Transcript Vernal Pools

VERTEBRATE ZOOLOGY
(VZ Lecture14 – Fall 2012 Althoff - reference PJH Chapter 10)
Amphibians: Reproduction &
Parental Care
PART III
In general….
• Considerable variety/diversity among
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amphibians when it comes to modes of
reproduction:
a) “behavioral lead-up”
b) type of fertilization
Several modes of parental care (or lack of it)
a) within orders
b) between orders
Like some charactersitics/features already
examined, this diversity/mix has likely served
amphibians well the past 250 MY
In general….con’t
• _____ species of amphibians lay eggs
• _____ that lay eggs deposit them in water…but
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some do on land
As noted previously, some eggs hatch into _____
forms…others into miniatures of terrestrial adults
_____ don’t offer any parental care
Two major things impact monitoring/studying
populations:
a) large annual fluctuations in productivity
(lots of eggs laid but much variation in how many
survive to become adults)
b) local, annual variation in breeding habitat
requires larger survey areas
Caecilians
Global distribution of Caecilians
Caecilians
• Exhibit __________ fertilization
• Some lay eggs, coil up around the eggs until they
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hatch
Some exhibit viviparity
Some (~75%) exhibit ______________________
Phase I – growth of fetus initially achieved
by yolk contained in the egg at time of
fertilization….but yolk is exhausted before
fetus fully develops (up to 9 fetus per female)
Phase II – balance of fetal growth achieved
by ____________ feeding!
________________ Feeding
• Fetus develops specialized “__________________”
• Using embryonic teeth, individuals scrape the
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material lining the walls of the oviducts that by this
time in is happening, the epithelium tissue has
thickened, become highly vascularized, and starts to
secrete a thick, white create substance referred to as
_________________.
“Biting” action probably stimulates further milk
production
Fetuses fairly evenly spaced out along oviduct
evening out accessibility to growing fetuses
______ that is basically non-functional _____________
Fetal caecilian – in utero
Salamanders – gamete exchange
• Some achieve fertilization externally
• Most, however, exhibit internal fertilization
by transfer of packet of sperm 
__________________ = sperm on
a gelatinous base
Species-specific spermatophores showing sperm caps
Dusky salamander
Red-spotted newt
Fig. 10-14, p237 PJH
Two-lined
salamander
Salamanders – marking & pheromones
• Evident in terrestrial species
• Males may “mark” females….involves direct
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physical contact
Male has specialized “courtship glands”….
known as _________ glands…..
applies secretion to
a) her nostrils or
b) her body
Some species, males have large gland under
chin known as _________ gland….applies
secretion to her nostrils with slapping
motion
Variations off of these two methods…
dermis
epidermis
Rough skinned newt
Fig. 10-15ab, p237 PJH
the “tail
walk”
chin on
snout
Jordan’s
salamander
Two-lined
salamander
male uses
tooth to
“scrape”
pheromone
Smooth newt
Fig. 10-15ab, p237 PJH
male wafts pheromones
toward female with tail
Among salamanders…3 ways they
get eggs and sperm together
(only one way used per species)
male deposits on female, then holding her with tail
or jaws uses feet to insert spermatophore into her
cloaca
 female deposits egg sac on top of spermatophore
 female picks off
sperm cap with cloaca
Vernal Pools – Breeding Locations for
Some Salamander & Frog Species
• Temporary wetlands
• Pools, because they dry out periodically, do ____
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support breeding populations of fishes (thus, no
predation/consumption of egg masses & larvae)
Typically in woodland ecosystem types
Some species are considered _______________
_____ species – a part of their life cycle must
take place in such a pool
ex. mole salamanders
wood frogs
Lots of breeding takes place, lots of egg laying
takes place in the vernal pools
Vernal pools - signs of breeding activity
spotted
salamander
egg mass
blue spotted salamander egg masses
Vernal Pools – Breeding Evidence
• ___________________
• Spermatophores
• Egg masses
• Larvae
SOME USE _______ BASIN of A VERNAL POOL
Marbled salamander with eggs. The marbled
salamander lays its eggs in the fall in the dried basin
of the vernal pool. The female remains with the
eggs which hatch when the pool fills in the fall.
