الفهرس 
Biological and ecological factorsOnly 14 pages are availabe for public view
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Abstract
present work was conducted t o c l a r i f y some b i o l o g i c a l , physiological md biochemical i n v e s t i g a t i o n s on Biampbalmia alexandrina snails as an intermediate host of Schistooopm mansoni in Egypt, a f t e r prolonged exTosure times t o the subl e t h a l conc ent r a t ion (LC~)of some chosen i n s e c t i c i d e s . -Be alexandrfna s n a i l s were c o l l e c t e d from s e v e r a l irrigation cannals and drainages located in Al-Gharbia governorate- The snalla were maintained under the laboratory constant condi t i o n s . The chosen i n s e c t i c i d e s were Trlazophos and Cyolane (:orGanophosphorous) ; Cypermethrin and Baythroid (pyrethroid) ; Methomy1 and Larvin (carbamate). Screening t e s t s were carried out t o determine the percentage of snail mortality f o r the six iasccticides, those which gave high mo r t a l i t i e s a t lm~erco ncentrations were chosen as t h e m a t e r i a l f o r our project while others were excluded. The i n s e c t i c i d e s used were Triazophos, Cyolane and Cypermethsin, The effectiveness of the insectidides used as molluscicides (LC ) against B. alexandrina snails were as followe: 50 - Triazophos: 5 -+ 1.730 p.p.m.; Cyolane; 5.58 + 0.220 p.p.19. and Cyperinethin: 11.23 2 2.260 p.p,m’., t h i s i n d i c a t e s t h a t Triazophos and Cyolane (organophosphorous i n s e c t i c i d e s ) are the most toxic i n s e c t i c i d e s while Cypemethrin (pyrethoid) is the least one. The growth r a t e of B-. alexandqi~as n a i l s exposed t o t h e sub -let ha1 conc en-hation of Triazopllos f or one week shoved a s i g n i f i c a n t decrease i n the shell diameter (P< 0.05) at 35 and 42 d a y s post exposure time a n d a s i g n i f i c a n t decrease i n t o t a l body weight (P (0.05) at 21, 35 and 42 d a y s post expo- On the other 1-mid, Cyolane treatment showed a sPgnif icant decrease i n the s h e l l diameter (P < 0.05) at 28, 35 and 42 days post-exposure time and a sipificant decrease i n t o t a l ure. Cypemethrin treatment showed a sisLficant decrease i n s h e l l diameter (PC 0.05) and i n the t o t a l body weight (P< 0.05) at 35 and 42 days post exposure. The egg laying capacity of treated B. alexandrina snails with sub-lethel concentration of the various i n s e c t i c i d e s f o r one week and two weeks showed t h e following: The snails pretreated f o r one week with Triazophos showed a signiff icant decrease i n the number of egg masses (P < 0.05) at 5, 10, 15, 209 25, ?0,35 and a s i g n i f i c a n t decrease i n the number of egg c e l l s (P< 0.05) at days 5, 10, 15 and 20 post exposure’. Consfdesing the snafls pretreated with the same i n s e c t i c i d e f o r two weeks there was a signif iccant decrease in the numbers of egg masses (I?< 0.05) at days 15, 20, 25, 30 and 35 whereas a s i g n i f i c a n t decrease in the number of egg c e l l s (P < 0.05) at days 5, 10, 15, 20, 25, 30 a n d 35 post exposure. Cyolane treatment f o r one week caused a slgnlficant decrease in the number of egg masses (P < 0,051 at days 5, 10, 15, 20 and 25 and a s i g n i f i c a n t decrease i n the number of egg c e l l s (P < 0.05) at days 5, 10, 15, 20, 25, 30 and 35 post exposure. For the s n a i l s pretreated f o r ’two weeks there was a slgnif icant deercase in the number of egg masses (I?