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Highest Growth Rate (highest + growth_rate)
Selected AbstractsComparison of some live organisms and artificial diet as feed for Asian catfish Clarias macrocephalus (Günther) larvaeJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2005A. D. Evangelista Summary Experiments were conducted to evaluate the efficacy of five live organisms (Artemia, Brachionus calyciflorus, Chironomus plumosus, Moina macrocopa and Tubifex sp.) and an artificial diet (40% protein) in the larval rearing of Asian catfish Clarias macrocephalus. The larvae were fed three times daily starting at the onset of exogenous feeding. Results showed that the catfish larvae utilized the live organisms more efficiently than the artificial diet. The Tubifex -fed larvae consistently showed the highest growth rate. In trial 1, length increment (64.9 mm), weight gain (3192 mg) and specific growth rate (13.1%) after 8 weeks of feeding were significantly higher (P < 0.05) in catfish larvae given Tubifex than those in all other treatments. In trial 2, length increment after 4 weeks of feeding was highest in larvae fed Tubifex (22.9 mm) although it did not significantly differ from that of larvae given Moina (21.0 mm). However, weight gain of larvae fed Tubifex (253.0 mg) was significantly higher than that of larvae fed Moina (171.6 mg). The specific growth rate was highest for larvae fed Tubifex (15.0%) followed by larvae fed Artemia (14.5%), Moina (14.4%) and Chironomus (12.0%). Survival rates of the catfish larvae ranged from 9 to 39% after 8 weeks in trial 1 and from 26 to 83% after 4 weeks in trial 2. The present results suggest that Tubifex is an excellent food and a potential substitute for Artemia in the rearing of catfish larvae. [source] Effects of temperature, irradiance and photoperiod on growth and pigment content in some freshwater red algae in culturePHYCOLOGICAL RESEARCH, Issue 2 2001Marcelo Ribeiro Zucchi SUMMARY The responses of relative growth rate (% day-1) and pigment content (chlorophyll a, phycocyanin and phycoerythrin) to temperature, irradiance and photoperiod were analyzed in culture in seven freshwater red algae: Audouinella hermannii (Roth) Duby, Audouinella pygmaea (Kützing) Weber-van Bosse, Batrachospermum ambiguum Montagne, Batrachospermum delicatulum (Skuja) Necchi et Entwisle,,Chantransia' stages of B. delicatulum and Batrachospermum macrosporum Montagne and Compsopogon coeruleus (C. Agardh) Montagne. Experimental conditions included temperatures of 10, 15, 20 and 25°C and low and high irradiances (65 and 300 ,mol photons m,2 s,1, respectively). Long and short day lengths (16:8 and 8:16 LD cycles) were also applied at the two irradiances. Growth effects of temperature and irradiance were evident in most algae tested, and there were significant interactions among treatments. Most freshwater red algae had the best growth under low irradiance, confirming the preference of freshwater red algae for low light regimens. In general there was highest growth rate in long days and low irradiance. Growth optima in relation to temperature were species-specific and also varied between low and high irradiances for the same alga. The most significant differences in pigment content were related to temperature, whereas few significant differences could be attributed to variation in irradiance and photoperiod or interactions among the three parameters. The responses were species-specific and also differed for pigments in distinct temperatures, irradiances and photoperiods in the same alga. Phycocyanin was generally more concentrated than phycoerythrin and phycobiliproteins were more concentrated than chlorophyll a. The highest total pigment contents were found in two species typical of shaded habitats: A. hermannii and C. coeruleus. The expected inverse relationship of pigment with irradiance was observed only in C. coeruleus. In general, the most favorable conditions for growth were not coincident with those with highest pigment contents. [source] Comparative performance of juvenile red abalone, Haliotis rufescens, reared in laboratory with fresh kelp and balanced dietsAQUACULTURE NUTRITION, Issue 2 2009Z. GARCIA-ESQUIVEL Abstract Juvenile Haliotis rufescens were reared in the laboratory in order to investigate the extent to which fresh kelp and formulated feeds with 250 g kg,1 (25P) and 380 g kg,1 protein content (38P) affected their growth rate, gut residence time (GRT), food consumption (C), food conversion ratio (FCR) and digestibility. Abalone from 38P attained the highest growth rate (70.5 ± 4.2 ,m day,1; 98.3 ± 6.95 ,g day,1), followed by 25P (47.9 ± 2.79 ,m day,1; 67.4 ± 2.82 ,g day,1) and kelp (23.6 ± 3.36 ,m day,1; 28.2 ± 4.11 ,g day,1). No significant differences were observed in consumption rate among treatments (0.61,0.68% body weight per day), yet kelp-fed abalone exhibited higher FCR (2.44), protein efficiency ratio (4.42), and apparent digestibility of dry matter (69.5%), protein (69.8%) and gross energy (79.2%) than 38P organisms (59.8, 62.4 and 62.2%, respectively). They also showed longer GRT (23.1 ± 0.93 h). This study demonstrated that formulated diets with 250 g kg,1 and 380 g kg,1 protein inclusion can sustain higher growth rates of juvenile H. rufescens than fresh algae. These differences seem to be due to the amount of dietary