PURSE 2006

Permanent URI for this collection

https://ir.lib.pdn.ac.lk/handle/20.500.14444/53

Browse

Browsing PURSE 2006 by Author "Jayawardena, U. A."

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Blocides enhance the severity of parasiteiInduced abnormalities in the hourglass tree frog (Anura: Ranidae)
    (University of Peradeniya, Sri Lanka, 2006-11-30) Jayawardena, U. A.; Rajakaruna, R. S.; Navaratne, A. N.; Amerasinghe, P. H.
    Trematode infections and biocide exposure have been shown to cause abnormalities, growth retardation and increased mortality in the common hourglass tree frog Polypedates cruciger, under laboratory conditions. This study investigates the synergistic effect of trematode infections and biocide exposure on survival, growth and development of abnormalities in P. cruciger. Egg clutches from natural populations were reared in the laboratory and five days post-hatch tadpoles were exposed to monostome type cercariae released by the snail species Thiara scabra (Gastropoda: Prosobranchia: Thiaridae), in the presence of biocides. Four biocides, including two herbicides (glyphosate and 3, 4- dichloropropionamide) and two insecticides (chlopyrifos and dimethoate), were used at a low, ecologically accepted dosage (0.5 ppm). Each tadpole was exposed to 48 cercariae in four equal doses for four consecutive days (12 cercariae x 4 days) by placing the tadpole in a small plastic container containing 5 ml of different biocide solutions. Tadpoles were then transferred into separate glass tanks (n= 20 per treatment) containing 2 I of the respective biocide, fed with commercial fish feed and raised until metamorphosis. Survival was recorded weekly and growth and development were assessed at metamorphosis by measuring their snout-vent length, weight and the time required for fcrelimb emergence in 50% of the tadpoles (TE50) in a given treatment. Abnormalities were recorded at 10, 30 days post-hatch and at metamorphosis. The observed abnormalities were mainly; tail bending, vertebral column curvature and lumps (almost everywhere on the body). A significant decline in the survival (X²=28.014, df= 3, P < 0.000) was observed for all the treatments in the presence of both biocides and cercariae. Moreover, synergistic effect caused significant lengthening of TE 50 value (X² = 14.130, df = 3, P = 0.003) compared to all other treatments. Abnormality percentage was significantly higher (X²=24 .983 , df=3, p