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Effect of photoperiod on testicular function in blinded and non‐blinded marbled newts, Triturus marmoratus (caudata, salamandridae)
Author(s) -
Fraile Benito,
Paniagua Ricardo,
Rodriguez Marina C.,
Saez Francisco José
Publication year - 1989
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1052000205
Subject(s) - biology , photoperiodism , darkness , salamandridae , caudata , triturus , metamorphosis , testicle , zoology , anatomy , ecology , botany , larva
Adult male marbled newts ( Triturus marmoratus ) were collected at the beginning of the spermatogenetic period and exposed to different photoperiods (natural photoperiod with progressively increasing daylengths, total darkness, 8L:16D, 12L:12D, 16L:8D, and continuous light) for 3 months at 20°C. To evaluate the effect of photoperiodic input via pineal gland photoreceptors, two additional groups of newts were blinded by a non‐aggressive method (an elastic rubber cap was adjusted to the head to cover the eyes but not the pineal photoreceptors). These animals were exposed either to the natural photoperiod or to 12 hr of light per day. Quantitative histologic studies on testicular development and germ‐cell volume revealed no significant differences between non‐blinded and blinded animals. Testicular size and germ‐cell development increased in the following order: total darkness, constant light, 8L:12D, natural photoperiod, 12L:12D, and 16L:8D. These results suggest that (1) long photoperiods enhance testicular development, whereas short photoperiods or an environment of continuous light have the opposite effects and (2) the effect of photoperiods on testicular function in newts is independent of the ocular photoreceptors.