Osmoregulation inthe Jaera AlbifronsGroup of Species [Isopoda, Asellota]

Abstract

The jaera albifrons Leach group of species is a common component of estuarine faunas in Britain, where each species may occur in considerable numbers. Some members of the group also occur in less variable, marine localities in Britain and elsewhere, indicating that each species is capable of survival in a wide range of salinity combinations and that the group as a whole is euryhaline (see, for example, Naylor & Haahtela, 1966; Jones & Naylor, 1971). Naylor & Haahtela (1966) showed that the four species of jaera which occur in Britain occupy preferred areas on an estuarine shore such that jaera ischiosetosa Forsman is common on stones in areas affected by freshwater seepage, jaera albifrons Leach occurs on stones either in pools or in parts of the shore where water is retained (around M.t.l.), jaera praehirsuta Forsman occurs on Fucus serratus (L.), and jaera forsmani Bocquet can be found under stones around L.w.s.t.-l.w.n.t. where there is little retention of water. A later investigation by Jones & Naylor (1971) has shown that these habitat preferences persist throughout a 2-year period, and that each of the jaera species is capable of successful reproduction and development in a characteristic pattern of fluctuation in salinity, temperature and exposure to air