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| | + | <big><center>[[Reproductive System|'''BACK TO REPRODUCTIVE SYSTEM''']]</center></big> |
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| | + | <big><center>[[Reproductive_System#Exotics|'''BACK TO EXOTICS''']]</center></big> |
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| | == Introduction == | | == Introduction == |
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| | ** Argenine vasotocin has the same function as Oxytocin in mammals. | | ** Argenine vasotocin has the same function as Oxytocin in mammals. |
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| | + | == Temperature Dependent Sex Determination (TDSD) == |
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| − | == Sex Determination == | + | == [[Reptile Reproductive Anatomy and Physiology- Chelonia - Anatomy & Physiology|Tortoises, Turtles & Terrapins (Chelonia)]] == |
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| − | Two types of sexual determination can occur in reptiles, Gynotypic or Temperature Dependent Sex Determination (TDSD).
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| − | | |
| − | === Gynotype Sex Determination ===
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| − | | |
| − | * Reptiles differ from mammals in that the female is heterogametic (ZW) and the male is homogemetic (ZZ).
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| − | | |
| − | === Temperature Dependent Sex Determination (TDSD) ===
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| − | | |
| − | * Occurs in many lizards, some turtles and all crocodiles.
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| − | * Sex of the embryo is not determines by sex chromosomes.
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| − | * Sex of the embryo is determines by the incubation temperature during the early and middle incubation period.
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| − | ** The time when the embryonic gonad develops into either testes or ovaries.
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| − | * Different temperatures act on the aromatase enzyme complex that converts testosterone to oestradiol.
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| − | ** Oestrogen then binds the its receptor on the gonads to create females.
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| − | ** To create males, enzymes convert testosterone to dihydrotestosterone, which binds to androgen receptors on the gonads.
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| − | | |
| − | ==== Crocodiles ====
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| − | | |
| − | * Pivotal temperatures are important.
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| − | * Produce females at both high and low temperatures and males at intermediate temperatures.
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| − | * e.g. in alligators:
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| − | ** Incubation at 30ºC produces all females which hatch at 74 days.
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| − | ** Incubation at 33ºC produces all males which hatch at 62 days.
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| − | ** Incubation at 34.5ºC produces all females that hatch faster.
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| − | | |
| − | ==== Chelonia ====
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| − | * Produce females at high incubation temperatures.
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| − | * Produce males at low incubation temperatures.
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| − | | |
| − | ==== Lizards ====
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| − | * Produce males at high incubation temperatures.
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| − | * Produce females at low incubation temperatures.
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| − | == The Male ==
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| − | === Testes ===
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| − | * Testes produce sperm and secrete the hormones responsible for mating behaviour and secondary sex characteristics.
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| − | * Size varies with season,temperature,light and food supply.
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| − | * Right testicle adjacent to the vena cava, connected to it by tiny vessels.
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| − | * Left testicle lies intimately associated with the left adrenal gland and has its own blood supply.
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| − | | |
| − | === Hemipenes ===
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| − | * Lizards and snakes have two extracloacal hemipenes.
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| − | * Lie side by side, just caudal to the cloaca.
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| − | * Blind-ended organs containing walls of blood and lymph plus a seminal groove.
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| − | * Become engorged and evert from their cavity for mating.
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| − | | |
| − | === Intracloacal Phallus ===
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| − | * Chelonia and crocodiles.
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| − | * Developed the ventral proctodeum of the cloaca into a single, unpaired intracloacal phallus.
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| − | * Protruded during copulation.
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| − | | |
| − | == The Female ==
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| − | === Ovary ===
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| − | | |
| − | * Ovaries function in the production of oestrogens and gametogenesis.
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| − | * Saccular in shape, covered with follicles.
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| − | * Right ovary lies adjacent to the vena cava and is connected to it by tiny blood vessels.
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| − | * Left ovary is intimately associated with the left adrenal gland and has its own blood supply.
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| − | | |
| − | === Oviduct ===
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| − | * Two oviducts
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| − | * Provide egg transport.
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| − | * Secrete albumin, protein and calcium for egg shell formation.
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| − | * Divided into:
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| − | ** Infundibulum
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| − | ** Uterine Tube
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| − | ** Isthmus
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| − | ** Uterus
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| − | *** In viviparous reptiles (give birth to live young), a large part of the uterus is thickened and muscular to hold the developing embryo.
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| − | ** Vagina
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| − | === Ovarian Cycle ===
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| − | The ovarian cycle of mature reptiles is divided into three phases.
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| − | ==== 1. Quiescent ====
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| − | * There is no development of the ovary or oviduct.
