PHOTOPERIODIC REGULATION OF PARTURITION IN THE SELF-FERTILIZING VIVIPAROUS POLYCHAETE NEANTHES-LIMNICOLA FROM CENTRAL CALIFORNIA

Seasonally-changing photoperiod controls the timing of parturition in the viviparous, self-fertilizing polychaete Neanthes limnicola (Johnson, 1901) from Watsonville Slough, a central California estuary. During 1987 to 1989, worms in the field gave birth mainly in the spring. Those born in late February from field-collected parents and maintained in the laboratory under in-phase photoperiodic conditions reproduced in 12 to 13 mo, under spring light-regimes. When maintained under light conditions 6 mo out of phase, they required only about 6 to 8 mo to reproduce, giving birth in the fall, but under spring light-regimes. Worms born in the laboratory in fall and then maintained in phase reproduced in the ambient spring, at 6 to 8 mo of age; those maintained out of phase took 12 to 13 mo, giving birth the following fall under spring light-regimes. Photoperiod treatments had no consistent effect on the number of young produced, and age and fecundity were only weakly correlated. Highest fecundities were in salinities of 15 to 20 parts per thousand, with lower fecundities at higher salinities. Worms maintained in full-strength sea water (33 parts per thousand S) showed abnormal development and produced very few or no young. Salinity did not affect timing of parturition. Temperature differences of 3 to 7C-degrees between treatments had no effect on timing of parturition or number of young produced, and marginal effects on life span. These results indicate that photoperiod regulates the timing of reproduction in N. limnicola in central California, while salinity mainly influences fecundity.