1)) were linked to larval biometrics. After 40 DAH, no significant difference was observed in growth (igf1), energy metabolism (cox1, atp) and survival rate between live feed and co-feeding diet treatments. However, there were significantly higher differences observed when these were compared to the starvation and micro-diet only treatments. The pancreatic enzymes and cck were regulated by dietary compositions and detectable from hatching and fluctuated throughout larval ontogeny. While pep was initially observed only after 15 DAH. Limits of larval survival and low enzyme activity were observed when the larvae were subjected to starvation for 10 days and were able to adapt to micro-diet only after 15 DAH accompanied with a 5-day co-feeding transitionary period.

Genetic variability and transgenerational regulation of investment in sex in the monogonont rotifer Brachionus plicatilis

In cyclical parthenogens such as aphids, cladocerans and rotifers, the coupling between sexual reproduction and the production of resting stages (diapausing eggs) imposes strong constraints on the timing of sex. Whereas induction of sex is generally triggered by environmental cues, the response to such cues may vary across individuals according to genetic and nongenetic factors. In this study, we explored genetic and epigenetic causes of variation for the propensity for sex using a collection of strains from a Spanish population of monogonont rotifers (Brachionus plicatilis) in which variation for the threshold population density at which sex is induced (mixis threshold) had been documented previously. Our results show significant variation for the mixis threshold among 20 clones maintained under controlled conditions for 15 asexual generations. The effect of the number of clonal generations since hatching of the diapausing egg on the mixis ratio (proportion of sexual offspring produced) was tested on 4 clones with contrasted mixis thresholds. The results show a negative correlation between the mixis threshold and mixis ratio, as well as a significant effect of the number of clonal generations since fertilization, sex being repressed during the first few generations after hatching of the diapausing egg.

Brachionus paranguensis sp. nov. (Rotifera, Monogononta), a member of the L group of the Brachionus plicatilis complex.

The Brachionus plicatilis complex represents the most studied group of rotifers, although the systematics of the species complex has not been completely clarified. Many studies have been conducted trying to explore the diversity within the complex, leading to the recognition of three major morphotypes: large (L), small-medium (SM), and small (SS). Currently six species have been described and classified under these types and another nine taxa have been identified but not formally described. Within the L group, three species have been officially described [B. plicatilis s.s. (L1), B. manjavacas (L2), and B. asplanchnoidis (L3)], while a formal description of L4, unofficially known as B. ‘Nevada’, is still lacking. In the present study, a new species, Brachionus paranguensissp. nov., is formally described and presented as a representative of the L4 clade. The species has been named after a high altitude saline crater lake from Central Mexico, where the specimens were collected. An integrated approach using DNA taxonomy through COI and ITS1 markers, morphology, and ecology was used to confirm the identity of the new species.

PRODUCTIVITY OF ROTIFER Brachionus plicatilis CULTURED UNDER BATCH SYSTEM BY USING SUGAR BEET MOLASSES AS A SUBSTITUTE MEDIUM

This study deals with the determination of availability of sugar beet molasses as a nutritional enrichment factor for rotifer cultures. A series of experiments under varying conditions such as ratio of sugar beet molasses in the nutrient complex were carried out in order to determine the effectiveness of sugar beet molasses as a carbohydrate and mineral source for the purpose of aquacultural operations. The culture water of Brachionus plicatilis with the salinity of 38% was treated through mechanical filtration and UV sterilization. 1 T cylindro-conical tanks are utilized for rotifer culture. Parameters of culture water were stabilized at values as following; Oxygen concentration:5 to 10 ppm, temperature: 27 0 C and pH:6.8 to 7.4. Rotifers were counted by using Sedgewick Rafter Cell on a daily basis in order to determine increase of number of individuals. The study was conducted as 3 different trial groups, each consisting three separate tanks, so triplicate determinations were obtained. For the Group I, 10% molasses by weight of Culture Selco Plus (200 gr Selco Plus+20 gr molasses per tank) was added 6 times a day with 4 hours’ intervals. For the Group II, 20% molasses by weight of Culture Selco Plus (200gr Selco Plus+40gr molasses per tank) was added and lastly for the control group, Group III, no molasses has been added and 200 gr Culture Selco Plus was only added per tank. The addition of molasses to nutritive complex has a decreasing effect on the number of rotifer and increasing effect on the number of ciliate. From the study, it is clear that sugar beet molasses should not be used as an additional nutritional factor for rotifer cultures due to its decreasing effect on the number rotifers and stimulating effect on the ciliate booming. Addition of 10% and 20% molasses resulted in 31.4% and 23.3% decrease in number of rotifers at the time of T3, respectively. On the other hand, it was observed that addition of molasses in the nutritive complex has not affected on the percentage of rotifers bearing eggs.

Chemical Profiling of Volatile Organic Compounds in the Headspace of Algal Cultures as Early Biomarkers of Algal Pond Crashes

Algae ponds used in industrial biomass production are susceptible to pathogen or grazer infestation, resulting in pond crashes with high economic costs. Current methods to monitor and mitigate unhealthy ponds are hindered by a lack of early indicators that precede culture crash. We used solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to identify volatiles emitted from healthy and rotifer infested cultures of Microchloropsis salina. After 48 hours of algal growth, marine rotifers, Brachionus plicatilis, were added to the algae cultures and volatile organic compounds (VOC) were sampled from the headspace using SPME fibers. A GC-MS approach was used in an untargeted analysis of VOCs, followed by preliminary identification. The addition of B. plicatilis to healthy cultures of M. salina resulted in decreased algal cell numbers, relative to uninfected controls, and generated trans-β-ionone and β-cyclocitral, which were attributed to carotenoid degradation. The abundances of the carotenoid-derived VOCs increased with rotifer consumption of algae. Our results indicate that specific VOCs released by infected algae cultures may be early indicators for impending pond crashes, providing a useful tool to monitor algal biomass production and pond crash prevention.

The effects of nanoplastics on marine plankton: A case study with polymethylmethacrylate

Marine biota is currently exposed to plastic pollution. The biological effects of plastics may vary according to polymer types (e.g. polystyrene, polyethylene, acrylate), size of particles (macro, micro or nanoparticles) and their shape. There is a considerable lack of knowledge in terms of effects of nanoplastics (NP) to marine biota particularly of polymers like polymethylmethacrylate (PMMA). Thus, this study aimed to assess its ecotoxicological effects using a battery of standard monospecific bioassays with four marine microalgae (Tetraselmis chuii, Nannochloropsis gaditana, Isochrysis galbana and Thalassiosira weissflogii) and a marine rotifer species (Brachionus plicatilis). The tested PMMA-NP concentrations allowed the estimation of median effect concentrations for all microalgae species. T. weissflogii and T. chuii were respectively the most sensitive (EC50,96h of 83.75 mg/L) and least sensitive species (EC50,96h of 132.52 mg/L). The PMMA-NP were also able to induce mortality in rotifers at concentrations higher than 4.69 mg/L with an estimated 48 h median lethal concentration of 13.27 mg/L. A species sensitivity distribution curve (SSD), constructed based on data available in the literature and the data obtained in this study, reveal that PMMA-NP appears as less harmful to marine biota than other polymers like polystyrene.

Different Nutritional Histories Affect the Susceptibility of Algae to Grazing.

We hypothesize that algae with different cell compositions are differently perceived by their predators and consequently subjected to selective grazing. Five populations of the diatom Phaeodactylum tricornutum that differed in organic and elemental composition, but were otherwise identical, were generated by acclimation to distinct growth regimes. The different populations were then mixed in pairs and subjected to predation by either the rotifer Brachionus plicatilis or the copepod Acartia tonsa. The presence of rotifers had no impact on the ratio between any two algal populations. The presence of copepods, however, affected the ratio between algae previously acclimated to a medium containing 1mM NH4+ and algae acclimated to 0.5mM NO3- , and to either a lower irradiance or a higher CO2 concentration. We discuss the possible reason for the influence of different nutritional histories on the vulnerability of algae to predators. The differential impact of grazers on the growth of algae with different nutritional histories may result from direct selective grazing (i.e., grazers can detect algae with the most palatable cell composition), alone or combined to an asymmetric utilization of the nutrients regenerated after predation by co-existing algal populations. Our results strongly suggest that the nutritional history of algae can influence the relationships between phytoplankton and grazers and hint at the possibility that algal cell composition is potentially subject to natural selection, because it influences the probability that algae survive predation.

