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DEVELOPMENT AND ECOLOGICAL ROLE OF PERIPHYTIC DIATOM (BACILLARIOPHYCEAE) MUCILAGES, WITH SPECIAL REFERENCE TO CYMBELLA SPECIES (MCCONAUGHY RESERVOIR, ELECTRON MICROSCOPY, PERIPHYTON, POLYSACCHARIDE)
Abstract
Periphytic diatoms adhere to submerged objects by mucilage produced between the cell and substrate. Mucilage is the gelatinous, polysaccharide-containing material which is secreted through the mature diatom cell wall. Field collections and clones of Cymbella were examined with electron microscopy to document mucilage development (intracellular origin/extracellular release) in species which form a sheath (C. triangulum), tube (C. prostrata) var. auerswaldii), stalk (C. mexicana, C. affinis, C. cistula), and trail of mucilage (C. cistula). Secretion of mucilage by C. triangulum resembles slime formation in root cap cells, as polysaccharide fibrils are concentrated in Golgi-derived vesicles, discharged from the protoplast by exocytosis, and passed through the diatotepum and silica wall via and raphe or value areolae. Attachment by C. cistula involves: (1) deposition of slime trails for 48 hours as cells move in a circular path; (2) cellular adhesion after 72 hours by a holdfast; (3) cell division followed by stalk secretion from both ocelli at the same cell apex yielding dichotomously branched colonies. Secretion is a progressive process in C. prostrata var. auerswaldii and C. mexicana, since the older epivalve already has a distinct organic coating when the younger hypovalve begins to release mucilage. Field studies involving the formation of seasonal biofilms on artificial and natural substrates incubated in McConaughy reservoir (Nebraska, U.S.A) have shown that diatom mucilage affects microcommunity structure as follows: (1) permits cellular adhesion; (2) increases surface area for attachment by other microbes; (3) traps euplanktonic algae; (4) binds detrital particulates; (5) permits storied vertical growth; (6) increases the standing biomass. Growth curves of periphytic diatoms showed a significant decline in the standing crop between the 13- and 22-day incubations, due to detachment of the upper tier of stalked Cymbella. Such losses may result from wave-scouring action on peeling biofilms which have been structurally disabled by the buoyant force of gas bubbles 1.4 ((+OR-)0.15) x 10('5) nN cm('-2) trapped within the diatom mucilage.
Subject Area
Biology
Recommended Citation
ROEMER, STEPHEN CHARLES, "DEVELOPMENT AND ECOLOGICAL ROLE OF PERIPHYTIC DIATOM (BACILLARIOPHYCEAE) MUCILAGES, WITH SPECIAL REFERENCE TO CYMBELLA SPECIES (MCCONAUGHY RESERVOIR, ELECTRON MICROSCOPY, PERIPHYTON, POLYSACCHARIDE)" (1985). ETD collection for University of Nebraska-Lincoln. AAI8518707.
https://digitalcommons.unl.edu/dissertations/AAI8518707