TY - JOUR

T1 - Diapause : a potent force in the evolution of freshwater crustaceans.

AU - Fryer, Geoffrey

PY - 1996/3

Y1 - 1996/3

N2 - After a brief historical review of the discovery of diapause in freshwater crustaceans, its dramatic nature in certain cyclopoid copepods, in which diapausing individuals may occur at densities of > 106 per m2, is used to illustrate the enormous ecological significance of the phenomenon. Some of the problems presented by dispause in cyclopoid copepods are noted, including the different behaviour in different lakes of what appears to be a single species. Different physiological cues or different genetic endowments are clearly involved. The wider incidence of diapause in freshwater copepods and ostracods is noted. Among freshwater crustaceans it it the Branchiopoda that have universally adopted diapause, always at the egg stage. Even such an ancient order as the Anostraca, perhaps the most primitive of all crustaceans, produces elaborately constructed resting eggs that are capable of cryptobiosis, can remain viable in a dry state for long periods, and can tolerate extreme conditions. The nature of branchiopod resting eggs is briefly reviewed. Of these, only those of the Anomopoda are protected by containers derived from the parental carapace. These are mechanically complex in the most advanced species but, as shown by fossils, are extremely ancient structures. Factors initiating the onset and termination of diapause in branchiopods are briefly noted, and the process of hatching of resting eggs is outlined.

AB - After a brief historical review of the discovery of diapause in freshwater crustaceans, its dramatic nature in certain cyclopoid copepods, in which diapausing individuals may occur at densities of > 106 per m2, is used to illustrate the enormous ecological significance of the phenomenon. Some of the problems presented by dispause in cyclopoid copepods are noted, including the different behaviour in different lakes of what appears to be a single species. Different physiological cues or different genetic endowments are clearly involved. The wider incidence of diapause in freshwater copepods and ostracods is noted. Among freshwater crustaceans it it the Branchiopoda that have universally adopted diapause, always at the egg stage. Even such an ancient order as the Anostraca, perhaps the most primitive of all crustaceans, produces elaborately constructed resting eggs that are capable of cryptobiosis, can remain viable in a dry state for long periods, and can tolerate extreme conditions. The nature of branchiopod resting eggs is briefly reviewed. Of these, only those of the Anomopoda are protected by containers derived from the parental carapace. These are mechanically complex in the most advanced species but, as shown by fossils, are extremely ancient structures. Factors initiating the onset and termination of diapause in branchiopods are briefly noted, and the process of hatching of resting eggs is outlined.

KW - diapause - freshwater Crustacea - antiquity - diversity - evolution

U2 - 10.1007/BF00016800

DO - 10.1007/BF00016800

M3 - Journal article

VL - 320

SP - 1

EP - 14

JO - Hydrobiologia

JF - Hydrobiologia

SN - 0018-8158

IS - 1-3

ER -