Salamanders, Anurans and Cealians
Chapter 10
Lissamphibia Monophyletic 3 lineages of Amphibians
considered orders of this class Varying body lengths
Lissamphibia Salamanders/Urodela
Elongated animals, terrestrial, usually with four legs; Have tails as adults
Frogs (Anurans): Frogs, toads, tree frogs Short bodies, no tails as adults; Large heads Large hind legs (walking, jumping, climbing)
Caecilians(Gymniophiona) = no legs are an order of legless amphibian. most have no tail, also called rubber eels Burrowing animals
General Characteristics Skin:
Smooth; thin;permeable; no scales; moist; & modified for gas exchange
All forms are carnivorous as adults Will eat whatever comes within range, that is not to long
Non-amniotes 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 area
General Characteristics Generally two –phase life history
Aquatic tadpole Terrestrial adult
Double circulatory system Systemic one to body generally and Pulmocutaneous one to lungs and
skin
Salamanders: Urodela 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 Tennessee has largest no of spp
Salamanders Hind legs only slightly larger than
front legs Many are paedomorphic
Larva attains sexual maturity before attaining adult body form
Due to progenesis Rapid devpt of reproductive organs
relative to somatic tissue (Neoteny = retention of larval embryonic traits past
reproductive maturity)
Salamanders 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 Largest living Salamanders include
Japanese & Chinese giant Salamanders - > 1m long
Mudpuppies (necturus) 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 Well known, interesting
specializations Lung less, terrestrial, aquatic Respiration wholly thru skin Protrusible tongue used to capture
even moving prey Seen a grp called the Bolitoglossines Can hit moving targets by projecting
their tongues the length of their trunk..
Plenthodontid Salamanders Presence of Nasolabial Groove
From external nares to the upper lip (figure 10.4)
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 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 Reproduction
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 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
Plenthodontid Salamanders 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 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 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 29 families > 4800 spp In all continents but Antarctica Specialized for jumping
hind limbs greatly enlarged for swimming or jumping
Tibia and fibula are fused into one solid bone
ANURANS: Frogs & Toads 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 Ribs are gradually reduced, usually
fused to the vertebral column 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 Largest frog is the West African :
Gigantorana goliath: > 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 Body forms reflect specializations for
different habitats Frogs have
long legs Move by jumping Webbed feet as seen in semi aquatic frogs
Toads Stout bodied, compact Make short hops Thicker skin; shorter hind limbs, little to no
webbing between toes.
ANURANS: Frogs & Toads Horned frogs
Extremely large heads and mouths Feed on small vertebrates including birds, frogs
and mammals Arboreal Frogs
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 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 Explosive Breeding
Short breeding season, even a few days
Common in toads & some anurans Males and females gather together in
large numbers
Frogs & Toads:Mating systems Prolonged Breeding
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 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 Require energy
More energy from one if many are calling at each time, trying to outcompete each other
Increase rate of predation
Frogs & Toads: Reproduction Reproduction is external in most spp Males & females engage in Amplexus
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 Anurans exhibit a variety of larval dvpt Many lay eggs in water
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 Epiphytic plants growing on trees in tropical
rain forest
Frogs & Toads: Reproduction 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 Direct development
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 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 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)
Complete reorganization of the body plan: tadpole to adult
Includes 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 Pre-metamorphosis
Growth phase, tadpoles increase in size, no change in form
Prometamorphosis Hind legs appear Growth continues
Metamorphic climax: see Fore legs appear, tail disappears Very rapid-only a few days
Metamorphosis: 3 stages Metamorphic Climax
Animals most vulnerable due to predation by snakes
In water snakes capture 30% of tadpoles 67% of transforming ones
On land snakes capture 45% of transformed frogs 90% of transforming ones
Skin of all amphibians Glandular skin No external scales Highly permeable to gases & water Mucus glands distribute all over the body-
keep skin moist & permeable Dry skin reduces oxygen uptake
Both water and gas pass readily thru skin Facilitates cutaneous respiration
Skin also retains urea and active take Na ions
Blood Circulatory system Left and right atrium divided by a
septum Ventricle undivided but has a complex
structure that keeps blood separated No mixing of poor with rich oxygen blood
Spiral valve is a structure in the ventricles used to separate blood
Blood Flow O2 rich blood from pulmonary veins
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 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 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.