scholarly journals Oxygen limitation fails to explain upper chronic thermal limits and the temperature size rule in mayflies

2020 ◽  
pp. jeb.233338
Author(s):  
David H. Funk ◽  
Bernard W. Sweeney ◽  
John K. Jackson
Keyword(s):  
Cell Size ◽  
Aquatic Insects ◽  
Adult Size ◽  
Tissue Oxygen ◽  
Larval Life ◽  
Thermal Limit ◽  
Rearing Temperature ◽  
Thermal Limits ◽  
Cloeon Dipterum ◽  
Oxygen Concentrations

An inability to adequately meet tissue oxygen demands has been proposed as an important factor setting upper thermal limits in ectothermic invertebrates (especially aquatic species) as well as explaining the observed decline in adult size with increased rearing temperature during the immature stages (a phenomenon known as the Temperature Size Rule, or TSR). We tested this by rearing three aquatic insects (the mayflies Neocloeon triangulifer and two species of the Cloeon dipterum complex) through their entire larval life under a range of temperature and oxygen concentrations. Hyperoxia did not extend upper thermal limits, nor did it prevent the loss of size or fertility experienced near upper chronic thermal limits. At moderate temperatures, the TSR pattern was observed under conditions of hyperoxia, normoxia, and hypoxia, suggesting little or no influence of oxygen on this trend. However, for a given rearing temperature, adults were smaller and less fecund under hypoxia due to a lowering of growth rates. These mayflies greatly increased the size of their gills in response to lower dissolved oxygen concentrations but not under oxygen-saturated conditions over a temperature range yielding the classic TSR response. Using ommatidium diameter as a proxy for cell size we found the classic TSR pattern observed under moderate temperature conditions was due primarily to a change in the number of cells rather than cell size. We conclude overall that a failure to meet tissue oxygen demands is not a viable hypothesis for explaining either the chronic thermal limit or TSR pattern in these species.

scholarly journals The Function of the Gills of Mayfly Nymphs from Different Habitats

1939 ◽  
Vol 16 (3) ◽  
pp. 363-373 ◽  
Author(s):  
C. A. WINGFIELD
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Content ◽  
The Body ◽  
Gaseous Exchange ◽  
Low Oxygen ◽  
Respiratory Mechanism ◽  
Tracheal Gills ◽  
Cloeon Dipterum ◽  
Gill Function ◽  
Oxygen Concentrations

1. The oxygen consumption of normal and gill-less nymphs of the mayflies Baetis sp., Cloeon dipterum and Ephemera vulgata has been measured at various oxygen concentrations. 2. It has been found that over the complete range of oxygen concentrations studied, the tracheal gills do not aid oxygen consumption in Baetis sp. In Cloeon dipterum, at all oxygen concentrations tested, no gaseous exchange takes place through the gills; at low oxygen concentrations, however, the gills function as an accessory respiratory mechanism in ventilating the respiratory surface of the body and so aid oxygen consumption. In Ephemera Vulgata the gills aid oxygen consumption even at high oxygen concentrations. In this species the gills may function both as true respiratory organs and as a ventilating mechanism. 3. It is shown that the differences in gill function can be related to the oxygen content of the habitat of each species.

scholarly journals Oxygen supply limits the heat tolerance of lizard embryos

2015 ◽  
Vol 11 (4) ◽  
pp. 20150113 ◽  
Author(s):  
Colton Smith ◽  
Rory S. Telemeco ◽  
Michael J. Angilletta ◽  
John M. VandenBrooks
Keyword(s):  
Heat Tolerance ◽  
Oxygen Supply ◽  
Alternative Hypothesis ◽  
Oxygen Limitation ◽  
Embryonic Stage ◽  
Lethal Temperature ◽  
Thermal Limits ◽  
Thermal Maximum ◽  
Pass Through ◽  
Oxygen Concentrations

The mechanisms that set the thermal limits to life remain uncertain. Classically, researchers thought that heating kills by disrupting the structures of proteins or membranes, but an alternative hypothesis focuses on the demand for oxygen relative to its supply. We evaluated this alternative hypothesis by comparing the lethal temperature for lizard embryos developing at oxygen concentrations of 10–30%. Embryos exposed to normoxia and hyperoxia survived to higher temperatures than those exposed to hypoxia, suggesting that oxygen limitation sets the thermal maximum. As all animals pass through an embryonic stage where respiratory and cardiovascular systems must develop, oxygen limitation may limit the thermal niches of terrestrial animals as well as aquatic ones.

