Effetto della temperatura sul ciclo biologico e la riproduzione di due popolazioni di Dinophilus gyrociliatus (Polychaeta: Dinophilidae).

The effects of temperature on life history characteristics of two populations from Ravenna and Genoa of the polychaete Dinophilus gyrociliatus were investigated. The tested temperatures (6, 12, 18, 24 and 30°C) are upper and lower the range of temperature in the natural environment. In the studied populations there are broad differences in timing of development and reproduction. The duration of the various phases of the biological cycle is very similar in both populations, but the Adriatic strain exhibits greater tolerance of low temperatures, slower development rate and lower development threshold temperature in respect of the Genoa population. Temperature and geographical origin have also strong effects on reproductive characteristics. The size of both male and female eggs varies in relation to temperature, the smallest female eggs generally being laid at the higher temperatures. Comparison of the two populations at the same temperature reveals considerable differences in the characteristics of the life history between the two populations. It is very likely that the extreme selectivity of the harbour environments has favoured the fragmentation of the species into genetically differentiated populations that have adapted to the conditions prevailing in the different localities.