EATING AND DRINKING

Feeding and Drinking Morphology

  • Main Concepts:

    • Digestion and nutrition

    • Water balance in mammals

Diversity of Mammalian Diets

  • Herbivores - General plant vegetation

    • Examples: Rabbits, cows

  • Carnivores - Animal protein

    • Examples: Lions, wolves

  • Insectivores - Insects

    • Examples: Shrews, many bats

  • Browsers - Shrubs and herbaceous vegetation

    • Examples: Deer, giraffes

  • Folivores - Leaves

    • Examples: Howler monkeys, colugos, koalas

  • Frugivores - Fruits

    • Examples: Many primates, many bats

  • Nectarivores - Pollen and nectar

    • Examples: Bats, many marsupials

  • Granivores - Seed eaters

    • Examples: Many rodents

  • Sanguinivores - Blood

    • Example: Vampire bats

Specialized Insectivores

  • Various adaptations for advanced feeding strategies.

Feeding and Drinking Adaptations

  • Cranial Modifications:

    • Form and Function are vital in adaptations for consumption and retention of nutrients and water.

Starting Point for Feeding Evolution

  • Insectivore with heterodont dentition (Incisors (I), Canines (C), Premolars (PM), Molars (M)).

  • Myrmecophagous - Termite and ant eating.

  • Aquatic toothed mammals have homodont dentition.

  • Aquatic baleen mammals have lost teeth and developed baleen to strain planktonic organisms.

Myrmecophagy and Convergent Evolution

  • Adaptations for ant and termite eating seen in:

    • Monotremata - Echidna

    • Dasyuromorphia - Numbats

    • Tubulidentata - Aardvark

    • Xenarthra - Anteaters

    • Carnivora - Aardwolf

    • Pholidota - Pangolin

Jaw Muscles and Dentition Adaptations

  • Types of Dentition:

    • Bunodont (e.g., human teeth)

    • Selenodont (e.g., deer)

    • Lophodont (e.g., certain rodents)

    • Hypsodont (e.g., horses)

    • Brachyodont (e.g., humans)

    • Zalambdodont (e.g., moles)

    • Dilambdodont (e.g., bats)

  • Enamel composition:

    • Primary mineral: hydroxyapatite - a crystalline calcium phosphate.

Digestive Enzymes and Processes

  • Oral Cavity:

    • Salivary amylase secreted; splits starches into simple sugars.

  • Stomach:

    • Gastric juice contains hydrochloric acid (HCl), pH 1.5 to 3.5, and pepsin.

    • HCl breaks down protein peptide bonds, activates gastric enzymes, and kills bacteria.

    • Pepsin splits protein chains into polypeptides.

  • Small Intestine:

    • Enzymes include: Lipase, α-Amylase, Trypsin, Chymotrypsin, Carboxypeptidase A & B, Ribonuclease, and Deoxyribonuclease.

  • Pancreas:

    • Pancreatic juice neutralizes gastric acids.

  • Bile Salts from Liver:

    • Help in fat digestion.

Digestive Tract Modifications

  • Types of Mammals:

    • Insectivore: Short intestine, no cecum.

    • Carnivore: Short intestine and colon, small cecum.

    • Nonruminant Herbivore: Simple stomach, larger cecum.

    • Ruminant Herbivore: Four-chambered stomach with large rumen, long small and large intestine.

  • Diversity Among Species:

    • Comparative anatomy among different mammal digestive systems: human vs. pig vs. dog, etc.

Herbivore Digestion Challenges

  • Plant material is tough to digest (cell walls and cellulose).

  • Protein content in plants is lower and hard to obtain.

Major Adaptations in Herbivore Digestion

  • Hindgut Fermentation:

    • Non-ruminant system in mammals like horses, rhinos, and some marsupials.

  • Rumination:

    • Multi-chambered stomach system found in many artiodactyls, kangaroos, and sloths.

Comparing Digestion: Hindgut vs. Foregut Fermenters

  • Hindgut Fermentation:

    • Singleton chewing (one-time), enzymatic digestion, shorter digesta passage rate (10-60 hrs).

    • Lower nutrient extraction per unit food.

    • Fast digestion.

  • Foregut Fermentation:

    • Multichambered stomach, cud chewing, microbial digestion.

    • Longer digesta passage rate (60-100 hrs).

    • Higher nutrient extraction per unit food.

Unique Feeding Specializations

  • Coprophagy - Certain mammals (lagomorphs, rodents) consume feces to maximize nutrient extraction.

  • Blood-feeding - Vampire bats adapt to diet by modifying their stomach to store blood and enhance flying capabilities.

  • Nectar feeding - Co-evolution in bats and flower species providing mutual benefit.

  • Gum feeding - South American marmosets gouging tree bark to access plant gums.

Water Balance and Adaptations

  • Critical in maintaining water levels in arid environments.

  • Potential threats:

    • Heat stress and water stress.

  • Sources of water loss:

    • Evaporation, respiration, excretion, and lactation.

  • Sources of water gain:

    • Drinking, dietary water, and metabolic processes.

Mechanisms to Enhance Water Gain & Limit Loss

  • Adaptations include reduced sweat glands, fur coats, burrowing behaviors, and dietary actions.

Structure of the Mammalian Kidney

  • Converts protein metabolism by reducing ammonia to urea for urine production.

  • Nephron Structure:

    • Divided into Bowman's capsule, glomerulus, and collecting duct.

  • ADH Function:

    • Regulates the collecting duct's permeability to control water retention during hydration variance.

Specific Adaptations in Desert Rodents

  • Active at night to minimize water loss and gain from seeds high in moisture.

Research Focus: Dearing Lab Studies

  • Investigating digestive challenges in small mammals, particularly related to diet and gut microbiota.

  • Applies various disciplines (physiology, ecology, etc.) to comprehend small mammal adaptation strategies.