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 placenta b) chorio-allantoic placenta Zygote  Embryo  Fetus  Uterus

YOLK SAC embryo

embryo

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

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

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) FSHf) estrogen b) LHg) 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

GENERAL MODEL

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

GENERAL MODEL Follicle growth Luteal activity Endometrial growth Endometria Involution Diestru s Proestrus Metestrus “HEAT” ESTRUS

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 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 sperm remain in male long after spermatogenesis; female does not ovulate until long after insemination

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) Water Protein Fat Sugar Ash Kangaroo Rabbit Harp seal W.t. deer Human Rat B-n dolphin Note: ASH = not water & not organic Giraffe