Celestial orientation and setting of the biological clock in the southern cricket frog Acris gryllus can be cued by light stimuli received by extraoptic receptors in the brain. These extraoptic photoreceptors may also be used in learning new orientational directions. A mechanism for a light-activated biological clock is discussed.

Animals↗

PubMed1970

Possible selective mechanisms in the development of insecticide-resistant fish.

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Animals↗

PubMed1967

Newts: sun-compass orientation.

Rough-skinned newts, captured from breeding ponds, oriented on courses that would have intersected the familiar shorelines at right angles, when released in a circular arena on land under the sun or moon. Pondward migrants oriented similarly. Reorientation failed under complete cloud cover and after 7 days of darkness in an environmental chamber, but persisted in newts whose eyes were excised and in those displaced more than 27 kilometers in darkness. Both normal and blind animals compensated for displacement in sunshine. Preliminary evidence suggests that alternative light receptors in blinded animals may be associated with the optic tectum. No evidence of olfactory guidance was observed.

Adaptation, Biological↗

PubMed1967

Sun compass orientation of the northern cricket frog, Acris crepitans.

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Animals↗