DOI: 10.5061/dryad.8cz8w9h2j
title: Fortified defense: Novel mechanisms allow a treehole mosquito to resist predation from a predatory mosquito

description: 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.
description: # Fortified defense: Novel mechanisms allow a treehole mosquito to resist
 predation from a predatory mosquito
 [https://doi.org/10.5061/dryad.8cz8w9h2j](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.