Testicular Microorganisms in Heliothis: Ultrastructure and Distribution in H. Virescens, H. Subflexa, F1 Hybrid, and Backcross Males

Abstract

Bacterial microorganisms were found in the testis lumen of three groups of F1 hybrid males and in first and second generation backcross (BC1 and BC2) males involving the interspecific cross Heliothis subflexa (female) × Heliothis virescens (male). Three pleomorphic forms (dense bodies, initial bodies, and intermediate bodies) were identified in adult moths of these groups, but only dense bodies were present in H. virescens and H. subflexa males. The intermediate form was not observed in either of the parental species and was only rarely seen in late-generation BC males. Intermediate bodies were absent from larval and pupal testes in each of the groups examined (F1, H. subflexa, H. virescens), but cytoplasmic forms in various developmental stages were observed in developing spermatids in pupal as well as adult testes. Spherical to oblong mitochondrial derivative bodies (MD bodies) were found associated with sperm of both species as well as in late-generation BC males. A hypothesis is presented to account for the presence of intermediate bodies in F1 and early BC testes and for their absence in the parental species. According to this hypothesis, each of the parental species harbors a similar but genetically distinct organism whose development is inhibited within its own host but not in a foreign host environment.