100- 



> 



< 60- 



o 



4 6 



DAYS OF EXPOSURE 



Figure 11-3. Batch variability in N. obsoletus larval 

 survival upon exposure to "1.0" ppm fuel oil (WAF). 



NOTE: Experiment "A" employed 1 5 larvae/vial and ran 4 days. Experiment 

 "B" employed 20 larvae/vial and ran 8 days. The range of mortality observed 

 in the 3 replicates run at each concentration is indicated. 



Static exposures of larval C fornicata ran only three days. No mortality was 

 observed at any oil level tested. However, no larvae were observed swimming at 

 "1.0" ppm by day two. Activity was normal at lower oil concentrations. 

 Moreover, the guts of larvae at "1.0" ppm were empty of food by the second 

 day, whereas veligers at lower oil concentrations continued to feed during the 

 three-day experiment. In the flow-through exposure, veligers held at "1.0" 

 ppm also stopped swimming by the second day of the experiment. These larvae 

 were alive but emaciated by day four, and dead by day six. Crepidula fornicata 

 larva had good survival at lower oil levels, although growth rates were affected 

 as discussed below. 



Gastropod Reproduction 



Adults of N. obsoletus collected in February, 1976, and October, 1976, 

 deposited their first egg capsules in laboratory control containers on 4/30/76 

 and 5/6/77, respectively, when the water temperature warmed to 

 approximately 10°C. Sastry (27) also obtained egg capsules at 10*^C from A^. 

 obsoletus collected in January at Beaufort, North Carolina. 



142 



I 



