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ANSC2005 > Mammals > Flashcards

Mammals Flashcards

1
Q

What is a mamma?

A

Tetrapods, Amniotes, Synapsids

Key features:

  • Endothermic
  • Respiration with a muscular diaphragm
  • Hair that provides insulation
  • Mammary glands
  • Differentiation of teeth
  • Refinement of ear bones
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2
Q

Tetrapod

A

A four-footed animal

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3
Q

Synapsid

A

mammals and “mammal-like reptiles” with modifications to skull and skeleton indicative of increase in metabolic rate

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4
Q

Amniote

A

An animal that develops embryonic membranes

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5
Q

Reptiles vs mammals

A

Retiles have one ear bone (Dimetrodon)

Mammals have multiple ear bones (Morganucodon)

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6
Q

3 mammalian groups that remain today

A

Monotremes - egg laying mammals

Marsupials - Give birth to small, embryonic young, have pouch

Placentals - Give birth to fully develop

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7
Q

Australian mammal origins

A

Monotremes and marsupials descend form ancestors that were on the continent when it detached from Antarctica

Eutherian mammals (rodents) came by island hopping from Indonesia and New Guinea via boats and floating vegetation

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8
Q

2 groups of marsupials

A

Australidelphia: Found in Australia & New Guinea

Ameridelphia: Found in the Americas

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9
Q

Australidelphia (marsupial) four orders:

A

Dasyuromorphia
Peramelemorphia
Diprotodontia
Notorycytemorphia

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10
Q

Marsupial morphology

A

Diverse group (range of sizes)

Morphology reflects function - e.g. dite, locomotion

General mammalian features with modification unique to marsupials

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11
Q

Polyprotodont

A

Multiple pairs of lower incisors

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12
Q

Diprotodont

A

One pair of incisors in the lower jaw

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13
Q

-dactyl:

A

A suffix that indicates “fingers or toes of a particular type or number”

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14
Q

Syndactyly

A

The normal occurrence of having two or more fused digits in a mammalian species

In many marsupial species syndactyly is common between digits II and III on the hindfoot

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15
Q

Order: Dasyuromorphia

A

Carnivorous or insectivorous marsupials

Polyprotodont dentition
• Three pairs of ~ equal-sized lower incisors
• Numerous, sharp teeth
• Numbat – teeth reduced in size and fewer incisors

Hindfoot has 5 separate toes (+/- digit 1): NO syndactyly

Forelimb length = hindlimb length

Non-prehensile tail

E.g. Tasmanian devil

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16
Q

Order: Peramelemorphia

A

Bandicoots and bilbies

Omnivorous marsupials

Long pointed heads and compact bodies

Polyprotodont dentition
- Three pairs of ~ equal-sized lower incisors (not as pointed as dasyuroids)

Hindlimb large with 4 toes:
• Syndactyly digit 2 and 3 fused, digit 1 absent/reduced

Forelimb shorter than hindlimb (→ bounding gait) with well-developed claws (digging)

Non-prehensile tail

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17
Q

Order: Notoryctemorphia

A

Marsupial mole

Ancient lineage with just two species (Southern and Northern marsupial mole)

Subterranean habit (occurring under the earths surface)
- Unusually low metabolic rate and highly variable body temperature – adaptation for a burrowing lifestyle?

Blind (eyes = non-functional buds beneath the skin)

Absence of external ears, heavily keratinised skin on nose

Tubular body form, with rear-ward opening pouch (females)

Forelimb short and powerful, digits 3 and 4 have developed into large, spade-like claws (digging)

Tail – shortened and immensely strong

Insectivorous/carnivorous – polyprotodont dentition

18
Q

Order: Diprotodontia

A

Koala, wombats, possums and macropods

Most specialised and recently evolved Order ~120 species

Mostly herbivorous or omnivorous

All have diprotodonts dentition

One pair of lower incisors, with NO lower canine teeth

Hindlimb syndactyly digit 2 and 3 (fused together, except at the tip)

Forelimb: Ability to oppose first two digits in most arboreal species (not in wombats, kangaroos and wallabies)

Non-prehensile tail (yes in possums)

Very successful group with two subforms:
•Vombatiformes (koalas and wombats)
•Phalangerida (possums, rat-kangaroos and kangaroos)

19
Q

Diprotodontia: Sub order - Vombatiformes

A

No tail

Adaptation for climbing (koala) or burrowing (wombats)

Rear-ward opening pouch

20
Q

Diprotodontia: Sub order - Phalangerida

A

Morphologically very diverse

Four principle lineages that can be viewed as superfamilies:

  • Phalangeroidea (Brushtail possums, scaly-tailed possum)
  • Burramyoidae (pygmy possums)
  • Petauroidea (ringtail possums, gliders)
  • Macropodoidea (kangaroos, wallabies and kangaroos)
21
Q

Phalangerida - Superfamily Phalangeroidea

A

Noticeably short face, eyes directly forward

Long, prehensile tail

Arboreal – excellent climbers

Variable herbivores (Brushtail possums well adapted to life in suburbia)

22
Q

Phalangerida - Superfamily Burramyoidea

A 
Pygmy possums 
Smallest of the possums 
Long, slender, prehensile tail 
Arboreal 
Insectivorous
23
Q

Phalangerida - Superfamily: Petauridae

A

Possum-like marsupials from four families

E.g. ringtail possums & gliders

Extreme morphological and ecological diversity

Arboreal

All are dietary specialists of one form of another:
•Folivores (e.g. ringtail possum)

