Angularella audubonensis sp. n. (Dilepididae) and Other Cestodes of Cliff Swallows in Colorado

One hundred forty-five cliff swallows, Petrochelidon pyrrhonota, were examined for cestodes in two separate surveys in Weld County, Colorado. Seven species representing four genera were found. Angularella audubonensis sp. n. is differentiated by the small size of the rostellar hooks (8.4-13.5 μm) and the medial relationship of the cirrus pouch to the osmoregulatory canals. Other species collected were Angularella beema, Anonchotaenia globata, Mayhewia ababili, Vitta magniuncinata, Vitta parvirostris and Vitta riparia. Seven new hosts and geographic distribution records were established for Colorado, and six new records were determined for North America.

Phytoplankton Dynamics in Three Rocky Mountain Lakes, Colorado, U.S.A.

In 1984 and 1985 seasonal changes in phytoplankton were studied in a system of three lakes in Loch Vale, Rocky Mountain National Park, Colorado. Three periods were evident: (1) A spring bloom, during snowmelt, of the planktonic diatom Asterionella Formosa, (2) a mid- summer period of minimal algal abundance, and (3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics in these lakes are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. formosa population in the most downstream lake has a net rate of increase of 0.34 d-1, which is calculated from the flushing rate and from the A. formosa abundance in the inflow from the upstream lake and in the downstream lake. Measurement of photosynthetic rates at different depths during the three periods confirmed the rapid growth of A. formosa during the spring. The decline in A. formosa after snowmelt may be related to grazing by developing zooplankton populations. The possible importance of the seasonal variations in nitrate concentrations were evaluated in situ enrichment experiments. For A. formosa and O. limnetica populations, growth stimulation resulted from 8- or 16-micromolar amendments of calcium nitrate and sulfuric acid, but the reason for this stimulation could not be determined from these experiments.