Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

The study of each subpopulation has shown that significant differences referring to prevalences (chi square test) do always refer to two geohelminths (M patens and S. mustelorum). These differences are the main reason for the differences mentioned above (NP and TP). For M. patens these are: MON-NW, MON-NE, MON-CN and MON-CS (p<0.01). For 5. mustelorum these are: MON-NW andNW-CS (p<0.05). In both nematodes significant differences have also been found (Mann-Whitney "U" test) in parasite intensity level. For M. patens these are: MON-NE (p<0.05); MON-NW, MON-CN and MON-CS (p<0.01). For S. mustelorum these are: NW-CN and NW-CS (p<0.05). These results seem to indicate that the ecological conditions in the Montseny are very favourable for the development of the free life forms of both helminths. However, the heterogeneity of the analysed sample (different altitudes and several seasons of capture) not allowed to establish any kind of correlation of infection rates of helminths with available climate data. The results, above all those referring to heteroxenous species, might be explained with the diet and ethology of M. nivalis in Iberia. It is known that the weasel's diet is fundamentally based on rodents as its main prey. According to the different studies carried out in European countries, those preys constitute approximately 60-90% of its diet. The diet is completed with secondary preys (birds, insectivores and lagomorphes), which represent from 5 to 35%, depending on the areas and the season. A remarkable aspect is the almost complete absence of invertebrate ingestions (Delattre 1987). However, those have to be often consumed as numerous species transmitted by Invertebrates, such as 5". nasicola (Fahmy 1964, Hansson 1968, King 1977, Lewis 1978, Aymerich et al. 1983, Gerard and Barrât 1986), were found in M. nivalis. Therefore, in Iberia, the occurrence of helminths transmitted by Invertebrates (C. melesi, F. martis and M. muris) is more important in the northern half, becoming specially evident in the Montseny Massif area. In the Montseny area there was a weasel in which all of the helmints transmitted by Invertebrates in Iberia were present. A fact that has to be marked, which is also helpful to corroborate this tendency, is the high prevalence detected for S. nasicola in this area (37.5%; n=8 analysed skulls). The environmental characteristics of the Iberian Peninsula, namely higher rainfall and milder temperatures in the northern half, could explain the south-north gradient for the helminths transmitted by Gastropods (C. melesi, F. martis and S. nasicola). This trend, evidenced in the case of M. nivalis, is also demonstrated in other Iberian Mustelids (Motje 1995). The only helminths that require in order to close their cycle that the weasel eats another Vertebrate are 7! mustelae and Trichinella sp. The prevalence of both helminths is rather disparate. Trichinella sp. has only been detected in a female from Avila (CN area). As it is an immigrant species for M. nivalis it can be concluded that the Mustelid does not decisively contribute to the maintenance of the life-cycle of this parasite in Iberia. On the contrary, T. mustelae has been detected with a general prevalence of 13.1%, and with an average parasitic intensity of 1.7 individuals, which means that it is a codominant species (1A=0.21). It is , moreover, a Taenid which accompanies M. nivalis uniformly all over Iberia. In fact, it has been detected in more than half of the prospected provinces, and it occurs in the five subpopulations. These data fit in properly with the chorology of the larval stage of the Taenid parasitizing different Iberian Rodents (Feliu et al. 1991). If we take into account the helminth faunas of all the Iberian Mustelids (Motje 1995), ecological data referring T. mustelae are more normal in M. nivalis than in M. erminea, which surprisingly enough shows a low prevalence for the Taeniid (Feliu et al. 1991). In the concrete case of the M. nivalis population in the NW area, which