Transcript Salamanders, Anurans and Cealians

Salamanders, Anurans and
Cealians
Chapter 10
Lissamphibia
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Monophyletic
3 lineages of Amphibians considered
orders of this class
Varying body lengths
Lissamphibia
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Salamanders/Urodela
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Frogs (Anurans): Frogs, toads, tree
frogs
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Elongated animals, terrestrial, usually with four
legs; Have tails as adults
Short bodies, no tails as adults; Large heads
Large hind legs (walking, jumping, climbing)
Caecilians(Gymniophiona) = no legs
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are an order of legless amphibian.
most have no tail, also called rubber eels
Burrowing animals
General Characteristics
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Skin:
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Smooth; thin;permeable; no scales; moist; &
modified for gas exchange
All forms are carnivorous as adults
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Non-amniotes
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Will eat whatever comes within range, that is not to long
No extra embryonic membranes
Eggs lack amnion, chorion, and allantois
Lungs present in all terrestrial forms except
Plenthodontid salamanders
Lungs are simple with relatively small surface
General Characteristics
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Generally two –phase life history
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Aquatic tadpole
Terrestrial adult
Double circulatory system
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Systemic one to body generally and
Pulmocutaneous one to lungs and skin
Salamanders: Urodela
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Order =Urodela
10 families & ~ 515 spp
See figure 10-1
Elongate body, 4 limbs of equal size
Walking trot gain coupled with anquilliform
motion of body while moving legs forward
Mostly in N America & Central America
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Tennessee has largest no of spp
Salamanders
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Hind legs only slightly larger than front
legs
Many are paedomorphic
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Larva attains sexual maturity before
attaining adult body form
Due to progenesis
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Rapid devpt of reproductive organs relative to
somatic tissue
(Neoteny = retention of larval embryonic traits past
reproductive maturity)
Salamanders
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Paedomorphs retain such larval
characteristics as external gills, lateral
line system, no eyelids & larval tooth
patterns
Several salamanders adapted to life in
caves due to their constant
Temperature & moisture
Salamanders
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Largest living Salamanders include
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Japanese & Chinese giant Salamanders - > 1m
long
Mudpuppies (necturus)
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Paedomorphic spp that retain external gills
Occurs in lakes and streams in eastern North America
All salamanders lack ribs
Use buccal pumping to get air into lungs
Uses a lot of muscles attached to the tongue
Plenthodontid Salamanders
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Well known, interesting specializations
Lung less, terrestrial, aquatic
Respiration wholly thru skin
Protrusible tongue used to capture even
moving prey
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Seen a grp called the Bolitoglossines
Can hit moving targets by projecting their
tongues the length of their trunk..
Plenthodontid Salamanders
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Presence of Nasolabial Groove
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From external nares to the upper lip
(figure 10.4)
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Liquids from substrates drawn into the NG
which then passes it into the nose and then the
vomeronasal (Jacobsen) organ which is used
for chemoreception
Thus NG & vomeronasal organ used for
olfaction and chemoreception
Plenthodontid Salamanders
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Produce unique pheromones
Used for marking territories for feeding
and mating
Neighbors are able to detect each
other’s pheromones and use the smell
to fight off intruders
Plenthodontid Salamanders
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Reproduction
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Mostly internal by use of a spermatophore
(a pkt of sperms)
Males deposit a spermatophore on
substrate
No intromittent organ, thus no direct
deposit of sperm into female
See fig. 10-14
Spermatophores vary in shape
Plenthodontid Salamanders
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Females may
Pick it up with cloaca
 Deposit egg sacs on spermatophore
 Some males deposit spermatophore on top of the
female & use their feet to insert the
spermatophore into her cloaca
Males clasp females during courtship to deposit
pheromones onto the skin of the females. Female
must give positive feedback to the male for him to
deposit the spermatophore
Read page 236
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Plenthodontid Salamanders
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Eggs hatch into gilled larval forms
Will undergo metamorphosis into an adult
Paedomorphosis occurs in which the larvae
becomes sexually mature without
metamorphosis into adult form
Viviparity
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Only a few spp are viviparous
Give birth to live young
Eggs maybe retained until hatching and get all
their nutrients from yolk
Young born as larvae
Plenthodontid Salamanders
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Terrestrial spp lay masses of eggs
under logs or in holes of soft dirt
Many spp remain near eggs to guard
them
