a1 Marine Biological Unit, C.E.G.B., Fawley, Southampton SO4 1TW
Cyathura is a genus of Anthurid isopods represented by some fourteen estuarine species around the world (Miller & Burbanck, 1961). They are unusual amongst the isopods in that the majority of individuals in a population show protogynous hermaphroditism, adults breeding as females in their first year, then changing to males over the following winter (Legrand & Juchault, 1963; Burbanck & Burbanck, 1974). The adults are tubicolous, virtually incapable of swimming, and have limited mobility, resulting in disjunct, stable populations, some of which, in the case of C. polita (Stimpson), are known to have maintained the same locations and densities over a period of 20 years (Burbanck & Burbanck, 1975). The embryos develop within a marsupium or brood pouch on the thoracic somites of the female, and are released as interstitial juveniles 1 mm or more in length. With populations averaging 200 to 400 individuals per square metre, these animals are convenient for autecological studies. Indeed, Burbanck & Burbanck (1979) considered that as hardy, euryokous animals, consistent in their tolerance to fluctuating environmental conditions, and convenient for study, Cyathura species are ideal ‘indicator organisms’ in estuaries.