Reproduction - A

1. Mammalogy(Fall 2013 Althoff - reference FDVM Chapter 10) LEC 08A Reproduction - A Direct vs. indirect evidence of reproduction

2. Mammalian Reproduction • ____________ than any other class of vertebrates • Except monotremes, young remain in uterus during embryonic and fetal life • Under most conditions, ____________ of fetuses

3. 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.

4. 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 __________________

5. Terms….terms….terms • Placenta a) chorio-vitelline placenta b) chorio-allantoic placenta • Zygote  Embryo  Fetus  • Uterus

6. embryo YOLK SAC

7. embryo

8. Terms….terms….terms • Blastocyst • Endometrium • Implanation • Villi a) diffuse placenta b) cotyledonary placenta c) zonary placenta d) discoidal placenta (p201, Fig. 10.13)

9. “unraveled” pig cow canids, felids, genet, seal raccoon

10. Terms….terms….terms • Afterbirth a) nondeciduous b) deciduous • Estrous cycle • Pregnancy • Partuition • Follicle, ovum, corpura luteum

12. Terms….terms….terms • Estrous cycles: a) polyestrous b) monestrous c) menstrual cycle • Fertilization • Delayed fertilization • Delayed implantation • Delayed implantation ovulation

13. Terms….terms….terms • Post-partum • Litter • Altricial • Precocial • Sexual maturity

14. Terms….terms….terms • Hormones a) FSH f) estrogen b) LH g) progesterone c) relaxin h) testosterone d) oxytocin e) prolactin

15. Themes • Timing of reproduction • Reproductive cycles • Physiological changes • Productivity relative to energy investment • Environmental influences on reproduction

16. 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 ______________________ ________________________

17. Estrous Cycle - Key Hormones • _______ - produced by pituitary • _______ - produced by pituitary *FSH & LH stimulate follicle & estrogen production • ______________ - produced by CL • ______________ - produced by ovary

18. GENERAL MODEL

20. GnRH (HT) (Gonadotrophin releasing hormone) • FSH (AP) • LH (AP) • ESTROGEN (OV) • PROGESTERONE (OV) HT =hypothalamus AP = anterior pituitary OV = ovary (oocyte folliclecorpus luteum

21. 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

22. “HEAT” ESTRUS Proestrus Diestrus Metestrus Diestrus Follicle growth Luteal activity Endometria Involution Endometrial growth GENERAL MODEL

23. The ovary

24. 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….

25. ...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.

26. 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

27. Implantation • Embryo “________” (i.e., attaches) in uterine wall in the __________________ • Delayed implantation vs. Delayed fertilization

28. 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

29. Pregnancy • Among eutherians, under hormonal control • Hormones secreted by pituitary, ovary, and uterus • Key hormone: __________ produced by CL, it “maintains” ___________________ during early pregnancy

30. ____-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)

31. 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

32. 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

33. _____-partum • = _______________________ • Hormone ___________, produced by pituitary stimulates mammay gland development and milk secretion (initially) • Milk production under neural control thereafter

34. 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

35. 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

36. 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

37. Advantages of VARIATION • Not at all well understood but… • 1) • 2) • 3)

38. 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

39. 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

40. 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 %

41. 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