A Cardinium-like symbiont in the proturan Acerella muscorum (Hexapoda).

Endosymbionts of the Cardinium-like genus are described in the testes and other tissues of the proturan Acerella muscorum (Ionescu). Few endosymbionts are present in the large apical cells of functional testes, but they become numerous at the end of the reproductive cycle. They are also found within sperm cells where induce their degeneration. The Gram-negative endosymbionts are characterized by the presence of microtubule-like structures (MLC) in their cytoplasm. It is suggested a possible role of the endosymbionts in the elimination of degenerating sperm cells when the testes activity is ended, thus somewhat playing a role in the timing of the reproductive cycle of the proturan species.