Intraspecific variation in thermal tolerance and heat shock protein gene expression in common killifish,<i>Fundulus heteroclitus</i>
Bibliographic record
Abstract
Populations of common killifish, Fundulus heteroclitus, are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by approximately 1.5 degrees C at a wide range of acclimation temperatures (from 2-34 degrees C), and critical thermal minima differed by approximately 1.5 degrees C at acclimation temperatures above 22 degrees C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes (hsps) we obtained complete cDNA sequences for hsc70, hsp70-1 and hsp70-2, and partial sequences of hsp90alpha and hsp90beta. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2, and only a single conservative substitution between populations in hsc70. By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern killifish significantly increased hsp70-2 levels above control values (T(on)) at a heat shock temperature of 33 degrees C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern killifish had a T(on) for hsp90alpha of 30 degrees C, 2 degrees C lower than that of northern fish. This observation combined with the ability of southern killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.
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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) | 0.000 | 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".