Trematode Parasite Infections in Freshwater Leeches from the Central Region of Lithuania: First Record of Posthodiplostomum (Dubois, 1936) in a Leech Host
Bibliographic record
Abstract
Leeches play a critical role in the transmission of digenean trematodes, yet their parasitic infections remain understudied in the Baltic region. This study investigates the diversity, prevalence, and molecular identification of trematode infections in freshwater leeches from central Lithuania. A total of five leech species (Alboglossiphonia heteroclita, Glossiphonia complanata, Glossiphonia verrucata, Helobdella stagnalis, and Erpobdella octoculata) were examined using compression and dissection techniques to detect trematode cysts, which were predominantly found in the soft tissues rather than the intestinal tract. Molecular sequencing of 18S rRNA, COI, and ITS markers, combined with phylogenetic analyses, confirmed the presence of three trematode genera: Cotylurus, Australapatemon, and Posthodiplostomum. The overall infection rate among leeches was 40.8%, with the highest prevalence observed in G. complanata (53.3%). Cotylurus spp. were the most frequently detected parasites, with genetic analyses revealing close affinities to Cotylurus syrius and Cotylurus spp. from Poland. Australapatemon species were also identified, though species-level classification remained inconclusive. Notably, this study provides the first molecular evidence of Posthodiplostomum cuticola utilizing leeches as intermediate hosts, extending the known range of hosts for this trematode. Phylogenetic analyses demonstrated the broad geographic distribution of these parasites, with close genetic matches to isolates from Poland, Russia, Canada, and Japan. The findings highlight the ecological significance of leeches in parasite transmission networks and contribute to the understanding of trematode diversity and host interactions in the Baltic region. Further molecular and ecological studies are needed to clarify species diversity and the role of leeches in the life cycles of aquatic parasites.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".