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.
Distribution of Necrophagous Copepods in the Cape d , Aguilar Marine Reserve, Hong Kong
Distribution of necrophagous copepods in the cape d'Aguilar marine reserve, Hong Kong. Zoological Studies 43(2): 304-313. Unbaited traps and traps baited with crushed crabmeat were deployed 60 mm off the seabed of LobsterBay, the Cape d'Aguilar Marine Reserve, for 3 d in the winter 1999. Each trap had a 5-mm-diameter opening. A common visitor to the bait was a species of Tisbe (Copepoda: Harpacticoida). