Kinetic Model for Micro Algae Cell Concentration and Size Distribution: Application to Nannochloropsis gaditana

The cell concentration and size distribution of the microalgae Nannochloropsis gaditana were studied over the whole growth process. Various samples were taken during the light and dark periods the algae were exposed to. The distributions obtained exhibited positive skew, and no change in the type of distribution was observed during the growth process. The size distribution shifted to lower diameters in dark periods while in light periods the opposite occurred. The overall trend during the growth process was one where the size distribution shifted to larger cell diameters, with differences between initial and final distributions of individual cycles becoming smaller. A model based on the Logistic model for cell concentration as a function of time in the dark period that also takes into account cell respiration and growth processes during dark and light periods, respectively, was proposed and successfully applied. This model provides a picture that is closer to the real growth and evolution of cultures, and reveals a clear effect of light and dark periods on the different ways in which cell concentration and diameter evolve with time.

Madrepora oculata and Lophelia pertusa mass and 210Pb-226Ra chronology, Røst Reef, Norway, 2011

Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of corals from one of the world's largest known cold-water coral reef, the Røst Reef off Norway. Two large branching framework-forming cold-water coral specimens, one Lophelia pertusa and one Madrepora oculata were collected alive at 350 m water depth from the Røst Reef at ~67° N and ~9° E. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and the corals trace element compositions were studied using ICP-QMS. Due to the different chemical behaviors of Pb and Ra in the marine environment, 210Pb and 226Ra were not incorporated the same way into the aragonite skeleton of those two cold-water corals. Thus to assess of the growth rates of both specimens we have here taken in consideration the exponential decrease of initially incorporated 210Pb as well as the ingrowth of 210Pb from the decay of 226Ra. Moreover a~post-depositional 210Pb incorporation is found in relation to the Mn-Fe coatings that could not be entirely removed from the oldest parts of the skeletons. The 226Ra activities in both corals were fairly constant, then assuming constant uptake of 210Pb through time the 210Pb-226Ra chronology can be applied to calculate linear growth rate. The 45.5 cm long branch of M. oculata reveals an age of 31 yr and a~linear growth rate of 14.4 ± 1.1 mm yr-1, i.e. 2.6 polyps per year. However, a correction regarding a remaining post-depositional Mn-Fe oxide coating is needed for the base of the specimen. The corrected age tend to confirm the radiocarbon derived basal age of 40 yr (using 14C bomb peak) with a mean growth rate of 2 polyps yr-1. This rate is similar to the one obtained in Aquaria experiments under optimal growth conditions. For the 80 cm-long specimen of L. pertusa a remaining contamination of metal-oxides is observed for the middle and basal part of the coral skeleton, inhibiting similar accurate age and growth rate estimates. However, the youngest branch was free of Mn enrichment and this 15 cm section reveals a growth rate of 8 mm yr-1 (~1 polyp every two to three years). However, the 210Pb growth rate estimate is within the lowermost ranges of previous growth rate estimates and may thus reflect that the coral was not developing at optimal growth conditions. Overall, 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals, however, removal of post-depositional Mn-Fe oxide deposits is a prerequisite. If successful, large branching M. oculata and L. pertusa coral skeletons provide unique oceanographic archive for studies of intermediate water environmentals with an up to annual time resolution and spanning over many decades.

Growth dependent silencing and resetting of DGA1 transgene in Nannochloropsis salina

Here we report recombinant expression and activity of the Saccharomyces cerevisiae type 2 diacylglycerol acyltransferase DGA1 functioning in parallel with the native Nannochloropsis salina genes. Expression of DGA1 shifted the chain length distribution of fatty acids produced and reflected an oleoyl-CoA substrate preference. Effect on the total FAME content was moderate and elevated by a maximum of 38%. Expression of the DGA1 transgene varied throughout the culture life cycle and evidence of growth dependent environmental silencing of the transgene was observed. This is to our knowledge the first example of silencing and subsequent resetting in a transgenic microalga. Results from this study add valuable insights into the efficacy of algal genetic engineering and use of these microorganisms as bio-platforms for chemical manufacture.

