Diel feeding ecology of the nymphs of Aeshna multicolor and Lestes unguiculatus (Odonata)

SUMMARY.

• 1 Diel feeding periodicity and diet composition of nymphs of Aeshna multicolor and Lestes unguiculatus were examined at 6 h intervals in a small pond. Feeding intensity of A. multicolor increased from 06.00 hours to approximately 18.00 hours whereas food intake by L. unguiculatus was uniformly high between 12.00 and 18.00 hours. Feeding of both species was reduced during the night.
• 2 Diel variation in diet composition was substantial in each species. Chironomid larvae were the major prey (48.9%) in the diet of A. multicolor. Zooplankton, mainly cladocerans (42.0%) and ostracods (21.1%), were the principal prey of L. unguiculatus. Detritus composed a substantial portion of the diets of both species.
• 3 Diet overlap (Cλ) at each 6 h interval was high (0.43–0.72) when detritus was included in the calculation and was low (0.48–0.54) when detrital material was omitted.

     

Feeding efficiencies of Chironomus plumosus (L.) and C. anthracinus Zett. (Diptera: Chironomidae) in mesotrophic Lake Erken

SUMMARY.

• 1 Absorption efficiencies of nitrogen and carbon in two Chironomus species found dominating in the profundal zone of mesotrophic Lake Erken were determined gravimetrically.
• 2 Absorption efficiencies for C. plumosus showed greater seasonal variation than those of C. anthracinus, with low efficiencies coinciding with the summer dominance of flagellate phytoplankton and with high C:N ratios.
• 3 Overall mean absorption efficiencies (±SE) for carbon and nitrogen, respectively, were 26.8% (±1.9) and 29.3% (±1.9) for C. plumosus, 24.6% (±1.7) and 28.1% (±1.8) for C. anthracinus.
• 4 Significant differences were found to exist between the C: N ratios of the superficial 2 cm sediment layers and those of Chironomus anterior midgut contents.
• 5 C. anthracinus appears to be a deposit feeder ingesting particulate matter scraped from the recently deposited surface sediments. The greater seasonal variation found in the absorption efficiencies of C. plumosus, together with the lower C:N ratios, support the contention that this species is a filter feeder with the nutritional quality of ingested matter depending primarily on pelagic inputs.

     

Genetics and Molecular Biology of Mouse Pigmentation

The formation of mouse coat color is a relatively complex developmental process that is affected by a large number of mutations, both naturally occurring and induced. The cloning of the genes in which these mutations occur and the elucidation of the mechanisms by which these mutations disrupt the normal pigmentation pattern is leading to an understanding of the way interactions between gene products lead to a final phenotype.