Some go to the aquatic life in larval
forms
Others bypass larval forms & hatch as
miniature adults
ANURANS: Frogs & Toads
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29 families
> 4800 spp
In all continents but Antarctica
Specialized for jumping
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hind limbs greatly enlarged for swimming
or jumping
Tibia and fibula are fused into one solid
bone
ANURANS: Frogs & Toads
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Pelvic girdle enlarged and anchored to
vertebral column
Ilium is elongate
Caudal vertebra are fused into a solid rod the
urostyle
Spinal column is short and inflexible with 9 or
fewer (usually 5) pre sacral vertebrae
Lacks a visible neck; appear neckless
ANURANS: Frogs & Toads
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Ribs are gradually reduced, usually
fused to the vertebral column
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Form distinctive transverse processes
See figure 10-7
Pectoral girdle and forelimbs absorb the
impact of landing
Eyes are large, placed forward on the
head giving binocular vision
ANURANS: Frogs & Toads
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Largest frog is the West African :
Gigantorana goliath:
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> 30cm body length
Weighs 7.5 lbs, eats rats, or ducks
Largest American frog is the bull frog
(Rana catesbiana): ~ 20 cm body
length
ANURANS: Frogs & Toads
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Body forms reflect specializations for different
habitats
Frogs have
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long legs
Move by jumping
Webbed feet as seen in semi aquatic frogs
Toads
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Stout bodied, compact
Make short hops
Thicker skin; shorter hind limbs, little to no
webbing between toes.
ANURANS: Frogs & Toads
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Horned frogs
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Extremely large heads and mouths
Feed on small vertebrates including birds, frogs
and mammals
Arboreal Frogs
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Large heads & eyes
Slim waists
Long legs, walk, climb & leap with all legs
Many spp have enlarged toe discs for clinging to
vertical surfaces. Produce a viscous substance for
sticking to wet surfaces
ANURANS: Frogs & Toads
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These frogs are able to stick to vertical &
even to the underside of leaves
Adhesion and detachment alternate as the
frog walks across a leaf
Because of the mechanism by which the toes
can cling to the surface, a tree frog must
orient with its head facing up for its toes to
remain pointed upwards & clinging to surface
Descending a vertical surface, move
backward inorder to keep the toes facing
upward
Frogs & Toads:Mating systems
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Explosive Breeding
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Short breeding season, even a few days
Common in toads & some anurans
Males and females gather together in large
numbers
Frogs & Toads:Mating systems
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Prolonged Breeding
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Long breeding season
Maybe several months long
Males are first to arrive at breeding sites
Green frogs establish territories, spend months
defending territories
Females join later & leave after breeding
Males compete for females thru vocalizations
Frogs & Toads: Vocalizations
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Frogs & toads very vocal
Calls are species specific
Serve as a premating,isolating mechanism for many
species
Mostly calls are used for mating & territorial defense
Called Advertisement calls
Affected by body size, spp
In most spp, only males call, spp respond only to
their own unique call types
Response is hormone triggered
Frogs and Toads:Cost of Calls
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Require energy
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More energy from one if many are calling
at each time, trying to outcompete each
other
Increase rate of predation
Frogs & Toads: Reproduction
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Reproduction is external in most spp
Males & females engage in Amplexus
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Male on back of female, grasps female with his
forelegs
Axillary amplexus: Clasping on pectoral region
Inguinal amplexus: clasping on pelvic region
Amplexus maintained for several hours/days
before female lay eggs
Frogs & Toads: Reproduction
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Anurans exhibit a variety of larval dvpt
Many lay eggs in water
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Some exceptions
Some tropical forms deposit eggs on leaves
overhanging water so that the as eggs
hatch, the larva drops into the water
Some use pools of water in bromeliads
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Epiphytic plants growing on trees in tropical
rain forest
Frogs & Toads: Reproduction
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Some encase in a frothy protective foam
mass consisting of air, sperms, eggs, cloacal
secretions, and some water
Other anurans posses dorsal pouches on their
backs in which eggs are incubated or eggs
maybe attached in some other manner to the
back of the parent where they remain until
hatching
See figure 10-21
Frogs & Toads: Parental Care
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Direct development
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No larval or tadpole stage
Eggs deposited in moist sites are guarded by male
parent
Males Chilean Rhinoderma darwini pick up eggs &
incubate them in his vocal pouch until young
complete metamorphosis and emerge as miniature
adults
Australian Rheabatrachus: Gastric brooder. Carries
eggs in stomach and tadpoles dvpt into miniature
adults in stomach.. The mothers then eject baby
frogs out of their mouths.
