Mammalian Feeding

Question 1

What are the different anatomical adaptations for capturing food in mammals?

Answer 1

• jaw shape and muscles
• manual claws of pangolins
• elongated fingers of aye aye
• elongated tongue of anteaters

Question 2

Give 2 examples of adapted jaw shape and muscles for capturing food in mammals

Answer 2

• 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

Question 3

Describe the elongated fingers in the ‘aye aye’

Answer 3

• 3rd digit especially elongated
• ball and socket joint swivels
• percussive foraging: tapping to hear hollow sections containing grubs in trees

Question 4

What bone provides skeletal support of the tongue?

Answer 4

hyoid apparatus

Question 5

Which papillae are present on the tongue?

Answer 5

• 3 different types in different distributions
• taste buds in epithelia - taste receptor cells

Question 6

What are the 5 taste receptors and in which mammals have they been lost or increased?

Answer 6

• 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

Question 7

Describe the evolutionary loss of sweet taste receptors in felines

Answer 7

• 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

Question 8

How have sea lions and dolphins taste buds adapted?

Answer 8

• lost taste function when returned to sea 35-50mya
• reduced taste buds
• feeding behaviour - swallow food whole

Question 9

What is a herbivore example of losing taste receptors?

Answer 9

• giant panda lacks umami gene Tas1r1
• feeds primarily on bamboo

Question 10

Describe the ‘spicy’ taste receptor

Answer 10

• 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

Question 11

Describe monophydonts

Answer 11

• 1 set of teeth throughout life
• baleen whales have teeth in utero - no adult teeth

Question 12

Describe diphyodonts

Answer 12

• 2 successive sets of teeth
• nearly all mammals

Question 13

Describe polyphyodonts

Answer 13

• several sets of teeth continuously replaced
• kangaroos, elephants, manatees

Question 14

How do you write dentitions of animals, using a sheep and a cat as examples?

Answer 14

• 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

Question 15

Describe brachydont teeth

Answer 15

• low crowned
• grow and stop
• enamel covering

Question 16

Describe hyposodont teeth

Answer 16

• high crowned
• alternating layers of dentine and enamel to maintain functionality of occlusal surface

Question 17

Describe hypselodont teeth

Answer 17

• teeth that continually grow via stem cells
• usually in rodents

Question 18

Describe an example species’ teeth in the order Tubulidentata

Answer 18

• 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

Question 19

What are 2 adaptations of teeth for non-feeding purposes?

Answer 19

• sexual selection
• fighting

Question 20

What are 3 structural differences in molar shape and cusp?

Answer 20

• bunodont - rounded peaks (omnivores)
• lophodont - cusp drawn into straight ridges (rodents, perissodactlys)
• selenodont - crescent-shaped cusps (artiodactlys)

Question 21

Describe baleen plates in baleen whales

Answer 21

• plates on maxilla
• made of keratin therefore not actual teeth
• homologous to ridges on roof of mammalian mouth

Question 22

What are the 2 methods of preparation of food orally?

Answer 22

• salivary glands
• muscles of mastication

Question 23

What are the 3 salivary glands?

Answer 23

• parotid
• submandibular
• sublingual

Question 24

What are the 4 muscles of mastication?

Answer 24

• temporalis
• masseter
• lateral pterygoid
• medial pterygoid

Question 25

What are the differences between carnivore and herbivore oral muscles?

Answer 25

• carnivore: large temporalis muscle for jaw snapping shut, smaller masseter & pterygoid muscles
• herbivore: larger masseter 7 pterygoid muscles for extensive chewing

Question 26

What are the general rules of carnivorous digestive tracts?

Answer 26

• simple stomach
• digestive tract relatively short and simple
• distinct hindgut absent in some species
• exceptions cetaceans: large multicompartment stomach conserved from herbivore ancestors

Question 27

Describe the general omnivorous digestive system

Answer 27

• 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

Question 28

Describe the general herbivorous digestive tract

Answer 28

• most obtain substantial part of nutrients by microbial fermentation of plant material
• in voluminous caecum, colon or foregut
• large compartmented/haustrated stomach

Question 29

Describe the ruminant stomach

Answer 29

• 4 chambered with specialized bacteria
• nearly all digestion in rumen
• food regurgitated up to 40 times to allow animal to re-chew food

Question 30

Describe the monogastric stomach

Answer 30

• single stomach - primary digestion
• low pH, pepsin

Question 31

Where does fermentation principally occur in small herbivores?

Answer 31

caecum

Question 32

Which enzymes are present in the small intestines?

Answer 32

• amylases
• trypsin
• lipase

Question 33

Describe caecotrophy

Answer 33

• eating of faecal products of caecum for nutritional purposes
• common in herbivorous rodents