  • Sap-eaters (e.g. wrist-winged gliders and Leadbeater’s possum )
  • Omnivorous (e.g. striped possum - wood-boring insects)
  • Nectivorous (e.g. feathertail glider and honey possum)
  • Variations in teeth and digestive tract anatomy
24
Q

Feathertail Glider

A

Belongs to superfamily: petauridae

  • Smallest gliding possum
  • Gliding membrane between elbow and knee
  • Nectivore and communal
25
Q

Sugar Glider

A

Belongs to superfamily: Petauridae

Small, omnivorous,

Gliding membrane btw wrist and ankle (termed wrist-winged glider, a trait common to 6 gliding species)

Omnivorous:
summer = insectivorous;
winter = exudativorous (feed on sap, manna and honeydew

26
Q

Greater Glider

A

Not closely related to other Petauridae gliders

Gliding membrane btw elbow and ankle - More controlled glides

Folivore, feeding almost exclusively on Eucalyptus leaves

Solitary - very vocal

27
Q

Superfamily: Macropodoidea

A

Kangaroos, wallabies and rat-kangaroos

Macropods: strong, powerful hindlimbs and long hindfeet

Three families:
• Macropodidae: kangaroos and wallabies (<25kg)

  • Potoroidae: potoroos and bettongs (“rat kangaroos”)
  • Hypsiprymnodontidae: Musky Rat-kangaroo

Adaptations to a hopping lifestyle

Syndactyly, with no opposable first digit

Terrestrial (except tree-kangaroo)

Essentially herbivorous

28
Q

Marsupial morphology

A

Some common morphological features:

  • Reproductive traits
  • Skeletal modifications
  • Slightly lower body temperature and metabolic rate (expend less energy than eutherian mammals of comparable size and activity)
  • Brain usually smaller
  • Most have an opposable 1st digit on hind feet
29
Q

Musculoskeletal Structure of marsupials

A 
Compared with eutherians: 
- Hard palate fenestrated
- Epipubic bones present 
- Lack fully developed patella 
•Have clavicles
30
Q

Skull of marsupials compared to eutherians

A

Large facial area to small cranial cavity

Mandibular symphysis may not be fused (many diprotodonts)

Often have narrow oral gape

Mandible: internal angular process (so-called “marsupial shelf”)

31
Q

Metabolism of marsupials

A

Resting body temperature 2-3 degrees lower than eutherians

Basal metabolic rate lower (‘primitive’?) but
–Nutritional requirements lower for maintenance
–Can increase greatly in response to cold (10-11 x) and peak metabolism of some marsupials may be higher than some eutherians
–Adaptations to cope with changes in temperature (e.g. torpor)

32
Q

Brain of marsupials

A

Small
Large olfactory bulbs
Basic sulci: limited surface area
Lacks corpus callosum

33
Q

Hopping (saltation)

A

Energetic advantages for animals - energy stored in elastic structures e.g. tendons

Pentapedal gait: alternately support weight on forelimbs + tail and hindlimbs

Top kangeroo speed = 70km/hr

34
Q

Common reproductive features of marsupials

A

Most polyoestrous

Most ovulate spontaneously

Pregnancy < or = oestrous cycle length

Ovarian activity suppressed by lactation

Under-developed offspring at birth

Long lactation and short gestation

Embryonic diapause in Macropodidae

Note: Marsupials also have a placenta (usually more primitive then eutherian mammals)

35
Q

Marsupial pouch

A

Provides high humidity and stable temperature

Formed by invagination of skin of ventral abdomen through a gap in the cutaneous muscles

Interior skin relatively hairless, and produces a brown secretion that coats the pouch wall

Mammary glands in pouch with long nipples (young initially permanently attached to one teat, and only that teat develops)

The pouch is full of bacteria

36
Q

Development of young joey

A

Small and immature at birth

Neonate has circular mouth

  • Teat expands inside mouth
  • Can breath and swallow concurrently

Remain dependent on mother for some time after leaving pouch/teat

37
Q

Lactation in marsupial

A

Suckling initiates lactation in suckled mammary gland

Milk composition changes during lactation

  • Protein, lipid and carbohydrate (CHO) concentrations and constituents change
  • Different glands can concurrently produce different milks to sustain young at different stages of development
  • Antibodies are transferred across the gut wall for relatively long period of time
38
Q

Embryonic Diapause (marsupials)

A

Refers to the phenomenon where a female will mate while she has a young in the pouch. The resulting conceptus is held in the uterus in “suspended animation” until the first young has finished suckling

Common in kangaroos and wallabies

Sucking inhibits corpus luteum = progesterone –> causes diapause

39
Q

Male reproductive anatomy of macropods (kangaroos & wallabies)

A

Scrotum located cranial to penis

Only 2 accessory glands:

  1. Prostate
  2. Cowper’s (bulbourethral) gland

Glans penis
- Usually bifid (‘split’)

Non erect penis withdrawn into common vestibule in S shaped curve

40
Q

Three basic patterns of sperm production in marsupials

A
  1. Capacity for continuous sperm production e.g. Kangaroos, Koalas, Tasmanian devil
  2. Seasonal breeders: only have sperm production during an annual breeding season e.g. greater glider
  3. Single cycle breeders: Sperm production over a short breeding season, males die within a short period of females becoming pregnant e.g. Antechinus
41
Q

Marsupial species with continuous sperm production

A

Sperm production occurs throughout the year, but males often “secondarily seasonal”

  • If females are seasonal, often see seasonal variation in accessory sex glands and testosterone production, which peak around the time of peak conception
42
Q

Marsupial species with seasonal sperm production

A

Testis size fluctuated throughout the year

ANSC2005 (18 decks)

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