The biomechanics and energetics of xylem feeding in the meadow spittlebug (Philaenus spumarius)
Bibliographic record
Abstract
The watery sap within the xylem vessels of vascular plants is thought to exist under high tensions (i.e., negative pressures) that routinely exceed -1 MPa, as well as being very nutrient poor. While this should make xylem sap an energetically unfavourable source of nutrition, some Hemipteran insects within the suborder Auchenorrhyncha feed on it exclusively, extracting copious quantities of this liquid using a muscular cibarial pump. However, neither the strength of the insect’s suction, and thus the maximum xylem tensions that the insect can feed at, nor the energetic cost of xylem feeding, have been determined. Here I used adult meadow spittlebugs (Philaenus spumarius) to address this gap in knowledge. First, the maximum suction they could generate was calculated from biomechanical principles using morphological data obtained from micro-CT scans of their cibarial pump. Second, the metabolic rates (MR) of adult P. spumarius were measured while feeding on hydroponically-grown plants (Vicia faba, Pisum sativum, and Medicago sativa) with known xylem tensions, while their rate of xylem sap extraction and cibarial pumping frequency (fpump) were obtained from simultaneously recorded video footage. Furthermore, during these feeding experiments, the plants were exposed to the osmolyte polyethylene glycol (PEG), revealing how the insects changed their feeding behaviour in response to increasing xylem tensions. These findings indicate that the cibarial pump is capable of generating an average maximum tension of -1.3 MPa. This is higher than any xylem tension recorded from their food plants using the Scholander-Hammel pressure bomb method. In addition, while it was calculated that the xylem sap likely contains sufficient sugars to sustain the energetic requirements of pumping, the total MR of the feeding insect could be satisfied only by assuming contributions from amino acids.
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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 | 0.000 | 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) | 0.000 | 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 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".