lect - more venom Flashcards
(24 cards)
tinbergen’s 4 questions adapted to venom evolution
- evolutionary function
- phylogeny
- causation
- development
primary function of snake venom
foraging; defence is secondary and inconsistent
life-dinner principle in venom evolution
defensive adaptations are more urgent for prey than predators, as failure means death
MitTX
toxin in Micrurus tener that causes pain by activating acid-sensing ion channels, no other known effects
pain trajectory studies
little evidence supports venom evolving mainly for defence
example of loss of venom due to diet specialization
Aipysurus eydouxii, egg eating sea snake with non-functioning venom
venom metering
adjusting venom volume depending on prey size or threat level
key genetic mechanism driving venom variation
- gene presence/absence
- transcriptional
- translational
post-translational modifications
example of distinct venom types within a species
Mojave rattlesnake
- Type A (neurotoxic)
- Type B (haemotoxic)
snakebite = neglected health problem
affects rural poor, is under-reported, and lacks effective treatment
symptoms of neurotoxic venom
- face paralysis
- difficulty swallowing
- respiratory failure
symptoms of haemotoxic venom
- bleeding
- coagulopathy
- tissue necrosis
- hemorrhage
challenges that limit antivenom use
- high costs
- need for early administration
- variable effectiveness
- logistical issues
venom variation affecting treatment
reduces antivenom efficacy and increases economic/logisitic burdens
production of antivenom
- venom extracted from snake
- venom injected into animal
- animal generates antibodies
- antibodies purified
- injected into patient after bite to neutralize venom
batesian mimicry
a harmless species imitates a venomous one to avoid predation
mertensian mimicry
dangerous species mimic less dangerous one to aid predator learning (largely refuted)
evidence for innate predator avoidance of coral snake patterns
naive birds avoid striped patterns without prior experience
aposematism
warning colouration signalling danger to predators
how does mimicry and aposematism affect snake evolution
promote diversification by protecting mimics, increasing ecological niche space
snake detection hypothesis
primates evolved enhanced vision and fear responses due to predation pressure from snakes
human influence on snake evolution
pressure for long-distance defence due to tool use and upright posture
(eg. spitting in cobras)
mimicry
evolutionary imitation of one species (model) by a second (mimic) to deceive a third (dupe)
mullerian mimicry
unprofitable prey mimic each other and share cost of predator “training”
(honest signal)
