Evidence of morphological adaptation to life underwater: sternal keel affects swimming speed in giant water scavenger beetles (Coleoptera: Hydrophilidae: Hydrophilini)
Bibliographic record
Abstract
Fundamentally, insects evolved on land and secondarily inhabited aquatic environments multiple times. To live underwater, aquatic insects have acquired enormously variable morphological, developmental, physiological, and ecological traits, such as gas exchange systems and swimming-related characteristics. Giant water scavenger beetles of the tribe Hydrophilini (Coleoptera: Hydrophilidae) are characterized by the presence of a sternal keel, which often extends posteriorly. Despite being a conspicuous morphological trait, its function remains unclear. Here, I verified two hypotheses: keel affects (1) submergence time following air replacement and (2) speed and oscillatory movement during forward swimming in Hydrophilus acuminatus Motschulsky, 1854. Submergence time was affected by body mass rather than keel removal; in other words, larger individuals replaced their gas gills more frequently. Keel removal reduced swimming speed by 12.5%. These observations support the second hypothesis, and are also consistent with previous speculations that the sternal keel is a key adaptation for swimming, but the results showed that the degree of oscillation was closely related to body mass but not to keel removal. Further studies are warranted to elucidate precise factors through which the presence of the keel increases swimming speed. Such studies would provide clues into understanding the associations among body size, swimming methods, and morphological traits.
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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 | 0.000 | 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) | 0.002 | 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".