The Earliest Japanese records of the invasive European ascidian <i>Ascidiella aspersa</i> (Müller, 1776) (Urochordata: Ascidiidae) from Mutsu and Ago Bays, with a brief discussion of its invasion processes

Abstract

Study of the ascidian collection at the National Museum of Nature and Science, Tsukuba, revealed some Japanese specimens of the non-native ascidian, Ascidiella aspersa (Müller, 1776), collected in 2007 from both mid-temperate Oominato, Mutsu Bay, in the northernmost part of Honshû, and from warm-temperate Ago Bay, Kii Peninsula, middle Honshû. These specimens were collected one year earlier than the previous earliest Japanese record from cool-temperate Funka Bay, Hokkaido. Mutsu Bay has an international port, which can be assumed to be the invasion gateway for this ascidian from abroad. On the other hand, this ascidian may have arrived at Ago Bay by domestic transport because all of the bay's ports are strictly for domestic use under governmental regulations. A comparison of the publicly available sequences for the 18S rRNA gene among this species and its allies suggested the possibility that it inhabited Korean waters as far back as the late 1990s, and it entered Japanese waters from Korea through an as yet unknown international port(s).

Genetic Diversity and Population Dynamics of Invasive Ascidiella aspersa: Insights from Cytochrome Oxidase Subunit I and 18S rDNA Analyses in Korean and Global Populations

“…aspersa is native to Norway in the NE Atlantic [9][10][11][12][13] and has also been found in the northern Mediterranean. However, this species has since invaded various parts of the world, including Australia [4,14], Argentina [15,16], Iceland [17], India [18], Japan [19][20][21], Republic of Korea [22], New Zealand [23,24], the NW Atlantic including the USA [25,26], Canada [27,28], and South Africa [29]. It spreads through ballast water or attachments ship hulls, allowing it to easily migrate and colonize farming facilities, fishing gear, and port infrastructure, resulting in significant damage.…”

A new record of Ascidiella scabra (M&uuml;ller, 1776) (Ascidiacea, Phlebobranchia) in the southwestern Atlantic

“…Ascidians (Tunicata, Ascidiacea) are ubiquitous organisms in all marine environments (Shenkar and Swalla 2011). Although their short-lived larval stage limits natural dispersion (Stolfi and Brown 2015), the transport of adult specimens as encrusting fauna of vessels' hulls can enhance long-distance colonization by these organisms to the North Sea and the northeastern Atlantic, currently has a wide distribution across the northwestern Atlantic and in Japan, Australia, New Zealand, India, and the southwestern Atlantic (Dybern 1969a;Tatián et al 2010;Nishikawa et al 2019;Ma et al 2019). This species can compete with native species for space and may affect their recruitment success (Osman and Whitlach 2000).…”