The intriguing relationship between coiling direction and reproductive mode in benthic foraminifera

Abstract

Changes in coiling direction in foraminifera have been used extensively as proxy data for paleoclimates. However, most of the studies centred around planktonic foraminifera, and various causes (including reproductive mode) were suggested for coiling direction changes. The relationship between mode of reproduction and coiling directions in benthic foraminifera is explored. Benthic foraminiferal species Cavarotalia annectens (Paarker & Jones) in 58 samples obtained from a core off Karwar, west coast of India, show sinistral and dextral coiling and also dimorphic (sexual and asexual) mode of reproduction. Proloculus size has been taken as indicator of change in reproductive behaviour. Results indicate that mean proloculus size and ratios of dextral/sinistral forms are inversely proportional (r = 0.49) and relationship is significant at 95% level of confidence (r = 0.29). It is therefore proposed that (1) coiling direction in benthic foraminifera are related to mode of reproduction and (2) forms with smaller proloculus have a preference to coil dextrally. This study may have significant consequences for interpretation of paleoclimatic records from shallow regions. However, these inferences need to be confirmed by additional culture and faunal studies with other species of benthic foraminifera