IMPACT OF A NOVEL, FEMINISING MICROSPORIDIUM ON ITS CRUSTACEAN HOST

We describe the transmission and pathogenic effects of a novel, femini sing microsporidium, probably a Nosema species, on its crustacean host Gammarus duebeni. The parasite prevalence in the field was high (46% of females were infected) and the parasite was transovarially transmit ted to 91% of embryos of infected females. The impact of the parasite on the host was assessed by means of a host breeding experiment. The p arasite feminised 66% of infected host young and was transovarially tr ansmitted by these individuals to the next host generation. The parasi te differed from other feminising microsporidia in G. duebeni in that early embryos had a high parasite burden (288 parasites per embryo) an d the infection was pathogenic, causing a reduction in both the growth rate of young hosts and in adult size. This study suggests that femin ising microsporidia are a diverse group in which a variety of host/pat hogen relationships have evolved.