Identification and Allometric Scaling of Megamouth Shark (Megachasma pelagios) Mother-Offspring Specimens from Dipaculao, Aurora, Luzon Island, Philippines
Bibliographic record
Abstract
Megachasma pelagios, commonly known as the megamouth shark, is the lone extant shark species belonging to the family Megachasmidae and genus Megachasma. It was first described in 1978 by Taylor et al. (1983), with fewer than three hundred specimens recorded to date. Given its rarity and elusiveness, no pregnant or neonate megamouth sharks have ever been documented. On 14 November 2023, a freshly dead adult female megamouth shark carrying seven pups washed up on the shores of Barangay Ipil, Dipaculao, Aurora, Luzon Island, Philippines. This event has confirmed that megamouth sharks are ovoviviparous. Here, we establish the identity of the specimens using morphological and molecular methods and identify their morphometric differences through allometric analysis. Morphological identification was performed using available photo documentation and morphometric data, with results compared with published literature. On the other hand, the mitochondrial cytochrome c oxidase subunit 1 (MT-COI) gene was used for molecular identification. A phylogenetic tree was constructed using the Kimura two-parameter (K2P) model with 1000 bootstrap replicates. Allometric analysis was investigated using linear regression of each of the 19 morphometric trait measures against the total body length of the specimens. Based on morphological and molecular evidence, the results confirmed the identity of the stranded sharks as M. pelagios. Furthermore, morphological scaling of the mother vis-à-vis pups revealed that while some traits scale isometrically, the presence of negative and positive allometry in most traits indicates that the offspring are not completely isometric with the mother. Thus, it implies that the pups are morphologically distinct from the mother. Overall, this study provides a definitive identification of the stranded megamouth sharks, and the allometric measurements show new information on the basic biology of this rare fish species.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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 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".