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 tlieir orientation and communication. These 

 communication signals may have chemical features, such as carbon skeleton, 

 functional groups, volatility, and solubiUty, in common with compounds in 

 petroleum (7). In an oil-polluted environment, different petroleum compounds 

 v^nll 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). One 

 can thus envisage the scenario when these chemical look-aUkes 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 whetlier 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, 10, 11). 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 



