# Inter- and Intraspecific Venom Variation in the Reclusive Rear-Fanged Black-Striped Snakes (Coniophanes)

## TL;DR

This study explores venom composition and delivery in black-striped rear-fanged snakes, revealing toxin diversity and variation between and within species.

## Contribution

First characterization of venom profiles and delivery systems in the genus Coniophanes using transcriptomics and imaging.

## Key findings

- Toxins make up 38.8% to 66% of the Duvernoy’s gland transcriptomes in Coniophanes.
- Eighteen toxin families were identified, with CRiSPs and SVMPs showing prominent expression.
- Intraspecific and interspecific venom variation was observed, along with detailed venom delivery anatomy in C. fissidens.

## Abstract

Our current understanding of snake venom is highly biased towards species known to be medically significant in human envenomations. This vastly under-represents the true evolutionary and ecological breadth of snake venom, with gaps spanning entire clades and unique lifestyles. As a result, many genera of rear-fanged snakes lack well-understood venom profiles despite these taxa composing around 65% of known extant snake species. Methodological challenges associated with venom extraction have long been a key reason responsible for the lack of venom research on this group. Modern advancements in venomics technologies have allowed researchers to overcome many of these challenges and investigate the venom components of understudied genera. The genus Coniophanes (black-striped snakes) presents an ideal system for investigating venom and the venom delivery system in a rear-fanged venomous species with well-documented accounts of human envenomations. We sequenced and annotated de novo transcriptomes of the Duvernoy’s gland (DVG) for seven individuals across four species of Coniophanes (Dipsadidae) and confirmed toxin expression in representative venom proteomes. We assessed interspecific venom variation within this genus and further examined intraspecific venom variation within C. imperialis. We found that toxins account for 38.8% to 66% of the total DVG transcriptomes and that 18 toxin families are represented in this genus, with prominent expression of cystine-rich secretory proteins (CRiSPs) in three species and snake venom metalloproteinases (SVMPs) in all four species. In addition, we used diffusible iodine-based contrast-enhanced computed tomography (diceCT) to better understand the venom delivery system for C. fissidens, a widespread species within this genus, showcasing enlarged, grooved, rear fangs in close proximity to a prominent DVG. We provide the first ever characterization of the venom profiles of Coniophanes, highlight venom variation between and within species, and outline the venom delivery system of this understudied genus.