Parasitology

Research Article

Hybridization experiments indicate incomplete reproductive isolating mechanism between Fasciola hepatica and Fasciola gigantica

T. ITAGAKIa1 c1, M. ICHINOMIYAa1, K. FUKUDAa2, S. FUSYUKUa2 and C. CARMONAa3

a1 Laboratory of Veterinary Parasitology, Faculty of Agriculture, Iwate University, Ueda 3-18-8, Morioka 020-8550, Japan

a2 Center for Laboratory Animal Science, National Defense Medical College, Tokorozawa 359-8513, Japan

a3 Laboratory of Parasitology, Institute of Hygiene, Montevideo, Uruguay

SUMMARY

Experiments on hybridization between Fasciola hepatica and Fasciola gigantica were carried out to clarify whether a reproductive isolating mechanism appears between the two Fasciola species. Molecular evidence for hybridization was based on the DNA sequence of the internal transcribed spacer 1 (ITS1) region in nuclear ribosomal DNA, which differs between the species. The results suggested that there were not pre-mating but post-mating isolating mechanisms between the two species. However, viable adults of the hybrids F1 and F2 were produced from both parental F. hepatica and F. gigantica. The hybrids inherited phenotypic characteristics such as ratio of body length and width and infectivity to rats from parental Fasciola hepatica and F. gigantica. These findings suggest that reproductive isolation is incomplete between Fasciola hepatica and F. gigantica. Adults of the hybrids F1 and F2 were completely different in mode of reproduction from aspermic Fasciola forms that occur in Asia and seem to be offspring originated from hybridization between F. hepatica and F. gigantica and to reproduce parthenogenetically.

(Received November 17 2010)

(Revised December 22 2010)

(Revised February 03 2011)

(Revised March 16 2011)

(Revised May 10 2011)

(Revised May 17 2011)

(Accepted May 18 2011)

(Online publication July 18 2011)

Correspondence:

c1 Corresponding author: Laboratory of Veterinary Parasitology, Faculty of Agriculture, Iwate University, Ueda 3-18-8, Morioka 020-8550, Japan. Tel: and Fax: +81 19 621 6219. E-mail: itagaki@iwate-u.ac.jp

Metrics