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Week 6Oct. 14

All About Milk Walt Hurley

Why Milk ?

Evolution of Mammals, Lactation, Milk

I

What are the main components in milk?

• Water• Lactose• Fat (Lipid)• Proteins• Minerals• Vitamins• Others

Bioactive factors

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Milk

Reproductive strategy

LactationWhy?

What are some of the differences?

Nature of parental (maternal) investment

Extent of offspring maturity when entering the world

Number of offspring per reproductive cycle, and per lifetime

Live birth vs hatchling

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Earth formed4.5 billion

years ago

Life starts3.5 billion

years ago

Big Bang

Our story begins

13.77 billion years

400 million years ago Today

~400 million years

400 mya Today

365 mya

Eggs are still laid in water, fertilization still occurs in water, requires larval stage (think tadpole)

They crawled out of the water

Tetrapods started living part of their life on land

first forests; plants developed more advanced vascular systems and refined reproductive structures

360 mya - first seed-bearing plants

385-360 mya

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400 mya

Assembly of supercontinent Pangea

175 mya – Pangea starts to break apart

Shift from large tracts of swampy wetlands to isolated rainforest tracts separated by

arid landscapes

335 mya

Today

Pangea

400 mya

312 mya Synapsids evolve; became dominant species 286-260 mya

Most likely had parchment-shelled eggs

Higher water loss from the egg

Living in drier environments

No fossil record of calcified egg shells, soft shells do not fossilize

Parchment shell can absorb water

Evolve behaviors that ensure eggs develop under moist conditions – to maintain fluid balance of the embryo

Dimetrodon, top-predator synapsid

Permian periodToday

Pangea

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400 mya Today

Permian-Triassic extinction event

Loss of biosphere:96% of all marine species70% all terrestrial vertebrate species

57% of all biological families83% of all genera

Causes:3 phases of the extinction

Meteor impact eventsMassive volcanic eruptionsRelease of underwater methane

251 mya

Permian Triassic

Mass extinction

Pangea

400 mya

Moder

n birds e

volve

dDinosaurs evolved within a

single linage of archosaurs

Archaeopteryx

(ancestor of modern birds)

Dinosaur extinction

Permian Triassic

Dinosaurs and Birds

Permian-Triassic extinction event

243-233 mya150 mya ~ 6

0 mya

66 mya

Jurassic Cretaceous Paleogene Neogene

Triassic-Jurassic extinction event

Pangea

251 mya

Early Proto-Mammals

Flowering plants125 mya

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From ~230 mya thru 66 myaClade: DinosauriaDominant terrestrial vertebrate after 201 mya

(Triassic-Jurassic extinction event)

Birds are modern feathered dinosaursBirds are the only dinosaur to survive past 66 mya

(Cretaceous-Paleogene extinction event)

Oh, yes we did!

400 mya Today

Permian-Triassic extinction event

Permian Triassic

275 mya Synapsids gave rise to the Therapsids in late Permian

Therapsids included the cynodonts (260 mya)

A cynodont (Oligokyphus)

Gave rise to the mammals in the late Triassic (225 mya)

251 mya

225 mya

Pangea

A therapsid (Instrancevia)

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400 mya

C-P extinction

Permian Triassic

P-T extinction

Jurassic Cretaceous Paleogene Neogene

T-J extinction

Pangea

tetrapods

synapsids

therapsids

cynodonts

mammals

reptilesdinosaurs

birds

Didelphodon vorax

dinosaur-hunting (?) marsupial-ancestor

69-66 mya

Oligokyphus 231-113 mya

Massetognathus

235 mya

Kayentatherium201-175 mya

125 mya

(oldest record of a mammal with spines and hair that can be examined on the cellular level)

Spinolestes xenarthrosus

Early Mammals/Proto-Mammals

Morganucodonta

210-140 mya

Eozostrodon210-190 mya

The first true mammal?

400 mya

a

b

c

d

e

f

g

a b cd e f g

Pangea

Permian Triassic Jurassic Cretaceous Paleogene Neogene

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Hard-shelled egg (chicken)

Parchment or soft-shelled eggs (reptiles)

What does a soft-shelled egg need that a hard-shelled egg does not need?

protection from:microbial action on the embryo

secretion of a water-based secreta from the mother

drying out, water loss

What do eggs need in order to hatch?

Incubation, warmth Mother (or other?) laying on the eggsnesting behavior

secretion of a water-based secreta from the mother that contains antimicrobial activity

Evolution of skin glands on the ventral surface of the animal

Exocrine glands that secreted a fluid loaded with antimicrobial activities

Components of the secretion of particular nutritional value to the young evolved later

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What does this have to do with milk?

