ON THE SEMIAQUATIC BEHAVIOR OF A NEW TROGLOBITIC MILLIPEDE FROM NORTHERN ITALY (DIPLOPODA, POLYDESMIDA, POLYDESMIDAE)

Three different types of adaptations facilitate the amphibious mode of life of Serradium semiaquaticum Enghoff et al., 1998, in caves of the Lessini Mountains near Verona: -1) Morphological: hydrophobic microtr ichia of the spiracles allow plastron respiration under water and smal l bubbles of atmospheric air in the water may be captured if the water current is above 75 cm/sec; the modified pectinate lamellae of the ma ndibular gnathal lobes allow uptake of organic particles from moist su rfaces along the edges of subterranean water bodies and under water. - 2) Ecophysiological: the presence of ion-catching chloride epithelia i n the intersegmental membranes presumably allows additional uptake of ions and of dissolved oxygen from the water. -3) Ecoethological: S. se miaquaticum is a stenothermal species which enters cold subterranean w ater bodies voluntarily (semiaquatic behaviour); submersion resistance under laboratory conditions reached 4 weeks in duration in aerated wa ter and one week in non-aerated water. The observations on S. semiaqua ticum are compared with original data obtained for specimens of the no n-amphibious Serradium hirsutipes Verhoeff, 1941, from the same cave, and of the troglobite Selminosoma chapmani Hoffman, 1978, a hygrophilo us paradoxosomatid millipede from Papua-New Guinea.