Mammals – Part III

VERTEBRATE ZOOLOGY (VZ Lecture31 – Spring 2012 Althoff - reference PJH Chapters 18-20)

Bill Horn

Basics

• ___________ glandsa) present in all mammalsb) mucilaginous material

present in anteaters & pangolins--sticky

• Various ____________ patterns for cutting(incisors), shearing (carnassials),

grinding (i.e., occlusal surfaces ofmolars & premolars)

• Stomachs: simple & complex

Collared anteater -- “toothless”

Salivary Glands…not just for “digestion”• Rich mixture of compounds that directly affect

individual survival and competitive success:1) provides access to nutrients2) maintains oral epithelial tissues3) maintains dental tissues4) maintains gastric tissues5) maintains nervous tissues (taste buds)6) in rodents, recently discovered pheromone

(think communication)7) transfer airborne molecules to vomeronasal

organ8) used for evaporative wetting (fur-wetting)9) provides some defense against disease10) transmission of disease (ex. rabies,

hantavirus, brucellosis, etc.)

Dentition: Molariform Occlusal Surfaces

• Considerable variety across the class Mammalia….

Even within certain orders considerable variety such as found in the order __________ (mice, rats, beaver, muskrat, porcupine, etc.)

mole-rat

voles, lemmings

old world porcupines

chinchilla

cuspid-pattern:

squirrel species

“folded” enamel:

some murid (rat) species

Dentition…some other specializations

• _________: well developed in many carnivores• ___________: in many carnivores (especially

well developed in cat (Felidae) and dog (Canidae) family….. Last upper premolar & first lower molar results in shearing action (“scissor”-like)

• ________________: many rodents. Important for sniping vegetation

Stomachs

• Simple: most species of mammals havesac-like compartment

• Complex: subdivided. a) ruminant artiodactyls b) cetaceans (whales & dolphins) c) sirenians (mantees & sea cows)

Simple Stomachs

• 1 major “chamber” for initial processing (i.e., stomach) in most mammalsa) no cecum (insectivores, vampire bats)b) “modest” cecum (carnivores)c) elongated cecum (rabbits & others)

• 3 major “chambers” for processing (in stomach) inruminants plusa) cecum “in-line” with entire tractb) small intestine

Koala

Complex Stomachs: RUMINANTS

• Artiodactyls such as bovidae(bison, bighorn sheep, mt.goats),antilocapridae (pronghorn), andcervidae (deer, elk, moose, caribou) in NorthAmerica

• All are exclusively herbivores

Ruminants...continued

• Digestion aided by micro-organisms that

inhabit stomach...referred to as _____________________ which are

small, various bacteria & protozoa

• Most lack enzyme cellulase (thus can’t handle cellulose)

• Four-chambered stomach

Ruminants: 4-chambered stomach

in the esophagus

rumen reticulum omasum abomasum

out the small intestine

4-chambered stomach

1 2

3

4

Rumen

• First chamber of stomach

• Storage chamber during feeding

• During rest, regurgitates the food to “chew cud”

• Also, it is a ________________ vat: carbon dioxide (CO2) & methane (CH4) produced

1

Rumen...continued

• Fermentation brought about by presence of microflora

• Microflora responsible for breakdown of cellulose a) composition varies ___________________ b) cattle more “advanced” than deer…(i.e., more efficient at processing veg, particularly grasses)

1

Note: If ruminants go very long without eating or eating proper diet, quantity of “active” microrganisms can decrease to point that not enough of them can be “supported”

....when this happens appetite and rumen activity can stop resulting in animal starving even in presence of newly provided/available food.

Products of Rumen Activity

• Gases: CO2 & methane

• _________________________ (VFAs)--the most important product of

fermentation because they readily absorbed from the rumen and are a major energy source

• ___________ (typical diet “incoming” is 6-7% protein…”squeezes” more out of food)

Note: In monogastric animals, most energy (from carbohydrates) is absorbed from the small intestine in the form of glucose...in ruminants this takes place with VFAs in the rumen (with rumen wall absorbing some) and subsequent chambers

Reticulum

• Second chamber of stomach

• Digestion, cellulose breakdown continue

• Squeezes out water in bacteria, recycles it some….

2

Omasum

• Third chamber of stomach

• Pummels contents once more

• Essentially, no digestion taking place here

3

Abomasum

• Fourth chamber of stomach

• “True” stomach

• Gastro-digestion occurs as stomach acids secreted to further breakdown contents...in other words, same “actions” that take place in monogastric systems

4

Summary Points/Comments

• _________ digestion takes place in rumen (1st chamber)

• Some digestion takes place past stomach complex...i.e., in the large & small intestines

• Nutrients ___________________ gastrointestinal tract

Advantages of Rumen Digestion

• Protein synthesis carried out by inorganic substances through ____________ activity

• Allows existence on ______ protein diet because proteins produced (most plant parts are low in protein (<12%, usually even lower) content relative to carnivore/insectivore diets (protein content ~15-50%)

Disadvantages of Rumination

• Carry “_______” food

• Fermentation is _______ processmouth-to-anus times: a) horses-- 8 - 24 hours b) cows-- 70-100 hours

• Must eat “_________” ....going days without food devastating

Basic Diet Categories• Insectivorous• Carnivorous• Omnivorous• Herbivorous

a) foregut fermentersb) hindgut fermentersc) gnawing mammals (do not produce

cellulase)

Specializations among Herbivores(besides those consuming leaves & stems)

• Granivorous—fruits, nuts, and seeds(Heteromyids: all cache seeds)

• Folviorous—leaf eating• Frugivorous—fruit eating• Nectarivorous—nectar eating

(some bats & honey possum)• Gumivorous— gums, saps, & resins• Mycophagous--fungus

Food Hoarding

• Hoarding = caching

• LARDER HOARDING—all food stored concentrated at one site

• SCATTER HORADING—one food item per site

• Common among mammals: (especially rodents) a) larder hoarding most common b) storage usually >10 days

Hoarding/Caching Sites

• Burrow• Cavity• Foliage• Ground• Litter

• Nest• Snow• Soil• Tree trunks/

branches• Water

Make ______ while the sun shines….

PIKA

Lagomorph (rabbits/hares)

“cuts, gathers, dries,

re-gathers, and stores

“hay” for the winter”