ULTRASTRUCTURAL OBSERVATIONS ON SYMBIONT DEGENERATION IN THE MALE LINE OF PSEUDAULACASPIS PENTAGONA (TARGIONI TOZZETTI) (HEMIPTERA: COCCOIDEA: DIASPIDIDAE)

Abstract

ULTRASTRUCTURAL OBSERVATIONS ON SYMBIONT DEGENERATION IN THE MALE LINE OF PSEUDAULACASPIS PENTAGONA (TARGIONI TOZZETTI) (HEMIPTERA: COCCOIDEA: DIASPIDIDAE). During the development of the immature stages of male scale insects, the mouthparts become lost at the prepupal stage and this is paralleled by the degeneration of the symbiont microorganisms inhabiting the mycetocytes. This degenerative process has been studied in the male line of the white peach scale, Pseudaulacaspis pentagona (Targioni Tozzetti). In the first two feeding instars, the mycetocytes appear as spherical cells, 30-40μm in diameter, filled with normal micro-organisms, round or oval in shape, 3-5μm long. In the prepupal and pupal stages, some symbionts undergo degeneration by a dissolution of the dense ribosomal granulations which characterize the microorganisms in the two feeding instars. In these symbionts, the fusing of the small vacuoles results in the appearance of larger, more centrally-placed, vacuoles. Other symbionts become loosely reticulated or, alternatively, condensed or contracted, to form regular or irregular bodies. The mycetocytes seem to undergo no reduction in size but their cytoplasm shows signs of dissolution as well. A great number of dense, crystalline-like granulations were found in their proximity. The nature and derivation of these granulations remains to be investigated.