EFFECTS OF MARINE CILIATES ON SURVIVABILITY OF THE FIRST-FEEDING LARVAL SURGEONFISH, PARACANTHURUS HEPATUS: LABORATORY REARING EXPERIMENTS
N. Nagano, Y. Iwatsuki, T. Kamiyama, H. Nakata - 2000
Hydrobiologia, 432 (1/3):149-157
Abstract:
The contribution of ciliates as a food source to survival of
first-feeding surgeonfish larvae, Paracanthurus hepatus, was examined in
rearing experiments. The larvae were exposed to eight treatments; i.e. a
tintinnid, Amphorellopsis acuta (1.0 × 10^4, 5.1 × 10^3 and 2.2 ×
10^3 cells l^-1) and a naked ciliate, Euplotes sp. (1.3 × 10^4, 8.0 ×
10^3 and 5.0 × 10^3 cells l^-1), plus two controls without ciliates.
Highest survival of the larvae over the first 4-8 days was observed in the
highest density of A. acuta. Rearing experiments also showed that the
survivals of larvae fed with A. acuta were higher than those fed with
Euplotes sp. Gut content analyses revealed loricae of A. acuta in the
larvae. Although Euplotes sp. (lacking loricae) was never recognized in
those larval guts, feeding on Euplotes sp. by larvae was confirmed using
the ciliate labeled with fluorescent microspheres, implying that the
feeding on naked ciliates by fish larvae has been overlooked. The results
strongly suggested that both tintinnid and naked ciliates play important
roles as alternative food sources to copepod nauplii by enhancing the
survivability of fish larvae, especially those with a smaller mouth.
(Miyazaki University, The United Graduate School of Agricultural Sciences, Kagoshima University, 1-1 Gakuen-kibanadai-nishi, Miyazaki 889-2192, Japan Tel.: +81-985-58-7222. Fax: +81-985-58-2884. E-mail: a02111u@cc.miyazaki-u.ac.jp)
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