< 0.05) at days 10, 15, 20, 25, 30 and 35 and in the number of egg c e l l s (P (0.05) at days 5, 10, 15, 20, 25, 30 and 35 post-exposure, Cypemethrh t r e a t - ment fox one meek caused a s i g n i f i c a n t decrease i n the number of egg masses (P< 0.05) at days 20, 25 md 30 and in the number of egg c e l l s (~0.045) at days 15, 20 and 25. For t h e anails pretreated f o r two weeks also there Mas a signSficant decrease in the number of egg masses (P 4 0.05) at days 10, 15, 20, 25, 30 and 35and in the number of egg c e l l s (P 4 0.05) at days 5, 10, 15, 20, 25, 30 aad 35 post-exposwe’, The percentage of hatching of eggs collected from snails pretreated f o r one week wlth Trfazophos, Cylolane and Cypernethrin was not s i g n i f i c a n t l y infleunced (~(0.05) as corqmxed with the control, while there w a s a significant reduction in the r a t e of hatching of the eggs collected from s n a i l s pretreate6 f o r two vieelcs (P< 0.05). The percentage of hatching of the f r e s h l y l a i d eggs collected fro~i.u nt r e a t ed snai ls then t r e a t e d f o r one week wi t h t h e subl e t h a l concentration of Triazophos, Cyolane and Cypensctllrin had no s i g n i f i c a n t o~icidale f f e c t f o r t h e t h r e e i n s e c t i c i d e s used (~(0.05)’. The percentage of the experimental 2. mansoni i n f e c t i o n ao the mean nunbers of the cercariae ahedding/snail were s i g n i f - i c a n t l y reduced (P< 0.05) a f t e r t r e a t i n g the s n a i l s f o r one week with the sub-lethal concentration of Triazophos and Cyolane while the treatment with Cypermetkrin showed no simficant e f f e c t (P(0.05). - Determination of haemolymph-glucose f o r the snails treated with t h e d i f f e r e n t i n s e c t i c i d e s and t h e i r control at ldaye-0,5,10 15, 20, 25 and 30 post-exposure period showed that: Triazophos exposure f o r one week resulted i n a signiflcant increase in the haemolymph glucose (P< 0.05) at days 0,5 10,. 15, 20,25 and 30~0~~-exposure. Cyolane exposure for one week r e s u l t e d in a significant increme i n the haemolymph glucose (P <0.05) at days 0,5, 10 and 30 post-exposure perf oda. The r e s u l t s also demonstrated t h a t , Cypermethrin exponuye f o r one week caused a s i g n i f i c a n t increase i n haemolymph-giucose (~<0*05)a t days 5, 10, 1 5 , 20, 25, 30 post-exposure per iod. -net ermination of haemolymph t o t a l protein f o r the snails treated with the sub-lethal concentration of the d i f f e r e n t i n s e c t i c i d e s and t h e i r . c o n t r o l at days 0, 5, 10, 15, 20, 25 and 30 post-exposue periods showed that: Piazophos exposure f o r one week r e s u l t e d i n s l i g h t reduction i n the h~ernolyrnph protein at days 15, 30 post expoowe (P< 8.05 1,. Cyolane treatment for one week caused a s l i g h t reduction i n the haemolymph protein a f t e r 25 day8 post-exposure period Cy~ennetlwin exposure f o r one week caused a s l i g h t reduction a f t e r 30 days post exposure period (P< 0.05). -Determination of haemolymph t o t a l l i p i d s f o r the s n a i l s pretreated with the sub-lethal concentration of the dif2erent i n s e c t i c i d e s for one week did not cause any s i g n i f i c a n t change (P< 0.05). -Determination of t i s s u e glycogen f o r the treated snails with the d i f f e r e n t i n s e c t i c i d e s a n d t h e i r control at days 0, 5, 10, 15, 20, 25 and 30 post-exposure periods shaved that: Triazophos exposure f o r one week resulted i n a s i g n i f i c a n t decrease i n the tissue glycogen (P< 0.05) at days 0, 5 20,20 9 and 30 . days post-exposure, Cyolane treatment f o r one week caused a s i g n i f i c a n t decrease i n the t i s s u e glycogen (P< 0.05) at days 0,5 10, 20 and 30 post-exposure’. Cypermethrin treatment f o r one week caused a s i g n i f i c a n t decresse in the t i s s u e glycogen (P< 0.05 ) at days 10, 20 postexposure’.