DORMANCY IN THREE CALANUS SPECIES (C. FINMARCHICUS, C. GLACIALIS AND C. HYPERBOREUS) FROM THE NORTH ATLANTIC
H.J. Hirche
Abstract:
Diapause in the copepod genus Calanus has in the past mostly been related to copepodite stage V (CV) of Calanus finmarchicus, although many Calanus species have a similar life cycle and should therefore undergo some form of dormancy. Here, the life cycles of the three North Atlantic copepods C. finmarchicus, C. glacialis and C. hyperboreus were searched for dormant stages. It is suggested that several developmental stages of these species are capable of dormancy depending on environmental conditions. Although knowledge on overwintering physiology is still very limited, the stages were grouped into 3 groups. The true diapause stages (Group 1) were subdivided into stages without gonadogenesis (CIII C. hyperboreus, CIV C. hyperboreus, CIV C glacialis, CIV C. finmarchicus), with gonadogenesis (CV C. hyperboreus, C. glacialis, C. finmarchicus), and diapausing females. Group 2 includes freshly moulted adults of all three species, of which a precise classification of dormancy is not possible due to lack of data. Finally, the possibility of a dormant state of non-feeding naupliar stages was mentioned (Group 3). The regulation of dormancy and the ecological significance of dormancy in the three species studied is discussed.
(Alfred Wegener Institute for Polar and Marine Research, Columbusstr. 1, D-27515 Bremenhaven)