Reproduction - A

Direct vs. indirect evidence of reproduction

Mammalogy (Spring 2015 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

• Placentaa) chorio-vitelline placentab) chorio-allantoic placenta

• Zygote Embryo Fetus

• Uterus

YOLKSAC

embryoembryo

embryoembryo

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)

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 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

• _____-OVULATION a) follicle growthb) 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 isessentially “finished”…only oneestrous 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 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 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, _______________ productionincreases 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 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 sperm remain in male long after spermatogenesis; female does

not ovulate until long after insemination

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 rapidex. 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

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