An integrative taxonomic study of the genus Theromyzon (Hirudinea: Glossiphoniidae), with description of a new North American species
Bibliographic record
Abstract
Theromyzon Philippi, 1867 is a genus of sanguivorous, freshwater leeches in the family Glossiphoniidae. The genus is broadly distributed across the globe, possibly due to the frequent feeding in the nasopharyngeal cavities of migratory waterfowl that may allow for long distance dispersal. The genus has a history of taxonomic confusion resulting from mischaracterisations of key morphological features of type specimens that have produced several re-descriptions and synonyms. Here, we bring partial order to this confusion through robust morphological investigations of newly collected North American (and a single South American) specimens, representing most of the known species diversity from this continent. We also produce the first species-level phylogeny for Theromyzon and attempt to understand species boundaries regarding both morphology and genetics. Our results demonstrate that there are at least five species of Theromyzon present in North America (T. bifarium, T. tessulatum, T. rude, T. trizonare, and a clade that needs further investigation), and a hitherto undescribed taxon that does not conform to any previously published description, and represents a unique lineage in the phylogeny; we describe this new species under the name Theromyzon tigris sp. nov. This study sheds light on the discriminatory power of select morphological characters and the distribution of phenotypes within the genus. We also provide a comprehensive classification framework for the known species within the genus designed to facilitate identification and minimise future taxonomic confusion.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".