Exploration of the utility of fluctuating asymmetry as an indicator of river condition using larvae of the caddisfly Hydropsyche morosa (Trichoptera: Hydropsychidae)

Organisms are subject to three types of morphological asymmetry: Directional Asymmetry, Antiasymmetry and Fluctuating Asymmetry, but only the latter (FA) is related to the environmental stress acting upon individuals during their development. Larvae of Hydropsyche morosa from five rivers in Ontario, Canada, each exhibiting different degrees of human impact, were examined for FA. Specimens were obtained from collections in the Royal Ontario Museum dating back to 1951, and from fresh collections to 1999. Twelve morphological characters were assessed on both the left and right sides of 297 larvae, and eight of them demonstrated FA. There was a tendency to increase the levels of FA over time. Levels of nitrogen, conductivity and chloride in the river water, used as an index of pollution, were significantly and positively correlated with increasing incidence of FA in four of the characters, the remainder were independent of pollution.     

Solitary hypothalamic neurons inherently express vasopressin and tyrosine hydroxylase

Hypothalamic neurons were grown as single cells in three-dimensional culture. Solitary neurons lacking cell contacts were immunocytochemically examined for inherent expression of vasopressin (VP), tyrosine hydroxylase (TH), and luteinizing hormone releasing hormone (LHRH). Immunoreactive VP and TH were detected within a day. Sixty to eighty-five percent of neurons displayed homogeneously distributed reaction product for VP or TH. One percent exhibited intense punctate staining of somas and varicosities. Few neurons stained for LHRH. Results indicate that hypothalamic neurons can express appropriate neuropeptides and transmitter-specific products without contacting other neurons or nonneuronal cells. Thus, this culture system may provide a useful model to study intrinsic neuronal processes.     

Dietary overlap and coexistence of chironomid larvae in a detritus-based stream

Hydrobiologia - Of the seven orders of macroinvertebrates that make up the DuffinCreek riffle community, the Chironomidae were the dominant taxonmaking up, numerically, 25.8–53.7% of the...     

Aids for visual impairment.

This article provides only a flavour of the type and range of aids available to the visually impaired person. Many other aids for leisure, learning, and daily living are illustrated in the RNIB equipment and games catalogue.     

The Natural History of a Nearctic Temporary Pond in Ontario with Remarks on Continental Variation in such Habitats

The seasonal succession of members of the invertebrate community of a temporary vernal pond in southern Ontario is described. Although succession was essentially continuous, 5 faunal groups are suggested, based on time of appearance and duration of active forms in the pond. Some species were found during virtually the entire aquatic phase, while others completed their life cycles in only 2-3 weeks. Analysis of growth rates revealed many different patterns between species and groups. Analysis of community structure in terms of trophic status indicated shifts which coincided with the seasonal occurrence of the pond's potential food resources. Comparison of this fauna with that of a similar pond on Vancouver Island, British Columbia (some 2,400 km to the west) showed many similarities in niche occupancy, including 6 species in common. The biological characteristics leading to the success of these cosmopolitan species in temporary aquatic habitats is discussed.