Effect of temperature and light on egg hatching of Sympetrum frequens
2006
Jinguji, H,(Akita Prefectural Univ., Ohgata (Japan). Faculty of Bioresource Sciences) | Tsuyuzaki, H. | Sato, T.
The aim of the present study is to obtain quantitative information on egg hatching with respect to temperature and light to clarify the effect of cultivation methods on Sympetrum frequens. Eggs of the spcies were collected on October in 2004 at Akita prefecture located at north of Japan, and the eggs had been laid on soil surface of paddy field till April in 2005. The eggs (3 trays with 30 eggs each) were held under four constant temperature (5 deg C, l0 deg C, 15 deg C and 20 deg C) with a photoperiod (L:D, 14:l0; relative light intensity, 3000 Lux) and 20 deg C in the dark. Cumulative hatching percentage under 20 deg C with and without light was 98.9%, and 95.6%, respectively. The percentage under 15 deg C, 10 deg C and 5 deg C were 95.6%, 88.9% and 84.4%, respectively. These results suggest that the dragonfly do not require light for hatching and hatching is suppressed by low temperature such as 5 deg C. Mean hatching days with light under 20 deg C, 15 deg C, l0 deg C and 5 deg C were 3.5, 4.8, 1l.6 and 41.0 respectively. Reciprocal of variance of hatching day under these conditions were 0.15, 0.09, 0.03 and 0.02 respectively. These results indicate that the eggs under 20 deg C and 15 deg C hatched faster and more uniformly than those under l0 deg C and 5 deg C. Based on these results, theoretical lower thermal threshold and thermal constants for hatching were estimated at 4.9 deg C and 54.6 degree-days. According to these results, the effects of cultivation methods on hatching of this species were discussed.
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