The water flea, Daphnia pulex,​ breeds prolifically and crowds out native water fleas. These water fleas produce “ephippia​ containing embryos” – which are notably tough eggs that can survive harsh conditions. Water samples were collected from 14 New Zealand lakes, including Lake Kapoai​ near Dargaville on the North Island. Dr Carolyn Burns,​ of Otago University, and Dr Michael Lynch​ collected the South Island samples in 2018. These water fleas are thought to have invaded Japan between 680 and 3400 years ago.

Source: Stuff May 16, 2021 16:52 UTC