Telmatogeton japonicus Tokunaga 1933

(9) Telmatogeton japonicus Tokunaga, 1933

Status in U.K. – non-native.

Larvae of non-biting midges, Chironomidae, have been consistently recorded from samples throughout the monitoring programme but they are not identified to species since pupae or adults are usually required to provide a definitive identification. The non-native Telmatogeton japonicus was recorded in Co. Clare, Ireland in 1999 by Murray (2000) and in Wales by Murray (2013). Langton and Hancock (2013) provided records of two Telmatogeton species from Scotland: T. japonicus from St Kilda and the closely related T. murrayi Saether, 2009 from Shetland. This latter species was described from Iceland based on material originally identified as T. japonicus by Murray (1999) but the taxonomic status of the species is uncertain and requires investigation (D. Murray, pers. comm.).

Telmatogeton japonicus was first recorded in Orkney in 2015 by L. Johnson (identity confirmed by P.H. Langton), based on adult specimens. Pupae from scrape samples collected in Gutter Sound in 2017 under the current sampling programme were also identified as belonging to T. japonicus using Langton and Visser (2003). It is, however, acknowledged that the pupa of T. murrayi is currently unknown and, since T. murrayi is recorded from Shetland (Langton and Hancock 2013), it is conceivable that the material could belong to that species. Nevertheless, based on the available information, in keeping with the previous Orcadian record, the present pupal records are retained as T. japonicus pending a formal review of T. murrayi.

Adults of T. japonicus are relatively short lived whilst the larvae are commonly regarded as members of the fouling community, indicating that larval transport is the species’ most likely dispersal mechanism over large distances. Failla et al. (2015) state that long-range movements of chironomids would be nearly impossible without human or animal assistance and the introduction to Europe is thought to have occurred with shipping from Japan (Brodin and Andersson 2008; Raunio et al. 2009; Failla et al. 2015). Dispersal within Europe may be aided by offshore structures such as navigation buoys and windfarm pilings (Kerckhof et al. 2007; Brodin and Andersson 2008); T. japonicus was not recorded on such structures in Orkney by Want et al. (2017) but sampling within a particular season would have been necessary to obtain the pupae required for identification.