Growth dependent silencing and resetting of DGA1 transgene in Nannochloropsis salina

Here we report recombinant expression and activity of the Saccharomyces cerevisiae type 2 diacylglycerol acyltransferase DGA1 functioning in parallel with the native Nannochloropsis salina genes. Expression of DGA1 shifted the chain length distribution of fatty acids produced and reflected an oleoyl-CoA substrate preference. Effect on the total FAME content was moderate and elevated by a maximum of 38%. Expression of the DGA1 transgene varied throughout the culture life cycle and evidence of growth dependent environmental silencing of the transgene was observed. This is to our knowledge the first example of silencing and subsequent resetting in a transgenic microalga. Results from this study add valuable insights into the efficacy of algal genetic engineering and use of these microorganisms as bio-platforms for chemical manufacture.

Two “pillars” of cold-water coral reefs along Atlantic European margins: Prevalent association of Madrepora oculata with Lophelia pertusa, from reef to colony scale

The scleractinian coral Lophelia pertusa has been the focus of deep-sea research since the recognition of the vast extent of coral reefs in North Atlantic waters two decades ago, long after their existence was mentioned by fishermen. These reefs where shown to provide habitat, concentrate biomass and act as feeding or nursery grounds for many species, including those targeted by commercial fisheries. Thus, the attention given to this cold-water coral (CWC) species from researchers and the wider public has increased. Consequently, new research programs triggered research to determine the full extent of the corals geographic distribution and ecological dynamics of “Lophelia reefs”. The present study is based on a systematic standardised sampling design to analyse the distribution and coverage of CWC reefs along European margins from the Bay of Biscay to Iceland. Based on Remotely Operated Vehicle (ROV) image analysis, we report an almost systematic occurrence of Madrepora oculata in association with L. pertusa with similar abundances of both species within explored reefs, despite a tendency of increased abundance of L. pertusa compared to M. oculata toward higher latitudes. This systematic association occasionally reached the colony scale, with “twin” colonies of both species often observed growing next to each other when isolated structures were occurring off-reefs. Finally, several “false chimaera” were observed within reefs, confirming that colonial structures can be “coral bushes” formed by an accumulation of multiple colonies even at the inter-specific scale, with no need for self-recognition mechanisms. Thus, we underline the importance of the hitherto underexplored M. oculata in the Eastern Atlantic, re-establishing a more balanced view that both species and their yet unknown interactions are required to better elucidate the ecology, dynamics and fate of European CWC reefs in a changing environment.

Prothoracic Gland Semiochemicals of Green Lacewings.

Adult chrysopids have paired prothoracic glands (PG) that are thought to produce defensive secretions (allomones). We analyzed PG extracts of the following green lacewings from North and South America, Australia, and China: Ceraeochrysa cubana (Brazil); Chrysopa (= Co.) oculata, Co. nigricornis, Co. incompleta, Co. quadripunctata (USA), and Co. septempunctata (China); Chrysoperla (= Cl.) rufilabris (USA) and Cl. sp. (Brazil); Plesiochrysa ramburi and Mallada spp. (Australia). PG secretions are characteristic for species within a genus, except for Chrysopa spp. (Z)-4-Tridecene is ubiquitous, but (Z,Z)-4,7-tridecadiene is a major PG constituent in some Chrysopa spp. and in P. ramburi. Earlier reports that Co. oculata and Co. nigricornis produce 1-tridecene were shown to be in error. Chrysopa PG secretions are distinguished by the presence or absence of N-3-methylbutylacetamide, plus skatole (3-methylindole). Skatole is also identified for the first time from the Plesiochrysa and Ceraeochrysa. The PG secretion in Plesiochrysa ramburi is characterized by the presence of (Z)-4-undecene instead of (Z)-4-tridecene, and N-3-methylbutylpropanamide instead of the acetamide, resembling the PG secretions of Chrysopa nigricornis, Co. septempunctata and Co. incompleta. The chemotaxonomic value of PG semiochemicals is discussed, including evidence for subgroups within the genus Chrysopa as it now stands.

