Morphological characterization and molecular phylogeny of zoonotic trematodes in the freshwater snail Asolene platae

Abstract

In the context of a broader program dealing with the symbiotic associations of apple snails, we sampled three species that coexist in Lake Regatas (Palermo, Buenos Aires, Argentina). The population ofAsolene platae, (but not those ofPomacea canaliculataandPomacea scalaris) showed trematode larvae (echinocercariae and xiphidiocercariae) in haemocoelic spaces and connective tissue of the digestive gland. The echinocercariae resembled those of the genusEchinochasmus, but lacked sensory hairs on their body and tail; whereas xiphidiocercariae were similar to the xiphidiocercariae armatae belonging to the Opisthoglyphe type. The phylogenetical positions of these trematodes were inferred by the 28S rRNA, ITS1 and mtCOXI gene sequences. The 28S rRNA gene linked the echinocercarial sequences with the polyphyletic genusEchinochasmus(Echinochasmidae), while the xiphidiocercarial sequences were linked with the genusPhaneropsolus(Phaneropsolidae). The molecular markers used were able to distinguish two cryptic molecular entities of the single echinocercarial morphotype. Although ITS1 and mtCOXI did not allow resolving phylogeny beyond the family level because of the scarce number of sequences in the molecular databases, both cercariae (echinocercariae and xiphidiocercariae) could be distinguished by the Internal Transcribed Spacer 1 amplicon size. This is the first correlative morphological and molecular study of zoonotic trematodes in Neotropical ampullariids.

Abundance and annual distribution of freshwater snails and some trematode cercariae at Damietta Governorate, Egypt

“…The external features of the gymnocephalus cercaria in the present investigation were consistent with the characteristics of the gymnocephalus cercariae emerging from Bellamya aeruginosa ( Xiao et al ., 2005 ). The morphological features of the xiphidiocercariae in the current study were also consistent with the characteristics of the xiphidiocercaria harvested from Asolene platae ( Dellagnola et al ., 2019 ). Based on our results, only Lanistes carinatus was intermediate host for transmitting trematodes larvae at Damietta Governorate.…”

“…Larvae of trematodes (cercariae) emerge from the snail tissue and might find the suitable secondary intermediate host or definitive host ( Bdir & Adwan, 2011 ; Chantima et al ., 2018). The genera of Biomphalaria , Bulinus , Lymnaea , Melanoides , Pomacea , and Asolene are important intermediate hosts for the trematode parasites Schistosoma , Stomylotrema , Echinochasmus , Phaneropsolus , and Fasciola ( Besprozvannykh et al ., 2013 ; Dida et al ., 2014 ; Pinto et al ., 2015 ; Dellagnola et al ., 2019 ). Therefore, freshwater snails perform significant roles in the human and veterinary health ( Okafor & Ngang, 2004 ).…”

First morphological and molecular identification of the cercaria of Stomylotrema vicarium from the endemic apple snail Pomacea americanista

“…There were no representatives of Stomylotrematidae in the database. Both trematode sequences found in apple snails, MW481318 from P. americanista (this work) and MH532426 from Asolene platae (Dellagnola et al, 2019a) were grouped together (62%). Both sequences were sisters with the sequence JQ231122 (Collyriclum faba, Collyriclidae, 66%).…”

“…Trematode larvae were also obtained from the digestive gland by the osmotic lysis of glandular cells, followed by sequential sedimentations (Dellagnola et al, 2019a). This fraction, enriched in trematode parasites, was used for morphometric and molecular (see next section) determinations.…”

“…A molecular approach involving loci with different evolutionary rates (e.g. rRNA 28S gene or ribosomic Intergenic Spacer 1; Schulenburg et al, 1999;Tkach et al, 2000;Olson et al, 2003;Blasco-Costa et al, 2016) has been helpful to identify trematode cryptic species (Miura et al, 2005;Vilas et al, 2005;Razo-Mendivil et al, 2010;Dellagnola et al, 2019a). Besides, integrated morphological and molecular approaches with ribosomal markers helped in the identification of fluke mixed larval infections (Dellagnola et al, 2019a).…”