Amphipods comprise an order of crustacea, which contains mostly marine and freshwater forms. Even though they appear to be quite different from crabs and shrimp, amphipods are considered to be relatively closely related to both groups. As such they are placed in a group called the Peracarida, or "near shrimps." All of the members of this group share a number of characteristics such as the same number of appendages found in each body region, and the general body form. However, the amphipods lack the shell found in crabs and shrimps. Another important difference is that female amphipods have a brood pouch while true crabs and shrimps don't have one.
Amphipods are extremely diverse and therefore it is no surprise that we colleagues have described another new species. The name of this one refers to the type locality (Iki Island) which is currently the only place the new species is found.
For the experts: A new species of anisogammarid amphipod, Jesogammarus (Jesogammarus) ikiensis sp. n., is described from freshwaters in the Iki Island, Nagasaki Prefecture, Japan, based on results of morphological and molecular analyses. The new species is distinguished from all members of the genus by the combination of small number of setae on dorsal margins of pleonites 1–3, short and small number of setae on posterior margins of peduncular articles of antennae, mandibular article 1 without setae, well developed posterior lobes of accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5, and pectinate setae on palmar margin of female gnathopod 2. A key to all the species of Jesogammarus is provided.