Sinsch, U., J. Kaschek & J. Wiebe

Heavy metacercariae infestation (Parastrigea robusta) promotes the decline of a smooth newt population (Lissotriton vulgaris). pp. 210-221.

Abstract. A previously unexplained decline of a Lissotriton vulgaris population following breeding habitat management measure improving the pond's physical features is reported. We used CMR-analyses, skeletochronology, trematode load and fat body assessment to evaluate the response of newts to local stressors with respect to demographic life-history traits. We provide evidence that in L. vulgaris survival and consequently longevity are deeply affected by infestation with Parastrigea robusta metacercariae. Demographic responses as compared with those of unaffected populations include earlier sexual maturation and decreased longevity. In fact, infested newts survived rarely to the next-year breeding period probably due to the lack of metabolic reserves (undeveloped fat bodies, starvation-hypothesis). The local decline of smooth newts is most probably the result of an exceptional combination of the invasion of a neophyte (Elodea) and a neozoon snail (Gyraulus parvus) promoted by pond restoration establishing the complete developmental cycle of a newt parasite (P. robusta) in the breeding pond. Future studies are needed to evaluate whether or not the observed fatal impact of the trematode on newt survival is general and a new threat in habitats favorable to support high parasite densities.

Key words. Amphibia, age at maturity, longevity, parasite-mediated mortality, population size, skeletochronology, starvation-hypothesis, Trematoda.