[Experiments in vitro with Litomosoides carinii (Nematoda: Filarioidea) II. Influence of different sera on the release of microfilariae and experiments on the readiness for copulation of the worms (author's transl)].

When fetal calf serum or human serum is added to the culture medium Tc 199, adult females of Litomosoides carinii release the same amount of microfilariae in vitro as after addition of cotton rat serum. In contrast, in media with serum of Meriones unguiculatus or Mastomys natalensis only a few microfilariae are released; moreover, addition of Mastomys serum immobilizes them. When males and females are kept together, the same amount of microfilariae is released as compared with single females. Worms 4 weeks of age (i.e., about 2 weeks before copulation) maintained in medium Tc 199 with 33% cotton rat serum do not mate (no insemination of the females). However, the females live 18 days (harmonic mean) in vitro and grow on average 5 mm in length (28%) and the males roll up their tails in characteristic manner. Worms 5 or 6 weeks of age kept in pairs for 45 to 6 days in vitro were implanted into cotton rats. In vivo they grew to normal length, copulated and delivered microfilariae into the circulating blood. Females implanted solely into the recipient grew as well but remained sterile; this means that no insemination took place in vitro.