Venom Composition in a Phenotypically Variable Pit Viper ( Trimeresurus insularis) across the Lesser Sunda...

Area of Science:

• Herpetology
• Biochemistry
• Venomics

Background:

• The genus Trimeresurus includes venomous pitvipers from Southeast Asia and the Pacific Islands.
• Trimeresurus insularis, the White-lipped Island Pitviper, is an arboreal, nocturnal species found across the Lesser Sunda archipelago.

Purpose of the Study:

• To evaluate the venom phenotypic characteristics of Trimeresurus insularis populations from eight Lesser Sunda Islands.
• To compare T. insularis venom composition with other Trimeresurus complex species.
• To assess the cross-reactivity of T. insularis venom with T. albolabris antivenom.

Main Methods:

• Venom samples from eight Lesser Sunda Islands were analyzed using SDS-PAGE, enzymatic activity assays, fibrinogenolytic assays, gelatin zymography, and RP-HPLC.
• Venomic analysis was performed on the Sumbawa sample.
• Comparative analyses included venoms from T. borneensis, T. gramineus, T. puniceus, T. purpureomaculatus, T. stejnegeri, and Protobothrops flavoviridis.
• Western blot analysis was conducted using T. albolabris antivenom.

Main Results:

• T. insularis venoms from all eight islands showed high similarity in SDS-PAGE and RP-HPLC profiles, containing key protein families like PDE, LAAO, SVMP, serine proteases, CRISP, PLA2, and C-type lectins.
• The Lombok sample uniquely lacked serine protease and CRISP bands; venomic analysis of Sumbawa venom identified these and additional minor components.
• Similarities were observed in thrombin-like and PDE activities, while LAAO, SVMP, and kallikrein-like activities showed minor inter-island variations.
• T. insularis venom composition was broadly similar to other Trimeresurus species, except for P. flavoviridis, which exhibited significant differentiation.
• Western blot confirmed T. albolabris antivenom recognized most T. insularis venom proteins and those of other Trimeresurus species, but not P. flavoviridis.

Conclusions:

• Trimeresurus insularis venom composition is remarkably conserved across the Lesser Sunda archipelago, despite geographical isolation.
• Minor variations in enzymatic activities exist but do not represent major compositional shifts.
• The findings support the conservation of venom phenotype within T. insularis and highlight its distinctiveness from P. flavoviridis.