Not Quite So Cuddly

This post will move away from the obvious venomous animals such as reptiles, arachnids and various sea life and on to the furry little creatures that are considered cute and cuddly.The literature surrounding venomous mammals is an active battlefield so I will try my best not to ruffle any feathers or fur. The definition used to describe a venomous animal is a secretion produced by an animal in a specialised gland and delivered to the target thought infliction of a wound. The secretion must contain a molecule which disrupts the victims physiological process Fry et al (2009). The few mammals described as venomous where done so using the following definition.

  There are currently only 4 orders of mammals considered to be venomous they are the Insetivora (Shrews and Solendons), Monotremata (Platypus), Chiroptera (Vampire bats) and arguably Primates which are the pygmy and slow lorises. Lorises are a spanner in the works of toxicology labelling as they lack any delivery apparatus. The toxin is produced in a gland located on the elbow, licked and spread onto the teeth. Due to this lorises are considered as indirectly venomous.

Slow loris (Nycticebus coucang)

http://www.bbc.co.uk/nature/life/Slow_loris 

1.35pm 21/03/14

  The concept of a venomous mammal has been around since the mid 1900s however any symptoms following a bite ware discarded as a bacterial infection.It was not until 1992 that the idea was taken seriously after extensive research. It was also proposed by Dufton (1992) that although venom is a rare feature in extant mammals it would be widespread in more primitive species. There was very little fossil evidence to support this until 2005 when a fossil shrew dating back 6 million years was found to have distinct grooves the canine teeth which was an indication of a venom delivery system. Since then there has been multiple discoveries of insectivore fossils found to have grooved teeth and other mammals with crural spurs similar to the platypus. This evidence strongly supported the hypothesis that venom in early primitive mammals was widespread.

   The evolutionary history of the venomous mammals is still unclear and has only recently been investigated. Interestingly  Solendons produce their venom in the submaxillary gland which are also found in the Gila monster and Mexican beaded Lizard. The effects of the venoms are also similar but are made up of two different protein structures. This is an excellent example of convergent evolution at a molecular level between reptile and mammal venom and delivery systems.

References

Braun, R, Veril, H, Carlini, C 2012, Venomous mammals: a review, Toxicon, vol. 59, iss. 7-8, pp.680-695.

Fry, B, Roelants, K, Champagne, D, Scheib, H, Tyndall, J, King, G, Nevalainen, T, Norman, J, Lewis, R, Norton, R, Renjifo, C, Vega, R 2009, The toxicogenomic multiverse: convergent recruitment of protiens into animal venoms, Annual Reviews, vol.10, pp.483-511.