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371.
Sisanda Felicia Mvandaba Martin Patrick Hill Julie Angela Coetzee 《Biocontrol Science and Technology》2019,29(1):44-58
Water lettuce, Pistia stratiotes, and red water fern, Azolla filiculoides, are floating aquatic macrophytes that have become problematic in South Africa. Two weevils, Neohydronomus affinis and Stenopelmus rufinasus, are successful biological control agents of these two species in South Africa. The aim of this study was to investigate the thermal requirements of these two species to explain their establishment patterns in the field. Laboratory results showed that both weevils are widely tolerant to cold and warm temperatures. The critical thermal minima (CTmin) of N. affinis was determined to be 5.58?±?0.31°C and the critical thermal maxima (CTmax) was 44.52?±?0.27°C, while the CTmin of S. rufinasus was 5.38?±?0.33°C and the CTmax?44.0?±?0.17°C. In addition, the lower lethal temperatures were ?9.85?±?0.06°C for N. affinis and ?6.85?±?0.13°C for S. rufinasus, and the upper lethal temperatures were 42.7?±?0.85°C for N. affinis and 41.9?±?2.52°C S. rufinasus. Using the reduced major axis regression method, the development for N. affinis was described using the formula y?=?12.976x?+?435.24, while the development of S. rufinasus was described by y?=?13.6x?+?222.45. These results showed that S. rufinasus develops twice as fast as N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. These results suggest that both species should not be limited by cold winter, nor warm summer temperatures, and should establish throughout the ranges of the weeds in South Africa. 相似文献
372.
Heleen L. Coetzee Maria M. Nel J. H. Swanepoel G. Van Aswegen 《Journal of morphology》1991,208(3):311-321
The wall of the stomach of the tigerfish is described and compared with that of other vertebrates. Light microscopic and ultrastructural characteristics of the stomach wall correspond to a large extent to those of other vertebrates, although some differences are found. The mucosa contains (1) surface epithelium characterized by narrow columnar cells with abundant mucous granules; (2) gastric glands consisting of pepsinogenic cells of variable height, containing tubulovesicles and bearing microvilli; (3) five granulated cell types located basally in the epithelium (types 1–5); and (4) lamina propria and muscularis mucosae. Connective tissue separating smooth muscle fibers of the muscularis mucosae constitutes a stratum compactum. The submucosa contains a loose connective tissue, a tunica muscularis of inner circular and outer longitudinal layers, and a serosa of mesothelium and subjacent connective tissue. Immunocytochemical tests with antisera to five polypeptides show gastrin/cholecystokinin (CCK), vasoactive intestinal polypeptide (VIP) immunoreactivities in some cells of the gastric glands, and somatostatin in cells lying among epithelial cells lining the gastric luminal surface or gastric pits. 相似文献
373.