Francisco Jose Saez

Effects of temperature and photoperiod on the Gambusia affinis holbrooki testis during the spermatogenesis period

and spermatozoa than the initial controls. The testes of group II fish were similar to those of the initial controls except for an increased volume of primary spermatocytes. Testes in groups III and IV were similar to those of the initial controls except for increased volumes of primary and secondary spermatogonia. These results suggest that mild temperatures are necessary and sufficient for spermatocyte formation. Mild temperatures are also necessary, but not sufficient, for meiosis and spermiogenesis, because these processes also require long photoperiods.

Effect of photoperiod on testicular function in blinded and non-blinded marbled newts, Triturus marmoratus (caudata, salamandridae)

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.

Effects of Photoperiod and Temperature on Spermiogenesis in Marbeled Newts (Triturus marmoratus marmoratus)

We investigated the effects of photoperiod and temperature on spermiogenesis in marbled newts (Triturus marmoratus marmoratus). Males showing testicular development up to round spermatids were allotted to four groups. Each of the groups was exposed to one of the following photoperiods for 3 mo: natural daylength photoperiod, total darkness, 8L:16D, and 16L:8D. Within each group, half of the newts were maintained at a temperature of 20 C and the other half at 30 C. We then performed quantitative histological studies on testicular development and germ cell volume per testis at the end of the experiment. Newts maintained at 20 C showed increased testicular weight and germ cell development up to complete spermatogenesis. No significant differences between photoperiods were found. However, the newts maintained at 30 C showed a similar testicular weight and germ cell development to those observed at the beginning of the experiment. This lack of spermiogenesis was observed under all photoperiods regimes. Our results suggest that: 1) photoperiod has no effect on spermiogenesis; and 2) high temperatures (<30 C) inhibit spermiogenesis regardless of photoperiods.

Effects of moderately high temperature on the testis of the marbled newt, Triturus marmoratus

In order to investigate the effects of a moderately high temperature on testicular function in urodele amphibians, marbled newts (Triturus marmoratus) wcrc collected from thc field and killed at the end of each period of their spermategenetic cyle; these were: germ cell proliferation up to round spermatids (June), spermiogenesis (September), and the early (December) and late (March) periods of testicular quiescence. The testes of these animals were studied by light microscopy and compared with those of newts which were killed at the same dates and had been exposed previously to moderately high temperatures (30°C) for 1 or 3 months. The results of quantitative studies indicatc that: (1) exposure to high temperatures (for 3 months but not for 1 month) induces germ cell development up to round spermatids during the early phase of testicular quiescence; (2) this temperature has no effect in the period of germ cell proliferation up to round spermatids; and (3) high temperatures inhibit (exposure for 3 months) or decrease (exposure for I month) spermiogenesis during the spermiogenesis period.