Out of the Pond: Frog Resources and Information
Author: Terry Newhaven
Frogs are tailless amphibians with a short body, protruding eyes, and webbed toes. Being amphibians, frogs can survive in water and land. Let’s look at these fascinating animals in more detail.
A frog’s habitat is usually humid and watery. Its skin absorbs oxygen directly from the atmosphere. Frogs lay eggs in ponds or lakes so that the tadpoles can develop in water. After metamorphosis, tadpoles develop into young adults. At this point, they can move out of the water or continue staying in the water. Frogs feed on invertebrates like annelids, arthrodpods, and gastropods. A fully developed frog can move out to the land because it can breathe through its lungs. There are more than 5000 species of frogs found in different regions of world. Most of the species are found in tropical rainforests where water is available for breeding. There are also some frogs that have adapted to cold climatic conditions such as the Wood frog which is found in the arctic region. In winters, the Wood frog buries itself in the ground.
Frogs have legs which are more suitable for jumping than walking. A frog can breathe through its skin. Frogs have a short vertebrae column with less than 10 free vertebrae. The size of a frog ranges from 10 mm to 300 mm. The skin can be made of loose connective tissues or it can be smooth. The eyelid has a membrane which is mostly transparent, enabling the frog to see in water. Frogs have a sticky elastic tongue which can be flicked out towards a prey, catching it at a great speed.
The feet of frog are specially constituted to enable superior jumping abilities. In this way, frogs can catch their prey easily. The webs of the toe are developed depending on how much the frogs live in water. The webbed toes make them excellent swimmers. Fully developed toes are found in African Dwarf frogs while White Tree frogs have one half or a quarter webs.
Frogs are exceptional jumpers. Some species can leap more than 50 times their body length. The musculo-skeletal of the frogs is developed to enable exceptional jumping abilities. The fibula and tarsal bones are joined to form a single bone. The ulna and radius bones are found in the forelimb to handle pressure upon landing.
The skin of the frog enables respiration as it contains blood vessels close to the surface. If the frog stays under water, it can take oxygen directly from the blood vessels. On land, the frog can breathe through its lungs. Frogs breathe through nostrils but there are no ribs to support the lungs. Instead, the throat puffs air into the lungs.
Sometimes, permeability of the skin causes water loss. Some frogs possess the capability to camouflage and change their skin color. The Tree frogs can change their skin color from brown to green. Some frogs have smooth skin which resembles leaves.
There are also frogs with poisons. An example is the Poison Dart frog. The poison is stored in the parotoid gland which is located at the top of head, behind the eyes.
All frogs belong to the order Anura. It includes the three suborders Archaeobatrachia, Mesobatrachia, and Neobatrachia. Archaeobatrachia is a family of four primitive frogs. Mesobatrachia is a family of five species of frogs including the evolutionary intermediate frogs.
Neobatrachians resemble modern frogs as they have a palatine bone and the upper jaw is braced to the Neurocranium. There are 24 species of frogs which are commonly found in various parts of the world. The suborder is further categorized into Hyloidea and Ranoidea. There are also certain hybridized frogs which belong to the order Anura. An example of the hybridized frog is the Edible frog, which is a hybrid of Marsh frog and Pool frog.
The skin of a frog should remain moist to enable it to breathe but it also raises the risk of coming in contact with environmental toxins. Across the world, the population of frogs is declining. Calculations suggest that the current extinction rate is around 211 times the prior estimates. A 2010 report released by the IUCN Red List indicted that there are 486 species of amphibians which are “critically endangered.”
Fungus Batrachochytrium dendrobatidis is an aquatic fungus which has been threatening the population of frogs. It infects frogs through skin and causes diseases. The World Organization for Animal Health has imposed screening on amphibians to prevent the spreading of this killer fungus. Pollution has also been causing deformities in frogs. It can cause malformed eyes or extra limbs, and it has many other effects such as altering the central nervous system. Herbicides have raised the mortality rate of tadpoles and frogs exposed to certain chemicals suffer from deformities of reproductive organs which has prevented growth in the population. The project called The Panama Amphibian Rescue and Conservation Project deals with the risk of chytridiomycosis, among other concerns. The Amphibian Conservation Alliance, the Amphibian Ark, and the World Wildlife Fund are some groups committed to educate people and create breeding programs for frogs.
- Newsletters: Archive of publications by Frog Watch USA.
- Education: A number of resources for teachers consisting of activities and media support.
- Frogs on the Net: Great resource center on frogs by Hamline University.
- Frog & Fish: Extensive list of frog and fish resources.
Fun Frog Resources
Popular Pond Supplies