Service Seeks Information on Petition To Halt
Spread of Amphibian Disease
See course website for link
Exam I
The U.S. Fish and Wildlife Service today announced it has posted a
notice in the Federal Register seeking information concerning the
possible designation of all live amphibians or their eggs that are
infected with chytrid fungus (Batrachochytrium dendrobatidis or Bd)
as “injurious wildlife” under the Lacey Act.
…
The petition and the Notice of Inquiry are available at:
http://www.regulations.gov under Docket No. FWS-R9-FHC-20090093. The public will have until December 16, 2010, to provide
information on the subject of the petition.
Mean raw score 79%
Your score = correct answers/63 * 100 +
6.5%
Additional 6.5% is based on my inspection of
class-wide patterns in answering – some
questions unclear…
See me:
Giglio,Elizabeth Mary
Knight,Monika Ann
Leiss,Anna Margaret
Mesick,Tyler
O'Riley,Melissa A
Amphibian Reproduction and
Life Histories
Caecilians
Salamanders
Frogs
Reproduction
Reproductive Strategies: Caecilians
Environmental
Stimuli
Reproductive
Behaviors
Brain
Pituitary
Gonads
Secondary
Sexual
Structures
Pheromone
Production
Gamete
Production
All have internal fertilization
~ 80% of species give
birth to live young (viviparous)
Oviparous caecilians lay eggs
on land near water and can have an aquatic larval
stage or hatch as small versions of the adult form
(direct development)
Viviparous caecilians retain their eggs until the
young have developed – feed on yolk and maternal
secretions in the oviducts
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Reproductive Strategies: Caecilians
Parental Care: Caecilians
Oviparous
Viviparous
larvae feeding on
maternal secretions
Dermatotrophy: young feed off the dead skin cells
from the mother’s body
Reproductive Modes: Salamanders
Reproductive Modes: Salamanders
Internal vs. External Fertilization
Internal vs. External Fertilization
External fertilization ~ eggs and larvae aquatic
ancestral condition (e.g. Cryptobranchidae)
• Female hellbenders lay 200-500
eggs in a nest made by the male
under a large rock.
• The male fertilizes the eggs
after they are laid.
• The male guards the nest until
the young hatch (2 - 3 months).
• Larval period can be as long as
a year and a half.
Internal fertilization ~ 90%
of salamanders
Most salamanders produce
"spermatophores" – sometimes
80-100 per male per season
Females pick these up with lips of cloaca
Intense courtship as males attempt to convince a
female to pick up their sperm packet
Which sex invests more in reproduction is not clear
Reproduction: Salamanders
Pheromones ~ increases female receptivity
• “Scratching” pheromone delivery by
Eurycea bislineata
• Protruding premaxillary teeth are visible
just in front of the pad of the mental gland.
• During scratching (below) the male swabs
the female’s surface with this mental gland
(releasing pheromone)
• Then abrades the site with premaxillary
teeth, introducing the pheromone.
Figure from Houck & Arnold (1984).
http://plethodon.science.oregonstate.edu/b
ehavior.html
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See courtship and spermatophore
pick-up video here:
Secondary sexual characteristics
http://plethodon.science.oregonstate.edu/beh
avior.html
Sperm Storage
Accomplished by females in specialized tubules
(generally the spermatheca)
Leads to the possibility of sperm competition and
multiple paternity of offspring
Also great flexibility in terms of female mate choice
Greater sexual selection may lead to evolution of
courtship, e.g. spotted salamanders
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Multiple paternity in an aggregate breeding amphibian: the effect of
reproductive skew on estimates of male reproductive success
E. M. MYERS and K. R. ZAMUDIO Molecular Ecology
Volume 13 Issue 7 Page 1951 - July 2004
Oviposition sites: aquatic
8 spotted salamander clutches
from near Ithaca
Genotyped all offspring
using microsatellite DNA
Determined that two to eight
males contributed to clutches
Multiple paternity is a common strategy
in this aggregate breeding species
http://blip.tv/file/get/Monrch-spottedSal225.wmv
Egg Symbioses
Local phenomenon involving an unicellular
green alga associated with Ambystomatid
eggs (Oophila amblystomatis).
Extremely abundant in inner envelope of
eggs and gives some egg masses a green
hue.
Elements of the symbiosis
Oxygen-sensitive microelectrode suggest
that alga produces O2 in excess of what it
and the larvae need
“Lens action” of globular egg mass
increases egg mass temperature by several
degrees
sets up water micro-currents
Alga may consumes excess CO2 and Nrich waste produced by developing larvae
Operational even in O2 limited
environments
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“Solar salamanders”
Other aquatic oviposition sites –
moving waters
Photosynthetic algae have been found inside
the cells of adult (first time in a vertebrate)
all over the spotted salamander's body
may be providing oxygen and carbohydrate to the
adult cells that encapsulate them
Passed from mother to embryo?
Immunological implications!
