The Curious Case of the "Neurotoxic Skink": Scientific Literature Points to the Absence of Venom in Scincidae.

Kartik Sunagar,Siju V Abraham

doi:10.3390/toxins13020114

Abstract

In contrast to the clearly documented evolution of venom in many animal lineages, the origin of reptilian venom is highly debated. Historically, venom has been theorised to have evolved independently in snakes and lizards. However, some of the recent works have argued for the common origin of venom in “Toxicofera” reptiles, which include the order Serpentes (all snakes), and Anguimorpha and Iguania lizards. Nevertheless, in both these contrasting hypotheses, the lizards of the family Scincidae are considered to be harmless and devoid of toxic venoms. Interestingly, an unusual clinical case claiming neurotoxic envenoming by a scincid lizard was recently reported in Southern India. Considering its potentially significant medicolegal, conservation and evolutionary implications, we have summarised the scientific evidence that questions the validity of this clinical report. We argue that the symptoms documented in the patient are likely to have resulted from krait envenomation, which is far too frequent in these regions.

Highlights

An anthropocentric interpretation of venoms has led to the consideration of only animals capable of inflicting clinically severe symptoms in humans as “venomous”, whereas the ecological roles of these toxic secretions have been largely neglected
Several studies have demonstrated the roles of diet, ontogeny, predator pressure, intraspecific competition, geographic distribution, and climatic conditions in shaping animal venoms [2,3,4,5,6]
The modern definition, defines venom as a specialised form of poison that is actively injected to facilitate the quotidian functions of the venomous animal, including predation, self-defence and intraspecific competition. Considering their clinical relevance to humans, snake venoms have been rigorously investigated to date

Summary

Introduction

An anthropocentric interpretation of venoms has led to the consideration of only animals capable of inflicting clinically severe symptoms in humans as “venomous”, whereas the ecological roles of these toxic secretions have been largely neglected. The modern definition, defines venom as a specialised form of poison that is actively injected to facilitate the quotidian functions of the venomous animal, including predation, self-defence and intraspecific competition Considering their clinical relevance to humans, snake venoms have been rigorously investigated to date. Considering the potential implications of this study study on our understanding of reptilian venom evolution, as well as its negative impact on our understanding of reptilian venom evolution, as well as its negative impact on on conservation, we summarise the scientific evidence that points to the absence of venom conservation, we summarise the scientific evidence that points to the absence of venom in in this enigmatic lineage of lizards and refutes the validity of this clinical report.

The Evolutionary

Evidence Supports the Lack of Venom in Scincidae

Potential Causes of the Observed Neurotoxic Envenoming

Findings

A Typical Case of “Early Morning Neuroparalytic Syndrome”