Chain Colony Formation of Marine Araphid Diatom Grammatophora marina (Lyngbye) Kutzing: Relationship between Chain Shape and Apical Sinne

Abstract

An epiphytic diatom Grammatophora marina (Lyngbye) Kützing, a well-known chain-forming species showing cosmopolitan distribution, was examined firstly based on the observation of chemically cleaned cell wall. We found that the valves had a spine only at one end. Subsequently, we deployed a method to remove the organic coat of the cells using a hot plate keeping the chain shape intact. The observation of the zigzag chain under SEM revealed: 1) the spine was always formed at the free (non-attached) end of the valve, and 2) newly formed sibling valves were linked to each other by both ends. In this case one spine-bearing end was more weakly attached than the other. Thus, it is likely that the adhesion of the spine-bearing end will be lost afterward. The determination of the valve polarity might randomly take place judging by the chain shape. The spine physically disturbs the adhesion of two opposed sibling valves, resulted in the detachment of the part. The randomly-formed spines facilitate chain formation, which is presumably beneficial in terms of nutrient and light competition in the epiphytic assemblage.