MATING BEHAVIOUR OF DEROCERAS RODNAE GROSSU & LUPU, 1965 AND D. PRAECOX WIKTOR, 1966 (PULMONATA: AGRIOLIMACIDAE)

The mating behaviour of Deroceras rodnae Grossu & Lupu,1965 and D. praecox Wiktor, 1966 was observed under laboratoryconditions. Both species differ by the shape and functioningof the sarcobelum, the timing and duration of courtship andthe colour of the sperm mass. Particularly the different timingof the courtship behaviour seems to act as an effective prezygoticisolation mechanism preventing interspecific crosses. Usually,sperm masses are exchanged mutually. In three homospecific pairings,unilateral sperm transfer was observed followed by a characteristicbehaviour of the donor slug. This observation is discussed inlight of the hermaphrodite's dilemma and sperm trading models. (Received 23 May 1994; accepted 1 December 1994)