In the Asia-Pacific region, the COI DNA test revealed the divergence of the bivalve mollusc Mactra chinensis into three species; can these species be distinguished using shell coloration and sperm structure?
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Bibliographic record
Abstract
Abstract According to COI DNA barcoding testing, the marine bivalve mollusc Mactra chinensis , which is native to the Asia-Pacific region, diverged into three species. These species were preliminary characterized as M. chinensis COI clade I, M. chinensis COI clade II and M. chinensis COI clade III. To find out whether it is possible to morphologically distinguish samples representing genetic clades, we examined the color of the shells and the structure of the spermatozoa. It was found that the number of detected coloration types exceeds the number of detected species. In addition, it was shown that individuals belonging to the same genetic clade can have shells of different colors. Consequently, it is impossible to choose one type of shell coloration as a species-specific trait. For sperm, the sperm morphological patterns found in each of the three species are consistent with the M. chinensis sperm model described in previous reports. However, the single sperm variant is also not applicable to discriminate between species derived from M. chinensis , since heterogeneous variants of spermatozoa differing in the length of the acrosomal rod were found. We hypothesized that genetic divergence of species could cause a shift towards predominance of one of the sperm variants, and that species-specific sperm morphs could be quantitatively dominant in molluscs belonging to different clades. However, the dominant sperm morphs were the same in COI clade I and COI clade III. Thus, dominant sperm morphs are useless as species-specific traits. However, shell color and sperm parameters are specific to different geographic regions, and it seems that unique environmental factors can determine shell color and sperm morphology. As a result, both shells and spermatozoa can be used to distinguish the geographical forms of M. chinensis , regardless of the belonging of the forms to a particular genetic clade. Here we propose the introduction of geographic identifiers, in which the shell color and parameters of sperm sets are used as morphological criteria to determine the geographical origin of mollusc specimens belonging to the M. chinensis species complex.
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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 | 0.003 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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 it