The spiny water flea Bythotrephes longimanus


The spiny water flea, or bythorephes longimanus, is a water dwelling insect commonly found in Great Britain and northern Europe, as well as Asia, and has made its way into the Great Lakes, hitching a ride in the ballast water of ships. It can grow up to 20 millimetres long, and grows four pairs of legs. 70% of its entire body is its long, barbed tail, which it uses as a deterrence to fish getting a little bored with their regular diet. Its head is dominated by a pair of large black eyes. This invasive was first discovered in lake Huron in 1984.


The spiny water flea's diet consists of only small zooplankton, which is a big problem in the Great Lakes, seeing as many native fish rely on the microscopic organism to survive. The invasive ingests all the zooplankton, and when the fish turn to it as an alternate food source, they choke on its' long spine. Even worse, each female specimen can give birth to up to ten offspring, thus the invasive is able to spread at alarming rates and consume even larger amounts of zooplankton. Like other water dwelling creatures, the spiny water flea likes to stay at the bottom of the lake it's inhabiting during the day, and comes up at night. it uses one pair of legs to catch and trap zooplankton, and another pair to help ingest it


  • Kingdom: Animalia
  • Subkingdom: Bilateria
  • Infrakingdom: Protostomia
  • Superphylum: Ecydsozoa
  • Phylum: Arthropoda
  • Subphylum: Crustacea
  • Class: Branchiopoda
  • Subclass: Phyllopoda
  • Order: Diplostraca
  • Suborder: Caldocera
  • Infraorder: Onychopoda
  • Family: Cercopagididae
  • Genus: Bythotrephes
  • Species: Bythotrephes Longimanus

Impact on invaded enviroment

As you already know, this rapidly spreading invasive survives on only zooplankton, and with the large population, it needs a lot of it. In fact it consumes so much that there's hardly any left for the small native fish such as minnows. This will cause a decline in the minnow population, and in turn all other species that rely on it, and so on. Basically, this little bug has the power to destroy the food chain, and therefore the biodiversity of the Great lakes.

Preventing further spread

The spiny water flea is incredibly clingy and is near impossible to stop once established in a suitable habitat, which underlines stopping spread. It likes to move small distances from lake to lake by sticking to boating and fishing gear and are amazingly good at it too. Sometimes clumps of over 200 water fleas are seen hanging from fishing lines and nets, which is also horrible for fisheries because the fish can see them and therefore try to avoid them. In fact they are such good survivors that even native areas require population control! However there is hope for the Great lakes. If everyone who goes boating or fishing in populated lakes cleans their gear before going to a pristine lake, then the invasive can be contained.

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