Low frequency acoustic pulse propagation in temperate forests.

Measurements of acoustic pulse propagation for a 30-m path were conducted in an open field and in seven different forest stands in the northeastern United States consisting of deciduous, evergreen, or mixed tree species. The waveforms recorded in forest generally show the pulse elongation characteristic of propagation over a highly porous ground surface, with high frequency scattered arrivals superimposed on the basic waveform shape. Waveform analysis conducted to determine ground properties resulted in acoustically determined layer thicknesses of 4-8 cm in summer, within 2 cm of the directly measured thickness of the litter layers.

Costs of parental care in the gastropod Conus pennaceus: Age-specific changes and physical constraints.

Age-specific changes in the allocation of reproductive energy to protective capsules, ova and intracapsular fluid are documented for the marine gastropod Conus pennaceus. As female snails grow in shell length they produce larger capsules with thicker and stronger walls. Because large capsules contain lower densities of ova than do small ones, growing females must increase the number, as well as the size, of egg capsules they produce.