（別紙様式第 6号） 主 指 導 教 授 宕 玲 、
f 全 た 電
学 位 論 文 要
l旨専攻名 生物圏生命科学専攻
7 7
ンティカムトゥ氏 名
PhanT h i Cam Tu ~i-
題＿且
Im・acts of short‑term s a l i n i and t u r b i d i t s t r e s s on the e a r l l i f e s t a g e s of aquatic plant and animals
（初期発育段階の海洋性動植物に与える塩分と濁度の短時間暴露の影響）
c Two s e r i e s of e x p e r i m e n i s were c o n d u c t e d i n t h e l a b o r a t o r y t o e s t i m a t e t h e s t r e s s t o l e r a n c e of a
brown a l g a Sargassum J u s i f o r m e g e r m l i n g s when e x p o s e d t o low s a l i n i t y o r h i g h t u r b i d i t y . R e s u l t s showed t h a t t h e g r o w t h of g e r m l i n g s was s i g n i f i c a n t l y a f f e c t e d (P < 0 . 0 5 ) by d a i l y s a l i n i t y change a c c o r d i n g t o d u r a t i o n of s t r e s s e x p o s u r e . The l o w e s t s p e c i f i c g r o w t h r a t e ( % / d a y ) of g e r m l i n g s was 1 . 1 % a t 1 7 p s u f o r 6 h e x p o s u r e ・ . S u r v i v a l of germ l i n g s was more t o l e r a n t compared t o t h e i n f l u e n c e on t h a t f o r g r o w t h . From t h e r e s u l t s of t u r b i d i t y t o l e r a n c e t e s t , t h e g r o w t h and s u r v i v a l of g e r m l i n g s r e d u c e d by i n c r e a s i n g t u r b i d i t y l e v e l s . I n c o m p a r i s o n w i t h c o n d i t i o n s of t u r b i d i t y from O and I 00 NTU, h i g h m o r t a l i t y was r e c o r d e d when g e r m l i n g s were e x p o s e d t o h i g h t u r b i d i t y s t r e s s of 700 NTU. The
．
︵ o n l y t r e a
囀t m e n t of I 00 NTU combined w i t h 2 h e x p o s u r e h a d a~pecific g r o w t h r a t e of o v e r 2%, whereas
o t h e r s were below 1 %. Germ l i n g s had t h e l o w e s t g r o w t h of a b o u t 0.2% when e x p o s e d d a i l y a t 700 NTU f o r 6 h .
S t u d y c o n d u c t e d t o a s s e s s t h e e f f e c t s of s h o r t ‑ t e r m low s a l i n i t y . a n d t u r b i d i t y s t r e s s on t h e embryonic
and e a r l y l a r v a l s t a g e s of J a p a n e s e f l o u n d e r , P a r a l i c h t h y s o l i v a c e u s . I n t h e f i r s t e x p e r i m e n t , t h e
embryos were e x p o s e d t o d i f f e r e n t c o m b i n a t i o n s of s a l i n i t y ( 3 4 , 3 0 , 2 6 , 2 2 , 1 8 , and 1 4 p s u ) and
t u r b i d i t y ( 0 , 100,300,500, a n d 700 NTU) f o r a s h o r t p e r i o d of3 h . E x p e r i m e n t 2 e v a l u a t e d low s a l i n i t y
t o l e r a n c e a t d i f f e r e n t d e v e l o p m e n t a l s t a g e s u n d e r t h e t u r b i d i t y l e v e l of 700 NTU. The r e s u l t s showed
t h a t t u r b i d i t y s i g n i f i c a n t l y i n f l u e n c e d h a t c h i n g r a t e , a b n o r m a l i t y r a t e , t o t a l l e n g t h , y o l k s a c v o l u m e , and
s u r v i v a l r a t e , w h e r e a s low s a l i n i t y o n l y a f f e c t e d t h e p e r c e n t a g e o f a b n o r m a l i t y . T h e r e was no i n t e r a c t i o n b e t w e e n s a l i n i t y a n d t u r b i d i t y on t h e s e p a r a m e t e r s .
The e f f e c t s o f low s a l i n i t y a n d t u r b i d i t y on t h e e m b r y o n i c s t a g e o f r e d s e a bream Pagrus major were examined u n d e r c o n t r o l l e d l a b o r a t o r y c o n d i t i o n s . I n t h e f i r s t e x p e r i m e n t , e g g s of t h e r e d s e a bream were e x p o s e d t o d i f f e r e n t s a l i n i t y s t r e s s e s [ 3 4 ( c o n t r o l ) , 3 0 , 2 6 , 2 2 , 1 8 , a n d 1 4 p s u ] f o r 3 h . I n t h e s e c o n d e x p e r i m e n t , e g g s w e r e ・ e
べp o s e dt o h i g h e r t u r b i d i t y l e v e l s o f 1 0 0 , 3 0 0 , 5 0 0 , a n d 700 NTU o b t a i n e d by d i s s o l v i n g k a o l i n c l a y w i t h f r e s h s e a w a t e r ( 0 NTU: c o n t r o l ) i n t h e same d u r a t i o n a s i n t h e f i r s t e x p e r i m e n t . The r e s u l t s showed t h a t t h e e m b 1 ‑ y o s of r e d s e a bream were t o l e r a n t t o s h o r t ‑ t e r m e x p o s u r e
C t o low s a l i n i t y s t r e s s . T h e r e were n o s i g n i f i c a n t d i f f e r e n c e s i n t h e h a t c h i n g r a t e , y o l k s a c c o n s u m p t i o n of
newly h a t c h e d l a r v a e , o r s u r v i v a l o f l a r v a e a t 6 d a y s p o s t ‑ h a t c h i n g . H o w e v e r , t h e s h o r t e x p o s u r e t o t u r b i d i t y s t r e s s r e d u c e d t h e h a t c h i n g r a t e , t o t a l l e n g t h a n d y o l k s a c volume o f newly h a t c h e d l a r v a e , a n d v i a b i l i t y o f l a r v a e of r e d s e a b r e a m . Tu~bidity had a s i g n i f i c a n t i m p a c t on t h e a b n o r m a l i t y r a t e a t h a t c h i n g , w i t h h i g h e r v a l u e s o b s e r v e d f o r e l e v a t e d t u r b i d i t y .
The embryos o f d i s k a b a l o n e H a / i o t i s d i s c u s d i s c u s a n d g i a n t a b a l o n e H a / i o t i s g i g a n t e a were exposed t o s a l i n i t y o r t u r b i d i t y c h a n g e s t o d e t e r m i n e t h e e f f e c t s o n s u b s e q u e n t h a t c h i n g a n d l a r v a l d e v e l o p m e n t . The s h o r t ‑ t e r m low s a l i n i t y s t r e s s d e c r e a s e d t h e h a t c h i n g a n d s u r v i v a l r a t e s , and i n c r e a s e d t h e
︵ a b n o r m a l i t y r a t e f o r b o t h s p e c i e s . As f o r t u r b i d i t y s t r e s s , n e g a t i . v e e f f e c t s o n l i a t c h i n g a n d s u r v i v a l r a t e s
were o b s e r v e d i n b o t h s p e c i e s when t h e i r embryos were e x p o s e d t o . i n c r e a s e d t u r b i d i t y . The a b n o r m a l i t y r a t e s o f b o t h s p e c i e s a t t u r b i d i t i e s of 500 a n d 700 NTU were s i g n i f i c a n t l y h i g h e r t h a n t h o s e a t t u r b i d i t i e s ofO a n d I 0 0 NTU.
（備考）日本語
