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 lie 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 KC1, 
9 mM CaCl 2 *2H 2 0, 23 mM MgCly6H 2 0, 26 mM MgS0 4 '7Ho0, 2 mM 
NaHCO^ (pH 7.3). This was used to eliminate introduction of day-to-day 
variations in natural seawater. Mussel juice was made by homogenizing 10 g 
wet weight o {Mytilus edulis 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. 
This 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 remained 
at saturation. Temperatures fluctuated with ambient water temperature, 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 CCLq-extractable lipids showed moderate (±20%) daily 
fluctuations within and between individual tanks. The dosing system was 
capable of maintaining relatively similar exposure levels. 
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