protein. Kelp meal appears to improve the consumption and digestibility of balanced diets, and its inclusion in formulated diets is recommended. [source] Effect of antibiotic treatment on the growth and survival of juvenile northern Chilean scallop, Argopecten purpuratus Lamarck (1819), and associated microflora in experimental culturesAQUACULTURE RESEARCH, Issue 12 2009Jorge Fierro Abstract Juvenile northern Chilean scallops of 937±55 ,m shell height were exposed to five different concentrations of chloramphenicol (CHL) (5, 10, 25, 50 and 100 ,g mL,1), plus a control without antibiotics. To determine the effect of CHL on the accompanying microflora, the number of colony-forming units (CFU) that grew on TGE culture medium was counted in the seawater of containers with juveniles, and in containers with microalgae used as food. Both were exposed to the same concentrations of CHL. The growth rates of juveniles treated with CHL and the control without antibiotic showed highly significant differences (P=0.0001). The growth rate was inversely proportional to the CHL concentration. The control sample presented the highest growth rate (84.4±14.3 ,m day,1), followed by the sample treated with 5 ,g mL,1 (64.2±14.3 ,m day,1). The survival in the control and in the treated samples with 5,50 ,g mL,1 was rather high, with a mean value of 95%. Only the sample treated with 100 ,g mL,1 had a low survival (36.7%). The CFU count was larger in the containers with juveniles, when compared with the ones with food. The CFU count tended to decrease with increasing CHL concentration in the juveniles. [source] Feeding rates, assimilation efficiencies and growth of two amphipod species on biodeposited material from zebra musselsFRESHWATER BIOLOGY, Issue 12 2008RENÉ GERGS Summary 1. Accumulation of organic material by the zebra mussel Dreissena polymorpha is assumed to be the source of a biodeposition-based food web. However, only little is known about the importance of the biodeposited material as a food source and its contribution to increased abundances of macroinvertebrates in the presence of D. polymorpha. 2. Feeding, assimilation and growth of the amphipods Gammarus roeselii and Dikerogammarus villosus on food sources directly and indirectly associated with D. polymorpha (biodeposited material and chironomids) and on conditioned alder leaves were measured. The stoichiometry of carbon, nitrogen and phosphorus of the diets was measured as an important determining factor of food quality. 3. Chironomids had the highest nitrogen and phosphorus contents, alder leaves were depleted in nitrogen and phosphorus, and the stoichiometry of biodeposited material was intermediate. 4. Both amphipod species had highest feeding rates and assimilation efficiencies on chironomids. Gammarus roeselii fed more on biodeposited material than on alder leaves, but assimilation efficiencies were similar; D. villosus also had similar feeding rates and assimilation efficiencies on the two diets. 5. Both amphipod species had highest growth rates on chironomids and lowest growth rates on alder leaves. Both grew at intermediate rates on biodeposited material of D. polymorpha. The growth rates of the amphipod species were related to food stoichiometry. Overall, the invasive D. villosus grew faster than the indigenous G. roeselii. 6. Food resources directly and indirectly associated with D. polymorpha are potential diets for amphipods, providing further evidence for a D. polymorpha biodeposition-based food web. [source] There are High Levels of Functional and Genetic Diversity in Oxyrrhis marinaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2005CHRIS D. LOWE Abstract. Oxyrrhis marina, a widely distributed marine protist, is used to model heterotrophic flagellate responses in microbial food webs. Although clonal variability occurs in protists, assessments of intraspecific diversity are rare; such assessments are critical, particularly where species are used as models in ecological studies. To address the extent of intraspecific variation within O. marina, we assessed diversity among 11 strains using 5.8S rDNA and ITS sequences. The 5.8S rDNA and ITS regions revealed high divergence between strains: 63.1% between the most diverse. To compare O. marina diversity relative to other alveolates, 18S rDNA sequences for five strains were analysed with sequences from representatives of the major alveolate groups. 18S rDNA also revealed high divergence in O. marina. Additionally, consistent with phylogenies based on protein coding genes, maximum likelihood analysis indicated that O. marina was monophyletic and ancestral to the dinoflagellates. To assess ecophysiological differences, growth rates of seven O. marina strains were measured at 10 salinities (10,55,). Two salinity responses occurred: one group achieved highest growth rates at high salinities; the other grew best at low salinities. There was no clear correlation between molecular, ecophysiological, or geographical differences. However, salinity tolerance was associated with habitat type: intertidal strains grew best at high salinities; open-water strains grew best at low salinities. These data indicate the need to examine many strains of a species in both phylogenetic and ecological studies, especially where key-species are used to model ecological processes. [source] |