Improved larval survival at metamorphosis of Asian seabass (Lates calcarifer) using ω3-HUFA-enriched live food
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Asian seabass (Lates calcarifer) larvae were fed Brachionus cultured on Chlorella and, as soon as ingestin was possible, different types of Artemia, i.e., nauplii of the San Francisco Bay (SFB) strain, Great Salt Lake (GSL) strain or GSL nauplii that had been bioencapsulated with an emulsion containing high levels of the ω3-HUFAs (highly unsaturated fatty acids) 20:5 and 22:6. San Francisco Bay Artemia with a good natural fatty acid profile and small body size could be offered earlier than the larger but HUFA-poor Great Salt Lake strain. The poor nutritional quality of the latter, however, could be corrected by enriching the nauplii with an ω3-HUFA emulsion for 24 h, after which time high levels of the ω3-HUFAs 20:5 and 22:6 were obtained. When the Artemia diet offered before metamorphosis included natural or supplemented essential fatty acids, no significant differences in dry weight, length or survival of the fish were noticed, as compared to fish fed the naturally deficient GSL Artemia. Onset of metamorphosis and physiological condition after metamorphosis, however, were influenced by the HUFA content of the ingested prey. Seabass larvae fed SFB or enriched GSL Artemia started metamorphosis on day 19, while those in the non-enriched series never achieved metamorphosis and died of a nutritional deficiency syndrome by day 27. An indication of the physiological condition of the larvae and the early detection of the syndrome was possible by subjecting 21- and 25-day-old larvae to a stress test: abrupt exposure of the larvae to 65-ppt saline water resulted in abundant and early mortality in HUFA-deficient fish larvae. Fry receiving ω3-HUFA-fortified Artemia had a superior physiological condition which was reflected by significantly lower mortality figures in the stress test.
CitationDhert, P., Lavens, P., Duray, M., & Sorgeloos, P. (1990). Improved larval survival at metamorphosis of Asian seabass (Lates calcarifer) using ω3-HUFA-enriched live food.
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The effect of tank color and rotifer density on rotifer ingestion, growth and survival of milkfish (Chanos chanos) larvae MN Duray -
The Philippine Scientist, 1995 - San Carlos Publications, University of San CarlosThe effect of tank color on rotifer ingestion, early growth and survival of milkfish larvae was assessed. The larvae were stocked at 30/L in 200-L fiberglass tanks coated black or unpainted (tan). Larvae were fed rotifers at densities of 5, 10, and 15/ml. Growth and survival were higher in black tanks than in tan tanks. Rotifers ingested were also higher in larvae reared in black tanks. In black tanks, the survival of the larvae was enhanced at high rotifer density of 15/ml. Rotifer ingestion and growth of larvae improved at higher feeding levels.
Conference paperMN Duray - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - Aquaculture Department, Southeast Asian Fisheries Development CenterThe feeding habits of hatchery-reared Epinephelus suillus larvae were determined by examining their gut contents. The larvae (2.6 mm TL) were initially fed rotifers on day 2 and newly-hatched Artemia nauplii on day 21 (9.1 mm TL). The amount of rotifers initially ingested averaged 1.3 individuals/larva. The ingestion rate increased as larvae grew. Larvae immediately showed strong preference for Artemia to rotifers on the first day of introduction. E. suillus larvae showed diurnal feeding pattern at day 7 (3.6 mm TL), day 14 (4.9 mm TL), day 21 (9.1 mm TL) and day 28 (11.1 mm TL). Feeding incidence decreased in the evening and was nil at 2100-2200 h. Active feeding started earlier in older larvae and satiation was between 0900-1000 h. The results of this study will be used as a basis in developing a good feeding scheme for E. suillus larvae.
mRNA expression patterns for GH, PRL, SL, IGF-I and IGF-II during altered feeding status in rabbitfish, Siganus guttatus. Feeding time is a major synchronizer of many physiological rhythms in many organisms. Alteration in the nutritional status, specifically fasting, also affects the secretion rhythms of growth hormone (GH) and insulin-like growth factor-I (IGF-I). In this study, we investigated whether the expression patterns for the mRNAs of GH, prolactin (PRL) and somatolactin (SL) in the pituitary gland, and insulin-like growth factor I and II (IGF-I and IGF-II) in the liver of juvenile rabbitfish (Siganus guttatus) follow a rhythm according to feeding time and whether these hormone rhythms changes with starvation. Hormone mRNA levels were determined by real time PCR. The daily expression pattern for the mRNAs of GH, PRL and SL was not altered whether food was given in the morning (10:00 h) or in the afternoon (15:00 h). The daily GH mRNA expression pattern, however, was affected when food was not available for 3 days. In contrast, the daily expression pattern for IGF-I mRNA reaches its peak at roughly 5–6 h after feeding. This pattern, however, was not observed with IGF-II mRNA. During 15-day starvation, GH mRNA levels in starved fish were significantly higher than the control fish starting on the 9th day of starvation until day 15. The levels returned to normal after re-feeding. In contrast to GH, PRL mRNA levels in starved fish were significantly lower than the control group starting on the 6th day of starvation until 3 days after re-feeding. SL mRNA levels were not significantly different between the control and starved group at anytime during the experiment. Both IGF-I and IGF-II mRNA levels in starved group were significantly higher than the control fish on the 3rd and 6th day of starvation. mRNA levels of both IGF-I and II in the starved fish decreased starting on the 9th day of starvation. While IGF-I mRNA levels in the starved group continued to decrease as starvation progressed, IGF-II mRNA levels were not significantly different from the control during the rest of the starvation period. The results indicate that aside from GH and IGF-I, PRL and IGF-II are likewise involved in starvation in rabbitfish.