saline started within 10 minutes after the removal of the antennule from the 

 animal. Test chemical stimuli were injected into the continuously flowing 

 saline bathing the antennule. Recordings were made by picking up a small 

 nerve bundle with a platinum electrode. The signal was amplified via a 

 Tektronix Type 122 Preamplifier, and displayed on conventional recording 

 equipment for later analysis. 



It is commonly accepted that neurophysiologically determined thresholds of 

 sensory receptors He an order of magnitude above the behaviorally determined 

 thresholds. Thus, to document the effects of #2 fuel oil on lobster antennular 

 chemoreception, we used the following test series: (1) mussel juice; (2) #2 fuel 

 oil, 10 ppm: (3) mussel juice plus oil; (4) artificial seawater; and (5) mussel 

 juice. Stock solutions were made at one time and refrigerated. Artificial 

 seawater was made according to the MBL formula: 420 mM NaCl , 9 mM KCl , 

 9 mM CaCl2-2H20, 23 mM MgCl2-6H20, 26 mM MgS04-7H20, 2 mM 

 NaHC03 (pH 7.3). This was used to ehminate introduction of "day-to-day 

 variations in natural seawater. Mussel juice was made by homogenizing 10 g 

 wet weiglit ofMytihis ediilis tissue in 100 ml artificial seawater. The suspension 

 was centrifuged at 27,000xg for 20 minutes and the pellet discarded. The 

 supernate was frozen in small aliquots until needed. The WAF of 10 ppm #2 

 fuel oil was made at the start of each preparation, due to the lability of the 

 oil-water suspension. 



Tliis protocol allowed us to compare the response to Stimulus (1) with the 

 response to Stimulus (5) for nerve fiber damage or fatigue, or lasting effects of 

 the prior oil test stimulus. Stimulus (2) and Stimulus (3) were used to 

 determine a) whether lobster antennules can detect oil as a chemical stimulus, 

 and b) if the presence of oil changes the response to mussel juice. Stimulus (4) 

 was used to determine the sensitivity of the preparation to a chemically neutral 

 stimulus; this allowed us to measure mechanoreceptor activity which can be 

 subtracted to discover purely chemosensory responses in the other tests. 



RESULTS 



Chemistry 



Water quality measurements showed that for all experiments, salinity and 

 pH remained constant, ammonia remained undetectably low, and 0^ remained 

 at saturation. Temperatures fluctuated with ambient water tempeFature, and 

 are listed below with each experiment. 



Gas chromatography showed that the water-accommodated fraction 

 recovered from the lobster tanks closely resembled whole #2 fuel oil. Infrared 

 spectroscopy of CCL4-extractable hpids showed moderate (±20%) daily 

 fluctuations v^thin and between individual tanks. The dosing system was 

 capable of maintaining relatively similar exposure levels. 



127 