Molecular identity and demographic responses to salinity of a freshwater strain of Brachionus plicatilis from the shallow Lake Pátzcuaro, Mexico

Molecular identity and demographic responses to salinity of a freshwater strain of Brachionus plicatilis from the shallow Lake Pátzcuaro, Mexico

Effect of salinity and food concentration on competition between Brachionus plicatilis Müller, 1786 and Brachionus calyciflorus Pallas, 1776 (Rotifera)

Natural populations of planktonic rotifers are affected by salinity and food density, among other stressors. Moreover, competition among congeneric species limits the abundance of certain rotifers in ecosystems without spatial heterogeneity and environmental fluctuations. We isolated Brachionus plicatilis and Brachionus calyciflorus from Salado River basin waterbodies and studied the demographic characteristics and competition between them at three salinity levels (0.75, 1.75 and 2.75gL–1 NaCl) and at two food concentrations (0.1×106 and 0.5×106 cells mL–1 Chlorella vulgaris). The lowest salinity level proved to be unfavourable for the population growth of B. plicatilis, but at higher salinity levels the growth was similar to that of controls (without competition), even in the presence of the competitor and at either food concentration. By contrast, the competitor almost always decreased the density of B. calyciflorus. Salinity greatly affected the peak density of B. plicatilis, whereas the effects of salinity and competition on B. calyciflorus were similar. Biomass was inversely related to salinity for both species, and was significantly affected by competition in B. plicatilis. These results show that B. calyciflorus is more adversely affected than B. plicatilis by competition and high salinity, and explain why both species can coexist in eutrophic saline lowland rivers and pampean shallow lakes.

Effect of Brachionus plicatilis density on pikeperch ( Sander lucioperca L.) larva performance at first feeding

Journal of Applied IchthyologyVolume 35, Issue 6 p. 1292-1294 SHORT COMMUNICATION Effect of Brachionus plicatilis density on pikeperch (Sander lucioperca L.) larva performance at first feeding Aiman Imentai, Corresponding Author Aiman Imentai aimentai@frov.jcu.cz orcid.org/0000-0001-6650-439X Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech Republic Correspondence Aiman Imentai, Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Zátiší 728/II, 389 25, Vodňany, Czech Republic. Email: aimentai@frov.jcu.czSearch for more papers by this authorCarlos Yanes-Roca, Carlos Yanes-Roca Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this authorOleksandr Malinovskyi, Oleksandr Malinovskyi orcid.org/0000-0003-0497-1747 Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this authorTomáš Policar, Tomáš Policar orcid.org/0000-0001-9245-4381 Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this author Aiman Imentai, Corresponding Author Aiman Imentai aimentai@frov.jcu.cz orcid.org/0000-0001-6650-439X Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech Republic Correspondence Aiman Imentai, Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Zátiší 728/II, 389 25, Vodňany, Czech Republic. Email: aimentai@frov.jcu.czSearch for more papers by this authorCarlos Yanes-Roca, Carlos Yanes-Roca Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this authorOleksandr Malinovskyi, Oleksandr Malinovskyi orcid.org/0000-0003-0497-1747 Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this authorTomáš Policar, Tomáš Policar orcid.org/0000-0001-9245-4381 Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, University of South Bohemia in České Budějovice, Vodňany, Czech RepublicSearch for more papers by this author First published: 14 August 2019 https://doi.org/10.1111/jai.13963Citations: 3Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume35, Issue6December 2019Pages 1292-1294 RelatedInformation

Infant mortality across species. A global probe of congenital abnormalities

Infant mortality, by which we understand the postnatal stage during which mortality is declining, is a manifestation and embodiment of congenital abnormalities. Severe defects will translate into death occurring shortly after birth whereas slighter anomalies may contribute to death much later, possibly only in adult age. While for many species birth defects would be nearly impossible to identify, infant mortality provides a convenient global assessment. In the present paper we examine a broad range of species from mammals to fish to gastropods to insects. One of the objectives of our comparative analysis is to test a conjecture suggested by reliability engineering according to which the frequency of defects tends to increase together with the complexity of organisms. For that purpose, we set up experiments specially designed to measure infant mortality. In particular, we studied two species commonly used as model species in biological laboratories, namely the zebrafish Danio rerio and the rotifer Brachionus plicatilis. For the second, whose number of cells is about hundred times smaller than for the first, we find, as expected, that the screening and weeding out effect of the infant phase (measured by the ratio of the death rate at birth to the death rate at the end of the infant phase) is of much smaller amplitude. Our analysis also raises a number of challenging questions for which further investigation is necessary. For instance, why is the infant death rate of beetles and molluscs falling off exponentially rather than as a power law as observed for most other species? A possible research agenda is discussed in the conclusion of the paper.

