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Lecture 8

by: Sierra

Lecture 8 FNR 251


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Reptilian Reproduction, Growth and Development
Ecology And Systematics Of Amphibians, Reptiles, And Birds
Rod N. Williams
Class Notes
Ecology, systematics, amphibians, reptiles, forestry, Natural Resources
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This 23 page Class Notes was uploaded by Sierra on Monday February 29, 2016. The Class Notes belongs to FNR 251 at Purdue University taught by Rod N. Williams in Spring 2016. Since its upload, it has received 15 views. For similar materials see Ecology And Systematics Of Amphibians, Reptiles, And Birds in Agriculture and Forestry at Purdue University.


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Date Created: 02/29/16
LECTURE 8: REPTILIAN REPRODUCTION, GROWTH AND DEVELOPMENT American Alligator Hatchlings I. Reproduction and Life Histories Major differences of reptilian reproductive features compared to amphibians: a) Internal Fertilization b) Direct Development c) Amniotic Egg All these factors allowed reptiles to become independent of standing water for breeding II. Gametogenesis and Ovulation Vitellogenesis is a very important process in egg-laying vertebrates: a) Accumulation of nutrients b) Nutrients will later become the yolk In reptiles, vitellogenin is selectively absorbed by oocytes and enzymatically converted to yolk proteins II. Gametogenesis and Ovulation Cleidoic egg (shelled): Shell prevents desiccation and contamination by environmental pathogens Creates own aquatic environment By folding and curling, the reptile embryo can attain surprising lengths Three extraembryonic membranes are formed: a) Allantois b) Chorion c) Amnion III. Fertilization and Copulation Copulatory organs: Turtles and crocodilians: a penis of spongy connective tissue erects and retracts via vascular pressure Squamates: penis lost and later replaced by hemipenes III. Fertilization and Copulation A B C D Photographs of hemipenis in snakes III. Fertilization and Copulation Sperm Storage: Delayed fertilization permits females to mate with more than one male and can result in multiple paternity In reptiles it is not as common as in amphibians Sperm storage tubules are located on the upper mid section of oviducts Mechanism for expelling sperm from these tubules is unknown IV. Reproduction Without Fertilization Asexual Reproduction One type in reptiles: Parthenogenesis Occurs when females reproduce without the involvement of males or sperm Inheritance is clonal Genetic variation within an individual is high, but among individuals is almost non-existent Premeiotic mitosis (doubling of chromosomes)  tetraploid oogonium  normal meiosis produces diploid gamete IV . Reproduction Without Fertilization Schematic representation of parthenogenesis in reptiles. Lizards belonging to the genus Lacerta are parthenogenic. V. Parental Care Three major types: a) Pre-depositional b) Post-depositional c) Live-bearing V. Parental Care Live-bearing: Two major types: a) Ovovivipary b) Vivipary V. Parental Care Ovovivipary: Involves the retention of eggs for much longer periods of time compared to oviparous species Embryos can be supported entirely by egg yolk Embryos also absorb some nutrients through the oviduct  Vivipary: Transfer of nutrient to developing embryo is through a placenta-like structure VI. Embryo Development Development is direct in all reptiles (not two “lives”) Clutch and egg size may be proportional to body size Reptilians that develop from terrestrial eggs: Humidity Temperature VI. Embryo Development Temperature-dependent Sex Determination (TSD) Widespread in reptiles Average temperature during 2nd trimester of development, and not sex chromosomes regulates gonad differentiation Crocs and lizards: ♂’s at high temp Turtles: ♂’s at low temperatures Reason? VI. Embryo Development Read-eared Slider Turtle (Trachemys scripta) VII. Growth Two growth pulses VIII. Age Absolute age is not as important as time required to reach major life history events: Reproductive periodicity is also very important Longevity can be great in some reptiles VIII. Age FNR 251 01/29/2007 IX. Dynamics of Reproduction Most reptiles exhibit seasonal patterns Turtles: gametogenesis is annual but asynchronous ♂’s ♀’s Crocodylians: cyclic annual breeders with synchronous gametogenesis Squamates: variety of patterns IX. Dynamics of Reproduction 1. 5. 2. 6. 3. 4. IX. Dynamics of Reproduction Mate attraction and selection Summary of Development in Amphibians and Reptiles Amphibians Reptiles Ovum Size 1 - 10 mm 6 – 100+ mm Review of Terms: Lecture 8  Gametogenesis and Ovulation: Allantois, Amnion, Corpora Lutea, Chorion, Cleidoic Egg, Ovulation, Pinocytosis, Vitellogenesis, Vitellogenin  Fertilization and Copulation: Copulatory Organs, Fertilization, Hemipenis  Reproduction without Fertilization: Asexual Reproduction, Parthenogenesis  Parental Care: Live-bearing, Vivipary, Ovovivipary, Post- depositional Parental Care, Pre-depositional Parental Care  Embryo Development: Temperature-dependant Sex Determination (TSD)


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