Species Boundaries in Gregarine Apicomplexan Parasites: A Case Study—Comparison of Morphometric and Molecular Variability in <i>Lecudina</i> cf. <i>tuzetae</i> (Eugregarinorida, Lecudinidae)
Bibliographic record
Abstract
Trophozoites of gregarine apicomplexans are large feeding cells with diverse morphologies that have played a prominent role in gregarine systematics. The range of variability in trophozoite shapes and sizes can be very high even within a single species depending on developmental stages and host environmental conditions; this makes the delimitation of different species of gregarines based on morphological criteria alone very difficult. Accordingly, comparisons of morphological variability and molecular variability in gregarines are necessary to provide a pragmatic framework for establishing species boundaries within this diverse and poorly understood group of parasites. We investigated the morphological and molecular variability present in the gregarine Lecudina cf. tuzetae from the intestines of Nereis vexillosa (Polychaeta) collected in two different locations in Canada. Three distinct morphotypes of trophozoites were identified and the small subunit (SSU) rDNA was sequenced either from multicell isolates of the same morphotype or from single cells. The aim of this investigation was to determine whether the different morphotypes and localities reflected phylogenetic relatedness as inferred from the SSU rDNA sequence data. Phylogenetic analyses of the SSU rDNA demonstrated that the new sequences did not cluster according to morphotype or locality and instead were intermingled within a strongly supported clade. A comparison of 1,657 bp from 45 new sequences demonstrated divergences between 0% and 3.9%. These data suggest that it is necessary to acquire both morphological and molecular data in order to effectively delimit the "clouds" of variation associated with each gregarine species and to unambiguously reidentify these species in the future.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".