From: PO2::"MUYLAERT.KOENRAAD@ucg.ie" "Koenraad Muylaert" 16-MAR-1995 08:52:46.22 To: Multiple recipients of list DIATOM-L CC: Subj: morphological variation in Cyclotella Dear fellow diatomists, During a survey of the spring phytoplankton in the Schelde estuary (Belgium) I found a bloom of a Cyclotella species in the freshwater tidal reaches of this estuary. This centric diatom ressembles Cyclotella meneghiniana in LM but differs from it in SEM by an unusual shape of the marginal rimoportula and characters which suggest an excessive deposition of silica (numerous granulae, ...). As the diatom was found in a heavily polluted water body with very high silicate concentrations I wonder wether it might have been induced to assimilate more silica then necessary and thus have changed its morphology. Changes induced by salinity are unlikely as this causes the species to switch over to a Cyclotella cryptica valve pattern, which was not the case. Numerous papers have been published about morphological changes of diatoms under low silicate concentrations. Does anyone have references/information about or observations of morphological variability of diatoms under extremely high silicate concentrations? Thanks in advance, Koenraad Muylaert email: muylaert.koenraad@ucg.ie Koenraad Muylaert Email: Koenraad.Muylaert@ucg.ie From: PO2::"gordonr@cc.umanitoba.ca" "Richard Gordon" 17-MAR-1995 05:05:17.49 To: Multiple recipients of list DIATOM-L CC: Subj: Re: morphological variation in Cyclotella Dear Koenraad, I'm fascinated by your speculation, since high silica could represent another environmental variable for manipulating and thus analyzing diatom shell morphogenesis. Have you seen my recent paper?: Gordon, R. & R.W. Drum (1994). The chemical basis for diatom morphogenesis. Int. Rev. Cytol. 150, 243-372, 421-422. Some "excess" silica deposition is reported in: Estes, A. & R.R. Dute (1994). Valve abnormalities in diatom clones maintained in long-term culture. Diatom Res. 9(2), 249-258. Best regards, -Dick Gordon[Mar17,95] From: PO2::"estesam@mail.auburn.edu" "Anne M Estes" 29-MAR-1995 23:19:24.07 To: Multiple recipients of list DIATOM-L CC: Subj: Re: morphological variation in Cyclotella On Thu, 16 Mar 1995, Koenraad Muylaert wrote: > Dear fellow diatomists, > > During a survey of the spring phytoplankton in the Schelde > estuary (Belgium) I found a bloom of a Cyclotella species in the > freshwater tidal reaches of this estuary. This centric diatom ressembles > Cyclotella meneghiniana in LM but differs from it in SEM by an unusual > shape of the marginal rimoportula and characters which suggest an excessive > deposition of silica (numerous granulae, ...). As the diatom was found in a > heavily > polluted water body with very high silicate concentrations I wonder > wether it might have been induced to assimilate more silica then > necessary and thus have changed its morphology. Changes induced by > salinity are unlikely as this causes the species to switch over to > a Cyclotella cryptica valve pattern, which was not the case. > > Numerous papers have been published about morphological changes of diatoms > under low silicate concentrations. Does anyone have references/information > about or observations of morphological variability of diatoms under extremely > high silicate concentrations? > > Thanks in advance, > > Koenraad Muylaert > email: muylaert.koenraad@ucg.ie > Koenraad Muylaert > Email: Koenraad.Muylaert@ucg.ie > Koenraad - I just ran across a book which might be of interest to you - Silicon and Siliceous Structures in Biological Systems edited by Simpson and Volcani. Hope it helps, Anne M. Estes