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Mammalogy (Fall 2013 Althoff - reference FDVM Chapter 10). LEC 08A. Reproduction - A. Direct vs. indirect evidence of reproduction. Mammalian Reproduction. ____________ than any other class of vertebrates Except monotremes, young remain in uterus during embryonic and fetal life
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Mammalogy(Fall 2013 Althoff - reference FDVM Chapter 10) LEC 08A Reproduction - A Direct vs. indirect evidence of reproduction
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 placenta b) chorio-allantoic placenta • Zygote Embryo Fetus • Uterus
embryo YOLK SAC
Terms….terms….terms • Blastocyst • Endometrium • Implanation • Villi a) diffuse placenta b) cotyledonary placenta c) zonary placenta d) discoidal placenta (p201, Fig. 10.13)
“unraveled” pig cow canids, felids, genet, seal raccoon
Terms….terms….terms • Afterbirth a) nondeciduous b) deciduous • Estrous cycle • Pregnancy • Partuition • Follicle, ovum, corpura luteum
Terms….terms….terms • Estrous cycles: a) polyestrous b) monestrous c) 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) estrogen b) LH g) progesterone c) relaxin h) testosterone d) oxytocin e) 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
GnRH (HT) (Gonadotrophin releasing hormone) • FSH (AP) • LH (AP) • ESTROGEN (OV) • PROGESTERONE (OV) HT =hypothalamus AP = anterior pituitary OV = ovary (oocyte folliclecorpus luteum
Four Phases of ________Cycle • DIESTRUS - lowest hormone levels • PROESTRUS - “pre-heat” • ESTRUS - heat (no “o”) a) highest hormone levels b) ovulation c) LH “spikes” • METESTRUS - progesterone peaks
“HEAT” ESTRUS Proestrus Diestrus Metestrus Diestrus Follicle growth Luteal activity Endometria Involution Endometrial growth GENERAL MODEL
The ovary
Estrous Cycle - more key points • _____-OVULATION a) follicle growth b) endometrial growth (gets ready uterus ready for anticipated “fertilized” embryo • _____-OVULATION a) after “heat,” after release of ovum b) corpus luteum (CL) kicks in & helps maintain pregnancy… otherwise it regresses….
...more key points • _____-OVULATION c) when CL regresses (if no implantation) it shrinks and is essentially “finished”…only one estrous cycle per follicle d) 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 implantation vs. 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 as a) nutritional, respiratory, and excretory interchange b) barrier to bacteria c) 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 uterus b) 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 by pituitary stimulates mammay gland development and milk secretion (initially) • Milk production under neural control thereafter
Typical FertilizationMost 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 sperm remain in male long after spermatogenesis; female does not ovulate until long afterinsemination
Delayed Implantation • Fertilization occurs shortly after insemination and some changes in blastocyst occur but… • Implantation does ____ take place 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 d ex. 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) WaterProteinFatSugarAsh Kangaroo 73.5 9.7 8.1 3.1 1.5 Human 88.0 1.2 3.8 7.0 0.2 Rabbit 71.3 12.3 13.1 1.9 2.3 Rat 72.9 9.2 12.6 3.3 1.4 Harp seal 43.8 11.9 42.8 0.0 0.9 B-n dolphin 44.9 10.6 34.9 0.9 0.5 W.t. deer 65.9 10.4 19.7 2.6 1.4 Giraffe 77.1 5.8 12.5 3.4 0.9 Note: ASH = not water & not organic