physiology of foraging Flashcards
what are the two states of food acquisition
finding food and securing food
how can food be located
by chance encounter or active hunting
how does the star nosed mole find food
an exaggerated touch sense using Eimer’s organs which cover appendages and sense touch through exposed nerve endings, merkel cells and lamellated corpuscles
how do bats use echolocation
changes in amplitude/timing between ears is directional. doppler shift detecting change in frequency tells it if the object is moving closer or away
how do bats generate calls
contraction of the larynx muscle. it becomes more rapid during buzz phase as it approaches its target
how are bats adapted to hear calls
funneled auricles and motor protein prestin which is on the basilar membrane and detects high frequency sound
who uses electrolocation and what does it sense
used by sharks and rays. they detect electrical fields generated by muscle contraction of prey
how is electrolocation detected
impulses travel through conducting gel- filled canals to stimulate ampulla of Lorenzini (sense organ). impulses are sent straight to the brain
what is IR
infrared ratiation with wavelength 700nm-1mm. most thermal radiation is IR
how do pit snakes detect IR
innervation of the pit membrane by trigerminal ganglia neurones which are rich in temperature- sensitive TRPA1 ion channels
how do pit snakes visualise IR
impulses from TG neurones converge with optic nerve impulses in the optic tectum so they ‘see’ IR
how do vampire bats detect IR
similarly to pit snakes with pit organs, however they use a short isoform of TRPA1 (TRPA1S) which is more temperature sensitive
how do vampire bats prevent self detection and why is this necessary
their nose (where the 3 pit organs are) is 9 degrees colder than the rest of the face. this is necessary as bats are warm blooded mammals
what are the three mechanisms of securing a meal
physical, electrical and chemical
how is spider silk formed
it forms micelle- like structures in the sac. a reduced pH in the spinning duct elongates proteins and forms fibres
which form of silk is most valuable in predation
swathing silk- around 300 aciniform glands simultaneously form a silk ‘sheet’ to wrap prey
what is the structure of electric organs
they are filled with stacks of around 5000-6000 electrocyte disks which have two distinct faces
how is a potential difference generated in electric organs
one face of the disk is depolarised and the other is polarised. the summative potential difference of the organ is around 860V
what is the composition of venom
it is made up of neurotoxins, enzymes and pore forming toxins
what do neurotoxins target
fast- acting proteins ie ion channels. these include Na, Ca, K, nAChR and iGluR
what are peptide neurotoxins
small peptides which have lots of disulfide bridges due to high quantities of Cys residues. they target all types of ion channels
which ion channels cause which paralysis in peptide neurotoxins
K and Ca cause rigid paralysis, Na, nAChR and iGluR cause flaccid paralysis
which ion channels cause which paralysis in non- peptide toxins
Na, Ca, nAChR and iGluR all cause flaccid paralysis
how is venom stored
as pro- venom to prevent self toxicity. it is enzymatically modified at release to become active
how is venom usually delivered
by fang, sting or modified leg. they have modified elongated holes/ deep grooves to prevent blockage or venom ducts
how do cnidarians deliver venom
toxic harpoons. they are stored inside out in nematocysts and are triggered by cnidocil touching prey
how do cone snails paralyse prey
in a two step paralysis- rigid then flaccid. they use toxic harpoon called radula
