Differences in PAH tolerance between Capitella species: underlying biochemical mechanisms

Area of Science:

• Environmental Toxicology
• Marine Biology
• Biochemistry

Background:

• The polychaete Capitella capitata is a species complex with observed variations in toxicant tolerance.
• Capitella sp. I is opportunistic and can biotransform polycyclic aromatic hydrocarbons (PAHs), while Capitella sp. S is more sensitive to stressors like PAHs.

Purpose of the Study:

• To investigate if differences in biotransformation capacity explain the varying tolerance to PAHs between Capitella sp. I and sp. S.
• To measure the production of fluoranthene (Flu) metabolites in both species as an indicator of biotransformation.

Main Methods:

• Exposure of Capitella sp. I and sp. S to sediment contaminated with fluoranthene (Flu) for 10-15 days.
• Quantification of Flu uptake, biotransformation (metabolite production), and accumulation in both species.
• Analysis of the subcellular distribution of Flu and its metabolites.

Main Results:

• Capitella sp. I exhibited higher Flu uptake but was significantly more effective at biotransformation (62%) compared to sp. S (11%).
• Net accumulation of parent Flu was similar between species due to differential biotransformation rates.
• Significant differences in subcellular distribution were observed: sp. I in cytosol, sp. S in membrane fraction.
• Genotoxicity was detected in sp. I upon biotransformation, but not in sp. S.

Conclusions:

• Biotransformation ability is a key factor determining PAH tolerance in Capitella sibling species.
• DNA damage is linked to biotransformation, but other toxicity mechanisms, like membrane disruption, are more critical for predicting tolerance differences.
• Understanding species-specific biotransformation is crucial for assessing PAH risks in marine environments.