Extraretinal photoreception in lacertilian tail regeneration: The lateral eyes are not involved in photoperiodic photoreception in the Gekkonid lizard,Hemidactylus flaviviridis
✍ Scribed by Ndukuba, Patrick I. ;Ramachandran, A. V.
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 658 KB
- Volume
- 248
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
The tail of the Gekkonid lizard, Hemidactylus Pauiviridis was autotomized and subjected to eight different photoperiodic lengths during the period of tail regeneration, namely, 1) continuous light (LL: LD 24:O) ofhigh intensity; 2) continuous light (LL: LD 24:O) of low intensity; 3) continuous (total) darkness (DD: LD 0:24); 4) normal light and darkness (NLD: LD 12:12); 5) 18 hours light and 6 hours darkness (LD 18:6); 6) 6 hours light and 18 hours darkness (LD 6:18); 7) 16 hours light and 8 hours darkness (LD 16%); and 8) 8 hours light and 16 hours darkness (LD 8:16). In an attempt to determine the potential contribution of the lateral eyes, or vision, on photoperiodic photoreception in H. flaviviridis during the process of tail regeneration, some animals had both the lateral eyes surgically removed (bilateral orbital enucleation) and the enucleated animals were exposed, along with the normal (unoperated) ones, to the various photoperiodic regimes. Our observations demonstrate that blinded Hemidactylus regenerate their lost (autotomized) tails similar to their sighted (unoperated) counterparts and under LL, LD 18:6, and LD 163 better than sighted (unoperated) animals exposed t o DD and NLD experimental lighting regimens. We, therefore, conclude that photoperiodic control of regeneration in the Gekkonid lizard, H. flaviviridis is mediated entirely by extraretinal photoreceptor(s) situated in the brain region of the head. Having established that the lateral eyes, or retinae, do not participate in photoperiodically significant photoreception and under the presumption that an extraretinal light receptor(s) may be involved, we discuss the pineal organ as the possible transmitter of the photic stimulus in these animals.