Two New Marine Species of <i>Placopus</i> (Vampyrellida, Rhizaria) That Perforate the Theca of <i>Tetraselmis</i> (Chlorodendrales, Viridiplantae)
Bibliographic record
Abstract
Vampyrellids (Vampyrellida, Rhizaria) are a major group of predatory amoebae known primarily from freshwater and soil. Environmental sequence data indicate that there is also a considerable diversity of vampyrellids inhabiting marine ecosystems, but their phenotypic traits and ecology remain largely unexplored. We discovered algivorous vampyrellids of the filoflabellate morphotype in coastal habitats in Atlantic Canada, established cultures by single-cell isolation, and characterised three strains using light microscopy, SSU rRNA gene sequencing, feeding experiments and growth experiments at various salinities. These strains exhibit orange, discoid trophozoites with ventral filopodia, moving granules ("membranosomes"), and rolling locomotion, similar to freshwater species previously assigned to Hyalodiscus Hertwig & Lesser, but here moved to Placopus Schulze (due to homonymy with Hyalodiscus Ehrenberg). SSU rRNA gene phylogenies place our strains in two distinct positions within "lineage B3" (here referred to as Placopodidae). Based on these morphological, habitat and molecular data, we describe two new species, Placopus melkoniani sp. nov. and Placopus pusillus sp. nov., both of which feed on chlorophyte flagellates (Tetraselmis, Pyramimonas) and the cryptophyte Chroomonas. They perforate the theca of Tetraselmis to extract the protoplast, and thereby represent the first vampyrellids known to degrade the biochemically exotic cell wall of the Chlorodendrales (Chlorophyta, Viridiplantae).
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 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".