Mad, bad and dangerous to know: the biochemistry, ecology and evolution of slow loris venom

Abstract

Only seven types of mammals are known to be venomous, including slow lorises (Nycticebus spp.). Despite the evolutionary significance of this unique adaptation amongst Nycticebus, the structure and function of slow loris venom is only just beginning to be understood. Here we review what is known about the chemical structure of slow loris venom. Research on a handful of captive samples from three of eight slow loris species reveals that the protein within slow loris venom resembles the disulphide-bridged heterodimeric structure of Fel-d1, more commonly known as cat allergen. In a comparison of N. pygmaeus and N. coucang, 212 and 68 compounds were found, respectively. Venom is activated by combining the oil from the brachial arm gland with saliva, and can cause death in small mammals and anaphylactic shock and death in humans. We examine four hypotheses for the function of slow loris venom. The least evidence is found for the hypothesis that loris venom evolved to kill prey. Although the venom’s primary function in nature seems to be as a defense against parasites and conspecifics, it may also serve to thwart olfactory-orientated predators. Combined with numerous other serpentine features of slow lorises, including extra vertebra in the spine leading to snake-like movement, serpentine aggressive vocalisations, a long dark dorsal stripe and the venom itself, we propose that venom may have evolved to mimic cobras (Naja sp.). During the Miocene when both slow lorises and cobras migrated throughout Southeast Asia, the evolution of venom may have been an adaptive strategy against predators used by slow lorises as a form of Müllerian mimicry with spectacled cobras.

Transcriptome and toxin family analysis of the paralysis tick, Ixodes holocyclus

“…For example, grooming is an important behavior in monkeys, cats and cattle to reduce the number of external parasites (Nekaris et al, 2013). The primary line of host defense also relies on complex hemostatic and immunological responses of the host against ectoparasites.…”

Traditions, taboos and trade in slow lorises in Sundanese communities in southern Java, Indonesia

“…Slow lorises are the only venomous primate, and one of a small number of venomous mammals (Nekaris et al 2013b). The venom comprises 2 components, saliva and oil from the brachial gland on the upper arm, which becomes active when the animal licks its brachial gland and mixes the two.…”

“…The venom comprises 2 components, saliva and oil from the brachial gland on the upper arm, which becomes active when the animal licks its brachial gland and mixes the two. When threatened, for instance when picked up by a human, slow lorises may administer a painful bite, which may cause swelling and tends to heal much more slowly than similar bites from non-venomous animals (Nekaris et al 2013b). Some people experience anaphylactic shock that may lead to death (Wilde 1972), whereas others experience necrosis of the infected tissue (Nekaris et al 2013b; see 'Results: Venomous primates').…”

“…When threatened, for instance when picked up by a human, slow lorises may administer a painful bite, which may cause swelling and tends to heal much more slowly than similar bites from non-venomous animals (Nekaris et al 2013b). Some people experience anaphylactic shock that may lead to death (Wilde 1972), whereas others experience necrosis of the infected tissue (Nekaris et al 2013b; see 'Results: Venomous primates'). The species is collected for the pet trade, and animals are sold at so-called bird markets ( pasar burung) in cities.…”

Trialling exudate-based enrichment efforts to improve the welfare of rescued slow lorises Nycticebus spp.

“…Slow lorises occur in 13 Southeast Asian countries and are protected in all of them; all species are listed in Appendix I of CITES (Convention on Inter-national Trade in Endangered Species of Wild Fauna and Flora) (Nekaris & Nijman 2007). The venomous bite of slow lorises can be harmful to humans (Nekaris et al 2013a), and thus throughout much of the species' range traders clip the sharp anterior teeth (toothcomb) to prevent the loris from easily delivering its venomous bite. Conducted crudely with wire cutters, nail clippers, or pliers, this procedure causes the death of many animals due to infection (Streicher et al 2008).…”