海洋小球藻Chlorella sp.甘油脂及脂肪酸、光合色素特征的研究

海洋微藻是海洋生态系统中最主要的初级生产者，也是海洋生物资源的重要来源。许多海洋微藻富含对人体具有重要的生理作用与保健功能的长链多不饱和脂肪酸，因此，筛选富含EPA、DHA等长链多不饱和脂肪酸的微藻和利用人工培养方法提高这些脂肪酸的产量是当前海洋生物学研究领域的热点之一。在本研究中，我们对被中科院海洋所定名为“Chlorella sp”（编号为1061）的一种海洋微藻的化学分类、甘油脂及其脂肪酸组成和外源葡萄糖和抗氧化剂（硫代硫酸钠）对这种微藻的脂肪酸含量的影响进行了研究，取得了以下主要结果。 海洋微藻是我固海水养殖中广泛使用的优良饵料藻。脂类物质是微藻最重要的营养指标之一，在本研究中，我们首先分析了被中科院海洋所定名为“Chlorellasp”的海洋微藻中的甘油脂及其脂肪酸种类和组成特点。结果表明，Chlorella sp.中的非极性脂主要为三脂酰甘油，极性甘油脂有10种。其中，一般培养条件下（温度23℃：光照，周期L/D14:10，强度60umolm-2-S-l）三脂酰甘油约占总脂的31 mol%，极性甘油脂约占总脂的69 rriol%。10种极性甘油脂是单半乳糖甘油二脂( monogalactosyldiacylglycerol． MGDG)、 双半乳糖甘油二脂( diagalactosyldiacylglycerol ， DGDG)、 硫代异鼠李糖甘油二脂( sulfoquinovosyldiacylglycerol，SQDG)、磷脂酰甘油(phosphatatidylglycerol，PG)、磷脂酰乙醇胺(phosphatidylethanolamine，PE)、磷脂酰胆碱( phosphatidylcholine，PC)、磷脂酰肌醇(phosphatidylinositol，PI)、磷脂酰丝氨醴(phosphatidylserine，Ps)、l，2-二酰基甘油-0-4，．（ⅣMⅣ-三甲基）高丝氨酸（diacylglyceryltrimethylhomoserine，DGTS）以及一种未能完全肯定，但可能是一中氯硫脂( chlorosulfolipid，CSL)。其中MGDG、DGDG、SQDG和PG是构成光合膜的主要成分，也是Chlorella sp中的主要极性脂。甜菜碱脂DGTS和磷脂PC是构成非光合膜的主要组分。Chlorella sp.中的主要脂肪酸为C16:0、C16:1耜C20：5（EPA)，后者主要存在于MGDG、DGDG和DGTS中，而三脂酰甘油也含有接近7%的EPA。 海洋微藻Chlorella sp.1061虽然被归属到绿藻纲绿藻目小球藻属，但是我们的研究表明，其色素、极性脂皮其脂肪酸组成与其它小球藻属藻类存在这很大差异Chl b是绿藻纲藻类中最主要的光合色素之一，1 6：4(n-3)和l 8：3(n-3)是绿藻微藻的主要脂肪酸，然而所有这些绿藻的特征化合物均未在Chlorella sp. 1061中检测到。DGTS和20:5(n-3)存在于很多的海洋微藻中，我们从Chlorella sp. 1061 中分离到占总极性甘油脂8 mo1%的DGTS，并从MGDG、DGDG和DGTS等极性甘油脂中检测到大量的20:5(n-3)。但是一般认为，小球藻属藻类中不舍这两种化合物。根据Chlorella sp. 1061的以上特点，这种藻不应该被归到小球藻属中。另外，由于Chlorella sp. 1061在色素、膜脂和脂肪酸组成特征方面大眼藻纲( Eustigmatophyceae)中的微绿球藻（Nannochloropsis）非常相似，因此，我们认为ChloreHa sp. 1061可能是Nannochloropsis中的一个种。但是未得到更进一步的证明和权威的认可之前，本文中我们仍然沿用ChloreHa sp,这一名称。 许多藻类中DGTS和PC -般不会同时存在，或者说一个存在时另外的一个的含量非常低。由此有人认为DGTS和PC之间存在着相互替代的关系。然而本研究中发现正常培养条件下Chlorella sp.中的DGTS和PC含量均较高（约10%）。磷处理实验结果表明，磷缺乏时Chlore Ha sp,中DGTS舍量大幅升高，而同时PC含量相应下降许多：但高浓度的磷并不能提高PC含量和降低DGTS含量，说明Chlorella sp,中DGTS仍可起替代PC的作用，然而PC可能并不能替代DGTS。Chlorella sp.中MGDG和DGTS脂肪酸组成及其位置分布结果显示，它们的组成和分布相似;在老化培养过程中MGDG和DGTS表现出周期性的相反的含量升高、降低的趋势，这进一步说明MGDG和DGTS之间存在着特殊的关系，MGDG可能合成自DGTS。 海洋微藻富含有利于人体健康的长链不饱和脂肪酸，如何提高微藻脂肪酸特别是多不饱和脂肪酸产量是目前研究的热点之一。本文首次报道了同时加入葡萄糖和硫代硫酸钠对Chlorelta sp,的生长、脂类组成和脂肪酸总产量的影响，结果显示葡萄糖和硫代硫酸钠存在明显而且强烈的互作，二者在培养液中的同时存在显著刺激了脂肪酸总产量的积累，在培养液中分别加入2.5 mM的葡萄糖和5mM的硫代硫酸钠，脂肪酸的产量可以比对照提高78%。而低浓度的葡萄糖和硫代硫酸钠对Chlorella sp.脂肪酸组成影响变化不明显，甚至在硫代硫酸钠存在下令人感兴趣的EPA含量还略有升高。显然，在Chlorella sp.培养中同时加入低浓度的葡萄糖和硫代硫酸钠是极具潜力的提高脂产量的方法，也可作为提高培养微藻其它活性物质产量借鉴的方法。在不久的将来，这种培养方法很可能发展成为生产实践中提高Chlore sp．乃至其它微藻脂肪酸、EPA和其它活性物质产量的经济有效的新途径。