Frogs & Toads: Parental Care
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Parental care ranges from several days to as long as
four months
May be in the form of transport of eggs and or larva
Tadpoles maybe carried on back of adults for a week
Some tadpoles hatch on land, attach to adult &
transported into water
Some tadpoles follow mother in water
African bull frog males guard both eggs and tadpoles
Ecology of tadpoles
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Aquatic
Gill bearing larva hatched (tadpoles) in aquatic environments
Morphological variations related to feeding habits and methods
Tadpole stage maybe 7-10 days in spadefoof frogs or as long as
2-3 yrs in bull frogs
Generally filter feeders
Species that graze/eat from surfaces have small keratinized
beaks for scrapping algae
Only a few are predators and these have larger horny beaks for
attacking prey (other tadpoles)
Metamorphosis (See table 10.15)
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Complete reorganization of the body
plan: tadpole to adult
Includes
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Growth of legs, loss of tail, loss of gills,
development of lungs, and reorganization
of the skull as modes of feeding
Process controlled by thyroxin which in
turn is controlled by thyroid stimulating
hormone (from pituitary gland)
Metamorphosis: 3 stages
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Pre-metamorphosis
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Prometamorphosis
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Growth phase, tadpoles increase in size, no
change in form
Hind legs appear
Growth continues
Metamorphic climax: see
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Fore legs appear, tail disappears
Very rapid-only a few days
Metamorphosis: 3 stages
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Metamorphic Climax
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Animals most vulnerable due to predation
by snakes
In water snakes capture
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30% of tadpoles
67% of transforming ones
On land snakes capture
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45% of transformed frogs
90% of transforming ones
Skin of all amphibians
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Glandular skin
No external scales
Highly permeable to gases & water
Mucus glands distribute all over the bodykeep skin moist & permeable
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Both water and gas pass readily thru skin
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Dry skin reduces oxygen uptake
Facilitates cutaneous respiration
Skin also retains urea and active take Na ions
Blood Circulatory system
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Left and right atrium divided by a
septum
Ventricle undivided but has a complex
structure that keeps blood separated
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No mixing of poor with rich oxygen blood
Spiral valve is a structure in the
ventricles used to separate blood
Blood Flow
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O2 rich blood from pulmonary veins
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Left atrium and then left side of common
ventricle
Ventricle contracts, pushes blood into the
left side of the ventral portion of spirally
divided conus
Blood is thus selectively distributed to the
tissues of the head
Blood Flow
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O2 poor blood from body enters the right
atrium and then the dorsal half of the spiral
valve conus
Goes to the pulmocutaneous arch, then to
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lungs for oxygen on land or to
Skin for oxygenation when frog is in water
Thus frogs can switch among gas exchange
modes (lungs vs. skin) depending on whether
animal is in water or on land.