ORIGINAL PAPER Evidence of phenotypic differences between resistant and susceptible isolates of Pseudosuccinea columella (Gastropoda: Lymnaeidae) to Fasciola hepatica (Trematoda: Digenea) in Cuba Received: 24 September 2002 / Accepted: 28 October 2002 / Published online: 13 February 2003 Ó Springer-Verlag 2003 Abstract Isolates of Cuban Pseudosuccinea columella susceptible and non-susceptible to Fasciola hepatica miracidial infection were compared for cellular reaction to miracidial development, shell morphometrics, mantle pigmentation pattern, and egg laying behaviour. At 24 h post-exposure, non-susceptible snails showed an early cellular host reaction to encapsulate and phagocytise the miracidium, whereas viable transforming miracidia were observed in exposed susceptible snails, indicating that non-susceptibility resulted from resistance rather than physiological unsuitability. Susceptible isolates (more than 80% susceptible to infection) showed significantly higher values of the morphometric indices shell width/ length and aperture width/length than resistant isolates (100% resistant). Mantle pigmentation pattern was analysed using Visilog software ; the cumulative dis- tances between mantle spots were plotted and compared between isolates, showing a clear distinction between groups. Egg-laying behaviour also showed significant differences with susceptible snails preferring to lay their eggs on the container’s walls whereas resistant snails preferred to lay their eggs on the bottom of the con- tainer. Introduction Two lymnaeid snails, Fossaria cubensis and Pseud- osuccinea columella live in Cuba. Fossaria cubensis is responsible for the transmission of the liver fluke, Fasciola hepatica to cattle and less commonly to people, although several important human foci have recently been reported (Brito et al. 1987; Espino et al. 1998). Natural infections of Pseudosuccinea columella with F. hepatica have never been found in Cuba, but the high susceptibility of this species to experimental infection has been demonstrated (Leo´n-Dancel 1970; Boray et al. 1985; Dacal et al. 1988), and it has been found naturally infected in Australia (Boray et al. 1985) and Brazil (Ueta 1980). Populations of P. col- umella have been found in the western and central regions of Cuba and in some places it may occur to- gether with F. cubensis. In 1996, a population of P. columella non-susceptible to infection by the mi- racidia of F. hepatica was discovered in the La Palma area in Pinar del Rı´o Province (Gutie´rrez et al. 2002). More recently, in 1999, another non-susceptible pop- ulation was discovered near the small town of Babinay in Matanzas Province. Gutie´rrez et al. (2002) showed that non-susceptible snails from La Palma had lower survival and fecundity rates as well as lower intrinsic and finite rates of increase compared to susceptible snails. In this paper, we described further observations made to compare susceptible and non-susceptible snails. We first searched for the presence/absence of host reaction towards the parasite in order to deter- mine the basis of non-susceptibility. Secondly we compared several phenotypic traits (shell morphology, mantle pigmentation pattern and egg-laying behav- iour), between non-susceptible and susceptible snails. Such external markers may be useful in field studies, allowing a rapid, first identification of susceptible or non-susceptible genotypes within and between natural populations. Parasitol Res (2003) 90: 129–134 DOI 10.1007/s00436-002-0824-z Alfredo Gutie´ rrez Æ Jean-Pierre Pointier Mary Yong Æ Jorge Sa´nchez Æ Andre´ The´ron A. Gutie´rrez Æ M. Yong Æ J. Sa´nchez Laboratorio de Malacologı´a, Instituto ‘‘Pedro Kourı´’’(IPK), Apartado 601, Marianao 13, Havana, Cuba J. Pointier Laboratoire de Biologie Marine et Malacologie, EPHE, UMR 5555 CNRS, Universite´ de Perpignan, 52 Av. de Villeneuve, 66860 Perpignan Cedex, France A. The´ron (&) Laboratoire de Biologie Animale, UMR 5555 CNRS-UP, Centre de Biologie et d’Ecologie tropicale et me´diterrane´enne, EPHE, Universite´ de Perpignan, 52 Av. de Villeneuve, 66860 Perpignan Cedex, France E-mail: theron@univ-perp.fr Fax: +33-4-68662281