Abstract
A new record of an individual of the invasive sea squirt, Styela clava, is reported from Scapa Flow in Orkney, Scotland. This represents a 1.54° latitudinal extension (168 km) from the previous northern-most record in UK waters. Diver surveys of hard substrates in the immediate area, part of local biosecurity protocols, did not find any additional individuals. Possible transport vectors, likelihood of an established reproductively active population, and implications to local biodiversity are discussed.
Highlights
The leathery or clubbed sea squirt Styela clava Herdman (1881) is a solitary ascidian tunicate with a distinct long tapering body and stalk (Lützen 1998; Clarke and Therriault 2007)
Settlement panels and the surrounding frame components deployed in Scapa Flow were heavily fouled, primarily by the sea squirt Ascidiella aspersa
Taxonomic guides (Hayward and Ryland 2017; Bowen et al 2018) were used to identify this organism as S. clava; verification was provided by the National Biodiversity Network (NBN 2021b)
Summary
The leathery or clubbed sea squirt Styela clava Herdman (1881) is a solitary ascidian tunicate with a distinct long tapering body and stalk (Lützen 1998; Clarke and Therriault 2007). S. clava is found from low intertidal zones to subtidal depths of up to 40 m and grows on artificial and natural hard substrates (Lützen 1998; Clarke and Therriault 2007). This species can survive a wide range of temperatures, from 2 to 23 °C (Clarke and Therriault 2007), but appears to be intolerant of low salinity (below 20‰) (Davis and Davis 2008). Styela clava is native to the northwest Pacific Ocean, from the Sea of Okhotsk to Shanghai, China (NBN 2021a) but has aggressively spread through temperate waters around the globe (Lützen 1998; Clarke and Therriault 2007; Goldstien et al 2011). In 1953, S. clava was found in English waters in the Plymouth area (Carlisle 1954) and has since spread extensively through the northeast
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
