Effects of agrochemicals on early development of Dawkinsia srilankensis ; a point endemic critically endangered fish

Effects of agrochemicals on early development of Dawkinsia srilankensis ; a point endemic critically endangered fish

Presented by
Sureni Sumathipala
University Of Peradeniya ,Department Of Zoology

P.S.H Sumathipala,G.N Hrimuthugoda,N.P.S Kumburegama

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Introduction: What conservation problem or question does your study address?

Dawkinsia srilankensis is a benthopelagic, tropical freshwater fish strictly restricted to Kalu ganga in the Eastern slopes of Knuckles World Heritage Site. The populations are in imminent danger of extinction due to increased use of agrochemicals during the last few years. Thus, this research aims to study the effects of agrochemicals on the early developmental/embryological stages of D.srilankensis.

Methods: What were the main research methods you used?

A group of individuals were caught in the wild and brought to the aquarium and they were reared under aquarium conditions. Males and females were kept separately over two weeks prior to practicing breeding and into the breeding setup females and males were introduced in a ratio of 2:1.To study the effects of the agrochemicals, most widely and commonly used agrochemical in the area was selected and a concentration gradient was prepared. For each concentration 100 eggs were exposed and percent survival, embryonic growth rates and induced malformations and deformities were studied and replicates were carried out for each concentration gradient. According to the results that are to be obtained, future conservation actions will be taken accordingly to minimize the damage caused by the agrochemical to existing populations in the wild.

Results: What are your most important results?

The early development of D. srilankensis was examined and documented under normal conditions to prepare a reference series prior to investigating the effects with the agrochemical. It revealed that each tested embryos spent a cleavage stage, blastula stage, gastrula stage, segmentation stage and a pharyngula stage and prior to hatching. All 100 tested embryos hatched within 48- 72 h post fertilization. The percent mortality was highest for 40 µgl-1 concentration.

Discussion: What are your important discussion points and what is the relevance of your results to conservation (if any)?

Embryological studies are very important in studying a physical or a chemical variable as they are the most susceptible stages of an organism. Finding the lethal dose will be crucial in conservation of this species. Further studies will be carried out using the above prepared series as the reference to compare the developmental rates, patterns, organ formation and to identify deformities or malformations. This will be valuable in conservation of this fish.

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