Influences of marine adhesive bacteria on settlement and metamorphosis of Styela conopus Savigny larvae

One hundred and eighty bacteria isolated from surface of tunics of Styela conopus Savigny, Styela plicata Lesueur, Molgula manhattensis Delay and their adhesive substrates, as well as 110 ones from nearby water, were investigated . On the basis of their morphological, biochemical and physiological characteristics, these bacteria belong to 10 genera and over 60% bacteria are Gram-negative. In bacteria from surfaces of sea squirt's tunics and their adhesive substrates, dominant colonies are Pseudomonas, while Aeromonas are primary in bacteria from water. Nine strains were screened out from 180 bacteria for their great ability of attachment. Then these 9 bacteria were cultured to form different bacterial films respectively, together with a mixed artificial film made of all 9 strains so that influences of these artificial films on settlement and metamorphosis of Styela conopus Savigny larvae were studied. It is revealed that different types of artificial films have dissimilar effects on settlement and metamorphosis of Styela conopus Savigny larvae. On one hand, 5 kinds of bacterial films, H6, H9, H13, H15 and the mixed film remarkably stimulate larva attachment, while H4 strongly inhibited and others are without evident influences. On the other hand, in 10 bacterial films, H4, H7, and H9 obviously restrain metamorphosis of lava of Styela conopus Savigny, but more larva are metamorphic when they grew on H13 and the mixed bacterial film. It illustrated that settlement and metamorphosis of Styela conopus Savigny larva were two correspondingly independent processes during these two courses, different effects were shown when larva grew on the same bacterial film.