Functional constraints on nest characteristics of pebble mounds of breeding male hornyhead chub Nocomis biguttatus

Breeding male hornyhead chub Nocomis biguttatus constructed nests in areas with relatively high but less than maximum flow rate and greater than average water depth. Nests comprised c. 3000 pebbles for a total mass of 11 kg. Males selected pebbles of smaller diameter but higher density than pebbles in the immediate vicinity. Thus, nests balanced the risk of mound erosion and energetic cost of nest construction with the benefits of protection from egg predators and a stable internal flow rate for oxygenation. These data help establish environmental management goals for the conservation of N. biguttatus and the lotic ecosystems dependent upon them.

Genetic stability of rotaviruses recovered from asymptomatic neonatal infections

The sequence of the VP7 gene from 19 rotavirus strains recovered from asymptomatically infected newborn infants was determined by direct analysis of transcript RNAs synthesized from virus present in the stool. For five viruses the entire VP7 gene was sequenced, whereas in the remaining instances only a portion of the gene could be sequenced. In 19 specimens collected over a 4-year period, only five nucleotide substitutions were detected. None of them resulted in an amino acid substitution. Examination of a 306-nucleotide segment of gene 4 in 11 specimens yielded similar results. These results suggest that the mutation rate of rotaviruses in nature is lower than that of single-stranded RNA viruses such as poliovirus and influenza virus.