(C) Ashok Captain
Venoms are an adaptive trait and a significant source of pharmacological discovery; however, the factors driving venom evolution and diversity remain poorly understood. Centipedes, the oldest venomous terrestrial arthropods, offer insights into these factors. We examined the patterns of venom diversity, its ecological drivers and evolution across one of the most diverse tropical centipede families, Scolopendridae. To do this, we sampled ~60 species across wet and dry forests of peninsular India. Venom extraction, proteomic analysis and venom gland transcriptome sequencing are completed for 40 species. Each individual's venom phenotype was defined using proteomic and transcriptomic data to identify venom components with putative toxin names and functions, thereby minimising annotation errors. In addition, we utilised venom data from 20 species from published studies, enabling us to capture 60% of the genus-level diversity within Scolopendridae.
The scolopendrid venoms were predominantly neurotoxic and dominated by low molecular weight >100 kDa proteins with 211 protein families. Species in the genus Scolopendra had the highest venom diversity, while Asanada had the lowest. We assessed whether ecological factors, including body size, elevation, latitude, and longitude, influenced venom diversity. Generalised linear models revealed a significant positive correlation between body size and venom diversity, supported by phylogenetically controlled regressions (Aditi, Roy et al., in prep).
We performed stochastic character mapping to investigate the evolution of venom complexity under various models. Proteins such as β-PFTx followed an all-rates-different model, while others showed unidirectional or equal-rate patterns, suggesting a dynamic evolutionary history involving parallel gains and losses. Bayesian analyses using FUSTr identified 2,443 venom-related proteins under strong positive selection. We show that scolopendrid venoms have evolved from simpler ancestral states to complex cocktails shaped by ecological pressures and evolutionary constraints, and scolopendrid venoms are indeed an adaptive trait (Aditi, Roy et al., in prep). Additionally, we are also interested in examining how venom functions as an adaptive trait that can influence diversification and speciation within Scolopendridae.
This research is part of Aditi's PhD project.
Funding:
Aditi is supported by the Council for Scientific and Industrial Research (CSIR) JRF fellowship
DBT/Wellcome IndiaAlliance Intermediate Fellowship