Early skin gland (proto-mammary gland) secretions:

Water-based

Rich in antimicrobials

lactoferrin lysozyme antibodies antimicrobial peptides others

Not rich in nutrients at least not initially

Rich in bioactivity

Evolution of Mammary GlandsMonotremes

Marsupials

Hair follicles and sebaceous glands are linked to development of the nipples; hair follicles penetrate the nipple epithelium, are then shed, leaving a duct (galactophore) that connects to the mammary gland to the surface of the nipple

No nipples; the mammary “patch” is comprised of the mammary glands associated with hair follicles and sebaceous glands

Placental mammals

Lost the direct association of hair follicles with the mammary gland Mammary glands are

associated with

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Was everything new, or just repurposing existing genes and functionalities?

Prolactin Oxytocin

Lysozyme

a-Lactalbumin

ancestral gene

has wide range of functionsuterine contractions during parturition

milk ejection/letdown

the “love” hormone

a brain neurotransmitter

social bonding, trust, parental carereproductive functions

fluid balance, mineral balance

prolactin and growth hormone evolved from a common ancestral gene 345 mya

ancestral gene evolved 500+ mya

maternal/paternal behaviors in mammals

brooding behaviors in birds

antimicrobial

lactose synthesis

Modern Mammals

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Mammals~5,400 species of mammals

We know things about the milk composition on <5%Classification

Kingdom

Phylum

Subphylum

Class

Animalia

Chordata

Vertebrata

Mammalia

Mammals What distinguishes mammals from reptiles and birds?

hair 3 ear bones

mammary glandshigher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language

neocortex

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1 ear bone

3 ear bones

Size range from: 1.5 inch

>100 feet

Craseonycteris thonglongyai

Bumblebee bat~5,400 species of mammals

Etruscan shrew

Suncus etruscus

Balaenoptera musculus

Blue whale

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Today’s Mammals

Monotremes Marsupials

Placental Mammals

Evolved into Evolved into

Monotremes diverged before the divergence of marsupials and

eutherian (placental) mammals

Echidna may be derived from a platypus-like ancestor

Evolution of Mammals

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Evolution of Mammals

Base

d on

Mor

phol

ogy

Base

d on

Gen

etic

Cha

ract

erist

ics

Monotremes

Egg laying mammals

Australia

New Guinea

Duckbilled platypus

Classification

Kingdom

Phylum

Subphylum

Class

Animalia

Chordata

Vertebrata

Mammalia

MonotremataOrder

Ornithorhynchus anatinus

Mammals

Genetic evidence indicates monotremes first evolved 180 – 210 mya

Oldest fossil is from only 120 mya

Platypus and echidna diverged between 19 and 48 mya

Male's spurs deliver a venom

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Lays 1-2 eggs in a burrow

Hatch at 12 days

Hair at 7 weeks, eyes open at 9 weeks, suckled for 16 weeks

Duckbilled platypusOrnithorhynchus anatinus

The unusual appearance of this egg-laying, duck-billed, beaver-tailed, otter-footed mammal baffled European naturalists when they first encountered it, and the first scientists to examine a preserved platypus body (in 1799) judged it a fake, made of several animals sewn together. [Wikipedia]

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4 species of Echidna(spiny anteater)

Family: Tachyglossidae

Australia

New Guinea

Genus: Tachyglossus

Tachyglossus aculeatus

Genus: Zaglossus

Zaglossus attenboroughiZaglossus bruijniiZaglossus bartoni

Monotremes

Egg laying mammals

Echidna Echidna

half-woman and half-snake,

lived alone in a cave

mother of many monsters of Greek mythology

perceived to have qualities of both mammals and reptiles

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Spines and fur of an echidna

TachyglossusThe “Pouch”

Do not have a permanent pouch. Have contracting muscles in the abdomen, which forms a pouch-like

fold.

Both male and female echidnas can form a pouch.

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††, the two tufts of hair in the lateral folds of the mammary pouch from which the secretion flows, b.m, Pouch; cl, cloaca; g.m, groups of mammary glands.

TachyglossusThe “Pouch”Lower surface of brooding female

dorsal view of the pouch and mammary glands

TachyglossusExposed mammary gland

After oxytocin injection

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Tachyglossus

Newly hatchedMilk ejected onto the skin

Tachyglossus

Newly hatched

Puggles

Lays 1 egg

Lives in mother's pouch for 12 weeks

Hatches in 9 days

Female lays her egg by lying on her back, rolling it down her stomach and enveloping straight into her “pouch”.

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Puggles

Tachyglossus

At 12 weeks eyes open, leaves the pouch for a nest burrow

Weaned at 20 weeks

Marsupials

Young born live, but very immatureAustraliaNew Guinea

kangarooswallabyskoalapossumswombatsTasmanian devilothers

Classification

Kingdom

Phylum

Subphylum

Class

Clade

Animalia

Chordata

Vertebrata

Mammalia

Theria

Metatheria

Subclass

Infraclass Marsupialia

South AmericaCentral AmericaNorth America

Nurse in a pouch

334 species:

Mammals

Macropus eugeniiTammar Wallaby

Adult

Marsupials have lactation lengths 5-10 times longer than placental mammals of comparable body weight

