Multiple symbiosis in a leafhopper, Helochara communis fitch (cicadellidae: Homoptera): Envelopes, nucleoids and inclusions of the symbiotes

Mycetomes in Helochara communis are paired syncytia each enclosed by an epithelium. Adjacent are loose aggregates of mycetocytes. Mycetomes harboured 3 kinds of inclusions: companion, a-and t-symbiotes according to Buchner’s classification of homopteran symbiotes. In the mycetocytes, a fourth kind of inclusion was found and named g-symbiotes. All inclusions were Feulgen and Gram negative. Nucleoids were revealed in companion symbiotes by osmium-HCl-Giemsa; and, in some g-and t-, but not in a-, symbiotes by RNase-papain Giemsa. DNase digestion caused loss of basophilia in g-and t-, but not in a-, symbiotes. By electron microscopy, using Kellenberger’s fixative, companion, g-and t-symbiotes had lucid areas with reticular strands 4 nm thick; a-symbiotes were in general, homogeneously densely granular. Companion symbiotes had Gram-negative profiles with additional surface material; a-and t-symbiotes had 3, g-symbiotes 2, peripheral, trilaminar membranes. Parallel striations and regularly arranged granules occurred in companion symbiotes; crystalline inclusions in g-and t-symbiotes; and fibrillar elements and dense bodies in a-symbiotes. Companion symbiotes may be Gram-negative bacteria or rickettsiae; g-and t-symbiotes, L-phase bacteria; but a-symbiotes are anomalous, apparently lacking DNA, and probably being derivatives of t-symbiotes, thus requiring that Muller’s hypothesis of homopteran evolutionary pathways be rephrased.