amphibian notes

AMPHIBIANNOTES

EXTERNAL STRUCTURE AND MOVEMENT

• Amphibian skin does not have scales, feathers, or hair.

• It does have secretions that help with protection. • These glands also keep skin moist to prevent

drying. • They also produce toxic chemicals that

discourage potential predators.

EXTERNAL STRUCTURE AND MOVEMENT

• Chromatophores are specialized cells in the skin that are responsible for skin color and color changes.

• Cryptic coloration, aposematic(warning) coloration, and mimicry are all common in amphibians.

Support and Movement

• Animals that live in water are partially supported by water.

• Animals that live on land have to support themselves against gravity.

• Amphibian skulls are flattened, are relatively small, and have fewer bones than water-dwelling animals.

• These changes keep the skull light so it can be supported out of water.

• Amphibians also have changes in jaw structure and muscles to allow them to crush prey held in the mouth.


• The amphibian vertebral column is modified to provide support and flexibility on land.

• Amphibians do have a neck. • They also have a sternum which supports the

forelimbs and protects internal organs. • Amphibians have a pelvic girdle that has 3 bones. • These bones attach pelvic appendages to the

vertebral column. • This is very important in providing support on

land.


• Amphibians depend more on appendages than on the body wall for movement.

• Therefore, muscles on the body wall are not as strong as muscles in their appendages.


• In the water, salamanders move like fish.• On land, they walk and it makes their body curve. • Caecilians move like an accordion, pushing and

pulling at the same time. • Anurans have long hindlimbs that are modified

for jumping. • They also have connective tissue and muscles in

the forelimbs that act as shock absorbers.

Nutrition and the Digestive System

• Most adult amphibians are carnivores and eat a wide variety of invertebrates.

• Some anurans are more diverse.• The main factors that determine what amphibians

will eat are prey size and availability. • Most larvae are herbivores and eat algae and

other plant matter.


• Most amphibians locate their prey by sight and simply sit and wait for it to pass by.

• Water amphibians depend more on their sense of smell.

• Many salamanders use only their jaws to capture prey.

• Some salamanders and most anurans use their tongue and jaw in a “flip-and-grab” method.


• Amphibians have the first true tongue. • Mucous and gland secretions make the tip of the

tongue sticky. • When prey comes within range, the tongue

comes out, the tip traps the prey, and then trapped in the mouth.

• This whole process happens in about 0.5 seconds! • The tongue then pushes the food toward the

esophagus, and the eyes sink downward to help force the food.

Circulation, Gas Exchange, Temperature Regulation

• Gas exchange occurs across the skin in amphibians, as well as in the lungs.

• So blood coming into the right side of the heart has almost as much oxygen as blood coming from the lungs.


• In addition to a vascular system that circulates blood, amphibians also have a well-developed lymphatic system that helps return fluids and proteins to the blood vessels and also helps transport water across the skin.


• Land animals expend much less energy exchanging gas than water animals do.

• This is because air contains 20 times more oxygen than water.

• There are 2 factors that permit amphibians to exchange gas across the skin: their skin is very moist, and their skin also has a rich supply of capillaries.

• Gas exchange across the skin is called cutaneous respiration and can occur on land or in water.

• This ability allows frogs to spend the winter in mud at the bottom of a pond.


• In salamanders, gas exchange can also occur in the mouth and pharynx.

• This is buccopharyngeal respiration. • Most amphibians have lungs. • Salamander lungs are very simple sacs. • Anurans have divided lungs, providing more

surface area for gas exchange. • Amphibians larvae and some adults breathe using

external gills.

Circulation, Gax Exchange, Temperature Regulation

• Amphibians are ectothermic (they depend on external heat sources to maintain body temperature).

• When in the water, they will take on the temperature of the water.

• On land, their body temperature can be different from the environment.

• Temperature regulation is mainly behavioral.• Many amphibians are nocturnal and remain in

cooler burrows or under leaves during the hottest part of the day.

• They may warm themselves by basking in the sun.

Nervous and Sensory Functions

• The nervous system of amphibians is similar to that of other vertebrates.

• Their brain has 3 sections: forebrain, midbrain, and hindbrain.

• Amphibians have many sensory receptors on their skin.

• They also have a lateral line system similar to fish and this helps aquatic amphibians.


• Chemoreception is an important sense for many amphibians.

• Smell is used in mate recognition, detecting toxic chemicals, and in locating food.

