Effects of temperature, salinity and food level on the life history traits of the marine rotifer Synchaera cecilia valentina, n. subsp.

Abstract

A strain of the marine rotifer Synchaeta cecilia valentina, n. subsp., isolated from the Hondo of Elche Spanish Mediterranean coastal lagoon at 22%o salinity, was cultured in the laboratory in 20 ml test tubes and fed with the alga Tetraselmis suecica. The effect of two temperatures (20 and 24°C), four salinities (20,25,30 and 37%o) and two food levels (15 000 and 25 000 cells ml-1) on the life history traits of this rotifer were studied in life tables performed with replicated individual cultures. Temper- ature and salinity had a significant negative effect (P < 0.001) on the average lifespan (LS) and on the number of offspring per female (RQ). The effect of food level on LS is unclear, whereas R$ is greater at 20°C with the lower concentration of algae and at 24°C with the higher algal concentration. The maximum values of LS and RQ, 5.6 days and 9.2 offspring per female, respectively, were recorded at 20°C, 25%o salinity and low food concentration. There is also a clear negative effect on the intrinsic growth rate (r) due to salinity. The effect of temperature depends on the food level and, as occurs with RQ, the maximum values of r occur with the lower algal concentration at 20°C, whereas at 24°C they are obtained with the higher algal concentration. These r values, from 1.04 to 1.10 day-', were reached at 24°C, salinities of 20-25%o and with high food concentration.