Now showing items 1-6 of 6

    • 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

      Effect of juvenile hormone and serotonin (5-HT) on mixis induction of the rotifer Brachionus plicatilis Muller 

      WG Gallardo, A Hagiwara & TW Snell - Journal of Experimental Marine Biology and Ecology, 2000 - Elsevier
      Juvenile hormone (JH) and serotonin (5-HT) were previously shown to enhance mictic (sexual) female production of the rotifer Brachionus plicatilis in batch cultures. To explore the basis of these effects, experiments were conducted on isolated individuals. JH treatment of maternal rotifers with 5 and 50 µg ml-1 (18.8 and 187.7 µM) resulted in significantly higher (P < 0.05) mictic female production in the second (F2) and third (F3) generations. JH treatment was effective even at a lower food concentration of 7 × 105 cells ml, but it was not effective when free ammonia was added at 2.4 and 3.1 µg ml-1. Mictic female production was not increased with exposure to 5-HT up to 50 µg ml-1 (129.1 µM) concentrations. When food level was reduced to 7 × 105 cells ml-1, however, 5-HT-treated rotifers produced significantly (P < 0.05) more mictic females than the control, particularly in F3 generation. Mictic female production of 5-HT-treated rotifers did not differ from that of the control with or without free ammonia, but the intrinsic rate of natural increase (r) of 5-HT-treated rotifers at 3.1 µg ml-1 free ammonia was significantly higher than the control. These results show that juvenile hormone increases mictic female production under optimum and sub-optimum food levels, whereas 5-HT increases both mictic female production at low food level and population growth rate at high free ammonia concentrations. These compounds could be used to manage rotifer cultures and probe the mechanisms controlling the rotifer life cycle as it switches to mictic reproduction.
    • Article

      Effect of some vertebrate and invertebrate hormones on the population growth, mictic female production, and body size of the marine rotifer Brachionus plicatilis Müller 

      WG Gallardo, A Hagiwara, Y Tomita, K Soyano & TW Snell - Hydrobiologia, 1997 - Springer Verlag
      Eight vertebrate and invertebrate hormones were screened for their effect on population growth, mictic female production, and body size of the marine rotifer Brachionus plicatilis. Growth hormone (GH) or human chorionic gonadotropin (HCG) at 0.0025-25 I.U. ml-1 and estradio1-17β (E2), triiodothyronine (T3), 20-hydroxyecdysone (20-HE), 5-hydroxytryptamine(5-HT), gamma-aminobutyric acid (GABA) or juvenile hormone (JH) at 0.05-50 mg l-1 were added to 5-ml of Nannochloropsis oculata suspension (7 x 106 cells ml-1). From an initial density of 1 individual ml-1, rotifers were cultured with hormones for 48 hours in 22 ppt seawater at 25 °C, in darkness. Rotifers were counted and classified into female types and transferred to a new algal food suspension without hormone every other day until day 8 when body size was measured. Population growth was significantly higher in treatments exposed to GABA (50 mg l-1), GH (0.0025 and 0.025 I.U. ml-1), HCG (0.25 and 2.5 I.U. ml-1), and 5-HT (5 mg l-1). E2 caused a decrease in population growth, whereas JH, 20HE, and T3 had no effect. Mictic female production was significantly higher at 0.05 and 0.5 mg l-1 JH and 0.05 and 5 mg l- 5HT. GH (0.0025 and 0.025 I.U. ml-1), E2 (50 mg l-1 ), GABA (0.5, 5 and 50 mg l-1), and 20-HE (0.05 mg l-1) treatments had significantly higher mictic female production only on day 8, 6, 4, and 6, respectively. T3 and hCG had no effect on mictic female production. Lorica length increased by 9.6% and 4.4% in rotifers treated with JH (0.05 mg l-1) and GABA (5 mg l-1), respectively. Correspondingly, lorica width increased by 8.9% and 2.6% in these treatments. In comparison, 20-HE-, T3-, and HCG-treated rotifers were smaller (3.9-8.2%) and GH, 5-HT and E2 had no effect on rotifer body size.
    • 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.
    • Article

      GABA, 5-HT and amino acids in the rotifers Brachionus plicatilis and Brachionus rotundiformis 

      WG Gallardo, A Hagiwara, K Hara, K Soyano & TW Snell - Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 2000 - Elsevier
      γ-Aminobutyric acid (GABA) and 5-hydroxytryptamine (5-HT) have been shown to increase the reproduction of the Brachionus plicatilis (NH3L strain). In the present study, the endogenous presence of GABA and 5-HT in the rotifers B. plicatilis (NH3L and Kamiura strains) and Brachionus rotundiformis (Langkawi strain) were confirmed by dot blot immunoassay and high-performance liquid chromatography (HPLC). HPLC showed that GABA and 5-HT concentrations in the three rotifer strains range from 71 to 188 pmol/mg and from 12 to 64 pmol/mg, respectively. A total of 33 amino acids were also detected in B. plicatilis and B. rotundiformis, with glutamic acid, serine, glycine, taurine, threonine, alanine, arginine, proline, valine and isoleucine in high concentrations relative to other amino acids.
    • Article

      Molecular cloning and localization of GABAA receptor-associated protein in the rotifer Brachionus plicatilis 

      HS Marcial, K Suga, S Kinoshita, G Kaneko, A Hagiwara & S Watabe - International Review of Hydrobiology, 2014 - Wiley-VCH Verlag
      γ-Aminobutyric acid receptor type A-associated protein (GABARAP) and its homologs constitute a protein family found in many eukaryotes from yeast to human, and are known to be involved in intracellular membrane trafficking of GABAA receptors and autophagy. In this study, we cloned cDNA-encoding GABARAP from the monogonont rotifer Brachionus plicatilis and examined for its tissue distribution at the protein level in neonates, males and females. Using reverse transcription (RT)-PCR and rapid amplification of cDNA ends (RACE) techniques, we showed that like other GABARAPs, rotifer GABARAP was also composed of 117 amino acids and highly homologous to vertebrate GABARAP2 ortholog (74–76% identity). GABARAP was demonstrated with its specific antibody to be ubiquitously distributed, irrespective of neonates, males, and females, in the coronal area that covers brain and contains most mechano- and chemoreceptors. Rotifer GABARAP was also expressed in the mature eggs but not in immature eggs. Double immunostaining with mammalian anti-GABA γ receptor antibody showed that rotifer GABARAP co-localized with GABA receptor, suggesting the association of the two proteins. The presence of GABARAP in rotifer implies that it is highly conserved during evolution, and plays important roles in various biological processes.