See:
http://www.nature.com/news/2010/100730/full/news.2
010.384.html
Non-aquatic eggs
Reproductive Modes: Salamanders
Non-aquatic eggs
Ovoviviparous (5 – 6 spp.)
terrestrial
Viviparous
(only Salamandra atra)
arboreal
Bolitoglossa pesrubra
Salamander parental care
Limited to egg guarding
Eastern newt
(Notophthalmus viridescens)
wraps eggs in vegetation
2) Tiger salamander (Ambystoma
tigrinum) guards aquatic clump
of eggs
3) Appalachian woodland salamander
(Plethodon jordani) coiled
around terrestrial eggs
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“Jeff Complex” locally
Reproduction without fertilization!
Some reproduction occurs without fertilization
These are unisexual, female-only species in which
eggs develop directly without fusion of egg and
sperm.
"Jeff complex" salamanders in NE North
America still under study
The silvery
salamander
Ambystoma laterale Blue-spotted
A. jeffersonianum Jefferson’s
Separated during glaciation period; diverged
slightly
Hedges, S. B., J. P. Bogart, and L. R. Maxson. 1992. Ancestry of unisexual
salamanders (genus Ambystoma). Nature 356:708-710.
Ambystoma
platineum
A female only
species!
One of the greatest wonders of zoology…
Ambystoma platineum (silvery) = all-female, triploid species
two sets of chromosomes from A. jeffersonianum
one from A. laterale
Gynogenesis: Female A. platineum mate with males of A. jeffersonianum,
but the sperm make no genetic contribution to the offspring
Reproductive Modes: Anurans
In contrast to salamanders and caecilians, nearly all
anurans have external fertilization
Ambystoma tremblayi (Tremblay’s) is an all-female triploid
species
1x A. jeffersonianum 2x A. laterale
Female A. tremblayi mate with males of A. laterale
How possible? Very occasionally sperm gets incorporated…
Ancestral Mode
External fertilization predominates
Costa Rican Red-eyed Tree Frogs
Africa Reed Frogs
Amplexus
Common Toads
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inguinal amplexus
Anuran amplexus
1)
2)
3)
4)
5)
6)
Axillary
Cephalic
Glued
Independent
Inguinal
Straddle
(Illustration by Dan Erickson)
axillary amplexus
Secondary sexual characteristics
Nuptial pad
External fertilization
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Thermal dimensions: “Communal
dumping”
Wood frog eggs act like tiny
lenses
Concentrate the sun’s rays
and increase egg
temperatures +3-5 C above
surrounding water.
Cumulative effect substantial.
Solar heating also promotes
tiny water currents through
the eggs masses,
Increase the availability of
oxygen to developing
embryos
Incredibly Diverse!!! Especially in the tropics
Reproductive Modes: Anurans
Reproductive Modes: Anurans
Foam nests
Trend towards terrestriality
Thought to be driven by lower rates
of predation in smaller bodies of water
and out of water
Reproductive Modes: Anurans
On leaves over water
In water ~ Leptodactylus insularum
Overhanging water ~ Chiromantis
Red-eyed tree frog ~
Agalychnis
Reproductive Modes: Anurans
Female dorsal pouch
Reproductive Modes: Anurans
Gastrotheca spp.
Eggs imbedded in skin of female
Pipa pipa
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Darwin’s frog ~Rhinoderma darwinii
Terrestrial eggs hatch and are
carried by males in their vocal
sacs until they complete
metamorphosis
Parental Care ~ Coqui
When males are experimentally
removed, only 23% of clutches
hatch (vs 77% in controls)
Die from desiccation (43%),
cannibalism from other males
(32%), and predation by
invertebrates (4%)
Reproductive Modes: Anurans
Internal fertilization occurs only in a few species
E.g. Ascaphus truei (tailed frog)
Alternative Development
Strategies
Heterochrony
The difference between timing of
development between an ancestral form and
a derived one
Paedomorphisis or neoteny is a prime
example
Metamorphosis in salamanders is simply shut
down at a very early age while other
developmental process, e.g. gonad
maturation, continue
Wild type (above) and
lab strains (below)
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Cause of heterochrony
Delayed secretion of the thyroid hormone thyroxine
will result in delayed metamorphosis
Results in larval somatic traits never lost although
sexual maturation and large size still attained
This developmental switch can cause divergence
between species, e.g., Ambystoma mexicanum and
A. tigrinum
Triturus vulgaris meridionalis
Variation in Neoteny
within Species
Notably, sometimes seen
within the same species and
even among local populations
– i.e., not obligate
Notophthalmus and
Ambystoma are good
examples.
What are those evolutionary
reasons?
Facultative neoteny in Notophthalmus
viridescens
Balancing the risk of metamorphosis versus
that of remaining in the aquatic habitat
Larvae may be 'forced' to metamorphose if
there is a lack of food in the aquatic habitat or
if that habitat is in danger of desiccation
But eft and adult stage is not seen in some
Long Island and Woods Hole populations
…why?
Evolutionary Selection Pressures
Larval habitat permanent Larval habitat temporary
Neoteny favored
Eft
habitat
good
No newts (…is bad
newts!)
Eft
habitat
poor
Neoteny
occasional
Metamorphosis
favored (typical
mode)
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When neoteny becomes viable
End reproduction…
Can prevail in populations inhabiting
permanent aquatic habitats where fishes are
rare or absent with uplands inhospitable for
efts
End: Amphibian Reproduction
and Life Histories
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