Marsupial Reproduction Flashcards
(17 cards)
How does the path of ureters from kidneys to bladder in marsupials to in eutherians?
- Path of ureters prevents fusion of vagina into single structure
2 lateral + 1 median vaginae
2 uteri
2 cervices - 1 external orifice for reproduction and excretion
Common reproductive features
- Polyoestrous
- Ovulate spontaneously
- Pregnancy < oestrous length cycle
- Ovarian activity suppressed by lactation
- Short gestation, long lactation
- Embryonic diapause in Macropodoidea
Polyoestrous
Multiple cycles in breeding season
Spontaneous ovulation
Ovulate whether mating takes place or not
Embryonic diapause
- Female mates while there is young in the pouch
- Resulting conceptus is held in uterus in “suspended animation” until the first young is finished suckling
- Some species are influenced by season - blastocyst will only reactivate at certain times of year
- Mate soon after giving birth
- Kangaroos (except western grey), wallabies, small possums
The Pouch
- Invagination of skin of ventral abdomen through a gap in the cutaneous muscles
- High humidity and stable temp
- Interior relatively hairless and brown secretion coats the pouch wall
- Mammary glands in the pouch
Development of the young (joey)
- Small and immature at birth with well developed olfaction and forelimbs
- Continues development attached to teat
- Can breath and swallow concurrently
- Dependent on mother for some time after leaving pouch/teat
Lactation
- Initiated by suckling
- Milk composition changes during lactation:
total solids increase
lipids increase
carbs are high in mid-lactation then decrease
Protein increases then decreases
Marsupial reproductive patterns
Divided into 4 groups based on:
- duration of oestrous cycle
- poly- vs monoestrous
- mono- vs polyovular
- type of placentation
Marsupial reproductive patterns - Group 1
Basic Pattern
- Polyoestrous, polyovular
- Gestation < 60% of oestrous cycle
- Birth inhibits further ovarian development
Marsupial reproductive patterns - Group 2
Derived Pattern
- Polyoestrous, polyovular
- Very short gestation
- Well developed chorioallantoic placenta
Marsupial reproductive patterns - Group 4
Derived Pattern
- Polyoestrous, polyovular
- Prolonged gestation associated with diapause of uncertain cause
Male reproductive tract
Glans penis - bifid (split)
Non-erect penis is withdrawn into common vestibule in S shaped curve
Patterns of sperm production and fertility
3 basic patterns:
- Continuous sperm production
- Seasonal breeders
- Single cycle breeders
Continuous sperm production
- Males often “secondarily seasonal” - they respond to changing condition of females
- Production may be impaired in very harsh conditions
Seasonal sperm production
- Sperm is only produced during the short female breeding season
- Testis size fluctuates throughout the year
Single cycle of sperm production
- Single wave of spermatogenesis
- Males die within days of the females becoming pregnant
- Thought to be related to stress and extremely high cortisol and testosterone levels
- Intensive mating period - males don’t eat, only frenzied fighting and mating
- Females may breed in second year
- Requirements for food extremely high for lactating females, males would compete for food
