Vision and the skin camouflage reactions of Ambystoma larvae: the effects of eye transplants and brain lesions.
Salamander larvae typically adapt their dermal melanophores to achieve camouflage, and it has been known for some time that removal of the eyes abolishes the response. Here we survey the contribution of the optic system to the bright and dark camouflage reactions and report that: the stimulus depends on an interaction between the direct and reflected light; an eye mounted atop the head and oriented vertically tended not to support camouflage, even though the animal responded to visual cues and learned a vision-dependent task; deviating the transplanted eye off the vertical axis enhanced the recovery of camouflage reactions; amputating or reorienting the telencephalon, epithalamus, pretectum or tectum did not abolish either camouflage reaction whereas lesions of the ventral optic pathway blocked brightening; transection near the midbrain-hindbrain junction--well posterior to known optic terminals--retarded the dark reaction; when the latter lesion was combined with disconnection of the telencephalon and epithalamus, contrary to predictions from the lesions executed separately, the animals lost the bright reaction; the hypophysis is necessary for darkening, but the organ supported this reaction even though detached, displaced or reoriented; and the pineal body was not essential for the grosser aspects of camouflage in Ambystoma larvae but may play an adjunctive role in fine tuning.
D000557:Ambystoma / Q000502:physiology*; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D005123:Eye / Q000637:transplantation*; D007814:Larva / Q000502:physiology; D008029:Lighting; D008547:Melanophores / Q000502:physiology; D008866:Microsurgery; D009900:Optic Nerve / Q000502:physiology; D010902:Pituitary Gland / Q000502:physiology; D012880:Skin Pigmentation; D013477:Superior Colliculi / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology