Ultrastructure and function of stalks of the diatom Didymosphenia geminata
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One of the most striking features of the diatom Didymosphenia geminata, which has increased markedly in abundance in a number of countries in recent years, is the very large branched stalks. In order to help understanding their role, an ultrastructural study was carried out on two populations, one from a stream in northern England and the other from a river on Vancouver Island, Canada. In both cases, the main part of the stalk had a central reticulate core surrounded by an outer region with dense fibres. A longitudinal structure in the uppermost part of the stalk just under the collar surrounding the base of the cell may perhaps correspond to a tube. The structure of the septa formed where branches divide is also described. Phosphomonoesterase activity known to be present in the stalks was shown to occur in the inner peripheral layers of the stalks and especially in the collar area. The results show that stalks have a complex structure suggesting their importance for their phosphatase activity to overcome low inorganic phosphate concentrations. Their large surface may function in herbivory avoidance, a better exposure of cells to turbulent conditions to increase nutrient uptake, adsorption of limiting elements and gas exchange.
KeywordsDidymosphenia geminata Ecology Monitoring Phosphomonoesterase activity Stalks Ultrastructure
We are indebted to Prof. M. Bothwell (National Water Research Institute, Vancouver Island) for sending material from Canada and Prof. B.A. Whitton (University of Durham) for sending the UK material and several comments on the manuscript. Grants CGL2006-09864 and CERT07-10321 from Spanish Ministry of Education and Science and Séneca Foundation from Murcia Autonomous Community partially financed the study.
- Drum, R. W., 1964. Ecology of diatoms in the Des Moines River. PhD Thesis. Iowa State University of Science and Technology, Ames, Iowa.Google Scholar
- Gomori, G., 1952. Microscopic Histochemistry. Principles and Practice. The University of Chicago Press, Chicago.Google Scholar
- Gretz, M. R., 2008. The stalks of didymo. In Bothwell, M. L. & S. A. Spaulding (eds), Proceedings of the 2007 International Workshop on Didymosphenia geminata. Canadian Technical Report on Fisheries and Aquatic Sciences 2795: 21 pp.Google Scholar
- Gretz, M. R., M. L. Riccio, T. R. Hungwe, H. M. Burger, S. N. Kiemle, M. D. Apoya & S. A. Spaulding, 2006. Extracellular polymers of the stalked diatom Didymosphenia geminata. In Spaulding, S., R. Wiltshire & L. Elwell (conference organizers), Current Knowledge of Didymosphenia geminata: Developing a Research and Management Response. Federation of Fly Fishers and EPA Region 8, held in association with Western Division American Fisheries Society Annual Meeting, May 15–16: 2006, Montana State University, Montana, USA: 13 pp.Google Scholar
- Huntsman, S. A. & J. H. Sloneker, 1971. An exocellular polysaccharide from the diatom Gomphonema olivaceum. Journal of Phycology 7: 261–264.Google Scholar
- Kilroy, C. A., 2008. Didymosphenia geminata in New Zealand: distribution, dispersal and ecology of a non-indigenous invasive species. In Bothwell, M. L. & S. A. Spaulding (eds), Proceedings of the 2007 International Workshop on Didymosphenia geminata. Canadian Technical Report on Fisheries and Aquatic Sciences 2795: 15–20.Google Scholar
- Kociolek, J. P. & E. F. Stoermer, 1988. A preliminary investigation of the phylogenetic relationships among the freshwater, apical pore field-bearing cymbelloid and gomphonemoid diatoms (Bacillariophyceae). Journal of Phycology 24: 377–385.Google Scholar
- Lee, P., M. M. Ring, C. Brown, B. W. Taylor & T. A. Wellnitz, 2008. How scour disturbance affects Didymosphenia geminata abundance and the associated epiphyte community. PS 35-13. 93rd ESA Annual Meeting, August 3–8, 2008, Milwaukee, Wisconsin, USA [available on internet at http://eco.confex.com/eco/2008/techprogram/P14254.HTM].
- Sherbot, D. M. J. & M. L. Bothwell, 1993. Didymosphenia geminata (Gomphonemaceae). A review of the ecology of D. geminata and the physiochemical data of endemic catchments on Vancouver Island. National Hydrology Research Institute, Environment Canada, Saskatoon, Saskatchewan, NHRI Contribution No. 93005: 55 pp.Google Scholar
- Wang, Y., J. Lu, J.-C. Mollet, M. R. Gretz & K. D. Hoagland, 1997. Extracellular matrix assembly in diatoms (Bacillariophyceae). II. 2,6-Dichlorobenzonitrile inhibition of motility and stalk production in the marine diatom Achnanthes longipes. Plant Physiology 113: 1071–1080.PubMedCrossRefGoogle Scholar
- Wang, Y., Y. Chen, C. Lavin & M. R. Gretz, 2000. Extracellular matrix assembly in diatoms (Bacillariophyceae). IV. Ultrastructure of Achnanthes longipes and Cymbella cistula as revealed by high-pressure freezing/freeze substitution and cryo-field emission scanning electron microscopy. Journal of Phycology 36: 367–378.CrossRefGoogle Scholar
- Whitton, B. A., A. H. Al-Shehri, N. T. W. Ellwood & B. L. Turner, 2005. Ecological aspects of phosphatase activity in cyanobacteria, eukaryotic algae and bryophytes. In Turner, B. L., E. Frossard & D. S. Baldwin (eds), Organic Phosphorus in the Environment. Commonwealth Agricultural Bureau, Wallingford: 205–241.CrossRefGoogle Scholar