Altered Lipid Accumulation in Nannochlropsis Salina CCAP849/3 Following EMS and UV Induced Mutagenesis

Microalgae have potential as a chemical feed stock in a range of industrial applications. Nannochloropsis salina was subject to EMS mutagenesis and the highest lipid containing cells selected using fluorescence-activated cell sorting. Assessment of growth, lipid content and fatty acid composition identified mutant strains displaying a range of altered traits including changes in the PUFA content and a total FAME increase of up to 156% that of the wild type strain. Combined with a reduction in growth this demonstrated a productivity increase of up to 76%. Following UV mutagenesis, lipid accumulation of the mutant cultures was elevated to more than 3 fold that of the wild type strain, however reduced growth rates resulted in a reduction in overall productivity. Changes observed are indicative of alterations to the regulation of the omega 6 Kennedy pathway. The importance of these variations in physiology for industrial applications such as biofuel production is discussed.

The long-term impacts of fisheries on epifaunal assemblage function and structure, in a special area of conservation

Fisheries can have profound effects on epifaunal community function and structure. We analysed the results from five dive surveys (1975–1976, 1980, 1983, 2003 and 2007), taken in a Special Area of Conservation, Strangford Lough, Northern Ireland before and after a ten year period of increased trawling activity between 1985 and 1995. There were no detectable differences in the species richness or taxonomic distinctiveness before (1975–1983) and after (2003–2007) this period. However, there was a shift in the epifaunal assemblage between the surveys in 1975–1983 and 2003–2007. In general, the slow-moving, or sessile, erect, filterfeeders were replaced by highly mobile, swimming, scavengers and predators. There were declines in the frequency of the fished bivalve Aequipecten opercularis and the non-fished bivalves Modiolus modiolus and Chlamys varia and some erect sessile invertebrates between the surveys in 1975–1983 and 2003–2007. In contrast, there were increases in the frequency of the fished and reseeded bivalves Pecten maximus and Ostrea edulis, the fished crabs Cancer pagurus and Necora puber and the non-fished sea stars Asterias rubens, Crossaster papposus and Henricia oculata between the surveys in 1975–1983 and 2003–2007. We suggest that these shifts could be directly and indirectly attributed to the long-termimpacts of trawl fishing gear, although increases in the supply of discarded bait and influxes of sediment may also have contributed to changes in the frequency of some taxa. These results suggest that despite their limitations, historical surveys and repeat sampling over long periods can help to elucidate the inferred patterns in the epifaunal community. The use of commercial fishing gear was banned from two areas in Strangford Lough in 2011, making it a model ecosystem for assessing the long-term recovery of the epifaunal community from the impacts of mobile and pot fishing gear.

The Portuguese continental shelf soft-bottom benthic habitats

