Effects of Constant and Cyclic Temperatures at Different Salinity Levels on Survival and Reproduction in Dinophilus Gyrociliatus (Polychaeta: Dinophilidae)
Abstract:The effects of temperature and salinity on survival and fecundity of the polychaete Dinophilus gyrociliatus was investigated in 108 temperature/salinity combinations. Seven constant temperatures from 10° to 35°C were employed as well as four kinds of 24-h temperature cycles in all of which the temperature difference was 5°C between high and low levels. The cycles ranged from 20–25° to 30–35°C with varying time spent at high and low temperature levels. Population parameters were obtained from a static life table. D. gyrociliatus had a short life span of about 10 weeks. The time from zygote to reproduction was 11 days. Peak reproduction occurred in the fourth week. An intrinsic rate of increase, r = 1.2, was observed at 22°C and 35‰ salinity that was close to optimum conditions observed in the temperature/salinity trials. At temperatures ≤28°C the fecundity at a salinity of 35‰ was better than at 30‰; at higher temperatures 30‰ yielded the highest fecundity. The same change was observed at constant temperatures and salinities above and below the broad optimum of 30 + 35‰. Up to about 22°C the fecundity at high salinities (40 + 45‰) was better than at low salinities (20 + 25‰); at higher temperatures these relations were reversed. Cyclic temperatures stimulated fecundity relative to comparable constant temperatures. The cycle that came closest to natural temperature fluctuations stimulated fecundity more than other temperature cycles. Cyclic temperatures had no similar effect on survival. At optimum salinities and a temperature range of 20–28°C, a trade-off (“cost of reproduction”) was observed between survival and fecundity. At cyclic temperatures near the upper thermal limit an increase of the time spent at the high temperature of the cycle negatively affected both survival and fecundity.
Document Type: Research Article
Publication date: March 1, 1991
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