scholarly journals Climate variability predicts thermal limits of aquatic insects across elevation and latitude

2017 ◽  
Vol 31 (11) ◽  
pp. 2118-2127 ◽  
Author(s):  
Alisha A. Shah ◽  
Brian A. Gill ◽  
Andrea C. Encalada ◽  
Alexander S. Flecker ◽  
W. Chris Funk ◽  
...  
Keyword(s):  
Climate Variability ◽  
Aquatic Insects ◽  
Thermal Limits

How Rearing Temperature Affects Optimal Adult Size in Ectotherms

1994 ◽  
Vol 8 (4) ◽  
pp. 486 ◽  
Author(s):  
R. M. Sibly ◽  
D. Atkinson
Keyword(s):  
Adult Size ◽  
Rearing Temperature

scholarly journals Narrow safety margin in the phyllosphere during thermal extremes

2019 ◽  
Vol 116 (12) ◽  
pp. 5588-5596 ◽  
Author(s):  
Sylvain Pincebourde ◽  
Jérôme Casas
Keyword(s):  
Heat Waves ◽  
Safety Margin ◽  
Thermal Limit ◽  
Apparent Paradox ◽  
Feeding Mode ◽  
Thermal Limits ◽  
Single Leaf ◽  
Arthropod Species ◽  
Species Vulnerability ◽  
Leaf Transpiration

The thermal limit of ectotherms provides an estimate of vulnerability to climate change. It differs between contrasting microhabitats, consistent with thermal ecology predictions that a species’ temperature sensitivity matches the microclimate it experiences. However, observed thermal limits may differ between ectotherms from the same environment, challenging this theory. We resolved this apparent paradox by showing that ectotherm activity generates microclimatic deviations large enough to account for differences in thermal limits between species from the same microhabitat. We studied upper lethal temperature, effect of feeding mode on plant gas exchange, and temperature of attacked leaves in a community of six arthropod species feeding on apple leaves. Thermal limits differed by up to 8 °C among the species. Species that caused an increase in leaf transpiration (+182%), thus cooling the leaf, had a lower thermal limit than those that decreased leaf transpiration (−75%), causing the leaf to warm up. Therefore, cryptic microclimatic variations at the scale of a single leaf determine the thermal limit in this community of herbivores. We investigated the consequences of these changes in plant transpiration induced by plant–insect feedbacks for species vulnerability to thermal extremes. Warming tolerance was similar between species, at ±2 °C, providing little margin for resisting increasingly frequent and intense heat waves. The thermal safety margin (the difference between thermal limit and temperature) was greatly overestimated when air temperature or intact leaf temperature was erroneously used. We conclude that feedback processes define the vulnerability of species in the phyllosphere, and beyond, to thermal extremes.

scholarly journals Larger Daphnia at lower temperature: a role for cell size and genome configuration?

Genome ◽  
2013 ◽  
Vol 56 (9) ◽  
pp. 511-519 ◽  
Author(s):  
Marwa Jalal ◽  
Marcin W. Wojewodzic ◽  
Carl Morten M. Laane ◽  
Dag O. Hessen
Keyword(s):  
Body Size ◽  
Low Temperature ◽  
Genome Size ◽  
Cell Size ◽  
Structural Changes ◽  
Daphnia Pulex ◽  
Adult Size ◽  
Binding Properties ◽  
Lower Temperature ◽  
Size Estimates

Experiments with Daphnia magna and Daphnia pulex raised at 10 and 20 °C yielded larger adult size at the lower temperature. This must reflect increased cell size, increased cell numbers, or a combination of both. As it is difficult to achieve good estimates on cell size in crustaceans, we, therefore, measured nucleus and genome size using flow cytometry at 10 and 20 °C. DNA was stained with propidium iodide, ethidium bromide, and DAPI. Both nucleus and genome size estimates were elevated at 10 °C compared with 20 °C, suggesting that larger body size at low temperature could partly be accredited to an enlarged nucleus and thus cell size. Confocal microscopy observations confirmed the staining properties of fluorochromes. As differences in nucleotide numbers in response of growth temperature within a life span is unlikely, these results seem accredited to changed DNA–fluorochrome binding properties, presumably reflecting increased DNA condensation at low temperature. This implies that genome size comparisons may be impacted by ambient temperature in ectotherms. It also suggests that temperature-induced structural changes in the genome could affect cell size and for some species even body size.

