Methods
Habitats
Bibliography
Glossary
Syllabus
Students

PHYCOLOGICAL SOCIETY OF AMERICA

Release of gametes in Silvetia or Pelvetia

The release of the gametes is correlated to the tidal cycle; when the thallus is exposed at low tide, the frond desiccates, causing shrinkage and extrusion of mucilage through the ostioles of conceptacles. When making sections, there is a great deal of cellular activity (cell division and extrusion of oogonia through ostioles) for a period of about 10 minutes after cutting the conceptacle after which activity ceases. It is possible that the changing hydrostatic pressure due to sectioning of the receptacle mimics signals leading to gamete extrusion.

The wall of the oogonium has a thin exochite, a thick mesochite, and a thin endochite. When the oogonium matures, the exochite ruptures and the packet surrounded the mesochite and endochite passively moves out the ostiole due to swelling of mucilage. The incoming tide washes over the alga, causing the endochite to imbibe water and swell which causes the mesochite to rupture; this exposes the endochite which then dissolves. The eggs become spherical from water uptake and float away. The antheridia undergo a similar process in release. The outer exochite ruptures while still attached to paraphyses and releases the endochite containing spermatozoids. This package passes passively out to sea through the ostiole whereupon the inner wall gelatinizes and the spermatozoa swim away.

© 1996 R. H.  Lin