Control of gamete release in fucoid algae: sensing hydrodynamic conditions via ...

• Author(s): Pearson, G. A. ; Serrão, Ester ; Brawley, S. H.
• Date: 1998
• Persistent ID: http://hdl.handle.net/10400.1/4113
• Origin: Sapientia - Universidade do Algarve
• Subject(s): External fertilization success; Fuccoid algae; Gamete release (spawning); Hydrodynamic conditions; Inorganic carbon; Intertidal; Reproductive ecology
• Document Type: Article
• Language: English

Description

We investigated the environmental factors providing signals for gamete release in fucoid algae, with a particular focus on the inhibitory effect of water motion. The release of gametes by Fucus distichus occurred in still water under high light and was associated with the depletion of dissolved inorganic carbon (DIC) in tide pools isolated from the ocean during daytime low tides. Diurnal patterns of gamete release that lasted for 2-3 d, as in natural populations, were found in receptacles cultured in a 12 h light: 12 h dark photoperiod under calm conditions or in a simulated tidal regime. Constant light disrupted the diurnal component of release, however, suggesting that an endogenous circadian periodicity was absent. The effects of increased [DIC] on cultured receptacles under calm conditions were similar to the inhibitory effects of high water motion; both conditions reduced release in several species from both tide pool and intertidal habitats. Bicarbonate concentration, rather than carbon dioxide, or carbonate, was shown to be the component of the DIC system most closely correlated (inversely) with gamete release in the intertidal fucoid Pelvetia compressa. The hypothesis that gamete release is triggered by DIC depletion in the unstirred boundary layer during periods of low water motion in the light was further supported by experiments with P. compressa. These showed that gamete release was not inhibited by high water motion when DIC was absent. In the same experiments, high water motion inhibited release at 2 and 20 mmol/L DIC, confirming that the sensitivity of gamete release to water motion is DIC dependent. The ability of fucoid algae to couple physiological processes (e.g., photosynthesis) with life history events (gamete release) allows external fertilization to occur under favorable hydrodynamic conditions, and may contribute greatly to reproductive success in organisms inhabiting periodically turbulent environments.