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Auxospore formation by the silica-sinking, oceanic diatom Fragilariopsis kerguelensis (Bacillariophyceae)
Assmy P.; Henjes, J.; Smetacek, V.; Montresor, M. (2006). Auxospore formation by the silica-sinking, oceanic diatom Fragilariopsis kerguelensis (Bacillariophyceae). J. Phycol. 42: 1002-1006
In: Journal of Phycology. Blackwell Science: New York. ISSN 0022-3646, more
Peer reviewed article  

Available in Authors 

Keywords
    Diatoms; Life history; Sexual reproduction; Fragilariopsis F. Hustedt in A. Schmidt et al., 1913 [WoRMS]; PS, Southern Ocean [Marine Regions]; Marine

Authors  Top 
  • Assmy P., more
  • Henjes, J.
  • Smetacek, V.
  • Montresor, M., more

Abstract
    Size restoration by the auxospore that develops from the zygote is a crucial stage in diatom life cycles. However, information on sexual events in pelagic diatom species is very limited.We report for the first time auxospore formation by the pennate diatom Fragilariopsis kerguelensis (O’Hara) Hustedt during an iron-induced bloom in the Southern Ocean (EIFEX, European Iron Fertilization EXperiment). Auxospores of F. kerguelensis resembled those described for Pseudo-nitzschia species. The auxospore was characterized by an outer coating, the perizonium; two caps, one at each distal end; and four chloroplasts, one at each end and two in the central part. Different stages of auxospore elongation were recorded, with a length of 24-91 lm, but only the largest auxospores contained the initial cell, whose apical axis ranged between 76 and 90 lm. Gametangial cell walls were often attached to the auxospores and ranged from 10 to 31 lm in length. Auxospore abundances were consistently higher in the fertilized patch, where an increase in the F. kerguelensis population was observed, as compared with surrounding waters.

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