Figure 42. — Sampling from experimental shrimp containers for quantitative measurement of 



food consumption. 



t 



^/0^^<^, 



x. 



\ 



SULiNirr I'/.,] 



Figure 43. — Survival of juvenile and subadult white 

 shrimp at various temperature and salinity levels. 



salinity for white shrimp of all sizes. We will 

 also make comparable tests with brown shrimp. 



George W. Griffith, Project Leader 



EFFECTS OF ELECTRICAL STIMULATION 



ON BOTTOM INVERTEBRATES OTHER 



THAN SHRIMP 



In our research on the responses of marine 

 annelid worms to electric shock, we have 

 experimented with various species of poly- 

 chaetes obtained from beach areas. In nine 

 of these species, a pulse length in excess of 

 200 |/sec. (microseconds) was necessary to 

 produce a twitch or contraction. A field 

 strength of from 0.3 to 2.0 v. (volts) was 

 necessary for threshold response. The pulse 

 rate used for determining threshold levels 

 of field strength and pulse length was 3 pulses 

 per second. Two other species are unrespon- 

 sive to electrical stimulation of any type 

 available to the experiment. 



In a second phase of the project, polychaetes 

 living in substrate were stimulated by varied 

 field- strength voltages and rates for periods of 

 time ranging from 5 sec. to 30 min. In no in- 

 stance did a worm emerge from the substrate. 

 When stimulated electrically, worms that were 

 visible responded by contracting and sometimes 

 moving deeper into the substrate. No worm 

 moved toward one electrical pole or the other. 



45 



