Speculations about petroleum hydrocarbon interference with the processes 
of chemoreception have appeared with a certain regularity in the literature, 
starting with Blumer (4). The reasons for this speculation are obvious: 
petroleum hydrocarbons are a mixture of organic chemical compounds, some 
of which are related to compounds such as pheromones and alarm substances, 
which are utilized by animals for their orientation and communication. These 
communication signals may have chemical features, such as carbon skeleton, 
functional groups, volatility, and solubility, in common with compounds in 
petroleum (7). In an oil-polluted environment, different petroleum compounds 
will be in solution or in emulsion in the water column, while the heavier 
fraction can become part of the benthic mud and affect the benthic ecosystem 
for many years, as shown by Blumer and Sanders, among others (5, 9, 10). One 
can thus envisage the scenario when these chemical look-alikes mimic or mask 
the reception of biologically important signals. Mimicked signals may result in 
“false alarm”, i.e., animals may look for imaginary food or mates, or avoid 
predator danger where there is none. If their chemical signals are masked, 
animals cannot respond to them and may miss opportunities to feed, or mate, 
or escape. A third possibility less frequently mentioned is that animals may 
become subject to two competing signals (3), for instance, an attractant signal 
from food (or mate) and a repellent signal from oil. In such cases 
chemoreception would be perfectly normal, but the animal may not be able to 
decide whether to feed or hide. Such delays may be more critical than apparent 
at first glance: even a slight delay in responding to food can put an individual 
at a significant disadvantage when competing with an unimpaired conspecific, 
or in escape from predators. 
Thus far, some cases of mimicked food attraction and delayed food 
responses have been observed, as well as increases and decreases in alarm and 
attraction behavior (1, 8, 11, 12). However, specific effects of oil on 
chemoreception itself have never been documented. Studies showing oil 
interference with chemoreception will provide us with a general understanding 
of the effects of oil pollution, since the processes of chemoreception — 
although essentially unknown — are probably similar in all animals. This would 
be especially true if similar effects for petroleum fractions were found in 
different animals. Interference with chemoreception or chemically mediated 
behavior also may be one of the most sensitive measures of low level oil 
pollution, since the much more obvious neuromuscular abnormalities appear at 
higher, although still sublethal, levels of oil exposure. 
For this study we chose the bait localization behavior of the lobster, 
Homarus americanus. The lobster uses two chemoreceptor organs. Aesthetasc 
hairs on the antennules represent their sense of smell, and function probably to 
detect distant chemical signals in low concentration. Hairs on the walking legs 
and maxillipeds are the equivalent of taste, and are essential in picking up food 
and bringing it into the mouth while testing its palatability for ingestion. In 
123 
