title: Multiple near-identical genotypes of Schistosoma japonicum can occur in snails and have implications for population-genetic analyses.
abstract: We genotyped (using 16 or 17 microsatellite loci) numerous adult Schistosoma japonicum raised in rabbits exposed to pooled cercariae from small numbers of naturally infected snails from several localities in China. As expected, duplicate multi-locus genotypes (MLGs) were found among these worms. Additionally, many more MLGs, often near-identical, were found than snails used as sources of cercariae. Explanations for these results include (i) genotyping errors, (ii) development within each infected snail of multiple sibling miracidia and (iii) somatic mutation producing genetically varied cercariae from a single miracidium. To control for genotyping errors we re-analysed samples from many individual worms, including repeating the initial PCR. Explanations invoking the development of multiple sibling miracidia within a single snail are not likely to be correct because almost all duplicate MLGs fell within same-sex clusters in a principal coordinates analysis. We would expect both sexes to be represented in a multi-miracidium infection. In addition, we exposed several snails to infection by a single miracidium. One such snail, via an experimentally infected mouse, yielded 48 adult worms. The presence of at least nine near-identical MLGs among these worms was confirmed by re-genotyping. We regard somatic mutation as the most likely explanation for our results. The implications of multiple MLGs for population-genetic studies in S. japonicum are discussed.
authors.affiliation: National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Rd II, Shanghai 200025, PR China.
authors.forename: Mingbo
authors.initials: M
authors.lastname: Yin
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.forename: Xiaojin
authors.initials: X
authors.lastname: Mo
authors.forename: Shengyue
authors.initials: S
authors.lastname: Wang
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Brindley
authors.forename: Donald P
authors.initials: DP
authors.lastname: McManus
authors.forename: George M
authors.initials: GM
authors.lastname: Davis
authors.forename: Zheng
authors.initials: Z
authors.lastname: Feng
authors.forename: David
authors.initials: D
authors.lastname: Blair
mesh_terms: D000818:Animals; D002681:China; D005838:Genotype; D018895:Microsatellite Repeats; D016133:Polymerase Chain Reaction; D011817:Rabbits; D012549:Schistosoma japonicum / Q000235:genetics* / Q000254:growth & development; D012554:Schistosomiasis japonica / Q000235:genetics*; D012908:Snails / Q000469:parasitology*