Genomic diversity of cercarial clones of Himasthla elongata (Trematoda, Echinostomatidae) determined with AFLP technique

Abstract

The aim of this study was to reveal genomic diversity formed during parthenogenetic reproduction of rediae of the trematode Himasthla elongata in its molluskan host Littorina littorea. We applied amplification fragment length polymorphism (AFLP) to determine the genomic diversity of individual cercariae within the clone, that is, the infrapopulation of parthenogenetic progeny in a single molluskan host. The level of genomic diversity of particular cercariae isolates from a single clone, detected with EcoR1/Mse1 AFLP reaction, was significantly lower than the variability of cercariae from different clones. The presence of intraclonal genomic diversity indicates a nonsexual shuffle of alleles during parthenogenesis in the rediae of H. elongata. The obtained polymorphic AFLP fragments were long enough to detect the sequences that may be responsible for clonal genomic variability. Based on this, AFLP can be recommended as a tool for the study of genetic mechanisms of this variability.

Reduced infectivity inHimasthla elongata(Trematoda, Himasthlidae) cercariae with deviant photoreaction

“…Moreover, the periwinkles in the studied population were previously shown to bear single-miracidium infection. Individual cercariae amplified fragment length polymorphism (AFLP) analysis showed that larvae cluster according to their origin – that is, according to the mollusc they were extracted from (Galaktionov et al ., 2016). So, in our case, multiple infection of the host by H. elongata miracidia cannot explain variation of cercarial photoreactions.…”

“…Several other systems with low PI and, hence, likely single miracidium infection provide evidence of genetic heterogeneity in cercariae produced within one snail individual (Khalturin et al ., 2000; Semyenova et al, 2005; Solovyeva et al ., 2013; Galaktionov et al , 2014). Intraclonal polymorphism in cercariae apparently emerges during their embryogenesis, because it is detected not just among cercariae emitted by one mollusc, but also among the offspring of one redia (Galaktionov et al , 2016) or sporocyst (Korsunenko et al , 2013). We suppose that genetic diversity in the absence of meiosis is assumed to be guided by several possible mechanisms.…”

“…For example, phenotypic variation in Schistosoma mansoni is induced by direct modulation of this parasite epigenotype (Cosseau et al ., 2010). Intraclonal genetic heterogeneity in H. elongata cercariae (Galaktionov et al ., 2016) may be linked to their phenotype and may manifest as variance in both their photoreactions and infectivity. It is not unlikely that the reduced mussel infection and in vitro encystment success in deviant cercariae is due to non-specific genomic rearrangements.…”

“…So, when prevalence of mollusc infection with trematodes is low (as observed in many Arctic and subarctic communities – Galaktionov & Bustnes, 1999; Levakin et al ., 2013a), probability of infection with several conspecific miracidia is very low. Among Littorina littorea infected with Himasthla elongata in our study region, no double infection has been detected with molecular genetic methods (Galaktionov et al ., 2016). So, cercariae produced by a group of parthenitae within one snail may be considered a clone.…”

Transposons-Based Clonal Diversity in Trematode Involves Parts of CR1 (LINE) in Eu- and Heterochromatin

“…Intra-and interclonal variability in infectivity rates and longevity [28], as well as in responses to light and gravity, have been observed in the larvae [29]. Clonal polymorphism in cercariae has been previously described [30], but the source of this phenomenon is unclear. In this work, we analysed the repetitive elements in the primary sequence of the H. elongata genome and in transcriptome data, identified clonal polymorphism in separate cercariae by using simplified amplified fragment length polymorphism (SAFLP), and annotated particular SAFLP fragments.…”