Was eradicated from Darwin after introduction in 1999. Wells (2019) suggested that the osmotic shock to veliger larvae when exposed to higher salinities outside of the marins where it was present may have reduced the risk of its potential spread in Darwin during the outbreak in 1999 (Willan et al., 2000; Bax et al., 2002).

Mytilopsis sallei has successfully invaded several major ports in East Asia (Wong et al., 2011), such as Taiwan, in 1977 (Chang, 1985) Japan in 1979 (Ishibashi and Kasaka, 1980) and in Hong Kong (Morton, 1980). M. sallei was introduced to Xiamen, China, as feed for cultured fishes and shrimps in the early 1990s, and shortly thereafter became the dominant species within its fouling community (Wang et al., 1999). In more recent times, it has established in tropical monsoon drains of Singapore (Tan and Morton, 2006), and has been reported as an invasive species in India (Gaonkar et al., 2010a, b).

Recent studies have called into question the current taxonomy of the group, with some treating several Mytilopsis spp. as synonyms (Tan and Tay, 2018), and others arguing that several populations in Asia may in fact not be M. sallei, but a closely related species (Wangkulangkul and Lheknim, 2008).

Summary Description

In its native habitat, M. sallei is a colonial surface dweller of sheltered waters such as coastal lagoons. In its introduced habitat, it is found in intertidal and shallow waters in wide temperature and salinity ranges. It has not been found any deeper than a few metres. It prefers to settle on vertical surfaces and objects, but is found on all types of substrata.

Mytilopsis sallei is a small, finger-nail sized mussel, growing to an average size of 25 mm. M. sallei settles in clusters, and is rarely seen as a single individual. It usually lives in shallow water in tidal areas and is tolerant of polluted waters. It attaches to surfaces using byssus threads and usually settles mostly on vertical surfaces. It has a varied shell colouration, from black through to a light colour, with some small individuals having a light and dark zig-zag pattern. The right valve overlaps the left valve, and is slightly larger.