Crangonyx islandicus is a species of groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 amphipods, endemic to Iceland

Iceland

Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...

, which was described in 2006. This species lives in freshwater beneath recent lava fields (no older than 10,000 years) and is relatively widespread in the geologically youngest parts of Iceland. Morphological

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 data, species distribution

Range (biology)

In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...

, genetic diversity and population structure

Population structure

Population structure may refer to many aspects of population ecology:* Population stratification* Population pyramid* Age class structure* F-statistics* Population density* Population distribution* Population dynamics and population growth...

 suggest that this species survived repeated glaciation periods in Iceland in sub-glacial refugia. Considering that this species is most closely related genetically to Crangonyx

Crangonyx

Crangonyx is a genus of crustacean in family Crangonyctidae. It contains the following species:*Crangonyx aberrans S. I. Smith, 1983*Crangonyx acicularis Zhang & Holsinger, 2003*Crangonyx africanus Missouli, 2006...

species from North America, the ancestor of C. islandicus might have colonized Iceland via Greenland

Greenland

Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...

.