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

Area of Science:

• Herpetology
• Venomics
• Evolutionary Biology

Background:

• Snake venom research is heavily biased towards medically significant species, neglecting the evolutionary and ecological diversity of venom in understudied groups.
• Rear-fanged snakes, comprising 65% of extant species, remain poorly understood due to methodological challenges in venom extraction and analysis.
• The genus Coniophanes (black-striped snakes) offers a valuable model for studying venom and delivery systems in rear-fanged snakes with documented envenomations.

Purpose of the Study:

• To characterize the venom profiles of four species within the understudied Coniophanes genus.
• To investigate interspecific and intraspecific venom variation within Coniophanes.
• To elucidate the venom delivery system of Coniophanes, particularly C. fissidens.

Main Methods:

• De novo sequencing and annotation of Duvernoy's gland (DVG) transcriptomes from seven Coniophanes individuals across four species.
• Analysis of representative venom proteomes to confirm toxin expression.
• Diffusible iodine-based contrast-enhanced computed tomography (diceCT) to visualize the venom delivery system.

Main Results:

• Toxins constitute 38.8% to 66% of the total DVG transcriptome in Coniophanes.
• Eighteen toxin families were identified, with prominent expression of cystine-rich secretory proteins (CRiSPs) and snake venom metalloproteinases (SVMPs).
• diceCT revealed enlarged, grooved rear fangs in close proximity to the DVG in C. fissidens, detailing the venom delivery apparatus.

Conclusions:

• This study provides the first comprehensive characterization of Coniophanes venom profiles and highlights significant venom variation.
• The findings underscore the importance of studying underrepresented snake groups to understand venom evolution and diversity.
• The detailed analysis of the venom delivery system contributes to a broader understanding of rear-fanged snake feeding and defensive mechanisms.