Lithophagic snail from southern British Honduras

A freshwater gastropod, Pachycheilus glaphyrus, responsible for unusual erosion in limestone has been located in southern British Honduras where it is abundant in streams flowing through areas of karst topography. These snails ingest algae that proliferate in solution grooves formed at the fluctuating air-water interface. Rasping action of the radula results in deepening of these grooves and appears to improve the algal habitat.     

Arginine and pyrimidine biogenesis in Neurospora

The growth-promoting activity of propionic acid and related compounds for the pyrimidine-less strain, Neurospora crassa 1298, is markedly inhibited by arginine. The data suggest that arginine exerts an inhibitory effect upon or represses the synthesis of an enzyme involved in pyrimidine formation.     

Observations at venus encounter by the plasma science experiment on mariner 10

Preliminary results from the rearward-looking electrostatic analyzer of the plasma science experiment during the Mariner 10 encounter with Venus are described. They show that the solar-wind interaction with the planet probably involves a bow shock rather than an extended exosphere, but that this is not a thin boundary at the point where it was crossed by Mariner 10. An observed reduction in the flux of electrons with energies greater than 100 electron volts is interpreted as evidence for somne direct interaction with the exosphere. Unusual intermittent features observed downstream of the planet indicate the presence of a comet-like tail hundreds of scale lengths in length.