As comunidades de macrofauna bentónica são ecológica e economicamente relevantes, sendo fonte de diversos bens e serviços. A sua identificação, caracterização e mapeamento são importantes para identificar áreas marinhas protegidas e para uma melhor utilização do ambiente marinho. Este trabalho apresenta um estudo holístico da diversidade e distribuição espacial das comunidades de macrofauna bentónica ao longo da plataforma continental Portuguesa. Cerca de 145 locais posicionados ao longo da plataforma ocidental e setentrional foram amostrados com uma draga Smith-McIntyre de área 0,1 m2, a profundidades que variaram entre os 13 e 195 metros. Os sedimentos foram caracterizados em termos de granulometria, de matéria orgânica e geoquímica. São propostos seis habitats bentónicos principais para a plataforma continental Portuguesa, analisada a relação entre os dados biológicos e ambientais e discutidas questões biogeográficas relacionadas com a distribuição espacial de espécies e das comunidades. A distribuição da granulometria e assinatura geoquímica dos sedimentos da plataforma continental revelou-se bastante complexa, refletindo importantes diferenças nas fontes (naturais e antropogénicas), origem fluvial, geomorfologia da plataforma, hidrodinamismo e atividade biológica. Relativamente à macrofauna, entre os mais de 30 mil indivíduos recolhidos, foram identificados cerca de 737 taxa, dos quais quatro são novas espécies e aproximadamente 40 correspondem a primeiras ocorrências para a costa Portuguesa. As espécies mais frequentes foram a Ampharete finmarchica, Ampelisca sp. e Lumbrineris lusitanica sp. nov. enquanto as mais abundantes foram Mediomastus fragilis, Polygordius appendiculatus e Ampharete finmarchica. A abundância por local de amostragem variou entre 7 e 1.307 espécimens e a diversidade alfa atingiu um máximo de 96 taxa. Os sedimentos mais grosseiros apresentaram maior diversidade e abundância comparativamente com os sedimentos envasados. Foram identificados seis habitats bentónicos na plataforma continental Portuguesa: (a) sedimentos grosseiros com Protodorvillea kefersteini, Pisione remota, Angulus pygmaeus e várias espécies intersticiais; (b) areias finas hidrodinamicamente expostas e próximas da linha de costa com Magelona johnstoni, Urothoe pulchella e Angulus fabula; (c) comunidade de Abra alba em areia envasadas da plataforma profunda do noroeste; (d) Galathowenia oculata, Lumbrinerides amoureuxi e outros poliquetas escavadores e tubícolas em areais envasadas muito profundas na plataforma sudoeste; (e) Euchone rubrocincta, Nematonereis unicornis e várias espécies setentrionais nas areias envasadas da plataforma sul; (f) vasas com Sternaspis scutata, Heteromastus filiformis e Psammogammarus caecus. A granulometria do sedimento (particularmente teor em finos), matéria orgânica, profundidade e hidrodinamismo foram as variáveis ambientais com a maior relação com os padrões de distribuição da macrofauna. As espécies cosmopolitas e de latitudes superiores (clima Boreal ou Temperado Frio) dominaram o setor noroeste, sendo substituídas por espécies mais quentes na área de transição entre os canhões da Nazaré e S. Vicente, que dominaram por conseguinte a plataforma sul. O presente estudo evidenciou a abundância e diversidade da macrofauna bentónica ao longo da área costeira de Portugal, na qual coexistem faunas das províncias biogeográficas do norte da Europa, bem como subtropicais. Integrado com outro estudos, este poderá ser a base para uma melhor gestão da plataforma continental Portuguesa.

