AB 13:293-302 (2011)  -  DOI: https://doi.org/10.3354/ab00374

ABSTRACT: After being exposed to anoxia for 24 h, with and without hydrogen sulfide (H₂S; 5 or 30 mg l⁻¹), the feeding activities of the Manila clam Ruditapes philippinarum were examined in the laboratory under normoxic conditions. The clearance rates of clams after exposure to anoxia with 30 mg l⁻¹ H₂S (5.1 l h⁻¹ ind.^–1) were significantly lower than in those exposed to normoxic or anoxic conditions (11.4 or 11.2 l h⁻¹ ind.^–1, respectively). The phytopigment concentration of the digestive glands of clams treated with 30 mg l⁻¹ H₂S under anoxic conditions (41.7 µg g⁻¹, wet weight of digestive gland) was significantly lower than that measured in other experimental treatments in this study (548.4 µg g⁻¹ for normoxia, 461.9 µg g⁻¹ for anoxia only, 479.8 µg g⁻¹ for 5 mg l⁻¹ sulfidic anoxia; p < 0.01). Histological examination of clam tissue revealed that the ciliary epi­thelium was damaged by a high concentration of H₂S. These findings indicate that once the clams suffered damage to their gills by exposure to H₂S, their feeding activity was impaired and they could not ingest prey, even when their environment was returned to optimal conditions.

KEY WORDS: Clearance rate · Gill · Digestive gland · Ingestion · Histology