# Adventist Youth Honors Answer Book/Nature/Amphibians

Amphibians :
| Nature General Conference See also Amphibians - Advanced | Skill Level 1 |
| Nature General Conference See also Amphibians - Advanced | Year of Introduction: 1945 |

## 1. What are the characteristics of amphibians?

Amphibians live half of their lives in water and half on land. They are cold-blooded vertebrates. Amphibians are able to breathe through their skin, making them very sensitive to anything they come in contact with, including human hands. When observing amphibians, one should never touch them. Amphibians have toes rather than claws.

## 2. Name the two main orders of amphibia and tell how to distinguish between them.
### Order Anura (frogs and toads)

    Adult frogs and toads are characterized by long hind legs, a short body, webbed digits, protruding eyes and the absence of a tail. Most have a semi-aquatic lifestyle, but move easily on land by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes; and their larvae, called tadpoles, have gills and develop in water.

### Order Caudata (newts and salamanders)

    Cuadata have slender bodies, short legs, and long tails. The moist skin of the amphibians fits them to habitats either near water or under some protection on moist ground, usually in a forest. Some species are aquatic throughout life, some take to the water intermittently, and some are entirely terrestrial as adults. Salamanders superficially resemble lizards, but are easily distinguished by their lack of scales. They are capable of regenerating lost limbs.

## 3. Distinguish between toads and frogs.

The use of the common names "frog" and "toad" has no taxonomic justification. From a taxonomic perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads". The use of the term "frog" in common names usually refers to species that are aquatic or semi-aquatic with smooth or moist skins, and the term "toad" generally refers to species that tend to be terrestrial with dry, warty skin. An exception is the Fire-bellied toad (Bombina bombina): while its skin is slightly warty, it prefers a watery habitat.

## 4. How do amphibians protect themselves?

The first line of defense for amphibians is to not be seen by a potential predator. The small size and coloration of many species help in this regard, but sometimes, rather than blending in, frogs are very brightly colored. The coloration in this case serves as a warning, for these frogs are poisonous.
Many frogs contain mild toxins that make them distasteful to potential predators. For example, all toads have large poison glands—the parotid glands—located behind the eyes on the top of the head. Some frogs, such as some poison dart frogs, are especially toxic.
Salamanders have the ability to detach their tails at will. When a predator captures a salamander by the tail, the salamander detaches its tail and escapes. The tail regenerates or grows back.

## Frogs

The life cycle of frogs, like that of other amphibians, consists of four main stages: egg, tadpole, metamorphosis and adult. The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise to a variety of breeding behaviours that include the well-known mating calls used by the males of most species to attract females to the bodies of water that they have chosen for breeding. Some frogs also look after their eggs—and in some cases even the tadpoles—for some time after laying.
The life cycle of a frog starts with an egg. Eggs are generally laid in water, and an individual female may lay egg masses containing thousands of eggs. While the length of the egg stage depends on the species and environmental conditions, aquatic eggs generally hatch within one week.
Some frogs do not have the tadpole stage going from egg to adult shape e.g. New Zealand's native frogs (pepeketua) belong to the genus Leiopelma. Eggs hatch and continue life as tadpoles (occasionally known as polliwogs). Tadpoles are aquatic, lack front and hind legs, and have gills for breathing and tails with fins for swimming. Tadpoles are typically herbivorous, feeding mostly on algae, including diatoms that are filtered from the water through the gills. Some species are carnivorous at the tadpole stage, eating insects, smaller tadpoles and fish. The tadpole stage may be as short as a week, or tadpoles may overwinter and metamorphosis the following year in some species, such as the Midwife toad (Alytes obstetricans) and the Common Spadefoot (Pelobates fuscus).
At the end of the tadpole stage, frogs undergo metamorphosis, in which they transition into adult form. Metamorphosis involves a dramatic transformation of body shape and function, as tadpoles develop hind legs and then front legs, lose their gills and develop lungs. Their intestines shorten as they shift from an herbivorous to a carnivorous diet. The final stage of development from froglet to adult frog involves the loss of the tail.
After metamorphosis, young adults may leave the water and disperse into terrestrial habitats, or continue to live in the aquatic habitat as adults. Almost all species of frogs are carnivores as adults, eating invertebrates such as spiders, insects, snails, and slugs. A few of the larger species may eat prey such as small mammals, fish and smaller frogs. Some frogs use their sticky tongues to catch fast-moving prey, while others capture their prey and force it into their mouths with their hands. However, there are a very few species of frogs that primarily eat plants. Adult frogs are themselves preyed upon by birds, large fish, snakes, otters, foxes, badgers, coatis, and other animals.

