Seasonality and thallus ontogeny of edible seaweed Monostroma latissimum (Kützing) Wittrock (Chlorophyta, Monostromataceae) from Tosa Bay, Kochi, Japan
Monostroma latissimum (Kützing) Wittrock is an intertidal rock-dwelling green algal species of commercial importance in Japan. This article reports on the seasonality of its growth and occurrence from three distinct habitats of marine and estuarine regions in Tosa Bay, Japan, for two consecutive growth seasons. Thallus lengths of individuals and environmental parameters were monitored monthly between November 2005 and July 2007. Culture studies were carried out to establish the species-level identity of the specimens. Nuclear encoded ITS 1 (Internal Transcribed Spacer 1) sequences reveal that the naturally occurring strain of M. latissimum has identical nucleotide sequences to those of the commercially cultivated strain from the Shimanto river estuary. We have also found that the two strains are cross-fertilizing. Seasonal fluctuations in thallus length were found to be distinctive to the habitat where the strain grows and re-occur annually. Algal cover was highest during winter months and lowest during the summer. However, we found only a very weak positive correlation between chosen environmental parameters and thallus length. Appearance and decay of thalli occurred earlier in high saline habitats. Therefore, it is likely that salinity influences the maturation of microscopic sporophytes or the growth and survival of germlings in M. latissimum.
KeywordsAlgal decay Seasonal growth Salinity Sexual reproduction ITS Monostroma latissimum
The work of FB was made possible by Grant-in-Aid Doctoral Fellowship from the “Monbukagakusho” Ministry of Education, Science, Sports and Culture, Japanese Government. This paper was improved by comments from Dr. Gayle I. Hansen, Oregon State University, USA, Dr. Ichiro Mine, Kochi University, Japan, and two anonymous reviewers. We also thank Fishermen’s Union of Shimanto City, Kochi Prefecture, Japan, for allowing us to use their administrative waters and Mr. Akihide Tokuyama for his help with maintenance of cultures. Part of this investigation was presented at the XIX International Seaweed Symposium, Kobe, Japan, during March 26–31, 2007.
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