The effect of butenolide on behavioral and morphological changes in two marine fouling species, the barnacle Balanus amphitrite and the bryozoan Bugula neritina

Abstract

Butenolide [5-octylfuran-2(5H)-one] is a very promising antifouling compound. Here, the effects of butenolide on larval behavior and histology are compared in two major fouling organisms, viz. cypris larvae of Balanus amphitrite and swimming larvae of Bugula neritina. Butenolide diminished the positive phototactic behavior of B. amphitrite (EC₅₀ = 0.82 μg ml⁻¹) and B. neritina (EC₅₀ = 3 μg ml⁻¹). Its effect on the attachment of cyprids of B. amphitrite was influenced by temperature, and butenolide increased attachment of larvae of B. neritina to the bottom of the experimental wells. At concentrations of 4 μg ml⁻¹ and 10 μg ml⁻¹, butenolide decreased attachment of B. amphitrite and B. neritina, respectively, but the effects were reversible within a certain treatment time. Morphologically, butenolide inhibited the swelling of secretory granules and altered the rough endoplasmic reticulum (RER) in the cement gland of B. amphitrite cyprids. In B. neritina swimming larvae, butenolide reduced the number of secretory granules in the pyriform-glandular complex.

Keywords:

• butenolide
• Balanus amphitrite
• barnacle
• Bugula neritina
• bryozoan
• antifouling
• behavior
• histology

Acknowledgements

The authors thank Professor Zhang Xi-Xiang for his help in coordinating the collaboration between the two research groups, Mr W. S. Lee and Mr Tze-Kin Cheung for their help with the TEM sample preparation, Dr On-on Lee, Dr Kiyotaka Matsumura and Dr Jung-Rung Wu, and Miss Angela Wu for helpful comments on draft of the manuscript. This study was supported by a joint research grant between GRC of HKSAR and NSFC of China (N_HKUST602/09) and an award SA-C0040/UK-C0016 from the King Abdullah University of Science and Technology to P.Y. Qian.