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Tammar WallabyMammary gland

Note nipples

Tammar Wallaby

70 day old

150 day old

200 day old

Macropus eugenii

Begins to leave the pouch ~200 days

Detaches from the nipple at ~100-125 days, but remains in the pouch

Weaned at about 300-350 days

Newborn

Born at ~28 days

Climbs unaided into the mother’s pouch

Swallows a nipple

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Wallaby

35 day old

Nipple suckled by 248 day old

60 day old

Nipple suckled by 260 day old

Nipple suckled by 210 day old Joey at time it first leaves the pouch

Wallaby Milk Composition

Days of Lactation

Perc

ent o

f Sol

ids

Birth Releases from nipple

First leaves the pouch Weaned

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100 200 300 400

Age of Young (days)

20

40

60

80

100M

ilk In

take

(mL/

day)

Tammar Wallaby Milk Intake

Releases from nipple

First leaves the pouch

Weaned

MarsupialsVombatus ursinus tasmaniensis

Common Wambat

Tasmanian Devil

Sarcophilus harrisii

Virginia Opossum

Didelphis virginiana

Onychogalea fraenata

Bridled nail-tailed wallaby

Macropus rufus

Red Kangaroo

Common Bushtail Possum

Trichosurus vulpecula

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Phascolarctos cinereus

Koala bear

Female koala carries her baby in her pouch for about six months.

Marsupials

Virginia Opossum

Didelphis virginiana

Teaspoon full of newborn opossums

Marsupials

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15 day old opossums Marsupials

Placental mammals

Young born more matureEverywhere

Largest orders are:

Classification

Kingdom

Phylum

Subphylum

Class

Clade

Animalia

Chordata

Vertebrata

Mammalia

Theria

Eutheria

Subclass

Infraclass Placentalia

Able to nurse independent of the mother

~95% of all mammalian species

Rodentia (1,500 species)Chiroptera (bats; >1,300 species)Soricomorpha (moles, shrews, solenodons; ~350 species)

Mammals

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Southern Short-Tailed Shrew

Blarina carolinensis

Etruscan Pygmy Shrew

Suncus etruscus

European Mole

Talpa europaea

Myodes glareolus

Bank vole

Soricomorpha

Hispaniolan solenodonCuban solenodon

Carnivorous

Nocturnal

Venomous

Dig in the dirt for insects worms, snails, small frogs and reptiles

Uses its teeth as a syringe to inject venom into its target

Venom is not lethal to humans, but wear gloves when you adopt one for a pet

Cuba

Haiti, Dominican Republic

Soricomorpha

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Cloven-hoofed, ruminant mammals

Bovidae

bison

African buffalo

water buffalo

antelopes

wildebeest

impala

gazelles

sheep

goats

muskoxen

domestic cattle

Classification

Kingdom

Phylum

Subphylum

Class

Family

Genus

Species

Animalia

Chordata

Vertebrata

Mammalia

Artiodactyla

Bovidae

Bos

Bos taurus

Order

Subfamily Bovinae

Mammals

even-toed ungulates

large mammals with hoofs

Classification

Kingdom

Phylum

Subphylum

Class

Family

Genus

Species

Animalia

Chordata

Vertebrata

Mammalia

Artiodactyla

Bovidae

Bos

Bos taurus

Order

Subfamily Bovinae

10 genera of medium to large-sized ungulates

Bovinae

bison

African buffalo

water buffalo

4-horned antelope

spiral-horned antelope

yak

domestic cattle

Mammals

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Subspecies of Bos taurus

Bos taurus supercutieous

Very prevalent in urban areasClassification

Kingdom

Phylum

Subphylum

Class

Family

Genus

Species

Animalia

Chordata

Vertebrata

Mammalia

Artiodactyla

Bovidae

Bos

Bos taurus

Order

Subfamily Bovinae

Mammals

Subspecies

Bos taurus primigeniusaurochs

extinct since 1627

Eurasian aurochs

Indian aurochs

North African aurochs

Classification

Kingdom

Phylum

Subphylum

Class

Family

Genus

Species

Animalia

Chordata

Vertebrata

Mammalia

Artiodactyla

Bovidae

Bos

Bos taurus

Order

Subfamily Bovinae

Mammals

plural: aurochsen

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Subspecies

Bos taurus taurus Bos taurus indicus

Bos taurus primigenius

Taurine cattle

aurochs

European cattleIndicine cattleHumped cattle

extinct since 1627

Eurasian aurochs

Indian aurochs

North African aurochs

Classification

Kingdom

Phylum

Subphylum

Class

Family

Genus

Species

Animalia

Chordata

Vertebrata

Mammalia

Artiodactyla

Bovidae

Bos

Bos taurus

Order

Subfamily Bovinae

Mammals

plural: aurochsen

Cattle breeds

Over 1,000 breeds of cattleOver 340 breeds of dogs

Holstein

Angus

Hereford CharolaisGir or Gyr

Kankrej

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Dual purpose

Triple purpose

Ayrshire

Guernsey

Jersey

Holstein-Friesian

Shorthorn

Brown Swiss

Thank you for your attention.Any questions?