The Wood Frog – A Biological Breakthrough

By James Remington Orozco Newton

Introduction

Many people have seen science fiction movies, about people being frozen in a block ice and then being thawed out in the future. But could this truly happen? Could we really freeze are selves in a block of ice and awake a thousand years later? Scientists have been puzzled with this question for years. Until recently, a new species of frog has been discovered that may yield the answer. The name of this new species is the wood frog or (Rana sylvatica).

Freeze tolerance allows the wood frog to live in cold climates as far north as the Arctic Circle. But can be also found as far south as Georgia. The problem is that, if a wood frogs body temperature dropped below 20° Fahrenheit, the wood frog wouldn’t be able to survive. But luckily for the

frog, snow pack and other natural insulators found in the wild can keep it warm during its winter hibernation. The key to the survival of the wood frog is a natural antifreeze known as Glucose, which stops the frogs’ cells from excessive dehydration during the process.

In the process two-thirds of the wood frogs body water freezes and the rest remains liquid. The water that remains is mostly inside cells, as to keep the cells hydrated well the process is in work. Next glucose is produced by the liver, which causes the freezing point of the amphibians’ tissues to lower. This is in the same nature as ammonia lowering a cars’ windshield wiper fluid, which contains mostly just water. The newly secreted glucose then limits ice formation in the frogs’ body and binds water molecules inside the frogs many cells. This slows down damage caused by cell shrinkage, which is very common with freezing. “Normally under those freezing conditions, without glucose, the cells would dehydrate completely” states Boris Rubinsky, who’s an engineer at the University of California at Berkeley.

Physical Features

The length of an adult wood frog ranges from 51 millimeters (2.0 in) to 70 millimeters (2.8 in), females being larger than males. The color of adult wood frogs ranges from either being brown, tan, or rust colored and usually they have a dark eye mask. Individual wood frogs are capable of varying their color. The undersides of wood frogs are pale with either a yellow or green cast. There isn’t any similar species in North America to the wood frog, so if you see a small brown frog with a dark mask in the woods, than it’s a wood frog.

Feeding Adult wood frogs eat a variety of small invertebrates off the forest-floor. While the omnivorous tadpoles feed on algae, plant detritus, as well as eating the eggs and larvae of other amphibians. Including their own species.

The wood frog’s feeding pattern is triggered by prey movement and consists of a body lunge that terminates with the frog’s mouth open and an extension of the tongue onto the prey. This is similar to most other ranids. The tongue is attached to the floor of the mouth and is flat when the frogs’ mouth is closed. This helps one to understand that in the feeding strike, the tongue is swung forward as though it is on a hinge. This makes sure that,

some portion of the normally dorsal and posterior tongue surface makes contact with the prey.

Geographic Range and Habitat The wood frog ranges from northern Georgia and northeastern Canada in the east to Alaska and southern British Columbia in the west. It is also found in Medicine Bow National Forest, as wood frogs are forest-dwelling ranids that breed primarily in ephemeral and freshwater wetlands. Long-distance migration is an important part in the life history of these frogs. Wood frog breeding pools range hundreds of miles away from their neighboring freshwater swamp, moist ravines and or upland habitats. Therefore, conservation of these ranids requires multiple habitats at spatial scales.

Wood frogs breed normally in ephemeral pools, rather than permanent bodies of water. This is to protect the adult and their offspring from predatory animals such as fish and other predators. Adult wood frogs come out of hibernation near the beginning of spring, and then migrate to nearby pools. There the males emit duck-like mating calls and the females deposit eggs in floating masses. These eggs are often aggregated with those of other females in rafts. An advantage is formed to breeding first, as the clutches of eggs closes to the center of the raft absorb heat and develop faster than those on the outside. But if pools dry before the tadpoles have metamorphosis into

froglets, the tadpoles die. This supports the risk counterbalancing the anti-predator protection of ephemeral pools. By breeding in early spring, however, it increases the chances of the wood frogs offspring to metamorphosis before the vernal pools dry. About 20% of the juveniles will disperse, permanently leaving their natal pools. While the majority return to breed.

Adult wood frogs spend their summers in moist woodlands forested swamps, ravines, or bogs. While during the fall, the ranids leave their summer habitats and move to nearby uplands. Some may remain in moist areas until winter is over. Then, after winter fully grown wood frogs migrate to thawed vernal pools in the spring.

Conclusion When will we start freezing ourselves in ice and waiting for the future? Can these frogs really lead us to such great discoveries? I don’t know, but what I do know is that the wood frog can do all I have said. And for that reason I end this essay. But don’t worry there will be plenty more information in the future and new discoveries just waiting to be found.