The rectal glands of Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) hermaphrodites and their role in symbiont transmission

Differential interference contrast, transmission electron and epifluorescence microscopy techniques were employed to examine the ultrastructure of the rectal glands in . Heterorhabditis bacteriophora hermaphrodites, with special attention to the location of . Photorhabdus bacteria symbionts within these structures. Three rectal glands were clearly visualized in all examined specimens, with two glands positioned sub-ventrally and another gland located dorsally. The dorsal rectal gland in all examined specimens is larger than the subventral ones. Our observations indicate that . Photorhabdus bacteria do not colonize the rectal glands of . H. bacteriophora hermaphrodites, but rather are present in the most posterior-intestinal cells.