Biomedical subjects
Publications and source records attributed to E Van Handel.
Lagoon fishes, in netted holding cages, were placed in an impounded salt marsh and submitted to a gradient of sulfide-rich artesian well water. Near the well head, all specimens of 13 species died within 5-45 min, while all individuals of 5 species survived. More distant from the well, survival time increased sufficiently to rank species in approximate order of sensitivity to sulfide.
Adult Culex quinquefasciatus, maintained from emergence on sugar, were fed blood and then fed either sugar (control) or water (starving) for 7 days. Analysis of ovaries and egg rafts for protein, lipids and glycogen showed that only glycogen levels were diminished by starvation. Eggs from both control and starving females, however, were equally viable. Nonbloodfed starving females lived longer than bloodfed starving females. These results suggest that the blood meal maximizes fertility, not longevity.
Aedes taeniorhynchus were collected on the wing at several times during the day and night, in Indian River and Brevard County, Florida. Nonblooded females were individually analyzed for fructose and glycogen. Fructose content of mosquitoes collected early in the morning and held without food during the day diminished to approximately the same level as in mosquitoes collected late in the afternoon. However, fructose content of mosquitoes collected before sunset and held without food overnight diminished greatly, whereas that of mosquitoes collected in the morning always exceeded that of evening collections. Maximum fructose content occurred within one or 2 hours after sunset. Apparently, these mosquitoes take little or no nectar during the day, and feed soon after the onset of darkness.
Wing length and protein content were compared in individual specimens of male and nonbloodfed, nongravid female mosquitoes. The following groups were tested: field-collected and colonized Aedes aegypti, field-collected Culex nigripalpus and Aedes vexans, and colonized Culex quinquefasciatus and Psorophora columbiae. The correlation coefficient varied from 0.91 in Ae. aegypti males to 0.98 in Ae. vexans females, and in each group the P value was less than 0.001. This close correlation suggests that both wing length and protein measurement are reliable expressions of size in adult mosquitoes.
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In blood-fed Culex nigripalpus Theobald, proteolytic activity appeared in the ectoperitrophic fluid after 3 h, but only after 6 h in a homogenate of the blood-filled midgut. The activity continued to be higher in ectoperitrophic fluid than in whole gut homogenate until about 40 h after the meal, when most of the intact clot had disappeared. Apparently, undigested blood inhibits proteolytic activity. The blood clot lacked activity and the inhibitor could not be removed by washing. The results are compatible with a hypothesis that the peritrophic membrane separates the digestion from the ingestion compartment.
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A simple method is presented to measure the nutrient load of wastewater. Suspended particles, including microorganisms, are collected on a membrane filter by vacuum filtration, followed by colorimetric protein assay. Soluble proteins can be determined in the filtrate by precipitation. In domestic sewage and agricultural dairy wastewater, the largest portion of protein was retained on the membrane. Young larvae of Culex nigripalpus, Cx. quinquefasciatus and Aedes aegypti pupated when maintained in wastewater or its sediment but not when maintained in a membrane filtrate. If mosquito larvae feed primarily on suspended particles, the assay can be used to identify major feeding areas and may result in more economic application of microbial larvicides that act as food poisons.
Individual female mosquitoes from field populations of Aedes aegypti, Culex nigripalpus and Coquillettidia perturbans were analyzed for sugar, glycogen and lipids. Controls were maintained in the laboratory for 7 to 10 days on 2% and either 10 or 20% sucrose. Mosquitoes held in the laboratory had significantly more glycogen and lipid than field-collected mosquitoes of the same species. Laboratory mosquitoes maintained on 10 or 20% sucrose contained more sugar than did field mosquitoes. Mosquitoes of the above species were collected at field sites in January, April, July and October and nutritional reserves were determined. Seasonal differences in reserves were documented in females of all species. However, even when reserves were at their highest in field-collected mosquitoes they rarely approached the reserves in mosquitoes of the same species maintained in the laboratory on 10 or 20% sucrose. Since laboratory-maintained mosquitoes are nutritionally different from those in the field, results of laboratory studies on flight performance, host attractancy, biting, disease transmission and oviposition behavior may be biased.
Larval growth recorded as accumulation of protein was measured in Aedes aegypti, Culex nigripalpus and Culex quinquefasciatus, raised on liver powder or dry brewer's yeast. In the early stages all 3 species grew faster on liver powder, but at pupation there was no significant difference in protein content between diets and among species. Aedes aegypti pupated one day ahead of Culex.
Sodium azide, at concentrations that prevent development of microorganisms, interferes with the anthrone and phenol sulfuric acid reactions for carbohydrates, and with the glucose oxidase reaction. It does not affect copper reduction and the ortho-toluidine reaction.
A method is presented for rapid determination of glycogen and sugars in individual mosquitoes. It is suitable for large scale field studies of correlations between nutritional status and behavior. The method also describes a one step procedure for total carbohydrates and the determination of nectar sugars and the hemolymph sugar trehalose.
Total lipids in individual mosquitoes can be determined by extraction with chloroform-methanol followed by reaction with sulfuric acid and a vanillin-phosphoric acid reagent. By subtracting the lipids determined in a starved population, the method is suitable to establish variations of lipid reserves in field populations.
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