title: An improved barnacle attachment inhibition assay.
abstract: The Balanus amphitrite attachment inhibition assay, developed by Rittschof et al. (1992), has been widely used for screening antifouling compounds. One shortcoming of this assay, however, is the low (often < 40%) attachment rate of cyprids, including in the controls that contain seawater only. In this study, trapping of cyprids at the air-water interface was found to be a main contributor to the low attachment rate. Procedures to eliminate the air-water interface were thus introduced. With the improved bioassay, a much higher cyprid attachment rate (>70%) was attained. To further illustrate the usefulness of the improved assay (ie eliminating the air-water interface), the effects of the length of cyprid storage and the effect of a reference biocide, tributyltin chloride, on the survival and attachment rate of the cyprids were examined. The length of cyprid storage was important, with newly molted cyprids, 3- to 9-day old cyprids and 12-day old cyprids having an attachment rate of 43%,>75% and 36%, respectively. The low attachment rate in the newly molted cyprids was due to a high percentage of cyprids that still swam at the end of exposure period, whereas the low attachment rate in the 12-day old cyprids was due to a high mortality rate. The cyprids showed an EC50 of 22 microg l(-1) for attachment inhibition and LC50 of 25 microg l(-1) for mortality. It is concluded that the air-water interface has an important confounding effect on cyprid attachment rate in the conventional B. amphitrite attachment assay. By eliminating the air-water interface more robust quantitative assay results were obtained.
authors.affiliation: Department of Biology, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong, People's Republic of China. qiujw@hkbu.edu.hk
authors.forename: Jian-Wen
authors.initials: JW
authors.lastname: Qiu
authors.forename: Oi Shing
authors.initials: OS
authors.lastname: Hung
authors.forename: Pei-Yuan
authors.initials: PY
authors.lastname: Qian
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001681:Biological Assay / Q000379:methods*; D007814:Larva / Q000187:drug effects / Q000502:physiology; D001468:Thoracica / Q000187:drug effects* / Q000502:physiology; D014220:Trialkyltin Compounds / Q000494:pharmacology; D014867:Water
chemical_list: D014220:Trialkyltin Compounds; D014867:Water; C011559:tributyltin