Now showing items 1-3 of 3

    • Article

      Effect of growth hormone and γ-aminobutyric acid on Brachionus plicatilis (Rotifera) reproduction at low food or high ammonia levels 

      WG Gallardo, A Hagiwara, Y Tomita & TW Snell - Journal of Experimental Marine Biology and Ecology, 1999 - Elsevier
      Growth hormone (GH, 0.0025 and 0.025 I.U. ml−1) and γ-aminobutyric acid (GABA, 50 μg ml−1) enhance rotifer population growth in batch cultures. In order to further understand the mechanism of their actions, we conducted experiments culturing isolated females at low food and high free ammonia levels. At an optimum food level of 7×106Nannochloropsis oculata cells ml−1 or at low free ammonia level of 2.4 μg ml−1, the F1 offspring of rotifers treated with GH at 0.0025 I.U. ml−1 had significantly higher population growth rate (r) and net reproduction rate (Ro), and shorter generation time than untreated rotifers. At a lower food level of 7×105 cells ml−1 or at high free ammonia level of 3.1 μg ml−1, rotifers treated with GABA at 50 μg ml−1 had significantly higher r and Ro, and shorter generation time. These results indicate that GABA is effective in enhancing rotifer reproduction when rotifers are cultured under stress whereas GH enhances rotifer reproduction when culture conditions are optimal. Significant effects were also observed in F1 and F2 generations which were not treated with hormones. These data may be useful for treating rotifer mass cultures to mitigate the effects of stress caused by high population densities.
    • Article

      Euryhaline rotifer Proales similis as initial live food for rearing fish with small mouth 

      A Hagiwara, S Wullur, HS Marcial, N Hirai & Y Sakakura - Aquaculture, 2014 - Elsevier
      The SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish larvae with a small mouth. However, there are commercially important fish species whose mouth sizes are too small to feed on SS-type rotifers. In 2004, we isolated a small (body length = 82.7 ± 10.9 μm; body width 40.5 ± 6.4 μm), flexible, and iloricate rotifer, Proales similis from an estuary in Okinawa, Japan. Under laboratory conditions (25 °C, 2–25 ppt) P. similis produced its first offspring on 2.5 to 2.8 days after hatching, and produced 4.3 to 7.8 offspring within 4.0 to 4.7 days life span. Batch cultured P. similis fed Nannochloropsis oculata suspension at 28.8 μg dry weight ml− 1 and cultured at 25 °C, 25 ppt filtered seawater, increased exponentially from 25 to 2400 ind ml− 1 after 11 days of culture with an overall intrinsic rate of natural increase (r) of 0.42 day− 1. The growth rate of P. similis was not significantly different when fed fresh N. oculata and super fresh Chlorella vulgaris-V12®. Total lipid per wet weight of P. similis fed by N. oculata and C. vulgaris were 2.4 and 2.6%, respectively. The compositions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) of P. similis fed N. oculata were 23.2, 0.0 and 5.3%, respectively, while these were 11.0, 17.5 and 0.5% respectively, when fed C. vulgaris. The use of P. similis to feed small mouth fish including seven-band grouper Epinephelus septemfasciatus, rusty angelfish Centropyge ferrugata, and humphead wrasse Cheilinus undulatus showed that it is an excellent starter food for these species because of their high selectivity index and improved survival. In addition, P. similis was ingested by Japanese eel Anguilla japonica larvae with a complicated digestive system. The use of P. similis as starter feed for small mouth fish larvae is highly recommended.
    • magazineArticle

      Live food: A lesser known essential 

      MB Surtida - SEAFDEC Asian Aquaculture, 2003 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This article is a short discussion of the requirements for live food production in aquaculture and a brief presentation of the processes involved.