Ultraviolet irradiation of eggs and blastomere isolation experiments suggest that gastrulation in the direct developing ascidian, <i>Molgula pacifica</i>, requires localized cytoplasmic determinants in the egg and cell signaling beginning at the two‐cell stage
Bibliographic record
Abstract
Gastrulation in the maximum direct developing ascidian Molgula pacifica is highly modified compared with commonly studied "model" ascidians in that endoderm cells situated in the vegetal pole region do not undergo typical invagination and due to the absence of a typical blastopore the involution of mesoderm cells is highly modified. At the gastrula stage, embryos are comprised of a central cluster of large yolky cells that are surrounded by a single layer of ectoderm cells in which there is only a slight indication of an inward movement of cells at the vegetal pole. As a consequence, these embryos do not form an archenteron. In the present study, ultraviolet (UV) irradiation of fertilized eggs tested the possibility that cortical cytoplasmic factors are required for gastrulation, and blastomere isolation experiments tested the possibility that cell signaling beginning at the two-cell stage may be required for the development of the gastrula. Irradiation of unoriented fertilized eggs with UV light resulted in late cleavage stage embryos that failed to undergo gastrulation. When blastomeres were isolated from two-cell embryos, they developed into late cleavage stage embryos; however, they did not undergo gastrulation and subsequently develop into juveniles. These results suggest that cytoplasmic factors required for gastrulation are localized in the egg cortex, but in contrast to previously studied indirect developers, these factors are not exclusively localized in the vegetal pole region at the first stage of ooplasmic segregation. Furthermore, the inability of embryos derived from blastomeres isolated at the two-cell stage to undergo gastrulation and develop into juveniles suggests that important cell signaling begins as early as the two-cell stage in M. pacifica. These results are discussed in terms of the evolution of maximum direct development in ascidians.
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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".