HORMONAL CONTROL OF REPRODUCTION IN BUSYCON: II. LAYING OF EGG-CONTAINING CAPSULES CAUSED BY NERVOUS SYSTEM EXTRACTS AND FURTHER CHARACTERIZATION OF THE SUBSTANCE CAUSING EGG CAPSULE LAYING

¹ Department of Physiology, Wayne State University, Detroit, MI 48201
² Department of Biochemistry, Wayne State University, Detroit, MI 48201
³ School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511

Ram (1977) previously observed that Busycon would lay empty egg capsules when injected with nervous system extracts and suggested that egg capsules contaning eggs would be laid only after a number of eggless capsules had first been laid. Data supporting this suggestion and characterizing the gel filtration behavior and species specificity of the substance causing capsule laying are reported.

Busycon capsule strings collected in the field always had empty egg capsules at the initially laid end (B. carica, 13-17; B. canaliculatum, 4-57). B. carica, collected while laying in the field, continued to lay capsules in the laboratory at the average interval of 1.9 ± 1.5 hours/capsule.

Injection of nervous system extracts into B. canaliculatum caused capsule laying. The least amount that would cause capsule laying was 1/16 of a nervous system. Injection of nervous system every two or three hours resulted in the laying of egg-containing capsules after a series of four or more empty capsules. The number of initial empty capsules was correlated with the percent of injections causing capsule laying. The percentage of hard capsules increased from 36 ± 24% before eggs were inserted to 59 ± 27% after eggs were inserted (P < 0.05).

The substance causing capsule laying in Busycon eluted from Sephadex G-50 at the same position as Aplysia egg laying hormone; however, cross-injection experiments between the two species failed to cause egg or capsule laying. Nervous system extracts from Strombus gigas caused capsule laying in Busycon; whereas, Busycon nervous system extracts did not cause laying in Strombus.