Freshwater snail trematodes: linking form and identity

This proposed pilot would build a small reference collection of larval trematodes from freshwater snails using suitable preserved material. Microscopy and specimen records would document recognizable forms. Selected DNA markers would then test identification where preservation permits. The intended result is an illustrated reference that connects each identification to its specimen, images and supporting evidence.

SEPS research concept · 23 October 2026

Research question

How much taxonomic information can be recovered from a small, carefully documented collection of larval trematodes associated with freshwater snails?

Scientific basis

Published studies have combined larval trematode morphology with ribosomal DNA to improve identification. They also show why a recognizable larval form does not always provide a species name. The proposed approach draws on Velázquez-Urrieta and Pérez-Ponce de León (2021) and Bawm et al. (2022).

Starting material and scope

Suitable archived or collaborator-provided material would be sought before work begins. Selection would prioritize reliable host records and preservation compatible with microscopy and DNA recovery. This would begin as a laboratory reference project. Material availability has not been established.

Proposed laboratory approach

Each specimen or clearly defined lot would receive a traceable record. Brightfield microscopy would document diagnostic structures and measurements. Stereo microscopy would support sorting and review of host material. Identification would begin with visible characters and relevant taxonomic literature.

Where suitable material permits, targeted PCR and external bidirectional Sanger sequencing would evaluate 28S rDNA or ITS2. Marker choice would depend on the suspected group and available references. Images and sequences would be linked to individual specimens whenever possible. Evidence linked only at the specimen-lot level would be labeled separately.

Intended outputs

The intended outputs are an illustrated reference of documented forms, a specimen and preservation register, and linked sequence records where obtainable. Retained specimens or photographic vouchers would preserve the basis of each identification. The pilot would also identify material worth pursuing in a larger comparative study.

Interpretation

Identification would stop at the most defensible taxonomic level. Unresolved specimens would remain unresolved. This initial collection would not establish population prevalence or transmission pathways.

Literature cited

Velázquez-Urrieta, Y., & Pérez-Ponce de León, G. (2021). Morphological and molecular assessment of the diversity of trematode communities in freshwater gastropods and bivalves in Los Tuxtlas tropical rainforest. Journal of Helminthology, 95, e44. https://doi.org/10.1017/S0022149X21000407

Bawm, S., et al. (2022). Morphological and molecular identification of trematode cercariae related with humans and animal health in freshwater snails from a lake and a dam in Myanmar. Parasitology Research, 121, 653–665. https://doi.org/10.1007/s00436-022-07428-4