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Reproduction - A
Direct vs. indirect evidence of reproduction
Mammalogy (Fall 2013 Althoff - reference FDVM Chapter 10)
LEC 08A
Mammalian Reproduction
• ____________ than any other class of vertebrates
• Except monotremes, young remain in uterus during embryonic and fetal life
• Under most conditions, ____________ of fetuses
and…• After birth, young nourished with milk
• Parental care until reasonably capable of taking care of one’s self
…compare to arthropods, fish, reptiles, etc.
RESULT:
High survival of fetuses and extended post-partum care is an __________ in efficiency of reproduction in terms of energy expenditure per young that reaches __________________
Terms….terms….terms• Placenta
a) chorio-vitelline placentab) chorio-allantoic placenta
• Zygote Embryo Fetus
• Uterus
YOLKSAC
embryo
embryo
Terms….terms….terms• Blastocyst• Endometrium• Implanation• Villi
a) diffuse placentab) cotyledonary placenta
c) zonary placentad) discoidal
placenta(p201, Fig. 10.13)
pig
cow
canids, felids,genet, seal raccoon
“unraveled”
Terms….terms….terms
• Afterbirtha) nondeciduous
b) deciduous• Estrous cycle• Pregnancy• Partuition• Follicle, ovum, corpura luteum
Terms….terms….terms• Estrous cycles:
a) polyestrousb) monestrousc) menstrual cycle
• Fertilization• Delayed fertilization• Delayed implantation• Delayed implantation ovulation
Terms….terms….terms• Post-partum
• Litter
• Altricial
• Precocial
• Sexual maturity
Terms….terms….terms• Hormones
a) FSH f) estrogenb) LH g)
progesteronec) relaxin h) testosteroned) oxytocine) prolactin
Themes• Timing of reproduction • Reproductive cycles• Physiological changes• Productivity relative to energy
investment• Environmental influences on reproduction
Ovarian Cycle• Growth of follicle and release of ovum• Development of corpus luteum (CL)
which results in production of progesterone
Follicle growth and development of CL both ______________________
________________________
Estrous Cycle - Key Hormones
• _______ - produced by pituitary • _______ - produced by pituitary
*FSH & LH stimulate follicle & estrogen production
• ______________ - produced by CL• ______________ - produced by ovary
GENERAL MODEL
• GnRH (HT) (Gonadotrophin releasing hormone)
• FSH (AP)• LH (AP)• ESTROGEN (OV)• PROGESTERONE
(OV)
HT =hypothalamusAP = anterior pituitaryOV = ovary (oocyte
folliclecorpus luteum
Four Phases of ________Cycle
DIESTRUS - lowest hormone levelsPROESTRUS - “pre-heat” ESTRUS - heat (no “o”)
a) highest hormone levelsb) ovulationc) LH “spikes”
METESTRUS - progesterone peaks
GENERAL MODEL
Follicle growth Luteal activity
Endometrial growth Endometria Involution
Diestrus DiestrusProestrus Metestrus
“HEAT”
ESTRUS
Theovary
Estrous Cycle - more key points
• _____-OVULATIONa) follicle growth
b) endometrial growth (gets readyuterus ready for anticipated“fertilized” embryo
• _____-OVULATIONa) after “heat,” after release of ovumb) corpus luteum (CL) kicks in &
helps maintain pregnancy…otherwise it regresses….
...more key points
• _____-OVULATIONc) when CL regresses (if no
implantation) it shrinks and isessentially “finished”…only one
estrous cycle per follicled) if pregnancy goes full-term
(or nearly full-term, CL will remain “enlarged” (but not producing progesterone) well past
partuition…useful for fertility est.
Copulation
• Internal fertilization (important adaptation for reproduction for terrestrial species)
• Sperm reaches oviduct, usually within minutes
• Fertilization occurs “________________”• Zygotes (then embryos) move down
oviducts by contractions of oviducts until it reaches uterus
Implantation
• Embryo “________” (i.e., attaches) in uterine wall in the __________________
• Delayed implantationvs.
Delayed fertilization
Few notes about the Placenta
• ___ unique to mammals…certain fishes & a few reptiles have similar structures
• the “________ structure” between the fetus and the uterus
• Functionally, serves asa) nutritional, respiratory, and
excretory interchangeb) barrier to bacteriac) produces some hormones
Pregnancy
• Among eutherians, under hormonal control• Hormones secreted by pituitary, ovary, and
uterus• Key hormone: __________ produced by CL,
it “maintains” ___________________ during early pregnancy
____-partum
• Key hormone: _____________ --its levels increase at the end of pregnancy,
causes relaxation of the pelvic ligments and public symphysis (in pocket gophers [Geomyidae], connective tissue is resorbed at puberty so relaxin not as “necessary”)
• Relaxin produced by uterus, placenta, or ovaries (varies by species)
Pre-partum…con’t• Besides relaxin, _______________ production
increases at end of pregnancy:a) initiates contractions of uterusb) promotes milk “letdown” post-partum
• Produced by hypothalamus, stored in pituitary
• Production blocked by ______________during pregnancy
Partuition• = ______________________• Highest levels of relaxin and oxytocin
--oxytocin promotes further contraction of uterus after
placenta expelled…collaspe reduces bleeding
• Increased levels of estrogen• Decreased levels of progesterone
_____-partum• = _______________________
• Hormone ___________, produced bypituitary stimulates mammay glanddevelopment and milk secretion(initially)
• Milk production under neural controlthereafter
Typical Fertilization Most mammal species exhibit “typical”
fertilization pattern
• Egg fertilized ________ after copulation (i.e., in the presence of sperm in oviduct)
• Embryo implants _______ after fertilization
Delayed Fertilization
• Copulation occurs but fertilization delayed for __________
• Typical among bats• NOTE: male & female reproductive
status ___________; viable spermremain in male long after spermatogenesis; female does not ovulate until long afterinsemination
Delayed Implantation
• Fertilization occurs shortly afterinsemination and some changes in blastocyst occur but…
• Implantation does ____ takeplace for 12 days up to 11 months (varies by species)
• Some bats, mustelids, some insectivores, some rodents
Advantages of VARIATION
• Not at all well understood but…• 1)
• 2)
• 3)
Reproductive Patterns additional notes...
• Great variation among species
• Litter sizes: a result of natural selection favoring most successful size in relation to survival of young (Lack’s principle)
• Litter size varies within a species
Reproductive Patterns additional notes...
• Litter sizes tend to be larger at northern latitudes and at higher elevations…may be response to ability to have more young to match rapid increases in food production in surrounding habitat
•• Litter sizes smaller for large animals than
small mammals
Growth of Young
• For some species, growth & development is rapid
ex. least shrew doubles wt in 4 dex. evening bat doubles wt in 18 d
• Impacted by amount of time… a) ___________ (i.e each day) b) ___________ of milk
ex. pinnipeds have high fat %
MILK CONTENT (%) by Species(selected from FDVMK Table 6.1, p103)
Water Protein Fat Sugar Ash
73.5 9.7 8.1 3.1 1.5Kangaroo
71.3 12.3 13.1 1.9 2.3Rabbit
43.8 11.9 42.8 0.0 0.9Harp seal
65.9 10.4 19.7 2.6 1.4W.t. deer
88.0 1.2 3.8 7.0 0.2Human
72.9 9.2 12.6 3.3 1.4Rat
44.9 10.6 34.9 0.9 0.5B-n dolphin
Note: ASH = not water & not organic
77.1 5.8 12.5 3.4 0.9Giraffe