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Physiological Mechanisms of Major Ion Toxicity in Aquatic Insects.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Physiological Mechanisms of Major Ion Toxicity in Aquatic Insects./
Author:	Orr, Sarah Elizabeth.
Description:	1 online resource (182 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-02, Section: B.
Contained By:	Dissertations Abstracts International84-02B.
Subject:	Physiology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29228699click for full text (PQDT)
ISBN:	9798841527763

Physiological Mechanisms of Major Ion Toxicity in Aquatic Insects.
Orr, Sarah Elizabeth.

Physiological Mechanisms of Major Ion Toxicity in Aquatic Insects. - 1 online resource (182 pages)

Source: Dissertations Abstracts International, Volume: 84-02, Section: B.

Thesis (Ph.D.)--North Carolina State University, 2022.

Includes bibliographical references

Human activities and changes in climate are profoundly influencing the ionic composition of freshwaters. Aquatic insects often dominate the ecology of these systems and ecologists report diversity losses associated with changes in salinity. Our central hypothesis is that the energetic cost of osmoregulation in saltier waters leads to detrimental toxicological consequences in sensitive aquatic insects. First, we postulated that temperature modulates ion transport rates. Radiotracer ( 22Na, 35SO4, and 45Ca) experiments with the lab-reared mayfly, Neocloeon triangulifer and other fieldcollected insects showed that increasing temperature generally increased ion transport rates. For example, increasing temperature from 15°C to 25°C, increased Na uptake rates by two-fold (p < 0.0001) in the caddisfly, Hydropsyche sparna. Then, we demonstrated that the toxicity of SO4 was influenced by temperature profoundly in a 96-hour toxicity test. Under the saltiest conditions (1500 mg/L SO4), N. triangulifer survival was 78% at 15°C, but only 44% at 25°C (p < 0.0036). We concluded increases in salinity and/or temperature influence ion flux rates and ultimately, organismal performance in several species of aquatic insects. Then, we asked if significant sensitivity differences occur among different larval life stages of N. triangulifer by conducting traditional 96-h toxicity tests with NaCl, CaCl2, and Ca/MgSO4. Using a general linear model, we observed that younger larvae were moderately more sensitive than older larvae in the three salts (p = 0.0065). To assess the potential changes in ion flux between larval stages, we used radiotracers (22Na, 35SO4, or 45Ca) in 18-day old and 25- day old larvae and found no significant differences in ion uptake rates (p = 0.17, p = 0.53, and p = 0.22, respectively). Our results indicate that ontogenetic differences should be considered in the future when using N. triangulifer. Next, we used N. triangulifer to ask how ionic exposure history alters physiological processes and responses to subsequent major ion exposures. Using radiotracers, we observed that mayflies chronically reared in elevated sodium or sulfate had 2-fold (p < 0.0001) and 8-fold (p < 0.0001) lower ion uptake rates than naive mayflies. These acclimatory ion transport changes provided protection in 96-hour toxicity tests for sodium, but not sulfate. Interestingly, calcium uptake was uniformly much lower and minimally influenced by exposure history, but was poorly tolerated in the toxicity bioassays. With qRT-PCR, we observed that the expression of many ion transporter genes in mayflies was influenced by elevated salinity in an ion-specific manner. To address the ion-specific physiological plasticity observed, we characterized the proteins on the gills of N. triangulifer through shotgun proteomic analysis, which revealed salinity-induced changes in protein expression. Ongoing analysis will elucidate the exact transporters involved in apical transport on the gill. We then asked if osmoregulatory traits could explain the salinity niches and tolerances of various aquatic insects. We performed radiotracer experiments in different waters (dilute to salty) with various species of mayflies (N. triangulifer, C. floridanus, D. coloradensis, M. modestum, and Isonychia sp.), a mosquito (A. albopictus), and a caddisfly (H. betteni). Statistical analysis is ongoing, but has revealed interesting relationships among species' ion transport rates and permeability (e.g., N. triangulifer lost 29% of its 22Na label after 9 h DI water challenge while H. betteni lost only 11%).

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798841527763Subjects--Topical Terms:

518431
Physiology.
Index Terms--Genre/Form:

542853
Electronic books.

Physiological Mechanisms of Major Ion Toxicity in Aquatic Insects.
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520 $a Human activities and changes in climate are profoundly influencing the ionic composition of freshwaters. Aquatic insects often dominate the ecology of these systems and ecologists report diversity losses associated with changes in salinity. Our central hypothesis is that the energetic cost of osmoregulation in saltier waters leads to detrimental toxicological consequences in sensitive aquatic insects. First, we postulated that temperature modulates ion transport rates. Radiotracer ( 22Na, 35SO4, and 45Ca) experiments with the lab-reared mayfly, Neocloeon triangulifer and other fieldcollected insects showed that increasing temperature generally increased ion transport rates. For example, increasing temperature from 15°C to 25°C, increased Na uptake rates by two-fold (p < 0.0001) in the caddisfly, Hydropsyche sparna. Then, we demonstrated that the toxicity of SO4 was influenced by temperature profoundly in a 96-hour toxicity test. Under the saltiest conditions (1500 mg/L SO4), N. triangulifer survival was 78% at 15°C, but only 44% at 25°C (p < 0.0036). We concluded increases in salinity and/or temperature influence ion flux rates and ultimately, organismal performance in several species of aquatic insects. Then, we asked if significant sensitivity differences occur among different larval life stages of N. triangulifer by conducting traditional 96-h toxicity tests with NaCl, CaCl2, and Ca/MgSO4. Using a general linear model, we observed that younger larvae were moderately more sensitive than older larvae in the three salts (p = 0.0065). To assess the potential changes in ion flux between larval stages, we used radiotracers (22Na, 35SO4, or 45Ca) in 18-day old and 25- day old larvae and found no significant differences in ion uptake rates (p = 0.17, p = 0.53, and p = 0.22, respectively). Our results indicate that ontogenetic differences should be considered in the future when using N. triangulifer. Next, we used N. triangulifer to ask how ionic exposure history alters physiological processes and responses to subsequent major ion exposures. Using radiotracers, we observed that mayflies chronically reared in elevated sodium or sulfate had 2-fold (p < 0.0001) and 8-fold (p < 0.0001) lower ion uptake rates than naive mayflies. These acclimatory ion transport changes provided protection in 96-hour toxicity tests for sodium, but not sulfate. Interestingly, calcium uptake was uniformly much lower and minimally influenced by exposure history, but was poorly tolerated in the toxicity bioassays. With qRT-PCR, we observed that the expression of many ion transporter genes in mayflies was influenced by elevated salinity in an ion-specific manner. To address the ion-specific physiological plasticity observed, we characterized the proteins on the gills of N. triangulifer through shotgun proteomic analysis, which revealed salinity-induced changes in protein expression. Ongoing analysis will elucidate the exact transporters involved in apical transport on the gill. We then asked if osmoregulatory traits could explain the salinity niches and tolerances of various aquatic insects. We performed radiotracer experiments in different waters (dilute to salty) with various species of mayflies (N. triangulifer, C. floridanus, D. coloradensis, M. modestum, and Isonychia sp.), a mosquito (A. albopictus), and a caddisfly (H. betteni). Statistical analysis is ongoing, but has revealed interesting relationships among species' ion transport rates and permeability (e.g., N. triangulifer lost 29% of its 22Na label after 9 h DI water challenge while H. betteni lost only 11%).
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