DOI: 10.5061/dryad.6q573n63f
title: Growth rate and oviposition preference of Oc. togoi & Ae. albopictus in salinity stress

description: Ochlerotatus togoi is a salt-tolerant euryhaline mosquito that lays its
 eggs in rock pools. Although it is a pest that transmits flaviviruses and
 filarial worms to humans, ecological studies have not been actively
 conducted because of its limited habitat. Rising sea levels have created a
 favorable environment for Oc. togoi to survive; additionally, the
 incidence of  Oc. togoi-borne diseases may increase with an
 increase in population of Oc. togoi. We examined oviposition and growth
 rates in the range of 0–35 psu to obtain ecological data for Oc. togoi.
 Ochlerotatus togoi exhibited the highest oviposition preference at 0 psu;
 however, the hatching rate was highest at 10 psu, the pupation rate was
 highest at 25 psu, and the emergence rate was highest at 5 psu.
 Ochlerotatus togoi showed the highest rate of growth into adults at 25
 psu. The results were verified for statistical significance using
 Mann–Whitney U and Kruskal–Wallis H tests (post hoc test: Bonferroni), and
 a regression equation was generated for the incidence of adult Oc. togoi
 based on the change in salinity (y = −14.318 + 9.821x; y = adult incidence
 rate; x = salinity). The oviposition habits and developmental conditions
 of Oc. togoi were confirmed and the number of Oc. togoi was predicted
 based on the changes in sea level and ocean salinity. The results of this
 study are expected to be used for controlling salt-tolerant vectors and
 responding to vector-borne diseases.
description: 1. Collection and
 Classification Samples of <em>Oc. togoi</em> were
 collected from Geoje, Jeju, and Pohang, South Korea. Larvae were collected
 from stagnant water of artificial structures or rock pools near the coast
 (Table 1). The collected samples were classified according to the salinity
 of the habitat, and transferred to the insectary (temperature 27°C ± 1°C,
 humidity 70%, L:D = 12:12) of the Animal Systematics & Taxonomy
 Laboratory of Kyungpook National University. They were raised under the
 same salinity in insectary as the salinity at the collection points. The
 hatched adults were then used for the oviposition preference experiment
 and the eggs laid by the adults were used for growth rate experiments. The
 collected <em>Oc. togoi</em> were morphologically classified
 according to the taxonomic keys described previously (Lee, 1987; Ree,
 2003). Molecular identification (forward primer: 5′-AGG ACA CAT GAA CAC
 CCA CA-3′; reverse primer: 5′-AGG CGG TGG AGT GTA TGG-3′) was performed as
 described previously (Bang, 2021).
 2. Oviposition
 preference Adult <em>Oc. togoi</em> females (n
 = 100) collected from the same collection points were randomly selected
 and set as one group. The experiment was conducted in nine groups
 according to nine collection points (Table 1). The <em>Oc.
 togoi</em> group was placed into an adult mosquito cage containing
 10% concentration sugar cotton and fed for 3 days. An acrylic case
 containing eight salinity concentration (0, 5, 10, 15, 20, 25, 30, and 35
 psu; psu: practical salinity unit) was made by aquarium salt with
 distilled water was then established. Then the number of eggs laid for 24
 h in each salinity concentration was counted (Fig 1). Each salinity
 concentration was replicated three times producing 27 experimental units,
 and 27 oviposition preference experiments were
 performed. 3. Growth rate
 As with oviposition
 preference, the experiments were conducted in an acrylic case divided into
 eight salinity concentration. The growth of <em>Oc. togoi</em>
 was determined by placing 100 eggs into each salinity concentration. All
 eggs were oviposited under the same conditions in insectary (temperature
 27°C ± 1°C, humidity 70%, L:D = 12:12) and all developing larvae were
 provided the same amount of food. The hatching rate was determined using
 the cumulative number of larvae hatched from the eggs, the pupation rate
 was determined using the cumulative number of pupae from the larvae, and
 the emergence rate was assessed using the cumulative number of adults
 emerging from the pupa. Finally, the adult rate (the number of eggs who
 made it to adult) was determined using the cumulative population of adults
 grown from eggs. A total of nine growth rate experiments were conducted
 for <em>Oc. togoi</em> collected from Geoje, Jeju, and Pohang,
 in triplicate. Experiments were conducted with <em>Oc. togoi
 </em>collected from as similar salinity as possible to minimize
 variables that are feared to be due to differences in salinity at
 collection points (Geoje: 0.5 psu; Jeju: 1 psu; Pohang: 1.2
 psu). 4. Control group
 To compare the salt-tolerance
 ability of <em>Oc. togoi</em>, a freshwater species,
 <em>Aedes albopictus</em>, was used as the control group.
 <em>Aedes albopictus</em> was raised individually in the
 insectary of the Animal Systematics & Taxonomy Laboratory of
 Kyungpook National University. The oviposition preference and growth rate
 experiments were conducted in the same way as that for <em>Oc.
 togoi</em> and repeated three or five times,
 respectively. 5. Statistical analysis
 Significance was verified by
 comparing the average growth rates of <em>Ae. albopictus</em>
 and <em>Oc. togoi </em>using Mann–Whitney U test. Using
 Kruskal–Wallis H test, the average growth rates of <em>Oc.
 togoi</em> collected from Geoje, Jeju, and Pohang and <em>Ae.
 albopictus</em> were compared to establish statistical significance
 among the four groups. To confirm which of the four groups exhibited
 statistical significance, a post hoc analysis was performed using
 Bonferroni’s multiple comparison test. Finally, a simple linear regression
 analysis was performed based on the adult rate.