title: Formation of a transient corticotype during excystment in Coniculostomum monilata (oxytrichidae, hypotrichida) and its modification by reorganizations.
abstract: Protargol impregnation revealed that Coniculostomum monilata, an advanced oxytrichid ciliate with the typical 18 Frontal-Ventral-Transverse (FVT) cirri but with multiple rows of right marginal cirri (RMC) and dorso-marginal cilia (DM), requires at least 3 morphogenetic cycles to acquire the normal vegetative ciliature during excystment. In the first cycle, the FVT cirral pattern is entirely different from that formed during division. The 'first ciliature' comprises 21-32 FVT cirri formed from 5 FVT primordia; these are substituted by 18 FVT cirri developed from 6 FVT primordia in the subsequent reorganization cycle. Furthermore, each successive cycle adds one RMC row and 2 DM rows while previous rows are not resorbed, unlike the FVT cirri and the left marginal cirri. Consequently, multiple RMC and DM rows develop to form a typical vegetative corticotype. Dual information for frontal ciliature appears to be a unique feature of C. monilata as a similar situation has not been observed in the other evolved oxytrichids. Presence of an alternate corticotype information (> 18 FVT cirri) possibly signifies phylogenetic relationship of C. monilata with the lower oxytrichids. Excystment morphogenesis data reaffirms the conclusion from previous investigations that C. monilata has inherited information for only 1 RMC row and 2 DM rows; multiple rows are attained through a characteristic retention of pre-existing/parental rows.
authors.affiliation: S. G. T. B. Khalsa College, University of Delhi, Delhi, India.
authors.forename: K
authors.initials: K
authors.lastname: Kamra
authors.forename: G R
authors.initials: GR
authors.lastname: Sapra