Abstract:
6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) is a chemical widely used as an
antidegradant in vehicle tires. 6PPD reacts with ozone in the air and produces 6PPD-Quinone
(6PPDQ), a chemical that has been classified by the U.S. Environmental Protection Agency as
very highly toxic to aquatic organisms along with adverse implications to terrestrial ecosystems
and human health. However, the potential sub-lethal, toxicological effects of 6PPDQ on
olfactory-mediated behaviors in fish have yet to be explored. This study examined how 6PPDQ
exposure affects the olfactory system of coho salmon (Oncorhynchus kisutch) through analysis
of avoidance behavior to L-serine or a conspecific alarm substance. Juvenile coho salmon were
exposed to 50 ng/L of 6PPDQ for 18 hours or 200 ng/L of 6PPDQ for 3 hours proceeding
Y-maze testing, and behaviors were recorded and analyzed for 10 minutes in which fish could
swim in the arm delivering the alarm substance (“scented arm”) or DI water (“unscented arm”).
Control fish were found to avoid the scented arm to a statistically significant degree. Statistical
analyses indicated that although control salmon showed avoidance of the scented arm, avoidance
in 6PPDQ-exposed coho salmon did not differ significantly from the controls (p>0.5). We noted
that exposed salmon did trend towards less avoidance compared to controls in several of the
trials, but further testing is needed to confirm observed trends. Our results provide some
evidence of potential inhibitory effects of 6PPDQ on olfactory systems, which could have
implications on foraging, migration, and predator-avoidance of coho salmon exposed to
environmentally-relevant 6PPDQ concentrations.