## 7. Explain the economic value of amphibians.

Amphibians are insect eaters, so they are very valuable for controlling mosquito populations. They are also the preferred dinner for several mammal, bird, fish, and reptile species.
Amphibians are valuable for medical research. They are raised and sold to research institutions.
The larvae of newts and salamanders are sold as fish bait.
Amphibians are closely monitored by ecologists, because they are among the first animals affected by environmental problems such as pollution and the destruction of the ozone layer.

## 8. Where do toads spend the winter or dry season?

Toads burrow below the frost line and hibernate for the winter. Plant matter actually generates a bit of heat as it decays, so toads prefer areas with plenty of leaf litter and fallen logs.

## 9. Identify two species of frogs by their sound or imitate the sounds of two different species of frogs.

Here are the calls of three frogs.
| European toad (Bufo bufo) | Spring Peeper (Pseudacris crucifer) | Big-eyed Tree Frog (Leptopelis vermiculatus) |
For more frog calls, Smithsonian Folkways Recordings has several frog calls available on CD or for download.

## 10. How do frogs and toads sing? What makes the noise so loud?

Frogs call by passing air through the larynx in the throat. In most calling frogs, the sound is amplified by one or more vocal sacs, membranes of skin under the throat or on the corner of the mouth that bulge out during the amplification of the call.
Some frogs lack vocal sacs, but these species can still produce a loud call. Their mouths are enlarged and dome-shaped, acting as a resonance chamber that amplifies their call. The body of a guitar does much the same thing, having a large hollow section that causes the sound to resonate inside before escaping to the outside atmosphere.

## 11. Do one of the following
### IMPORTANT

    In the 1990's, amphibian populations in the United States and Canada began a precipitous and mysterious decline. Many frogs were discovered in Minnesota with unexplained deformities, including extra limbs, missing limbs, deformed limbs, and missing eyes. As a result, many species of amphibians are now protected by state and federal laws. When observing wild amphibians, it is extremely important that they not be handled. Doing so can spread disease to these creatures, causing further decline. Before venturing out, make sure your Pathfinders understand and appreciate the danger facing amphibians today. Do not allow your group to capture or otherwise harass them, and do not destroy their environment. Rather than pursuing the two options (a and b) listed for this requirement, it may be wiser to substitute an alternate requirement. One possibility is to have your Pathfinders research the amphibian population crash.

### a. Observe a toad in your yard or neighborhood to find out.(1) Where and when it sleeps,(2) When it leaves its home for food,(3) How fast it can travel,(4) How far it can jump, and as many other interesting things as you can find out about it, and write an essay covering the details requested in the first section of this question.

It is recommended that instead of investigating wild amphibians, the student should research them using other available resources, including the Internet, books, and encyclopedias. It is recognized that observing them in the wild is by far more fascinating, but it also carries the potential to do great harm to the amphibian population. See the notes in section b for more details.

### b. Hatch some amphibian eggs and watch them through their growth cycle and write an essay covering the details.

Frog eggs can be purchased from http://www.nilesbio.com/subcat367.html - but only in the spring.
According to Field Guide of Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa, a publication of the U.S. Geological Survey (USGS), "State and federal laws protect amphibians from exploitation. Collection permits are required from the appropriate state or federal authorities before capturing, handling, or collecting amphibians."
It is therefore recommended that you not attempt to collect amphibian eggs on your own. You can download this book as a PDF from the page cited above. Even if you do not live in Minnesota, Wisconsin, or Iowa, the species covered in this book may be indigenous to your area.
The USGS publication further states, "To prevent the spread of disease to native populations, any frogs or salamanders you raise should not be released back into the environment. Lab-raised amphibians can be anesthetized and euthanized with benzocaine or tricaine methanesulfonate (MS 222, Green 2001). If you anticipate difficulty complying with this guidance, you should not undertake raising larvae in captivity."

## References

* Wikipedia article on frogs
* Wikipedia article on salamanders
* http://www.wnrmag.com/stories/1996/apr96/frog.htm
* http://www.californiaherps.com/index.html