Abundance of naked amoebae in sediments of Hiroshima Bay, Seto Inland Sea of Japan

The present paper provides the first data on naked amoebae from sediments o f Hiroshima Boy. Three stations in the inner part of the bay were sampled o ver a three-month period. Abundance of naked amoebae ranged from 1,019 to 4 5,561 cells/g dry sediment. Results indicate: (i) surface sediment populati ons in most cases were higher than subsurface populations; (ii) there was s ome evidence of temporal variation with counts generally increasing from Ma rch to May; and (iii) the site located near Hiroshirna City had fewer amoeb ae on several occasions than the other two sites. There was a negative expo nential relationship between acid-volatile sulfide concentration and abunda nce of amoebae. Most amoebae were small with the average size ranging from 6.6-14 mu m. Morphotype 1, amoebae that extend lobose pseudopodia or subpse udopodia during normal locomotion, were dominant (40-100% of enumerated amo ebae). Morphotypes 2 and 3 (limax amoebae) were found in lower numbers than the ether two morphotypes. The proportion of amoebae occupied by Morphotyp e 4 (fan-shaped or discoidal-flattened amoebae) was higher at a lower total abundance.