Atractaspidinae

Abstract: The majority of living snakes belong to the superfamily Colubroidea. This group includes viperids, elapids, and atractaspidines that are well-recognized for inflicting medically significant bites. Some of these snakes cause mortality and morbidity in humans. A large number of colubroid species have been traditionally and inaccurately grouped in an artificial family, the Colubridae, for convenience. Although most of this taxonomically fluid assemblage is not known to be venomous biologically or clinically, bites from some of its species have produced effects in humans. These effects range from insignificant or trivial injuries to death. Some investigators have reassigned the distinctive mole vipers, burrowing asps, or stiletto snakes (Atractaspis spp.) from their own family (Atractaspididae) to subfamily status (Atractaspidinae) of the almost wholly non-front-fanged colubroid family, Lamprophiidae. The aforementioned reassignments, as well as those involving other genera, such as Alsophis portoricensis (Borikenophis), Boiga blandingi (Toxicodryas), and so on, emphasize the importance of taxonomic considerations in clinical toxinology.

Abstract: Summary The burrowing asp, Atractaspis bibronii, causes a significant proportion of cases of snakebite near Empangeni, Natal. Data from 8 cases are presented. All were in rural Zulus, and the bites were usually inflicted on the foot during summer nights, in or near the patient's home. There was no sexual bias, but over 50% of the victims were under 14 years of age. Envenoma­ tion was mild, characterised by moderate to intense pain and localised swelling, regional lymphadenopathy with occasional discoloration, blistering or necrosis at the bite site. Neuro­ logical signs were absent, but symptoms of headache, painful eye movements, dry mouth and hoarseness were recorded. Minor haematological abnormalities were detected in a few patients. Treatment involved analgesics and limb elevation, with antibiotic cover and intravenous fluids when necessary. Antivenom is not effective and was not used. There were no deaths. S AIr Med J 1989; 75: 327-331. Burrowing asps (Arraetaspis) are unusual African snakes that were for many years considered to be related to vipers and commonly called mole vipers or burrowing adders. Lanerly they have also been called 'stileno' or 'side-stabbing' snakes in reference to their mode of biting. Their long, hinged front fangs are rotated differently from those of true vipers, and they are now placed in a separate colubrid subfamily (Atractaspidinae) and are believed to be closely related to 'aparallactine' colubrids, e.g. the Natal black snake (Macrelaps microlepidorus) and the purple-gloss snake (Amblyodipsas concolor). This reclassification adds more species to the rela­ tively long list of venomous African colubrid snakes. Bites from these snakes are not unusual among herpetologists. They are easily mistaken for harmless snakes and may be picked up carelessly, resulting in a binen hand. In fact, these snakes cannot even be picked up with care, despite being held behind the head, since their unique maxillary kinesis allows a single fang to be protruded without opening the mouth (Fig. 1) and this, along with exceptional neck flexure, allows the fangs to be jabbed backwards and sideways into the restraining fmgers. Such 'illegal' bites are not unusual.

Abstract: Fangs are a putative key innovation that revolutionized prey capture and feeding in snakes, and – along with their associated venom phenotypes – have made snakes perhaps the most medically-significant vertebrate animals. Three snake clades are known for their forward-positioned fangs, and these clades (Elapidae, Viperidae, and Atractaspidinae) contain the majority of snakes that are traditionally considered venomous. However, many other snakes are “rear-fanged”: they possess potentially venom-delivering teeth situated at the rear end of the upper jaw. Quantification of fang phenotypes – and especially those of rear-fanged species – has proved challenging or impossible owing to the small size and relative rarity of many such snakes. Consequently, it has been difficult to understand the evolutionary history of both venom and prey-capture strategies across extant snakes. We quantified variation in the dentition of 145 colubriform (“advanced”) snake species using microCT scanning and compared dental characters with ecological data on species’ diet and prey capture method(s) to understand broader patterns in snake fang evolution. Dental traits such as maxilla length, tooth number, and fang size show strong phylogenetic signal across Colubriformes. We find extreme heterogeneity and evolutionary lability in the rear-fanged phenotype in colubrid (colubrine, dipsadine, and natricine lineages) and lamprophiid snakes, in contrast to relative uniformity in the front fanged phenotypes of other groups (vipers and, to a lesser extent, elapids). Fang size and position are correlated with venom-use in vipers, elapids, and colubrid snakes, with the latter group shifting fangs anteriorly by shortening the entire maxillary bone. We find that maxilla length and tooth number may also be correlated with the evolution of dietary specialization. Finally, an ancestral state reconstruction suggests that fang loss is a recurring phenomenon in colubrid snakes, likely accompanied by shifts in diet and prey capture mode. Our study provides a framework for quantifying the complex morphologies associated with venom use in snakes. Our results suggest that fang phenotypes, and particularly the rear-fanged phenotype, in snakes are both diverse and labile, facilitating a wide range of ecological strategies and contributing to spectacular radiations of these organisms in tropical and subtropical biomes worldwide.