Does temperature affect dimorphic reproduction in benthic foraminifera? A culture experiment on Rosalina leei

The possible effects of environmental factors on the dimorphic mode of reproduction in benthic foraminifera have been reported in the literature. Published observations based on field samples have indicated an inverse relationship between the ratio of microspheric/megalospheric forms and temperature or salinity. These findings imply their potential use in palaeoclimatic studies. Two experiments were conducted on the benthic foraminifera Rosalina leei (Hedley and Wakefield) collected from Vineyard Sound near Woods Hole, Massachusetts, USA. In the first experiment, a large number of specimens were maintained at four different temperatures (5, 15, 20 and 25°C) and observations were made on the frequency of pairing (an indication of sexual activity). The percentage of pairs formed was directly related to the temperature, i.e. 0 pairs at 5°C to 19.3% pairs at 25°C. In the second experiment, paired and unpaired specimens were maintained separately at three different temperatures (15, 20 and 25°C). Nearly one-half of the unpaired specimens reproduced at all three temperatures, while none of the paired specimens reproduced. Type and frequency of feeding were common in all the experiments. We surmised that dimorphic reproduction in R. leei requires a different environment.