The fine structure of the mycetome symbiotes of the aphids Brevicoryne brassicae, Myzus persicae, and Macrosiphum rosae

Abstract

The ultrastructure of the mycetocytes and of the mycetome symbiotes of the aphids Brevicoryne brassicae, Myzus persicae, and Macrosiphum rosae is described. Fixation in either of two solutions, each containing both glutaraldehyde and osmium tetroxide, gives better preservation of the tissues of the aphids and of the symbiotes than does the use of either compound alone. The symbiotes of B. brassicae and Myzus persicae and the ‘primary symbiotes’ of Macrosiphum rosae are very similar to each other. Macrosiphum rosae also has a second type of symbiote; the two types are housed in separate mycetocytes. It is suggested that the symbiotes resemble the Rickettsiaceae and may have arisen from a member of this group. However, it is also possible that they arose from free-living bacteria rather than from non-symbiotic rickettsiae, the likeness being due to convergence rather than relationship.