Mammalogy Exam 2 Reproduction
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- Monotreme reproduction
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-ancestral amniotic pattern, +period of lactation
-egg 3mm at ovulation
-coated in albumin
-shell gland lays down shell that calcifies
-2-3 weeks in uterus before laying
-15 mm when laid
-embyonic development and growth fueled by yolk - 3 layers in placenta of therians
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-maternal layer - endometrium (highly vascularized)
-outer embyonic later = chorion
-inner embryonic layer = vitellin and allamtois - general metatherian reproduction
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-retain shell gland - shell membrane deposited around fertilized egg
-placenta is choriovitelline - parts of the placenta, from outer to inner
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-chorion
-extraembryonic coelom
-vitellin or allamtois
-amnion
-embryo - metatherian placenta
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-attaches loosely to endometrium
-shallow depression at point of attachment
-allamtois recedes, vitelline expands to fill coelomo
-maternal nutrients taken up indrectly
-"uterine milk" bathes embryo, nutrients diffuse into yolk sac - eutherian placenta
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-vitelline recedes
-allamtois expands to fill coelom
-implants deeply into endometrium
--penetration by highly vascularized chorionic villi
--endometrium erodes at point of implantation
--increases surface area for absorption of nutrients from maternal to fetal circulation - 6 layers separating maternal from fetal blood
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-maternal capillary endothelial cells
-connective tissue
-epithelium of endomettrium
-chorion
-connective tissue
-endothelial cells of embyronic capillary - epitheliochorial
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-6 tissue layers separating maternal from fetal blood
-small degree of erosion of endometrium
-Cetaceans, Suids, Equids - Endotheliochorial
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-maternal capillaries in direct contact with chorion
-4 tissue layers separating maternal from fetal blood
-Carnivora - hemochorial type
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-maternal capillary walls erode, chorionic villi bathed in maternal blood
-Chiroptera, Insectivora, Primates - Hemoendothelial
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-all maternal tissues erode, chorion and embryonic tissue erode
-single layer separating maternal from fetal blood
-some insectivorans, Rodentia - Which type of placenta is most efficient in nutrient transfer between maternal and fetal blood?
- -Hemoendothelial
- afterbirth
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-maternal portion of placenta shed
--large amount of bleeding - deciduous
--little afterbirth - nondeciduous - Peramelidae (reproduction)
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-has chorioallamtoic placenta
-almost no endometrial erosion - iteroparous
- -more than one reproduction cycle per lifetime-most mammals
- Antechinus
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-semilparous
-one cycle per lifetime - estrous cycle contains two cycles, what are they?
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-ovarian
-uterine - differences between reproduction cycle of eutherians vs. metatherians
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-eutherians - pregnancy interrupts estrous cycle, post-partum estrus after birth
-metatherians - gestation occurs within an estrous cycle - control of cyclicity
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-pituitary hormones
-regular or induced - three types of induced cyclicity
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-visual cues
-behavioral cues
-environmental cues - visual cues for cyclicity
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-testicles quiescent (housed in abdomen), body temp too high for spermatogenesis
-descend into scrotum via inguinal canal
-sight of scrotal testicles incudes estrous cycle - behavioral cues
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-suckling
-copulation (felids) - environmental cues
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-seasonality of reproductive cycles
-Microtus montanus - G-MBOA
--ensures young are born when food is available
-Dipodomys - low seed set -> 0% individuals may become reproductively active - four ways to optimize time of birth within an estrous cycle
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-delayed fertilization
-delayed development
-delayed implantation
-embryonic diapause - delayed fertilization
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-Vespertilionids, e.g. Myotis
-spermatogenesis ends in late August
-sperm stored in epididymis until breeding season
-breeding occurs at hybernacula in late October
-females store sperm in uterus
-fertilization in late February, give birth late to mid spring when insect populations are highest - delayed development
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-few Phyllostomids, e.g. Artibeus
-fertilizaiton occurs normally
-blastocyst implants into endometrium mid-summer, development ceases until early winter
-birth at end of dry season when fruit is plentiful - delayed implantation
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-some bats, carnivorans, xenarthrans, artiodactylans
-fertilization occurs normally, development continues to blastocyst stage
-development halts prior to implantation
-blastocyst floats in oviduct or uterus encased in zona pellucida up to 9 months
-when zona pellucida deteriorates, implantation occurs - examples of delayed implantation
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-ursus americanus (obligate)
-many rodents (facultative) - evolution of delayed implantation
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-evolved once, has been lost multiple times independently, esp. Mustelidae
-seasonality - temperate climates = evolution of DI
-longevity - shorter-lived = loss of DI - embryonic diapause
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-like delayed implantation, except that metatherians don't implant
-facultative - only occurs if older joey is suckling
-post-partum estus - second fertilization after birth of first
-suckling triggers endocrine system to hormonally suppress development of second embryo
-can last up to 235 days
-ceases if older joey dies or starts leaving pouch
-two adjacent nipples providing different nutrient content - relationship between body size and number of offspring
- -larger body size = fewer offspring
- small body size
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-high BMR and short lives
-large litters
-short gestation
-altricial young
-rapid post-partum growth rate
-reach reproductive maturity at young ages
-short generation times
-R-selected traits - R-selected traits
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-optimize contribution to future generations by creating large number of low quality offspring
-high population growth rates - large body size
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-low BMR and long lives
-long gestation times
-long estrous cycles
-low litter sizes
-young tend to be precocial
-long periods of lactation, slow post-partum growth rates
-K-selected traits - K-selected traits
- -genetic contribution to future generations is optimized by creating a low number of high quality offspring
- exceptions to the body size reproduction thingy
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-Microchiroptera (small, low BMR, heterothermic, one or two offspring annually, late age at first reproduction)
-Macroscelids (1-2 young after long gestation, precocial young)
-Histricognathous rodents (e.g. Ctenomys - longer gestation period) - Mirounga
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-pinnipeds execption to rule - rapid post-partum growth rates
-Mirounga young double body weight in 10 days` - altricial vs. precocial young
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-risk of mortality high - altricial
-risk of mortality low - precocial
-seasonality not predictable - altricial (loss of litter has less impact on energy budget)
-seasonality predictable - precocial
-predator avoidance passive - altricial
-predator avoidance active - precocial