Enrichment of bioactive compounds in microalgae for aquaculture

Microalgae are promising microorganisms for the production of food and fine chemicals. Several species of microalgae are used in aquaculture with the purpose of transfer bioactive compounds up to the aquatic food chain. The main objective of this project was to develop a stress–inducement strategy in order to enhance the biochemical productivity of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. for aquaculture purposes having in account their growth and organizational differences. In this regard, two experiments were design: the first one consisted on the alteration of overall nutrient availabilities in growth medium; and the second one comprised changes in nitrogen and sulfur concentrations maintaining the concentrations of the other nutrients present in a commercial growth medium (Nutribloom plus), which is frequently used in aquaculture. Microalgae dried biomass was characterized biochemically and elemental analysis was also performed for all samples. In first experimental design: linear trends between nutrient availability in growth media and microalgae protein content were obtained; optimum productivities of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) were attained for both R. marina and N. gaditana in growth media enriched with 1000 L L-1 of nutrient solution whereas for Isochrysis sp. the double of Nutribloom plus was needed; the decrease of glucans and total monosaccharides with nutrient availability for R. marina and Isochrysis sp. showed the occurrence of a possible depletion of carbohydrates towards lipids and proteins biosynthesis. Second experimental desing: N. gaditana exhibited the highest variation in their biochemical composition against the applied perturbation; variations observed for microalgae in their biochemical composition were reflected in their elemental stoichiometry; in N. gaditana the highest nitrogen concentrations lead to overall maximum productivities of the biochemical parameters. The results of the present work show two stress-inducement strategies for microalgae that may constitute a base for further investigations on their biochemical enhancement.

Cultivo masivo de microalgas en Biorreactores verticales

El cultivo masivo de microalgas en biorreactores presenta una alta tasa de productividad frente a los cultivos abiertos, esta ventaja, aunada a determinados factores ambientales, se relaciona directamente con la cantidad y calidad de biomasa algal obtenida como producto final en el proceso de cultivo. El presente trabajo centró sus investigaciones en la evaluación de los parámetros físicos del ambiente (temperatura e intensidad lumínica), así como, físico-químicos (temperatura, pH y CO2) en la capacidad de carga de los cultivos. La investigación se desarrolló en el invernadero del Área de Biotecnología Acuática, del Instituto del Mar del Perú, dentro del marco del Proyecto IMARPE-EEP-FINCyT, denominado “Determinación de la Biomasa Microalgal potencialmente acumuladora de lípidos para la obtención de combustibles”, según contrato Nº025-FINCYT-PIBAP-2007. Los cultivos se realizaron empleando la cepa IMP-LBA-009, correspondiente a la microalga Nannochloropsis spp., con un flujo de producción semi-continuo por 48 horas, en un periodo de 6 meses, entre julio a diciembre, Bajo condiciones de iluminación (22,003.93 Lux.m-2.seg-1 ±10640.94), temperatura ambiental (31.7°C±2.8), temperatura de cultivo (25.7°C±1.2), CO2 (0.2 g.L-1) y pH (8.36 ±0.18); los resultados mostraron que la producción de biomasa húmeda fue 0.48g.L-1, equivalente a 0.13 g.L-1 de biomasa seca, durante los meses de octubre y noviembre, con una razón de conversión BS/BH del 28%. El impacto lumino-térmico, al interior del invernadero, favoreció el incremento progresivo de la concentración celular del cultivo en biorreactores, por ende, la producción de biomasa húmeda y seca, durante el periodo de trabajo.

