The gular pouch in northern hemisphere parasitic lampreys (Petromyzontidae)
Bibliographic record
Abstract
The gular pouch is a large structure, of unknown function, that is present in sexually mature males of two parasitic species of southern-hemisphere lampreys. Our study showed the presence of a similar structure, of much smaller size, in both spawning and prespawning males and females in seven parasitic species of northern-hemisphere lampreys. Homology between the structure present in southern-hemisphere and northern-hemisphere lampreys was established based on the position of the pouch in the gular region and the fact that northern-hemisphere and southern-hemisphere lampreys have a sister-group relationship. The presence of lipids in the gular pouch was established in prespawning specimens of Entosphenus tridentatus (Gairdner in Richardson, 1836) and Petromyzon marinus L., 1758. The proposed hypothesis is that these lipids act as an energy source to sustain these two anadromous species during their protracted spawning migration. The hypothesis that the gular pouch is used to help carry stones for nest building was tentatively rejected pending further testing, because despite having a much smaller gular pouch, P. marinus has been observed carrying much larger stones than those carried by Geotria australis Gray, 1851. The statistically significant difference in gular-pouch volume between spawning males and females of P. marinus suggests that males use their larger pouch for courtship display. The gular pouch possessed a single lumen in the genera Ichthyomyzon Girard, 1858, Petromyzon L., 1758, and Caspiomyzon Berg, 1906, as in southern-hemisphere lampreys, whereas it comprised two lumens in the genera Entosphenus Gill, 1862 and Lampetra Bonnaterre, 1788. This is phylogenetically significant, as the two lumen gular pouch, interpreted as the derived condition, identifies a major clade of northern-hemisphere lampreys.
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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".