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| − | ==== 2. Vitellogenic ====
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| − | * Phase of rapid hypertrophy of the ovaries and oviduct.
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| − | * Under the influence of oestrogen, yolk is produced by the liver and transported via the blood to the ovary.
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| − | * Largest follicles mature first and become heavily filled with yolk.
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| − | * Increased oestrogen activity mobilizes calcium from the bone into the bloodstream.
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| − | * Increase in serum calcium concentration is concomitant with serum lipid being drawn into fat bodies.
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| − | ==== 3. Gravidity/Pregnancy ====
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| − | * Gestation period is from the time of fertilization to oviposition, not from the time of mating.
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| − | * Either eggs or embryos are present within the oviduct following ovulation.
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| − | * Follicle becomes the corpus luteum, which secretes progesterone to maintain the gravid/pregnant state and inhibit oviposition or parturition.
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| − | * Most species undergo ecdysis (skin-shedding) just before oviposition/parturition.
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| − | ** Signal to provide a nest for the captive reptile.
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| − | | |
| − | === Sperm Storage ===
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| − | Fertilization is always internal in reptiles. Many species of snake and turtle can store sperm so that mating can occur in one season, and reproduction in the next.
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| − | * Sperm is stores in the oviduct.
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| − | * Fertilization triggered when the ova enter the oviduct.
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| − | * Ranges from several months to ~6 years.
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| − | === Oviparity ===
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| − | * Chelonia, Crocodiles, Iguanas, Monitor Lizards, Geckos and Phythons
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| − | * Eggs are laid quite early
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| − | * Embryos relatively undeveloped
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| − | * Eggs are white with soft, leathery shells.
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| − | ** Contain large amounts of yolk.
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| − | ** Yolk is the only source of nutrients to the developing embryo.
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| − | *** Rich in fat, protein and calcium
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| − | * Produce 2-3 clutches during the breeding season.
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| − | * Unable to reproduce in cold climates because low temperatures prevent the eggs developing.
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| − | | |
| − | === Viviparity ===
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| − | * All Boas, Vipers, Garter Snakes, European Lizard and Slow Worm,some Skinks and Chameleons.
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| − | * Involves placental exchange between the mother and foetus.
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| − | * Corpus luteum is maintained and secretes progesterone, which inhibits oviduct contraction.
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| − | * One clutch a year.
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| − | * Gestation can last 1.5-6 months.
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| − | * Added space of the foetus puts pressure on the gastrointestinal tract.
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| − | ** Pregnant females rapidly lose condition.
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| − | == The Egg ==
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| − | The reptile egg has three membranes and a leathery shell.
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| − | === Shell ===
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| − | * Protective
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| − | * Water resistant
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| − | * Allows gas exchange
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| − | * Rich source of calcium to the developing embryo.
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| − | | |
| − | === Amniotic Membrane ===
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| − | * Surround the embryo.
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| − | === Chorionic Membrane ===
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| − | * Covers the inside of the egg.
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| − | | |
| − | === Allantoic membrane ===
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| − | * Lies between the amniotic and chorionic membrane.
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| − | * Attached to the chorion.
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| − | * Stores the urea/uric acid waste products.
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| − | == Fat Bodies ==
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| − | * Lie adjacent to the kidneys and gonads in the caudal ceolomic cavity.
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| − | * Some reptiles from temperate climates use these to provide yolk for the first clutch of eggs after the winter.
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| − | * Males show similar cycles, but have smalles fat bodies than females.
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| − | == Maternal Care ==
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| − | | |
| − | Most reptiles do not exibit parental care because it poses too much of a risk to adult survival.
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| − | | |
| − | === Pythons ===
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| − | * Female coils around the clutch of eggs.
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| − | * Generates heat by shivering.
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| − | * Muscle twitching keeps the body temperature raised above the ambient temperature.
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| − | | |
| − | === Crocodiles ===
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| − | * Often make a nest.
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| − | * Guard the young for up to a year.
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| − | == [[Chelonian Reproduction - Anatomy & Physiology|Tortoises, Turtles & Terrapins (Chelonia)]] ==
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| − | == [[Snake and Lizard Reproduction - Anatomy & Physiology|Lizards, Snakes and Tuataras (Lepidosauria)]] ==
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| | + | == [[Reptile Reproductive Anatomy and Physiology- Lepidosauria - Anatomy & Physiology|Lizards, Snakes and Tuataras (Lepidosauria)]] == |
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| − | [[Category:Exotic Reproduction]] | + | == [[Reptile Reproductive Anatomy and Physiology- Archosauria- Anatomy & Physiology|Crocodiles (Archosauria)]] == |
| − | [[Category:Bullet Points]]
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