STUDIES ON TAXONOMY, DISTRIBUTION, ECOLOGY AND REPRODUCTIVE POTENTIAL OF ROTIFERS FROM SELECTED CENTRES IN COCHIN BACKWATER SYSTEM, KERALA

The studies were conducted in nine stations with varying ecological characteristics along Cochin backwaters and adjoining canals. Many workers opined that the distribution of rotifers is cosmopolitan. The significance of rotifers as first food for early larvae was indicated by Fujita. Aquaculture is a fast growing field in fisheries sector and it is gaining more importance as the fish landings and supply are getting irregular. A consistent supply of fish/shellfish can only be achieved through aquaculture. The success of any culture activity depends on the timely production of seeds of finfishes/shellfishes. The availability of wild seed is seasonal and erratic. So, a dependable source of seed of fishes and shellfishes is possible only through large scale production in hatchery. A successful seed production activity depends on the availability of a variety of suitable live feed organisms in sufficient quantities at the proper time for use in the larval stages. As the live feeds promote high growth rates, easy digestion, assimilation and the quality of not contaminating the culture water when compared to other artificial feeds, make the culture of live feed organisms the principal means of providing food for the larvae of finfishes and shellfishes. Rotifers are considered to be an excellent and indispensable food for larvae of many finfishes and crustaceans. It (1960) was the first to culture Brachionus plicatilis for feeding marine fish larvae, and now it is being extensively used as live feed in hatcheries all over the world. They are a group of microscopic organisms coming under the Phylum Rotifera which comprises of about 2000 species. Their slow swimming habits, ability to tolerate a wide range of salinities, parthenogenetic mode of reproduction and ability to get enriched easily, make rotifers an ideal live feed organism. The major factors such as temperature, salinity and food that influence the reproductive potential and thereby the population size of rotifer, Salinity is one of the most important aspect influencing the reproductive rate of rotifers. The feed type and feed concentration play a vital role in influencing the reproductive rate of rotifers. For culture of rotifers, the commonly used micro algae belong to Chlorella, Nannochloropsis, Isochrysis and Tetraselmis. While some studies have suggested that, algal diet has little effect on reproductive rates in 1979 while using the rotifer, Brachionus plicatilis as feed for the larvae of red sea bream, Pagrus major. It is generally accepted that rotifers play a pivotal role in the successful rearing of marine fish larvae.

“Effects of monospecific and mixed algal diets on survival, development and biochemical composition of Penaeus monodon larvae”

The main objective of the present work is to acquire information regarding the growth responses of P. monodon larvae (from PZ1 upto PL1) to various mono specific and mixed diets. Evaluate the nutritional quality of selected species of micro algae viz. Chaetoceros calcitrans, Dunaliella salina, Isochrysis galbana and Nannochloropsis salina, larvae at three cell concentrations 10x104 cells/ml, 25x104 cells/ml and 50x104 cells/ml. The P. monodon larvae were transported, at the Nauplius stage, to the laboratory. The larvae were stocked at density of 150 larvae per litre in 5 litre FRP tanks with 3 litres of sea water. The algal cell density given to the larvae varied. The larval stages were fed with increasing densities of algae to evaluate the relationship between the food densities, ingestion rates, development and growth of the larvae. The water quality parameters, the percentage of survival rate, the growth estimation and the algal cell count were done. Each experiment was carried out in triplicate with a control group of larvae fed with Chaetoceros calcitrans. For the estimation standard procedures were used.to P. monodon