Distribution and summer diapause of Canthocamptus staphylinus (Jurine) (Copepoda: Harpacticoida) in Lake Ladoga
The spatial distribution of Canthocamptus staphylinus (Jurine) in Lake Ladoga was examined. C. staphylinus is one of the most numerous species of harpacticoids in the lake. It can dwell in almost all littoral biotopes. In profundal biotopes strongly exposed to anthropogenic influence (pollution and eutrophication) only this species of harpacticoid was found. A peculiarity of C. staphylinus biology is that in summer individuals are in the resting stage as cysts. In summer active individuals were found in littoral habitats at a water temperature of 20 °C, but their number was small in comparison with cold periods of the year. In the littoral zone the relative number of individuals in cysts was clearly related to water temperature. Twelve degrees temperature appears to be critical for development of littoral populations of C. staphylinus.
Die Populationsdynamik Von Canthocampt Us Staphylinus (Jurine) (Copepoda, Harpacticoida) Im Litoral Des Bodensees
The population dynamics of Canthocamptus staphylinus in the littoral zone of Lake Constance are described (fig. 2). Adult animals aestivate as cysts. The main part of the population emerges from the cysts in autumn. During the resting stage and the first spell after emerging, mortality is very low (fig. 3). Reproduction, expressed as numbers of ovigerous females, begins in November and reaches its maximum in January. The new generation becomes adult in May/June and encysts without previous reproduction. According to Sarvala (1979) it may be possible, that in littoral populations dormancy is induced by long day periods and temperatures of over 12° C (figs. 1, 2). In the profundal zone C. staphylinus also forms cysts, however, both light and temperature are not likely to induce this stage in depths of over 60 m.
Écologie des crustacés benthiques du lac de Port-Bielh (Pyrénées centrales) : II. Cycles biologiques
Les cycles biologiques de quelques populations de Cladoceres et de Copepodes d'un lac de haute montagne ont ete suivis de juin a novembre 1971, periode ou les eaux etaient degagees des glaces. Dans la plupart des cas le cycle vital des especes (croissance, reproduction) se deroule durant la periode estivale, le lac etant gele le reste de l'annee. La majorite des especes sont monocycliques. Le cycle des Cladoceres debute au moment du degel avec l'eclosion des oeufs de duree, suivie d'un maximum de reproduction parthenogenetique en aout - septembre. Une phase generale de gamogenese marque la fin du cycle. Les Copepodes sont deja en cours de reproduction au moment du degel; le renouvellement des populations s'effectue pendant l'ete. Les especes s'adaptent aux conditions extremes du milieu en adoptant des processus morphologiques et physiologiques particuliers : ephippies de Cladoceres, enkystement et phase de dormance des Copepodes.