REPRODUCTION OF THE POLYCHAETE GLYCERA DIBRANCHIATA AT SOLOMONS, MARYLAND

¹ Department of Biology, Catholic University of America, Washington, D. C., and Chesapeake Biological Laboratory, Natural Resources Institute of the University of Maryland, Solomons, Maryland

1. This report is based on field observations made at Solomons, Maryland, between June, 1960, and February, 1961, and on histological examination of material collected during this period. It appears that bloodworms breed twice a year at Solomons: certainly during fall and very likely in late spring or early summer as well. Gametogenesis probably requires close to a year for completion. Both temperature and seasonal plankton variation are suggested as factors that may influence the timing of reproductive activity. There is reason to suspect that bloodworms also spawn biannually in the Maritime Provinces and Maine, but conclusive evidence is not available.

2. Swarming occurred mostly over shallow water, during late afternoon on November 5-8, 1960. It covered a moderately large area, but individual worms were widely dispersed. Data suggest that the onset of swarming may be coordinated with tidal conditions. Shedding is by dehiscence, through the posterior end, and is apparently an automatic process initiated by serpentine swimming movements that differ from the usual locomotion of immature animals.

3. Epitokes are characterized by atrophy of the musculature and alimentary canal, elongation of the parapods and increase in the number of setae. There are indications that the saccular apparatus of the brain releases a substance to the exterior during swarming. Although there is variation in the degree of atrophy attained at spawning, bloodworms apparently undergo less severe degenerative changes than other Glycera species.