SOME DO NOT USE A VERNAL POOL – Example
would be red-backed salamander ( “ a non-vernal
pool species)…it is not aquatic. Spends its entire
life on the forest floor = ______________________
•Lays eggs in small nest
•Nest under logs and forest litter
Finally…on salamander reproduction
• Some give birth to young (rare)
most that do thisyoung not fully
developed, don’t look like adults
“really different”: alpine salamander give
birth to “fully” developed young…
apparently same ____________________
nourishment as described for some
caecilians
Anurans
• Vocalizations, not pheromones, play large role in
reproductive behavior…specifically attracting
mates
• Two basic mating systems:
1) ______________ – short-time period
(few days)
vs.
2) _____________ –extend period (few
months)
_____________ Breeding Mating System
• Many toad species, few frog species do this
• Often involves the vernal pool scenario—
response to temporary aquatic habitat availability
• Males & females usually present in equal
numbers….and lots of them
• Both sexes tend to arrival at breeding sites (i.e.,
vernal pools) at same time
• Males have to out compete other males for
breeding opportunity by out-positioning, etc.
_____________ Breeding Mating System
• Most frog species
• Males arrive first to the area and establish
territories…..some species, the males arrive at
breeding calling site at night and return to a
daytime retreat
• Few females come each day to breed
• Few males do MOST of the breeding
• Vocalizations seem to be critical to attracting
females, breeding females
Vocalizations
• Risk: can attract predators…but some evidence
that, at least in vernal pools, likelihood of being
“the” predated one is less than if in smaller
groups or isolated…so large volume of calling
attracts female
• Calling is energetically costly…
a) call louder, takes more energy
b) call more often, takes more energy
VO2 while calling, ml O2/gram/hour
ENERGETIC COST OF CALLING
Calling rate, calls/hour
Fig. 10-18, p242 PJH - gray tree frogs
Evidence for …_____________ hypothesis…
From gray tree frog studies….
• Louder calling, longer calling by males
resulted in those males attracting more
females
• Good gene hypothesis predicts that the
characteristics of males that are favored by
females identify ___________________
males
Anurans – gamete exchange
• Most exhibit _______________ fertilization
• For those that exhibit internal fertilization, male
has his own extension of the cloaca that allows
him to introduce sperm into the cloaca of the
female
• Typical ‘coupling’….
Male mounts female, uses his fore legs to
clasp either in her pectoral region or pelvic
region. He hangs on for several hours, maybe
days until she lays her eggs at which time
he fertilizes them.
Anurans….reproduction continued
• Viviparity is rare…usually eggs left to develop
on their own…but exceptions
• Adults may guard eggs, sometimes even males
• Some sit beside eggs, some sit over eggs
• Some guard post-hatching forms
• Posion dart frogs deposit eggs on ground and
stay nearby until hatched—visually deterring
predation of eggs
• Some carry their tadpoles
• Lot more variations….
Fig. 10-21, p237 PJH
Example of “cycle”
Wood frogs are an amphibian species of upland
forests. They venture to vernal pools in early
spring, lay their eggs, and return to the moist
woodland for the remainder of the year.
The tadpoles develop in the pool and eventually
follow the adults to adjacent uplands. The
presence of evidence of breeding by wood
frogs (chorusing or mating adults, egg masses
or tadpoles) indicates that a pool is a vernal pool
Some Australian frog genera….
• Swallow eggs or newly hatched
• Two “areas” develop in stomach….one portion
has reduction/cessation of HCl secretions, other
retains normal “digestive” function—at least for
one of species this has been discovered in,
other species doesn’t do exactly same thing
• Young remain there through metamorphsis
• Just another illustration of diversity in
approaches to reproduction—in this care post
breeding strategies to ensuring perpetuation of
the species