The changes in the biochemical compositions and enzymatic activities of rotifer (Brachionus plicatilis) and Artemia, enriched and stored at 4 degrees C temperature, were determined. The total starvation period was 16 h and samples were taken at the end of the 8th and 16th hours. In present study, the rotifer and nauplii catabolized a large proportion of the protein during the enrichment period. Lipid contents of both live preys increased during the enrichment period and decreased in nauplii and metanauplii throughout the starvation period but lipid content of the rotifer remained relatively constant during the starvation period. The changes observed in the amino acid compositions of Artemia and the rotifer were statistically significant (P < 0.05). The conspicuous decline the essential amino acid (EAA) and nonessential amino acid (NEAA) content of the rotifer was observed during the enrichment period. However, the essential amino acid (EAA) and nonessential amino acid (NEAA) contents of Artemia nauplii increased during the enrichment period. The unenriched and enriched rotifers contained more monounsaturated fatty acid (MUFAs) than polyunsaturated fatty acid (PUFAs) and saturated fatty acids (SFA). However, Artemia contained more PUFAs than MUFAs and SFA during the experimental period. A sharp increase in the amounts of docosahexaenoic acid (DHA) during the enrichment of the rotifer and Artemia nauplii was observed. However, the amount of DHA throughout the starvation period decreased in Artemia metanauplii but not in Artemia nauplii. Significant differences in tryptic, leucine aminopeptidase N (LAP), and alkaline phosphatase (AP) enzyme activities of Artemia and rotifer were observed during the enrichment and starvation period (P < 0.05). The digestive enzymes derived from live food to fish larvae provided the highest contribution at the end of the enrichment period. In conclusion, the results of the study provide important contributions to determine the most suitable live food offering time for marine fish larvae. Rotifer should be offered to fish larvae at the end of the enrichment period, Artemia nauplii just after hatching and before being stored at 4 degrees C, and Artemia metanauplii at the end of the enrichment and throughout the starvation period.

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Variations in digestive enzymes and hormones during the larval development of gilthead seabream (Sparus aurata) fed on live prey (Artemia nauplii) enriched with free lysine were investigated for 16 days (from day 24 to day 40). Prior to initiation of the experiment, newly hatched larvae were transferred from incubators to fiber glass tanks (300 l) with black walls and fed the same diet until day 24. Each experiment was performed in triplicate. The amount of free lysine in the Artemia nauplii was increased by adding a 5.3 mM free amino acid solution to the culture water during a 16-h enrichment period. Larvae were sampled four times at four-day intervals, for 16 days. Larvae fed on the control group had lower growth than those fed on the lysine group at the end of the study but the difference was not significant (P [ 0.05). The highest trypsin activity and lap/leu-ala peptidase ratios were observed in the control group (P \ 0.05). Significant differences between bombesin activities of the treatment groups were not found in the fifth minute after the start of feeding (P [ 0.05) but were significant in the fifteenth minute (P \ 0.05). Significant differences between the CCK levels of the treatment groups were found (P \ 0.05). In conclusion, three main ideas are presented in this study. First, Artemia nauplii can successfully be enriched with free lysine. Second, bombesin (GRP) and cholecystokinin (CCK) activity can be stimulated by free lysine. Third, the mechanisms controlling adaptation of the activity of the trypsin to the amount of dietary protein were not activated until day 40.

No abstract

The aim of this study was to determine the potential inhibitory effects of commercial diets on protease activities of Dentex dentex larvae and live foods. The highest and lowest protease activity of larvae was 387.08 ±0.23 U/mg protein and 54.66 ±0.15 U/mg protein, respectively. The highest and lowest protease activities of live foods were found in Artemia metanaupli (414.5 ±0.41 U/mg protein) and rotifer (156.25 ±0.09 U/mg protein), respectively. The significant differences between inhibition amounts of commercial diets on protease activities of larvae and live foods were found (p<0.05). Also, the significant differences between the inhibition percents were observed (p<0.05). The highest inhibition percents of Caviar (200-300µ), Caviar (300-500µ) and copepod were found as 91.86 ±0.26%, 90.72 ±0.13% and 90.82 ±0.22% in enriched rotifers, respectively. In addition, the highest inhibition percents of Caviar (100-200µ) and Proton (200-400µ) were observed as 93.57 ±0.18% and 93.34 ±0.22% in the larvae on day 35, respectively. The effect of Caviar (200-300µ) on protease activities of rotifer was the lowest. In general, copepod had the lower inhibitory effect than those of other commercial diets on protease activities of larvae. Copepod showed the lowest effect on protease activity of larvae on day 30. The inhibition percents of commercial diets on protease activities of live foods were high except for rotifers. Our study revealed that the inhibitory effects of commercial diets used through weaning on protease activities of larvae and live foods should be taken into account. In conclusion, the potential inhibitory effects of commercial diets on protease activities of marine fish larvae and live foods to increase the survival and growth rates in hatcheries should be investigated in future studies.Bu çalışmanın amacı, Dentex dentex larvaları ve canlı gıdaların proteaz aktiviteleri üzerine ticari yemlerin potansiyel inhibitör etkilerini belirlemektir. Larvaların en yüksek ve en düşük proteaz aktiviteleri sırasıyla 387,08 ±0,23 U/mg protein ve 54,66 ±0,15 U/mg protein olarak tespit edildi. Canlı gıdaların en yüksek ve en düşük proteaz aktiviteleri sırasıyla Artemia metanaupli (414,5 ±0,41 U/mg protein) ve rotiferde (156,25 ±0,09 U/mg protein) bulundu. Larvaların ve canlı gıdaların proteaz aktiviteleri üzerine ticari yemlerin inhibisyon miktarları arasında istatistiksel olarak önemli farklılıklar bulundu (p<0,05). Aynı zamanda, inhibisyon yüzdeleri arasında da istatistiksel olarak önemli farklılıklar gözlendi (p<0.05). Zenginleştirilmiş rotiferler üzerinde, Caviar (200-300µ), Caviar (300-500µ) ve copepod'un en yüksek inhibisyon yüzdeleri sırasıyla %91.86 ±0.26, %90.72 ±0,13 ve %90.82 ±0.22 olarak bulundu. Buna ilaveten 35 günlük larvalarda, Caviar (100-200µ) ve Protonun (200-400µ) en yüksek inhibisyon yüzdeleri sırasıyla %93.57 ±0.18 ve %93.34 ±0.22 olarak gözlendi. Rotiferlerin proteaz aktiviteleri üzerine Caviar'ın (200-300µ) etkisi en düşük seviyede oldu. Genelde, larvaların proteaz aktiviteleri üzerinde kopepod'un diğer...