Duminda S.B Dissanayake, R.P.V.Jayantha Rajapakse, S.A.M Kularatne and J.S.G Ranasinghe
Posters-Accepted Abstracts: Biol Syst Open Access
Sri Lanka is an island in the middle of the Indian Ocean with a rich biodiversity. The island is home to around 40 species of venomous snakes and some of which are highly venomous; abundant and can cause serious envenomation leading to death. The spectacled cobra, Najanaja is the only recognized species of cobra in Sri Lanka and is also responsible for a considerable number of envenomations and deaths due to snakebite in Sri Lanka. However, basic data such as the genetic diversity, venom variation, toxicity and sexual dimorphism of the species is not known. In this study, we collected samples in different geographic areas in Sri Lanka to evaluate genetic diversity, SSD and toxicity. To assess the population genetic diversity, we sequenced the mitochondrial Cytochrome_b gene.SSD in 38 specimens was investigated by examining 11 metric and 9 meristic characters. To examine the toxicity, an in-vivo toxicity study was conducted using mouse models to calculate the LD50 value. Maximum likelihood analysis of the Cytochrome-b gene revealed two strongly supported (Bootstrap support >70%) monophyletic clades corresponding to Sri Lanka andthe Indian subcontinent. This might indicate the long term isolation between the Indian and Sri Lankan populations of N. naja since the last geological connection between India and Sri Lanka ~10000 years ago during the Pleistocene low sea levels. Toxicity of the Sri Lankan N. naja was high (0.5mg/Kg) compared to the recorded Indian values. Thus our findings indicate that long term isolation of the Indian and Sri Lankan populations of N. naja has driven genetic divergence and venom variation in the two populations. The findings of this study therefore has important implications for snake bite management in Sri Lanka indicating the requirement for a specific antivenin for the Sri Lanka population of spectacled cobra. This Project is funded by the Ministry of Technology and Research of Sri Lanka through Grant_No_MRT/TRD/AGR/3/1/7.
