Preliminary Studies on Distribution of Marine Fouling Hydroids <i>Ectopleura</i> and on Laboratory-based Actinula Larval Settlement Assays

Abstract

Only a few studies have been devoted to the species identification and the distribution of marine hydroids Ectopleura in Japanese coastal waters, despite the scale of fouling problems that they pose. We collected polyps from the coast of the western and northern parts of Japan, and analyzed their morphological characters and mitochondrial COI genes. As a result, while polyps settled on fishing nets along the coast of Hokkaido were Ectopleura radiata, E. crocea were spotted along the Pacific coast of Honshu. Dense polyp colonies on pontoons along the coasts of Seto Inland Sea in mid-to-late winter were also identified for the first time as E. radiata. In addition, phylogenetic analysis has identified Ectopleura sp. JRH-2014 spotted in the China Seas as E. radiata. Regarding actinulae of E. radiata, we devised a new assay composed of hexagonal columnar cell using test slide glasses, and a magnetic stirrer, and examined the settlement inhibitory effects of the silicone-based coatings. The results found that actinulae proved very sensitive to copper pyrithione contained in anti-fouling agents and the age of coatings.