• Vision is one of the most important senses for amphibians because they are primarily sight feeders, often responding to the movements of their prey.


• Some amphibian eyes are on the front of the head and some are more to the side.

• The lower eyelid is movable, and it cleans and protects the eye.

• Much of it is transparent and is called the nictitating membrane.


• Amphibians auditory system is an adaptation for living on land.

• It transmits both underground and airborne vibrations.

• Anuran ears are made up of tympanic membrane, a middle ear, and an inner ear.

• Anurans can screen out either high or low frequency sounds, depending on the situation.

• Salamanders have no tympanic membrane or middle ear.

• They have no mating calls, and the only sounds they hear are probably low-frequency vibrations.

Excretion and Water Regulaton

• Amphibians do have kidneys. • Their waste product is either ammonia or urea,

depending on where they live. • One of the biggest problems amphibians have is

controlling the amount of water and salt in their body.

• In water, they must get rid of excess water while keeping essential ions.

• On land, they must conserve water.

Excretion and Water Regulation

• They can not replace water in the usual ways. • So they limit water loss by using behavior that avoids

exposure to conditions that cause water loss. • For example, many amphibians are nocturnal. • Those that are active day AND night can rehydrate by going

back in the water. • Some amphibians have protective covering that reduce

water loss. • Others may form cocoons that cover the body during

dormancy. • They can also temporarily store water in the urinary

bladder and lymph sacs.

Reproduction, Development, Metamorphosis

• Amphibians have separate males and females.• Fertilization is usually external, and because the

developing eggs do not have protective covering, development must take place in moist habitats, usually water.


• Some anurans have nests on land that are kept moist by a foam covering or by being near water.


• The main exception to external fertilization are the salamanders.

• All caecilians have internal fertilization and about 75% have internal development.

• Amphibian development usually includes larval stages called tadpoles.

• Tadpoles are different from adults in how they breathe, how they move, and what they eat.

• This helps reduce competition between adults and larvae.


• Reproductive activity is often controlled by outside factors such as temperature (in temperate regions) and seasons (such as the rainy season in tropical regions).

• Courtship behavior helps individuals locate breeding sites and identify potential mates.

• Salamanders rely mostly on smell and vision clues in courtship and mating.

• Anurans, especially males, rely on sound.


• Sound production is mainly used in male anurans.• These sounds will attract females and let other males know

that a certain territory is taken. • These sounds are species specific. • Females respond by making the same call that indicates

her willingness to mate. • Release calls let a frog know that the partner is incapable of

reproducing. • Distress calls are associated with pain or with being seized

by a predator. • Sound production in frogs comes from the larynx and vocal

cords. • Males also have a vocal sac.


• Parental care increases the chance of any one egg surviving but requires a lot of energy from the parent.

• The most common form of care is protecting the egg clutch, usually done by either parent.

• Maternal care occurs in species with internal fertilization (salamanders and caecilians), and paternal care may occur in species with external fertilization (anurans).

• This care may involve providing oxygen to aquatic eggs, cleaning and/or moistening land eggs, protecting eggs from predators, or removing dead or infected eggs.


• Eggs may be transported if development occurs on land.

• Females of genus Pipa carry eggs on their back. • Rheobatrachus females grow tadpoles in their

stomach, and the young emerge from the female’s mouth.


• Metamorphosis is a series of abrupt structural, physiological, and behavior changes that transform a larva into an adult.

• Several conditions influence the time required for metamorphosis, such as crowding and food availability.

• Most changes, however, are controlled by hormones.


• Caecilian and salamander changes are minimal. • They develop reproductive structures, lose their

gills and caudal fin. • Anurans have dramatic changes. • Limbs and lungs develop, tail is reabsorbed, skin

thickens, and noticeable changes in the head and digestive tract occur.

AMPHIBIANS IN PERIL

• Frogs and salamanders are disappearing at an alarming rate—and no one knows exactly why.

• Local events can affect populations—clear-cutting forests, mining, drilling, and urban sprawl destroy habitats.

AMPHIBIANS IN PERIL

• Two other factors are thought to be affecting amphibians—acid deposits and UV radiation.

• Embryos are very susceptible to changes in the pH of their water.

• UV radiation also kills eggs and embryos.

amphibian notes

Documents

water amphibians

skin color

movementamphibian skin

skin moist

true tongue

tongue sticky

waterdwelling animals

jaw structure