Effect of tank colour on foraging capacity, growth and survival of milkfish (Chanos chanos) larvae

Larviculture of milkfish (Chanos chanos) associated with issues like larval deformity, mass mortalities which contribute in variable seed production. Effect of abiotic factors as rearing tank colour and illumination on larvae foraging behaviour, prey localization and ingestion were investigated to improvise milkfish larval rearing system. Reinforced Cement Concrete (RCC) tanks (capacity, 8 t; water salinity, 32 ppt) with three different background colors, white, blue and yellow were divided in five (05) treatment groups with triplicates, i.e. indoor white (T1/C), blue (T2), yellow (T3) color tanks with artificial illumination and semi outdoor blue (T4), yellow (T5) color tanks with solar illumination. Newly hatched milkfish larvae (tl., 3.4 mm) were stocked in the experimental tanks @ 2.5 no l−1 and apart from background colour and source of illumination uniform water quality and feeding regime were maintained in all treatments. Phytoplankton, Chlorella salina @ 103–104 cells ml−1 were maintained from 2 dph to 20 dph; Chlorella grown rotifers, Brachionus plicatilis (enriched with Nannochloropsis oculata paste) were provided @ 20–30 no ml−1 from 3 dph to 14 dph depending on the larval density. Artemia nauplii @ 0.5–1.0 no ml−1 was introduced from 15 dph. At the end of the experiment- 20 dph, highest (p < 0.05) larval survival (45 ± 5.63%) was achieved in tanks providing yellow background colour (T5) compared to control and other treatments. Larval growth (tl., 17.1 ± 1.37 mm) was also found to be highest (p < 0.05) in T5. Increased survival and growth of milkfish in T5 was synchronized with significantly higher (p < 0.05) specific growth rate (SGR), larval gut content relative to other treatments. Milkfish larvae being a day feeder did maximum foraging during 0700 h to 1600 h evident from decreeing prey abundance during that period and as a result positive correlation found between larval standard length and gut content. Larval visibility enhancement in solar illuminated yellow tank act synergistically to perform necessary foraging to acquire nutritional energy for metamorphosis to fry. Above phenomenon may not have occurred in other treatments except T5 and partially in T3. Solar illuminated yellow colour tanks significantly contribute towards mass scale seed production of milkfish.

Impact of different rearing systems on survival, growth and quality of mud crab (Scylla paramamosain) megalopae reared from early zoeae

This study aimed to compare the effects of four different rearing systems—namely clear water, green water, recirculating water and biofloc water systems—on survival, growth and quality of mud crab (Scylla paramamosain) megalopae reared from early zoeae. Twelve 60-L plastic buckets filled with 50 L of disinfected seawater were stocked with 20 larvae of zoea 1 (Z1) L−1. The larvae were fed both probiotic-enriched L-strain rotifers (Brachionus plicatilis) and probiotic-enriched Artemia (Artemia franciscana) in all systems. After 20 days of culture, the green water system resulted in the highest survival to megalopae than all the other systems. The survival of megalopae reared under the biofloc water system was similar to that of the clear water system, but both systems exhibited higher survival than the recirculating water system. However, larval growth performance was not affected by the various rearing systems. The quality of megalopae produced under these systems was determined by ammonia and simulated transport stress tests. The ammonia stress test did not show a significant difference in the quality of megalopae, but the simulated transport stress test demonstrated a significant effect of rearing system on the quality of mud crab megalopae. The resistance to the air exposure until the end of the 48 h of transport was observed in the green water system. Overall, the results of the present study revealed that the green water system is the most suitable for rearing Scylla paramamosain larvae from Z1 to megalopa stage.

