Platorchestia platensis (Krøyer, 1845)

Synonymy restricted to South African records.

Orchestia platensis . ― Griffiths, 1975: 170.

Platorchestia platensis . ― Griffiths, Mead & Robinson, 2009: 242 (invasive). ― Griffiths, Robinson, & Mead 2011: 242. ― Mead, Carlton, Griffiths & Rius, 2011a: 1998, table 1. ― Mead, Carlton, Griffiths & Rius, 2011b: 2488. ― Milne & Griffiths, 2013: 77, 88 (Appendix).

Types. Lectotype, male, 12.3 mm, ZMUC CRU 8221(selected by Serejo, 2004). Paralectotypes, 1 male, 6.8 mm; 1 female, 7.6 mm, 7 damaged specimens, ZMUC 7803 (selected by Serejo, 2004) Montevideo. 13/12 40. Type locality. Banks of the Rio Plata , Montevideo, Uruguay .

Material examined. 11 specimens, AM P.88484, Plettenberg Bay, South Africa (~ 34°3.445'S 23°22.741'E), dissipative beach, underneath seagrass, F. Porri, March 2012 (in 95% ETOH).

Remarks. Miyamoto & Morino, 2004 divided the genus into three groups. Group 1 which is characterised by antenna 2 and pereopods 6 and 7 sexually dimorphic, is represented by six supralittoral species: P. munmui Jo, 1988, P. pacifica Miyamoto & Morino, 2004; P. pachypus (Derzhavin, 1937), P. parapacifica Kim, Jung & Min, 2013; P. paraplatensis Serejo & Lowry, 2008; P. platensis (Krøyer, 1845) . Of these six species P. platensis appears to be the only traveller.

According to Mead et al. (2011a) P. platensis was first discovered at Danger Point, Gansbaai in 1904, not an area of high ship activity. The new population discovered in 2010 from Plettenberg Bay, 440 km to the east is also not from an area of high ship activity. Mead et al. 2011b considered it to be an introduced species to South Africa mainly because of its restricted distribution. Its South African distribution is now confined to three disjunct bays along the southern coast.

Distribution. South Africa. False Bay (Griffiths 1975); Danger Point, Gansbaai (Mead, Carlton, Griffiths & Rius 2011a); Plettenberg Bay (this study).