Biochemical correlates of genetic variation in marine lower invertebrates.

In this paper extensive data on enzyme variation in 23 species of coelenterates and sponges were used to investigate the possible correlation of levels of genetic variation with various parameters of enzyme molecular structure and function. The data provide an opportunity not only to look for such correlations for the first time in lower invertebrates, but also to study organisms with far higher average levels of genetic variability than those used in any previous work. A clear inverse relationship was found between enzyme subunit number and levels of polymorphism, with monomers being more variable than dimers or tetramers. No significant difference in polymorphism could be found in enzymes of the functional groups I and II of Gillespie and Langley (1974). Regulatory enzymes appeared to be significant relationship was observed between regulatory power and subunit structure which could bias this result. The results suggest that both neutralist and selectionist ideas may have a useful role to play in the understanding of the factors which can influence or limit levels of genetic variation.

Colonial nervous control of lophophore retraction in cheilostome Bryozoa.

Nervous impulses causing lophophore retraction over large areas of Membranipora membranacea and Electra pilosa were recorded with external electrodes. The response propagates at about 100 centimeters per second, presumably through the colonial nerve plexus of Hiller and Lutaud. Impulses are rapid up to 200 per second. A second impulse was recorded from individual zooids, probably generated by the polypide's nervous system. The retractor muscle shortens at more than 20 times its own length per second and is apparently the most rapidly contracting muscle known.