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PubMed1999

The importance of the feeding current for oxygen uptake in the water flea daphnia magna

In the planktonic crustacean Daphnia magna (Branchiopoda, Cladocera), different views exist on the mechanism of respiratory gas exchange, ranging from gill breathing to general integumentary respiration. The presumed structures for specialized gas exchange are located ventrally within the filter chamber, which is continuously perfused with the ambient medium for food gathering. To localize respiratory gas exchange in D. magna, we determined the contribution of the feeding current to total oxygen transport. Combining microscopy with special optical techniques, we used a phosphorescent oxygen-sensitive dye for oxygen partial pressure (PO2) measurements and applied fluorescent microspheres for flow-rate analysis. Appendage beat rate was determined by digital image-processing. All experiments were carried out on hypoxia-adapted animals with a body length ranging from 2.3 to 2.7 mm at 20 degreesC. External PO2 measurement revealed oxygen depletion in the ventral body region but essentially no change at posterior, lateral and dorsal positions. The PO2 difference between the inflow and outflow of the feeding current was 13.0 mmHg (1.73 kPa). The flow rate of the feeding current ranged from 1.2 to 5.2 ml h-1 and showed a close correlation with appendage beat rate, which varied from 310.4 to 460.7 beats min-1. Model calculations based on the Fick principle suggest that oxygen extraction from the feeding current satisfies most of the total of oxygen requirement of D. magna.

Journal Article↗
PubMed2004

Yield reduction in Brassica napus, B. rapa, B. juncea, and Sinapis alba caused by flea beetle (Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae)) infestation in northern Idaho.

Phyllotreta cruciferae is an important insect pest of spring-planted Brassica crops, especially during the seedling stage. To determine the effect of early season P. cruciferae infestation on seed yield, 10 genotypes from each of two canola species (Brassica napus L. and Brassica rapa L.) and two mustard species (Brassica juncea L. and Sinapis alba L.) were grown in 2 yr under three different P. cruciferae treatments: (1) no insecticide control; (2) foliar applications of endosulfan; and (3) carbofuran with seed at planting plus foliar application of carbaryl. Averaged over 10 genotypes, B. rapa showed most visible P. cruciferae injury and showed greatest yield reduction without insecticide application. Mustard species (S. alba and B. juncea) showed least visible injury and higher yield without insecticide compared with canola species (B. napus and B. rapa). Indeed, average seed yield of S. alba without insecticide was higher than either B. napus or B. rapa with most effective P. cruciferae control. Significant variation occurred within each species. A number of lines from B. napus, B. juncea, anid S. alba showed less feeding injury and yield reduction as a result of P. cruciferae infestation compared with other lines from the same species examined, thus having potential genetic background for developing resistant cultivars.

Agriculture↗
PubMed1972

Fleas of Korea.

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Journal Article↗
PubMed1976

A review of the South American flea subgenus Ectinorus Jordan 1942, with descriptions of two new species and a key (Siphonaptera: Rhopalopsyllidae).

Ectinorus (E.) chilensis sp. n. from Abracoma bennetti and E. (E.) matini sp. n. from Aconaemys fuscus are described from collections from Chile. A diagnosis for the genus Ectinorus is given and differences between the nominate subgenus and the subgenus and the subgenus Dysmicus are briefly discussed. A key to the presently recognized species of the subgenus Ectinorus is included.

Animals↗
PubMedDate not supplied

[Crystals in the epithelial nuclei of the midgut of fleas].

On studying the changes in the epithelium of the midgut of Ceratophyllus tesquorum, C. laeviceps and Leptopsylla segnis intranuclear crystals were found during the process of digestion. They were recorded both from young and adult insects. The crystals were absent from nuclei of cells of regeneration nests, epithelium of the fore-intestine, any other organs or from nuclei of epithelial cells of the stomach of young non-feeding individuals. They were found neither in young nor in adult individuals of Xenopsylla conformis and Neopsylla setosa.

Cell Nucleus↗