Gel filtration of the sperm attractants of some marine hydrozoa

Elution patterns of sperm chemo-attractants isolated from female hydroids of the genera Campanularia, Gonothyrea, Tubularia and Clava were obtained by comparative gel filtration chromatography. Generally one major and one minor peak of activity were obtained for each of the species used, except Gonothyrea which yielded two large active peaks. The Rf values of these peaks fall into two non-overlapping groups. The first group consists of the major peak obtained from Campanularia calceolifera, the first major peak from Gonothyrea and the minor peak obtained from each of the three species of Tubularia, all of which have Rf values near 0.7. The second group consists of the major peaks from the three species of Tubularia, the second major peak from Gonothyrea, the minor peak from C. calceolifera, and the major peak from Clava, all of which have Rf values near 0.5. Separation of mixtures of some of the attractants was possible using this method. Correlation between chromatographic elution position and species-specificity determined by testing the extracts from the various species against live sperm, is not perfect in all cases, in part, at least, because gel filtration is not capable of separations other than on the crude basis of molecular size. Gonothyrea and Campanularia calceolifera extracts and sperm show cross-reactivity and their active agents elute together during chromatography. The same is true for the three species of Tubularia tested. However, the second Gonothyrea peak elutes at the same position as the major peak of Tubularia activity, but these genera do not attract each other's sperm. These results suggest that methods other than chemotaxis are used by many hydroids to prevent exposure of eggs to sperm from the wrong species and that more specific separation methods will have to be used to determine the molecular basis for chemotactic specificity in hydroids.