Jassa marmorata Holmes, 1905

Kakkonen, Jenni E., Worsfold, Tim M., Ashelby, Christopher W., Taylor, Andrea & Beaton, Katy, 2019, The value of regular monitoring and diverse sampling techniques to assess aquatic non-native species: a case study from Orkney, Management of Biological Invasions 10 (1), pp. 46-79 : 58

(18) Jassa marmorata Holmes, 1905

Status in U.K. – cryptogenic.

Jassa marmorata has been recorded from several sites from the monitoring programme, each year since 2013, mainly from scrape samples. It is less common in the samples than the congeneric J. herdmani (Walker, 1893) , which is considered native.

Conlan (1990) concluded that J. marmorata has a cosmopolitan distribution and further stated that the worldwide distribution of the species would make suspect any native species of Jassa from heavily populated areas. Historic confusion, especially between J. marmorata and J. falcata (Montagu, 1808) , has led to the distributions of many species being misinterpreted. Establishing the origin of J. marmorata is therefore problematic. Chapman (2000) considered it to be introduced to the northeastern Atlantic from a native range of the north-western Atlantic but this is not certain. Due to these uncertainties, and in keeping with Marchini and Cardeccia (2017), we here consider it cryptogenic in the U.K.