Mammalian Feeding Flashcards
What are the different anatomical adaptations for capturing food in mammals?
- jaw shape and muscles
- manual claws of pangolins
- elongated fingers of aye aye
- elongated tongue of anteaters
Give 2 examples of adapted jaw shape and muscles for capturing food in mammals
- Giant Anteater: long, tubular snout, teeth lost
- Baylean Whale: jaw not fused to allow mouth to open wider, plates of baleen (no teeth), arched upper jaw
Describe the elongated fingers in the ‘aye aye’
- 3rd digit especially elongated
- ball and socket joint swivels
- percussive foraging: tapping to hear hollow sections containing grubs in trees
What bone provides skeletal support of the tongue?
hyoid apparatus
Which papillae are present on the tongue?
- 3 different types in different distributions
- taste buds in epithelia - taste receptor cells
What are the 5 taste receptors and in which mammals have they been lost or increased?
- bitter: T2r receptor, decreased (pinnipeds, cetaceans), increased (insectivorous bats & shrews)
- sweet: Tas1r2 & Tas1r3 receptors, decreased in cats, hyenas, pinnipeds and cetaceans
- sour: PKD2L1, decreased in cetaceans
- Umami: Tas1r1 & Tas1r3, decreased in cetaceans
- Salty: ENaC, retained in cetaceans
Describe the evolutionary loss of sweet taste receptors in felines
- Tas1r2 gene in cats: 246bp microdeletion in exon 3 and stop codons in exons 4 & 6
- Tas1r2 similar deletions for tiger, cheetah, 6 breeds domestic cat
- Tas1r3 functional and expressed but needs combination of Tas1r2
How have sea lions and dolphins taste buds adapted?
- lost taste function when returned to sea 35-50mya
- reduced taste buds
- feeding behaviour - swallow food whole
What is a herbivore example of losing taste receptors?
- giant panda lacks umami gene Tas1r1
- feeds primarily on bamboo
Describe the ‘spicy’ taste receptor
- capsaicin/vanilloid receptor conded by TRPV1 gene
- present in birds but only responds to heat and protons, not capsaicin
- capacity to detect capsaicin-like inflammatory substances is a recent acquisition of mammalian vanilloid receptors
Describe monophydonts
- 1 set of teeth throughout life
- baleen whales have teeth in utero - no adult teeth
Describe diphyodonts
- 2 successive sets of teeth
- nearly all mammals
Describe polyphyodonts
- several sets of teeth continuously replaced
- kangaroos, elephants, manatees
How do you write dentitions of animals, using a sheep and a cat as examples?
- Sheep: 0/4, 0/0, 3/3, 3/3
- Cat: 3/3, 1/1, 3/2, 1/1
- Incisors, Canines, Premolars, Molars
- 1st number upper jaw, 2nd number lower jaw
- only 1 side of jaw is shown
Describe brachydont teeth
- low crowned
- grow and stop
- enamel covering
Describe hyposodont teeth
- high crowned
- alternating layers of dentine and enamel to maintain functionality of occlusal surface
Describe hypselodont teeth
- teeth that continually grow via stem cells
- usually in rodents
Describe an example species’ teeth in the order Tubulidentata
- Aardvark teeth - distinctive tubulidentate microstructure
- lack incisors and canines
- teeth lack enamel-rouned structures of dentine
- teeth ever growing, unrooted, diphyodont
- small milk teeth lost before birth
What are 2 adaptations of teeth for non-feeding purposes?
- sexual selection
- fighting
What are 3 structural differences in molar shape and cusp?
- bunodont - rounded peaks (omnivores)
- lophodont - cusp drawn into straight ridges (rodents, perissodactlys)
- selenodont - crescent-shaped cusps (artiodactlys)
Describe baleen plates in baleen whales
- plates on maxilla
- made of keratin therefore not actual teeth
- homologous to ridges on roof of mammalian mouth
What are the 2 methods of preparation of food orally?
- salivary glands
- muscles of mastication
What are the 3 salivary glands?
- parotid
- submandibular
- sublingual
What are the 4 muscles of mastication?
- temporalis
- masseter
- lateral pterygoid
- medial pterygoid
What are the differences between carnivore and herbivore oral muscles?
- carnivore: large temporalis muscle for jaw snapping shut, smaller masseter & pterygoid muscles
- herbivore: larger masseter 7 pterygoid muscles for extensive chewing
What are the general rules of carnivorous digestive tracts?
- simple stomach
- digestive tract relatively short and simple
- distinct hindgut absent in some species
- exceptions cetaceans: large multicompartment stomach conserved from herbivore ancestors
Describe the general omnivorous digestive system
- simple stomach
- digesta retention aided by caecum in hindgut
- haustrations of caecum and varying length of colon in some species
- colon of pigs, some primates haustrated throughout entire length
Describe the general herbivorous digestive tract
- most obtain substantial part of nutrients by microbial fermentation of plant material
- in voluminous caecum, colon or foregut
- large compartmented/haustrated stomach
Describe the ruminant stomach
- 4 chambered with specialized bacteria
- nearly all digestion in rumen
- food regurgitated up to 40 times to allow animal to re-chew food
Describe the monogastric stomach
- single stomach - primary digestion
- low pH, pepsin
Where does fermentation principally occur in small herbivores?
caecum
Which enzymes are present in the small intestines?
- amylases
- trypsin
- lipase
Describe caecotrophy
- eating of faecal products of caecum for nutritional purposes
- common in herbivorous rodents
