Lecture 7-Reptiles 4 (Reproduction) Flashcards
What does it mean that reptiles are ectotherms?
-use their behaviour to maintain heat -have a more efficient Krebs cycle (fewer protons are lost) -being ectothermic provides reptiles with lot of flexibility on where they can live and what they can do, (life histories)
What is the behaviour of a reptile during the day like in terms of maintaining core temperature?
-temperature is quite stable throughout the day -regulate behaviourally, have to move between shade and sun depending on the temperatures -when high= go into shade, low=go into sunny areas -use external energy and environment to regulate body temperature
Do ectotherms have lower energy needs than endotherms?
-yes -more efficient body system, don’t need to generate as much heat -cost of life is lower -metabolic rate decreases with mass -low energy, variable temperature systems
How are reptiles as ectotherms limited in where they can live in the world?
-can’t go too close to the poles= about 40S and 40N as they need sun
What is a life history?
-An animal’s pattern of allocation, throughout life, of time and energy to various key activities, such as growth, repair of cell and tissue damage, and reproduction. -growth, maintenance, reproduction
What is maintenance?
-keeping the systems at some level -maintaining homeostasis
What are the K and R selected species? example: lizard and turtle
K- turtle= long life slow growing , takes 30 yrs to grow up, then some maintainance, then some ebergy to reproduction R- lizard= only takes 9 months to grow, puts more resources into reproduction than anything else
What is the life history of a green Sea turtle?
-turtles born, go into the ocean, then dispersing and finding habitat -grow in pelagic habitat= in the currents, spend that just floating in a raft and eating, growing (good for them, not as much predation) -when big enough move to feeding habitat, then spend 30 years there to grow, then mature sexually -females huge input= 120 eggs every 5 to 6 years -males don’t have to pay costs as much (no migration or egg production) so the males can reproduce more times -more reproductive opportunities= males -overall restricted in reproduction opportunity so they try really hard to succeed
What are the three factors influencing life histories of reptiles?
- Environment (temperature) 2. Ecology (diet) 3. Phylogeny (limits of design= can’t fly if doesn’t have wings etc.)
What does reproduction comprise?
-physiology, morphology, behaviour -these can act together to produce different life-history traits (different schedules) -reproduction is the big ticket item in the life history of all animals!
What is the variation in reptile life histories: Age to reproductive maturity?
Age to reproductive maturity: 9 month to 45 years (lizard/turtle)
What is the variation in reptile life histories: Active output per breeding event?
2 vs 600 offspring (geckos 2- turtles= 600 in a season)
What is the variation in reptile life histories: number of breeding events?
1-20+
Can environment change the strategies of breeding of different populations of the same species?
-even different populations of the same species that live in slightly different environments change their strategies depending on the environment etc.
What three factors of reproduction does temperature affect in reptiles?
1.Timing/patterns of annual reproduction 2. Modes of Incubation 3. Sex determination
What are the 5 stages of a reptilian reproductive cycle and their comparative duration?
- Physiological activation of reproductive system: make sperm and maturate eggs
- Courtship and mating
- Ovulation and fertilization (1+ times)
- Egg laying and incubation/or embryo development in utero (1+ times)
- Hatching or birth
How do the reproductive cycles differ in a lizard living in warmer and colder climate?
- depends on where you are, if in the north= try to time it so the offspring come out in early summer
- southern part= activate in autumn, then go to sleep, then in spring= courtship, hatching is in late summer
picture:
- Physiological activation of reproductive system: make sperm and maturate eggs
- Courtship and mating
- Ovulation and fertilization (1+ times)
- Egg laying and incubation/or embryo development in utero (1+ times)
- Hatching or birth
Does temperature have effect on reptilian development in eggs and in utero?
yes, crucial!
What effects does temperature have on development of eggs?
-the rate at which eggs develop is dependent on the environment -that is why the dig to bury them but small reptiles can’t dig very deep
What are oviparous reptiles?
-Reptiles that lay eggs
What is oviposition?
-The act of laying eggs
What do viviparous reptiles do?
-bear live young -extended retention of eggs -loss of shell nutrient transfer -placenta
How many times has viviparity evolved in reptiles and in mammals?
-100 times in reptiles -1 time in mammals
What causes viviparity in reptiles?
-environment -cold temperatures -that way the mother can control the temperature of the eggs, otherwise they would die in the cold -Allows female lizards to control developmental temperature of offspring.
Can the effect of temperatures during development be seen after birth/ hatching?
-Developmental temperatures have a major affect on the fitness of reptiles by influencing phenotypes of offspring -if you incubate at different temps= get different phenotypes -developmental tem has a huge influence on the performance of the hatchlings -permanent developmental effect -hot nests= fast runners, cold nests= slow runners
How can sex be determined in reptiles?
- ZZ (male)/ ZW (female) or XX / XY Chromosones. 2. non-genetic temperature sex determination (TSD or ESD)
What reptiles have temperature dependent determined sex?
-some turtles -some lizards -all crocodiles -no snakes! (as far as we know)
What are the three patterns of TSD involving temperature of incubation of the eggs?
- as temp increase = more females for lizards
- opposite for turtles, higher temp=males
- females produced at both extremes
Why did some reptiles evolve TSD?
-Selection should favour TSD over genotypic sex determination when the developmental environment differentially influences male versus female fitness. That means that under certain incubation temperatures one sex performs better than the other!!
How do reptiles maximize offspring fitness in reproduction?
-Because temperature influences offspring phenotypes, reptiles have evolved ways to maximize offspring fitness through viviparity and temperature sex determination.
