Week 4 - Monotremes Flashcards
What are the sub-classes of mammals?
3 sub-classes of mammals
- Prototheria (Monotremes)
- Metatheria (Marsupials)
- Eutheria (Placentals)
What does Endemism mean?
Native animals
found nowhere else in the world
83% marsupials
eutherians
Why do we have so many animals only here in australia
isolated from the rest of the world - experienced different climate.
- Australia was part of Gondwana
- > 45 MY geographic isolation
- Unique climate and geology
- Isolated from global climate change
- Increasingly arid climate - arid spp
- Wet monsoon belt - tropical spp
- ~5.3 MYA- collision with Asia collid with asian mass…caused wave of animals to travel in from asian areas hence sharing animals with PNG
Where did out mammals come from and where did they originate from?
160 MYA: Gondwana= Australia + South America + Antarctica
110 MYA: Australia had monotremes but no marsupials
110 MY: Earliest known fossil marsupial Kokopellia wasound in Utah (n. hemisphere)
theory - spread from north america, to south america to australia
Did marsupials spread to S America and Gondwana ?
55 MY: first fossil marsupial in Australia
55 MY first fossil eutherian in Australia
What was the oldest australian eutherian?
Condylarth (Tingamarra porterorum) this ancient
group includes ancestors to
dogs, cats, horses & whales
What are the two theories for the dying out of the Australian megafauna? and how did giantism occur.
isolation often lead to animals being able to increase largely in size. There are two theories as to why they died out;
extreme climates at the time - resource availability was limited or human civilization increased
What makes a mammal?
characteristics
hair, produce milk to feed young, high body temperature to (endothermic), maintain hemostasis
large brains
3 middle ear bones
single jaw bone
Convergent evolution within mammals
Between Australian marsupials & northern hemisphere eutherians
Physical similarities
Behavioural similarities
Occupy similar ecological niche
example (koala and sloth)
What is the Monotremata taxonomy?
Class: Mammalia
subclass: Prototheria
Order: Monotremata (single hole = cloaca)
Family: Ornithorhynchidae (platypus) or Tachyglossidae (echidnas)
What are the mammalian and monotremata features of subclass Prototheria, order Monotremata?
4 spp echidnas, platypus
Mammals:
* Endothermic
* Hair
* Produce milk
* Single lower jaw bone
* 3 middle-ear bones
4 spp echidnas, platypus
Monotremata: one hole (cloaca)
* Oviparous: soft-shelled eggs
* Milk pores on abdomen
* Venom - possession preventive state
* Electroreception - hunt through the preception and electro fields
* Reptile-like gait - move
* Edentate - don’t have teeth`
What are so features about the platypus?
Platypus
Ornithorhynchus anatinus
‘bird-snout, duck-like’
* semi-aquatic
* endemic to freshwater creeks
& rivers (1 – 7 km home range) - territorial
* hunts with electricity (electroreception)
* walks like a lizard
* fights with venom
What are facts about platypus?
Platypus facts
* 40 – 55 cm, 0.7 – 2.4 kg
* 6 – 15 year lifespan
* Dense fur
* Dense bones provide ballast
* Sensitive bill - flat and pliable, mechanoreceptors
* Edentate (deciduous milk teeth in juveniles )
* Tail stores fat - for times when food is less available or mothers incubating within burrows
* Webbing between toes, long claws - paddles, they tuck and fold claws under
* can knuckle walk, swim & burrow - larger claws
* Adult males have sharp venomous spurs (12 mm) linked to crural/femoral gland: seasonally active. Only animals in the world with this trait. Sexually dimophism.
What is crepuscular ?
feeding at dawn and dusk
How to platypus feed?
Feeding
* Usually crepuscular, nocturnal and cryptic
* Close eyes and ears underwater
* 10 min dives, bradycardia - using less oxygen during the dive
* Soft, pliable, sensitive bill: electroreception
* detect electrical fields generated by
muscular contractions of prey
(worms and crayfish)
* determine direction of prey by signal
strengths of receptors - swing head side-to-side
Sift prey from sediment using bill (touch receptors)
* Cheek pouches
* Chew at surface
* Adults are edentate, horny grinding plates in mouth
What are mating season characteristics factors for platypus?
Reproduction 1
* Breed June to Oct
* Mostly solitary and territorial
* No social groupings - only during mating season
* Males fight over females in mating season, spurs are weapons
* Mate in water -
* Females dig burrows - high dry above the water level.
What are factors about the reproduction of female platypus?
Oviparous
* 28 days gestation
* Lay 1-3 eggs in burrow, female curls tail around eggs
* 10 days incubation until egg hatches
* Lactation for 3 – 4 mo: mammary glands are very extensive with pores,
no nipples: milk is ‘sweated out’ - modified sweat glands and young lap it off fur
Where are the platypus found?
stretch from cook town to eastern coast of australia, tasmania and south australia. Mostly associated with permanent water way - need to eat aquatic vertebrates.
Changes in platypus distribution? and why is it occuring?
Historical data suggests:
Decline in distribution & abundance
41% of sub-catchments have no
sightings for last 10 y
Near threatened status (2016)
- Historical fur trade
- Degradation of waterways - loss of water ways, agriculture practices, redirecting water flow
- Pollution, fishing nets
- Foxes, cats
- Drought, climate change - increasing severity. they need refuge pools. need stable embankments, stability (vegetation, logs)
How do they survey for platypus?
- Concentric rings on surface - dive
- Bubble trail - underwater
- Bow-wave – surface swim
- Burrow entrances ~10–15 cm diam, usually above
waterline in vegetation - Well-worn slide marks from burrow into water
- Characteristic footprints
- eDNA (new survey tool)
What are characteristics about Short-beaked echidna?
‘swift-tongue, furnished with spines’
* Most widespread native
mammal in Aust.
* 5 sub-species
* Terrestrial burrower - depends on outside climate on how long they remain inside
* Slow metabolism, tolerant of
low O2
* hunts with electricity
* rolls into a spiky ball