scholarly journals Flow increases tolerance of heat and hypoxia of an aquatic insect

2021 ◽  
Vol 17 (5) ◽  
Author(s):  
James I. Frakes ◽  
Jackson H. Birrell ◽  
Alisha A. Shah ◽  
H. Arthur Woods
Keyword(s):  
Aquatic Insects ◽  
Oxygen Supply ◽  
Aquatic Insect ◽  
Hypoxia Tolerance ◽  
Western North America ◽  
Metabolic Demand ◽  
Thermal Limits ◽  
Lower Oxygen ◽  
Impacts Of Climate Change ◽  
Sufficient Oxygen

Recent experiments support the idea that upper thermal limits of aquatic insects arise, at least in part, from a lack of sufficient oxygen: rising temperatures typically stimulate metabolic demand for oxygen more than they increase rates of oxygen supply from the environment. Consequently, factors influencing oxygen supply, like water flow, should also affect thermal and hypoxia tolerance. We tested this hypothesis by measuring the effects of experimentally manipulated flows on the heat and hypoxia tolerance of aquatic nymphs of the giant salmonfly (Plecoptera: Pteronarcys californica ), a common stonefly in western North America. As predicted, stoneflies in flowing water (10 cm s −1 ) tolerated water that was approximately 4°C warmer and that contained approximately 15% less oxygen than did those in standing water. Our results imply that the impacts of climate change on streamflow, such as changes in patterns of precipitation and decreased snowpack, will magnify the threats to aquatic insects from warmer water temperatures and lower oxygen levels.

scholarly journals Tissue hypoxia inhibits prostaglandin and nitric oxide production and prevents ductus arteriosus reopening

2000 ◽  
Vol 279 (1) ◽  
pp. R278-R286 ◽  
Author(s):  
Hiroki Kajino ◽  
Yao-Qi Chen ◽  
Sylvain Chemtob ◽  
Nahid Waleh ◽  
Cameron J. Koch ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Oxygen Concentration ◽  
Ductus Arteriosus ◽  
Tissue Hypoxia ◽  
No Production ◽  
Active Tension ◽  
Tissue Oxygen ◽  
Ambient Oxygen ◽  
Inner Vessel ◽  
Oxygen Concentrations

Regulation of ductus arteriosus (DA) tension depends on a balance between oxygen-induced constriction and PG and nitric oxide (NO)-mediated relaxation. After birth, increasing PaO2 produces DA constriction. However, as the full-term ductus constricts, it develops severe tissue hypoxia in its inner vessel wall (oxygen concentration <0.2%). We used isolated rings of fetal lamb DA to determine why the constricted ductus does not relax and reopen as it becomes hypoxic. We used a modification of the 2-(2-nitro-1 H-imidazol-1-yl)- N-(2,2,3,3,3-pentafluoropropyl) acetamide (EF5) technique (Clyman RI, Chan CY, Mauray F, Chen YQ, Cox W, Seidner SR, Lord EM, Weiss H, Wale N, Evan SM, and Koch CJ. Pediatr Res 45: 19–29, 1999) to determine mean tissue oxygen concentration. A decrease in the ductus' mean tissue oxygen concentration from 1.4 to 0.1% lowers the isometric tone of the ductus by 15 ± 10% of its maximal active tension (the maximal tension that can be produced by the ductus). Although decreases in oxygen concentration diminish ductus tension, most of the vasoconstrictor tone in the ductus is independent of ambient oxygen concentration. This oxygen-independent tone is equivalent to 64 ± 10% of the maximal active tension. At mean tissue oxygen concentrations >0.2%, endogenous PGs and NO inhibit more than 40% of the active tension developed by the ductus. However, when tissue oxygen concentrations drop below 0.2%, the constitutive relaxation of the ductus by endogenous PGs and NO is lost. In the absence of PG and NO production, tension increases to a level normally observed only after treatment of the ductus with indomethacin and nitro-l-arginine methyl ester (inhibitors of PG and NO production). Therefore, under conditions of severe hypoxia (tissue oxygen concentration <0.2% oxygen), the loss of PG- and NO-mediated relaxation more than compensates for the loss of oxygen-induced tension. We hypothesize that this increased ductus tone enables the vessel to remain closed as it undergoes tissue remodeling.

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