Effect of copper and cadmium on three Malaysian tropical estuarine invertebrate larvae.

Three species of tropical estuarine invertebrates were exposed to copper sulfate and cadmium chloride to investigate their potential as test specimens for sediment toxicity assays in the South-east Asian regions. The larvae of the reef sea urchin (Diadema setosum), the oyster (Crassostrea iradalei), and the mud crab (Scylla seratta Forskall) were used in the 48-hr assays with copper and cadmium as reference toxicants. In addition the sea urchin were tested for end point measurements at different stages of the larval development and a 60-min sperm bioassay. The study revealed that the sea urchin first cleavage, which is an assay end point and which takes place about 1 hr after fertilization, was the most sensitive stage for both toxicants, with copper being more toxic than cadmium. Sensitivity comparisons between the three invertebrate larvae revealed the mud crab zoea larvae to be most sensitive for cadmium with an LC50 value of 0.078 microgram/ml, while the sea urchin was more sensitive for copper, with EC50 values of 0.01 microgram/ml at the first cleavage stage and 0.04 microgram/ml at the pluteus larva stage. All the invertebrates tested gave responses that made them suitable test organisms for metal bioassays in the tropical estuarine environment.

Notes on sugar feeding and selected wild mammalian hosts of black flies (Diptera: Simuliidae) in Newfoundland.

This study, done on the Avalon Peninsula, Newfoundland, identified selected wild mammalian hosts and quantified the incidence of sugar feeding for several species (species complexes) of black flies. Female flies were taken from fox, snowshoe hare, lynx, caribou, and human baits. Simulium truncatum/venustum complex females took blood from fox, lynx, rabbit, and caribou and were frequently taken in sweep net collections around humans. Blood-fed females of the Simulium rostratum/verecundum complex were collected only from caribou, were rarely attracted to the other mammalian baits, and were not attracted to humans. Although most females had sugar-free before seeking a host, significant interspecific differences in the incidence of fructose-positive females were found among the four species (species complexes) examined (Prosimulium mixtum, 92.9%; S. truncatum/venustum complex, 87.4%; Stegopterna mutata (triploid cytospecies), 83.3%; Simulium vittatum complex, 67.4%). No significant differences were found in the proportion of sugar-fed flies among three habitats examined (forest, scrubland, and pasture) for either P. mixtum or the S. truncatum/venustum complex. However, the percentage of sugar-fed S. truncatum/venustum complex females was significantly higher in the evening than in the morning. Time of day did not influence the incidence of sugar-fed P. mixtum.

Persistence of mermithidae (Nematoda) infections in black fly (Diptera: Simuliidae) populations.

Data on the persistence of mermithid infections in black fly populations over several years indicate mermithid infection rates are relatively stable over several years in a stream. These data were from specific sites in a variety of streams all having the same simuliid fauna present each season. This suggests that the suitability of the stream bed for the free living phase is very important in regulating mermithid populations.

Notes on the Tabanidae (Diptera) of western Labrador.

The seasonal distribution and relative abundance of adult Tabanidae were studied in 2 mining communities of western Labrador during 1984. Four collecting methods were compared. Fifteen species belonging to 2 genera were collected (6 Chrysops and 9 Hybomitra). Results were compared with other studies conducted in adjacent northern areas. Chrysops excitans was the most abundant species collected. The horizontal distribution of adult host-seeking C. excitans was investigated. A list of species collected in previous years and in central Labrador is also given.

The distribution and biology of Austrosimulium pestilens, a serious biting-fly pest following flooding.

The distribution of A. pestilens is expanded with records from the southern Gulf of Carpentaria Rivers. The value of sampling specific adult resting sites for the assessment of host range and vector potential is recorded. The value of CO2 as an attractant and the truck trap, or modifications thereof, as a collector of A. pestilens is also demonstrated.