Abstract
The sequence of postmarsupial stages of Tanais dulongii is described on the basis of separately reared individuals. In addition, gonad differentiation was studied histologically. More postmarsupial stages could be recognised than in previous studies on tanaid development. As in other Tanaidacea, T. dulongii passes two rnanca stages. In females, the manca stages are followed by 2–5 neutrum stages. It is only in the subsequent juvenile stages that female sexual differentiation becomes obvious, females exhibiting the anlagen of oostegites and ovaries. In the following three preparatory stages, the oostegites grow to form a paired ovisac (marsupium). Simultaneously, oocytes develop in the ovaries. With the maturation molt, the marsupium reaches its final size. Males pass through 1–3 neutrum stages only, thereafter presenting genital cones and differentiated gonads. The development of females comprises more instars and takes significantly more time than in males. The development of T. dulongii deviates from the “normal type” of tanaid development.
