INTRASPECIFIC VARIABILITY IN ANTARCTIC TINTINNIDS - THE CYMATOCYLIS-AFFINIS CONVALLARIA SPECIES GROUP

Analyses of the morphometry of 630 loricae belonging to the described species Cymatocylis affinis and Cymatocylis convallaria retrieved from 21 samples collected in the Weddel Sea (6O-73°S) strongly suggest that both taxa, including the four formae into which C.affinis was originally divided, are members of a single species. The only feature which varies significantly and consistently among the samples surveyed is the total length of the lorica, lowest average lengths being positively correlated with lowest absolute abundances of this tintinnid in the waters sampled. This relationship points to some unfavorable factor(s) which affects both tintinnid reproduction/ survival and growth; the data analysed suggest that drops in the availability of food might be responsible for the size (and abundance) variations observed. © 1990 Oxford University Press.