Homing amphibians

Amphibians have been shown to discriminate the odor of their home pond from other mud or water odors (Forester and Wisnieski 1991 Grubb 1973, 1976 McGregor and Teska 1989 Ogurtsov and Bastakov 2001). In a two-way choice apparatus, an animal chooses between mud or water from the home pond and some control mud or water from a different source. This experiment tests the ability to home by chemical cues, one aspect of orientation in space use newts, frogs or toads, depending on animals available. 

Zasloff is quick to note that nobody has a clue how a giant squid or an octopus—which have neither antibodies nor white blood cells called lymphocytes—avoids becoming consumed by microbes Over the years, he and his colleagues have uncovered many frog-made peptides that possess potent microbe-killing properties. Such a chemical defense system operates by virtue of the peptides ability to poke holes in the cell membranes that serve to protect bacteria from the outside world. In addition to the peptides, scientists including Zasloff have found hundreds of other types of molecules called alkaloids in amphibian skin. When inside cells, many alkaloids home in on structures called ion channels—tunnel-like assemblies through which important electrolytes pass. These are key cellular fixtures,... 

CHEMORECEPTION IN THE HOMING AND ORIENTATION BEHAVIOR OF AMPHIBIANS AND REPTILES, WITH SPECIAL REFERENCE TO SEA TURTLES... 

One could broadly define chemical orientation to include food-finding and reproductive behaviors where chemoreception is involved however, we have chosen not to discuss these better known areas of amphibian and reptile behavior. On the other hand, where semiochemicals or conspecific habitat marking appear to have a function in home range factors or homing to a specific site, we have chosen to include the available data in this discussion. 

It is our general prejudice that the proportion of chemical sensing within the total sensory capabilities is greater in aquatic and semi-aquatic animals than in more terrestrial forms where vision in particular dominates. Thus it was somewhat of a surprise to us when we were unable to locate many recent publications on orientation and homing in the more aquatic amphibians. While our finding of an apparent lack of research on amphibians may be partially due to our own admitted historical bias towards the reptilian literature, we also believe that there indeed has been relatively less work on amphibians. It appears that since the important pioneering studies of Twitty (summarized in Twitty, 1966), very few scientists have had an interest in this area. 

Researchers have not found it easy to design experiments that clearly indicate chemoreception to be the primary orientation system in amphibians and reptiles. In many cases (e.g., newts such as Taricha or chelonlans such Clemmys or Chelonia) chemoreception has been singled out as important for homing more by a process of elimination of the other senses than by sound laboratory and field research. 

Many species of amphibians return to the same sites each year to breed (recently reviewed by Sinsch 1990), and several studies have examined the cues used in homing and orientation. To examine the role of cues used in orientation, investigators often have used experiments where amphibians are transported from a home area (e.g., breeding pond) to an area away from where they were captured. They are then monitored to see if they can successfully home back to or orient toward their capture site after one or more of their senses are obliterated. In other studies, investigators have examined the role of chemical cues in amphibian orientation in laboratory test chambers. The basic methods used in these studies are reviewed below. 

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