Fortified defense: Novel mechanisms allow a treehole mosquito to resist predation from a predatory mosquito
Data files
Sep 08, 2025 version files 169.32 KB
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Dahlberg_and_Yee_Master_Raw_Data_updated_.xlsx
164.88 KB
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README.md
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Abstract
Insects often use a suite of antipredatory defenses to avoid predation. Although larval mosquitoes exhibit behavioral modifications to avoid aquatic predators, it is not clear if other antipredator mechanisms exist for this group. Larvae of the treehole species Orthopodomyia signifera are known to coexist with the predatory mosquito Toxorhynchites rutilus, which often eliminates all other available prey.
We tested three hypotheses that could explain how Or. signifera resists predation. First, Or. signifera larvae may exhibit behavioral changes that limit interactions with Tx. rutilus, second their long thoracic setae may serve as a physical defense, and third their unusual orange color may reflect a chemical defense (aposematic coloration sequestered from secondary plant compounds form larval environments). We tested these hypotheses under laboratory conditions. For the first, we allowed predators to feed on either Or. signifera or Aedes albopictus, a species with short setae known to be susceptible to predation by Tx. rutilus. Late instar Or. signifera were then recorded in water from either trials to determine their behavioral responses to predation cues. For the second hypothesis we amputated setae to determine if this affected predation by Tx. rutilus. Finally, we grew Or. signifera to late instars in water rich in tannins from natural tree holes or water lacking tannin and subject those to predation by Tx. rutilus and recorded strike rates and handing times.
When Or. signifera were exposed to conspecific and heterospecific predation cues both caused Or. signifera to change to less risky behaviors, with conspecific cues causing the most stringent defensive behavior. Amputation of setae from Or. signifera larvae led to mass drowning. However, we detected no differences in strike rates between Or. signifera (mean strikes = 2.38 ± 0.50) and Aedes albopictus (2.00 ± 0.49). Finally, regardless of an artificial or a natural diet containing secondary plant compounds, Or. signifera had significantly longer handling time (11,536.3 sec) versus Ae. albopictus (4,772.8 sec) and Tx. rutilus made significantly fewer strikes after consuming an Or. signifera (0.25 ± 0.6) compared with Ae. albopictus (2.00 ± 0.49). 4. Orthopodomyia signifera use both behavioral and an additional unknown antipredatory mechanism(s) to avoid predation by Tx. rutilus, a unique finding for mosquito larvae. Despite past research into larval mosquito predator avoidance Or. signifera may be the first mosquito to be shown to possess multifaceted defensive capabilities. The complex responses to predation may suggest additional selection pressures experienced by mosquitoes and other insects not typically investigated.
https://doi.org/10.5061/dryad.8cz8w9h2j
Description of the data and file structure
We tested three hypotheses that could explain how Or. signifera resists predation. First, Or. signifera larvae may exhibit behavioral changes that limit interactions with Tx. rutilus, second their long thoracic setae may serve as a physical defense, and third their unusual orange color may reflect a chemical defense (aposematic coloration sequestered from secondary plant compounds form larval environments). We tested these hypotheses under laboratory conditions. For the first, we allowed predators to feed on either Or. signifera or Aedes albopictus, a species with short setae known to be susceptible to predation by Tx. rutilus. Late instar Or. signifera were then recorded in water from either trials to determine their behavioral responses to predation cues. For the second hypothesis we amputated setae to determine if this affected predation by Tx. rutilus. Finally, we grew Or. signifera to late instars in water rich in tannins from natural tree holes or water lacking tannin and subject those to predation by Tx. rutilus and recorded strike rates and handing times.
The dataset for the below descriptions is Dahlberg_and_Yee_Master_Raw_Data.xlsx
Tab 1 (Toxorhynchites Feeding Rates): This sheet details the treatment, species, and time intervals for the expirement detailing the predation rates of the Toxorhynchites. Time is measured in minutes and and broken into 15 minute segments. The last time interval represents 24 hours after the expirement started. The treatments are reprsented by the abreviations at the top and rep number. SA= Sterile water Aedes albopictus, SO= Sterile Water Orthopodoimya signifera, TA= Treehole water Aedes albopictus, TO= Treehole Water Orthopodoimya signifera
Tab 2 (Albopictus Raw Data Behavior): This sheet represents the raw data for Orthopodomyia signifera responding to predation fro Toxorhynchites rutilus while feeding on Aedes albopictus. The date represents when the recording took place. Species reprsents the genus of the species tested. Orthopdomyia signifera. Treatment represents the water the Orthopodomyia signifera was tested in. DI water is a negative control and Albo Fed Toxo is water Toxorhynchites rutilus inhabited and fed on Aedes albopictus. Rep is the replicate number. Time represents the activity and location of the larvae at a given time point a 1 represents the larvae doing that activity and what location it inhabited. Cells containing "n/a" are blank due to a lack of that behavior or location at the time of observation.
Tab 3 (Orthopodomyia Raw Data Behavior): This sheet represents the raw data for Orthopodomyia signifera responding to predation from Toxorhynchites rutilus while feeding on Orthopodomyia signifera. The date represents when the recording took place. Species reprsents the genus of the species tested. Orthopdomyia signifera. Treatment represents the water the Orthopodomyia signifera was tested in. DI water is a negative control and Ortho Fed Toxo is water Toxorhnchites rutilus inhabited and fed on Orthopodomyia signifera. Rep is the replicate number. Time represents the activity and location of the larvae at a given time point a 1 represents the larvae doing that activity and what location it inhabited. Cells containing "n/a" are blank due to a lack of that behavior or location at the time of observation.
Tab 4 (Handling Time Raw Data): This sheet represents the handling times for Toxorhynchites rutilus when it was feeding on Aedes albopictus and Orthopdomyia signifera. The treatment represents the diet the larvae was raised on. Replicate is the replicate number. Species is the species of larvae consumed by the Toxorhynchites rutilus, albo stands for Aedes albopictus and Ortho stands for Orthopdomyia signifera. Time Consuming prey is the amount of time Toxorhynchites rutilus spend feeding on a larvae. Time Between Prey is the amount of time between Toxorhynchites rutilus consuming a prey item. Handling time is the handling time for Toxorhynchites rutilus feeding on that prey item. Accuarcy of Strike is how many strikes Toxorhynchites rutilus makes to sucessfully grasp an indvidual prey item. A cell with "n/a" represents a missing value.