unit 6: reproduction and life history

factors that initiate reproduction

environmental factors, hormones and nervous system

gametogenesis

formation of gametes

reproduction

triggers by environmental factors (temperature, rainfall, photoperiod)

“big nights”

predictable conditions (warm rain, melting ponds,) where amphibians and reptiles come out in droves for reproductive purposes

external fertilization

male releases sperm on the eggs as they exit the female, found in most frogs, Cryptobranchid salamanders and Hynobiidae

internal fertilization

requires morphological structures to deliver sperm to the ova and it often accompanied by mating rituals, found in all salamanders, caecilians and reptiles

cloacal apposition/kiss

internal sperm transfer process done by tuatara that does not require morphological structure

amplexus

male grasps female and positions his cloaca near hers

spermatophore

salamanders, thick mucous pedicel, cap holds the sperm, deposited by male and picked up by female

hemipenes

paired penis of squamates

sperm storage

occurs in most salamanders, one frog, caecilians, groups that have internal fertilization

storing sperm advantage

multiple matings at once, sperm competition with spermathecae

spermathecae

cloacal glands that also function as receptacle for sperm storage

nest

discrete structure designed by a reproductive adult for egg deposition

frog nests

foam, ponds

newt nests

lay individual eggs

reptile nests

constructed by reptiles for egg deposition

turtle nests

dug in the ground

lizard and snake nests

deposit eggs in damp soil/rotting logs + humus

other nests

ant/termite mounds, rock crevices/under loose bark of trees

most vulnerable life stage

egg stage

factors influenced by female’s selection of clutch site

duration of incubation, developmental rate, hatching success, size of offspring

viviparity

females retain developing eggs inside reproductive tracts or body cavity and give birth to offspring capable of a free-living existence

viviparity statistics

evolved independently at least 114 times mostly with squamates, occurs in about 1% of known amphibian taxa, provides parents with more control over development

oviparity

females deposit eggs that develop and hatch in the external environment, receive all their fetal nutrition from yolk within an egg

dermatophagy

feeding on shed skin, found in caecilian young

direct devlopement

no aquatic larval stage or metamorphosis, large eggs are deposited on land and the young develop inside the egg, emerging as fully formed but tiny version of adults

direct development statistics

allowed amphibians to breed entirely on land, occurred independently in all amphibian clades

parental care

any form of post-ovipositional or post-birth parental behavior that increases the survival of the offspring at some expense to the parent

parental care pros

increase offspring survival, increased investment in each offspring, thermoregulation, strength in numbers

parental care cons

increased predation risk, energy demand/split resources, dependence, future reproductive potential

nest or egg attendance

a parent remains with the next or eggs but without detectable nest defense

nest or egg guarding

a parent remains with the next or eggs and actively depends against conspecifics or predators

egg, larval or hatchling transport

a parent carries offspring from one place to another

amphibian egg brooding

used for species that retain embryos somewhere on or in the body but not in the oviducts

reptile egg brooding

a parent facilitating incubation by raising the temperature of the eggs

feeding of young

a parent brings food to offspring

guarding or attending young

a parent stays with young after the eggs hatch

genetic sex determination (GSD)

sex of individuals is determined by sex chromosomes passed on from parents, humans and mammals, all studied amphibians

temperature-dependent sex determination (TDSD)

sex of individuals is determined by incubation temperature, a form of environmental sex determination (ESD), occurs during 2nd trimester

environmental sex determination factors

light intensity, photoperiod, temperature, nutrient availability, pheromones

threshold temperature

the temperature for temperature-dependent sex determination in which the gonads of the developing embryo can become ovaries or testes

sexual reproduction

the production of new living organisms by combining the genetic information from 2 individuals of different sexes and typically produces a diploid organism

parthenogenesis

occurs when females reproduce without the involvement of males or sperm, AKA cloning, inheritance is clonal and females ar genetically identical to their mothers, obligate or facultative

kleptogenesis

a reproductive system in which unisexual individuals (all females) “steal” nuclear genomes from sexual individuals (sperm donor)

model kleptogenesis system

Ambystoma laterale-jeffersoniaum, populations consist of diploid males and females AND polyploid females

number and size of offspring

natural selection should favor offspring size yielding the highest probability of survival and future reproductive success, limited to the size of the mother

pelvic opening size in turtles

as it increases, egg size increases

life history

a set of co-evolved traits that affects an individual’s survival and reproductive potential

life history facotrs

age specific survivorship, brood size, size of young at birth or hatching, age and size at reproduction, growth rates, interaction of reproductive effort with adult mortality

fecundity costs

represents the energy expenditure of reproduction, energy invested in reproduction is energy not expended on growth/maintenance

survival costs

increased vulnerability of females that are carrying eggs or embryos, either directly from the effect of clutch mass on mobility or indirectly due to reduced physical condition following parturition and its effects on escape behavior or overwintering

amphibian seasonality in reproduction

temperature and rainfall are important for timing, asynchronous

late winter breeder

wood frog

spring breeder

spotted salamander

early to mid summer breeder

New Jersey chorus frog

late summer breeder

bullfrog

fall breeder

marbled salamander

reptile seasonality in reproduction

majority are seasonal, tropical species may be continuous

general reptile reproduction pattern

ovulation in spring, egg deposition in early to mid summer, hatching in late summer