Lecture 14- Monotremes I (platypus) Flashcards
What is the classification of a platypus?
- Subclass: Prototheria
- Order: Monotremata
- Family: Ornithorhynchidae
- platypus= 1 species
What are the 6 characteristics that are special about the platypus?
- cloaca (one hole)
- lay eggs
- lactate
- electroreception
- low Tb compared to other mammals
- reptilian pectoral girdle (walk in a push up position, legs not below the body)
What does the pectoral girdle mean in platypus?
-cannot move as fast on land
What does it mean that fossils of platypus were found far inland in Australia?
used to have forests inland, with permanent water
Why are there few echidna fossils?
-don’t have teeth and the ancestors didn’t either so not preserved
Why is there lot of platypus fossils around?
-ancestors of platypus had teeth and those are more easily fossilised
How old are the oldest fossils of platypus?
- 120MY
- early Cretaceous
- must have existed before that, overlapped with dinosaurs
Do today’s platypus have teeth?
-no, born with them but these drop quite early on
Where are the monotremes today?
-Australia and PNG
Are monotremes Gondwanan?
-Yes, found fossil in Patagonia (60MY old)
What are the skulls of the modern platypus and the ancient one like?
- obdurodon species (ancient) were larger, had teeth, extinct about 25MYA)
- today’s Ornithorhynchus anatinus is smaller and no teeth
What is the modern distribution of the platypus?
On the east coast of Australia, abundant, not affected too much by european settlement
- cannot live in too high temperatures (38C and above) so global climate change could pose harm to it
- alpine to sea level, north Qld to Tas
- need permanent water
What is the habitat of the platypus?
- permanent lakes and streams, including estuaries (but not marine environments)
- the water can be shallow or deep
- swim near the surface
What are the functions of the burrows platypus dig? (4)
- resting
- predator avoidance
- avoidance of temperature extremes
- safe environment for raising young
- use multiple burrows, the ones for young are deeper
Where does the platypus live most of the day and when is it active?
live in water for half a day, rest during the day
- nocturnal typically
- sometimes also active diurnally
- problem with flooding= babies washed out
When do platypus forage?
-from dusk to dawn
What do platypus eat and where do they find it?
- mainly eat aquatic invertebrates
- forage mainly on the stream bed
How do platypus catch their prey?
-use electro- and mechanoreceptors to locate their pray
(eyes and ears are closed under water)
-crayfish= have high lipid content
-crayfish when escaping, tail flip= any movement of the animal= contraction of the muscle= electricity= platypus can detect(can detect very small signals, like 2-3 cm big larvae)
Do platypus have teeth?
- adult platypus don’t have true teeth
- have horny plate can exert lot of pressure
- store small prey in cheek pouches and surface to chew
- when attacking crayfish hit and retreat so they don’t get caught by the claw/pincer
How much food does a platypus eat a day?
- about 1/3 of its bodyweight
- up to 1/2 of its bodyweight
Where do platypus store their fat?
-in their tail
How can you tell if a platypus is in good shape?
-by the feel of the tail and how much fat there is
How does the male platypus distribution of fat change during the year?
-low during breeding season (July to September)
What type of a breeder the platypus are and when do they breed?
- seasonal breeders
- July to September
Where do the males have their testes?
- inside
- Testicond
Do platypus have spurs?
-yes, but only males
Are the spurs poisonous?
- yes
- males have crural gland in their thigh connected to the spur that makes toxin
- quite venomous= can kill a small dog and a platypus
Who is bigger, males or females?
- males much larger
- 2.7kg but females only 1.9kg the biggest one
Does the testis weight change?
-yes, seasonally
What does an annoyed male platypus do?
- lock in their spurs= very rigid
- when swimming normally then more free
When does the crural gland get more active?
-more testosterone and crural gland action during breeding season
Do maple platypus home ranges overlap?
- yes in non-breeding season, there is extensive overlap
- in breeding season evidence of avoidance
Is there a male-male competition between platypus?
- yes, intense
- seasonal patterns in testosterone, more fighting and venom production
Which ovary is functional in female platypus?
-left only
How long is gestation?
-1 month
How many eggs do they lay?
1-3
- 1-2 babies most common
- egg is sticky and sticks to the mother and she sits on them for 10 days
How long is incubation?
10 days
Where are the young left?
-in the burrow
How long does lactation last?
-4 months
Can platypus breed every yearM
-no
When do the young ones leave the burrow?
- February
- safest to wean the babies then as not much flooding
When is progesterone highest in females?
- ovulation
- July to September
Do platypus dig a burrow?
- yes, females for young, very extensive
- use the same one for years
- bigger than resting burrow
- high energy costs
What is the seasonal change in glucocorticoids in female platypus?
- breeding season = highest stress hormone
- helps with mobilising energy and flight response
What do glucocorticoids do in mammals?
- cause increased plasma concentrations of energy substrates
- in platypus increased concentration of glucocorticoids=increased plasma free fatty acids instead of glucose
- ability to mobilise energy in breeding season and during lactation
Is short term stress response good?
-yes cannot be chronic though, then very bad for the animal