A toxic effect at molecular level can be expressed at community level: A case study on toxic hierarchy

This study demonstrated hierarchical toxicity and addressed the relevance and differences of toxic effects at the molecular, individual, population, and community levels. Superoxide dismutase (SOD) activity, photosynthetic oxygen production, filtration rate, life span and densities of Platymonas helgolandica var. tsingtaoensis, Isochrysis galbana, and Brachionus plicatilis in single-species tests and customized community tests were examined in response to a concentration gradient of aniline ranging from 0 to 50.0 mg L−1. The SOD activity was the most sensitive endpoint with the fastest response to aniline according to the calculated no-detection of toxic effect concentration (NDEC) and the EC50. The individual- and population-level endpoints, showing a lower response to aniline, could be constructed from the SOD activity in a stepwise manner. A multi-scale hierarchical model with endpoints at 4 levels was used to characterize toxic effects, at the scales of time and size. Linkage of SOD activity to toxic effects at a community level was established level by level to express the change in the customized community with the concentration of aniline. The calculated threshold concentration of aniline for the customized community was nearly equal to the minimum NDEC, demonstrating as great an impact on interactions by the toxic effect at subpopulation-level as that at the community level. However, we identified a trend of higher sensitivities of measured endpoints at sub-population level, decreasing sensitivity at higher levels but a great variety of sensitivities at community level. Although the characteristics of toxic effects are different at different levels, the structure and process of endpoints at adjacent levels are related to and interact with each other. The resulted indirect effects, together with direct effect, determine the toxic effect at every levels of biological complexity. The toxic effects at adjacent levels should be studied at the same time to better understand the ecological risk of contaminants.

The Use of Selected Bacteria and Yeasts to Control Vibrio spp. in Live Food.

Vibrio species are a significant causative of mass mortality in mariculture worldwide, which can quickly accumulate in live food and transmit into the larval gut. With restrictions on the use of antibiotics in aquaculture, finding a proper solution to reduce the risk of Vibriosis is vital. This study aimed to evaluate the susceptibility of Vibrio harveyi, V. campbellii, V. anguillarum, and V. parahaemolyticus to twenty-six bacterial and yeast strains and use the beneficial ones to enrich live food (Branchiopod, Artemia franciscana, rotifer, Brachionus plicatilis and copepod, Tigriopus japonicus). Thus, a modified disk diffusion method was applied. After a susceptibility assay, the bacteria and yeast beneficial in suppressing the Vibrio species were labeled by fluorescent stain and used to measure the accumulation potential in different live foods. Also, the beneficial bacteria and yeast were used to enrich live foods, and then the count of loaded Vibrio was estimated after 5, 10, 15, and 20 h by the serial dilution method. From the total bacteria and yeast strains that were used, Candida parapsilosis, Pseudoalteromonas flavipulchra, Lactobacillus sakei, Bacillus natto, and B. amyloliquefaciens inhibited all four Vibrio species. The results of microbial labeling showed that L. sakei in Artemia, C. parapsilosis in rotifers, and V. harveyi in copepods had the highest accumulation rate. The results of the estimation of loaded Vibrio in different live foods also showed that the use of beneficial bacteria and yeast each significantly reduced the count of Vibrio. Application of bacteria and yeast to suppress pathogenic Vibrio maybe a sustainable method for preventing this pathogen from harmfully invading aquaculture and may also aid in reducing the chances of antibiotic resistance in pathogenic Vibrio.

Spotted sand bass, Paralabrax maculatofasciatus, larviculture in Mexico: current status and perspetives

The spotted sand bass Paralabrax maculatofasciatus is an essential component in the commercial fisheries along the Pacific coast of Mexico. It has been considered as a promising species for seed production under culture conditions, and research have shown that photo-thermal manipulation induces the spotted sand bass broodstock to spontaneously spawn high-quality eggs in captivity almost throughout the year with at least 88% hatching rate. Additionally, larval performance in intensive culture conditions have shown many favorable characteristics like resistance to high rearing densities (50-100 larvae L -1 ), acceptance of rotifer Brachionus plicatilis as first prey, fast developmental rate including a totally functional digestive tract around 16 days after hatching (DAH) and high growth rate reaching the juvenile stage in nearly 35-40 DAH with an 11% survival. In the present review, the main achievements in biological knowledge and culture protocols through larval research of the spotted sand bass during the past 20 years are described, and new research lines and culture parameters towards the establishment of a culture strategy as an economical alternative in the region are proposed.