Ultrastructural Bacteriocyte Characterization among Chemosymbiotic <i>Alviniconcha</i> Snails from Hydrothermal Vents in the Indo-Pacific Oceans
Bibliographic record
Abstract
Symbiotic associations between deep-sea invertebrates and chemoautotrophic bacteria vary widely in terms of symbiont type, localization, and host nutritional strategy, yet host-symbiont dynamics remain poorly understood in some taxa. Here we advance knowledge of host-symbiont interactions within the snail genus Alviniconcha, which are abundant members of hydrothermal vent communities in the Indian and West Pacific Oceans. Using electron microscopy, we use comparative analyses based on the ultrastructural characteristics of the host bacteriocytes and bacterial symbionts. Despite previous assumptions that all Alviniconcha host endosymbiotic bacteria, we find that A. boucheti hosts episymbiotic bacteria, which densely populate the microvilli of bacteriocytes and appear to be endocytosed. Alviniconcha may also use species-specific organizational and nutritional strategies within bacteriocytes, supporting differences in symbiont maintenance and digestion. Alviniconcha adamantis and A. hessleri hosted endosymbionts in individual vacuoles with little evidence of symbiont digestion, A. kojimai and A. strummeri housed their symbionts similarly but with comparatively more evidence of digestion, and A. marisindica and A. boucheti stored symbionts in large multibacterial vacuoles, with the highest apparent degree of digestion in A. boucheti. Host species also differed in the density and morphotype of symbionts present, with all species hosting one to three morphotypes of symbionts resembling thiotrophic bacteria. In addition, both A. adamantis and A. hessleri harbored symbionts resembling methanotrophic bacteria, which genetic studies (16S rRNA amplicon and genomic) to date have not detected. This study provides the first genus-wide comparison of host-symbiont interactions in Alviniconcha, revealing key cellular features and advancing understanding of the diverse associations between hosts and their bacterial symbionts.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".