Invertebrate Physiology

In 1980-8l, I participated in the following research projects at BML. 1. Transport of Amino Acids by Nemertean Worms In collaboration with G.C. Stephens (U.C. Irvine), L.M. Crowe, (U.C. Davis), I have been involved in studies on uptake of amino acids by juvenile nemertean worms found on Dungeness crabs. We have shown that the water found in the joints of the legs, where the worms are also found, contains high concentrations of primary amines. We have identified these primary amines as amino acids, and have shown that the worms are capable of removing the amino acids from solution. We have also shown that the source of these amino acids is almost certainly the crabs: using isolated pieces of arthrodial membrane mounted in a miniature Ussing chamber, we have shown that amino acids found in the blood of the crabs can leak across these membranes. This work produced two publications and a paper was presented at the annual meeting of the American Society of Zoologists in December 1980. 2. Divalent Cations and Membrane Permeability In collaboration with J.S. Swinehart (U.C. Davis) I have participated in studies on effects of divalent cations on permeability of membranes of bivalve molluscs. We have shown that deletion of Ca from the medium results in an efflux of amino acids from gills of Mytilus californianus, while Mg seems to be required for the influx of amino acids into the same tissue. In addition, we have shown that certain cations such as Ca , known to have toxic effects on these organisms, stimulates an efflux of amino acids. We suggest that Ca may displace Ca bound to the cell membrane, and have provided some evidence to that effect already in our first publication on this subject (Swinehart et al., 1980. J. Exp. Zool.). Dr. Swinehart presented some of this work at the ASZ meeting in December. 3. Freezing Tolerance of Marine Organisms In collaboration with L.M. Crowe and S.J. O'Dell (U.C. Davis) I have been involved in studies on freezing of intertidal limpets and cysts of Artemia. We have shown that limpets collected at Bodega Bay are capable of surviving freezing, with lethal temperatures well below -lOoC. We have also shown that the lethal temperature may be altered by elevating the [Ca ] in the blood. We suspect that this Ca effect may be related to Ca binding to cell membranes in these animals, and we are presently investigating this possibility. One paper on this subject has already been submitted for publication (Oâ Dall and Crowe, 1980. Cryobiology, Submitted). Mr. Oâ Dell presented a paper on part of the work at the annual meetings of the Society of Cryobiology in Victoria, B.C. (August 1980). In the work on Artemia, we have found that cysts survive freezing in liquid nitrogen, provided that their water content is less than 0.6 g H2O/g dry weight. Thermal analysis showed that the cysts contain 0.6 g unfreezable H2O/g dry weight, so ice is not formed in the animals until higher H2O contents are reached. This work has been submitted for publication (Crowe et al., 1980. Cryobiology. Submitted), and I presented a paper on the same subject at the annual meeting of the society of Cryobiology in Victoria, B.C. (August 1980). 4. Other Projects Our main research efforts are conducted at Davis, where we carry out studies on hydration dependent phase changes in membranes. While almost none of this work is done at BML, we do use the lab for writing and some minor experimentation, and thus acknowledge the BML on these papers as well as those mentioned above.