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

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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.