Threat or treat: the role of fish exudates in the growth and life history of <i>Daphnia</i>
Bibliographic record
Abstract
In kairomone studies, it is often implicitly assumed that the only effect of predator exudates on their prey is to trigger anti‐predator defenses. However, chemicals originating from fish activity may also fertilize the environment and enhance the growth of zooplankton prey by increasing bacterial food availability. It is necessary to separate these two effects in order to examine the adaptive significance of zooplankton anti‐predation defenses and the ability of the prey to benefit from fish‐related food. Here, we have employed differential filtration of media to permit assessment of these two effects on growth rate and life history adjustments in two Daphnia species that differ in body size and the ability to collect small particles (greater in small‐bodied D. cucullata than in larger D. hyalina). Filters of three mesh sizes were employed: 2 μm (most bacteria pass, but detritus is retained), 0.45 μm (standard) and 0.20 μm (most bacteria and detritus retained). The concentration of kairomones in the fish medium was assumed to be unaffected by filtration. However, the abundance of bacteria in the fish and no‐fish media was dependent on the filter mesh size. This influenced the food level and its impact on Daphnia growth rate and life history. The effect of fish‐related bacterial food was greater under low than under high algal food conditions (0.1 and 1.0 mg C/L) and more significant in D. cucullata. Use of media with a diminished bacterial abundance revealed the effect of kairomones alone as (1) reduced growth rate, size at reproduction, number of pre‐adult instars, age at maturation, level of the integrated egg and body lipids, egg volume, and (2) increased number of eggs per clutch vs. body length. These effects were equally strong in both species, despite differences in body size, and were greater at the higher algal food concentration. The findings of this study indicate the need to re‐analyze and possibly revise the results of previous kairomone studies, especially those using media filtered through mesh sizes coarser than 0.2 μm that were performed under limiting algal food conditions or with species particularly able to benefit from bacterial food.
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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 | 0.001 | 0.002 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".