FLAGELLAR APPARATUS TRANSFORMATION AND DEVELOPMENT IN PROROCENTRUM MICANS AND P-MINIMUM (DINOPHYCEAE)

Flagellar transformation was studied in Prorocentrum minimum (Pavillard) Schiller on free-swimming cells using low-illumination light microscopy. Cells bear two ventrally inserted, heterodynamic flagella. Prior to cell division, two new transverse flagella are produced. The parental longitudinal flagellum (1) remains unaltered during cell division, while the parental transverse flagellum (2) is either retracted or abscissed, and regrows as a longitudinal flagellum (1(2)). The basal apparatuses of both P. micans Ehrenberg and P. minimum show the typical complement of dinophycean roots at interphase. Two new daughter basal bodies (2(1) and 2(2)) are formed prior to any alteration of the parental basal apparatus. The parental longitudinal microtubular root (LMR) and basal body connective (BBC) appear to be maintained unaltered and associated with the parental longitudinal basal body (1). A new longitudinal microtubular root (Imr), basal body connective (bbc) and fibrous connectives (fc's) are produced between the transforming transverse basal body (2) and its daughter (2(2)). New striated root connectives (src's), transverse striated roots (tsr's) and their associated microtubules (tsrm's) are formed next to the new, transverse daughter basal bodies (2(1) and 2(2)). Basal body 2(1) forms its own transverse microtubular root (tmr) while the same root on basal body 2(2) might be derived from the parental transverse striated root microtubule (TSRM) as a result of root transformation and transfer. The parental transverse striated root (TSR) and transverse microtubular root (TMR) are disassembled during cell division. The pattern of flagellar root development is compared to other known root developmental processes for which we introduce a system of classification. We also introduce a flagellar root nomenclature similar to the flagellar nomenclature to indicate unaltered parental roots, newly formed roots, transferred roots and transformed parental roots that constitute another root type in the new daughter cell.