Structure and development of air bladders in Fucus and Ascophyllum (Fucales, Phaeophyceae)

Abstract

D.J. Garbary, A. Brackenbury, A.M. McLean and D. Morrison. 2006. Structure and development of air bladders in Fucus and Ascophyllum (Fucales, Phaeophyceae). Phycologia 45: 557–566. DOI: 10.2216/05-62.1

Using optical and scanning electron microscopy the structure and development of the air bladders of Fucus vesiculosus and Ascophyllum nodosum are described in an ecological context from Nova Scotia. The air bladders consist of a bladder wall that surrounds an air space traversed by a complex network of white fibers. Microscopically, the fibers consist of branched, uniseriate filaments in which cells are uninucleate with a thin cytoplasmic region and thick cell walls. The filaments are formed from irregular sheets of cells consisting of a cluster of filaments surrounded by mucilaginous material. These become detached from the surrounding material as the bladder inflates. In very large bladders the filamentous network can be broken and leave a felt-like mat on the bladder wall. Bladders of F. vesiculosus have thinner walls than A. nodosum (300 µm vs 500 µm, respectively). In addition, successively older bladders in the former species become damaged and lose their structural integrity, whereas this does not occur in the latter species. After 10 years of age, almost 90% of bladders in A. nodosum are still intact with no change between year 1 and year 10. In the shorter-lived F. vesiculosus, more than 50% of the visible bladders have been damaged, and only one or two bladders remain intact near the apices of branches. We conclude that the bladders of A. nodosum are able to undergo repair when the bladder wall is punctured, whereas those of F. vesiculosus do not.

Key Words::

• Air bladders
• Ascophyllum nodosum
• Fucus vesiculosus
• Fucaceae
• Morphogenesis
• Phaeophyceae
• Ultrastructure

ACKNOWLEDGMENTS

We thank Ricardo Scrosati for making one of the algal collections and for comments on the manuscript, and Monica Schuegraf, David Clarke and Dolna Garbary for field assistance. Robert DeWreede and two anonymous referees provided valuable input to an earlier version of the manuscript. Research was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) to DJG. DM was supported by a Research Capacity Development grant from NSERC to St. Francis Xavier University.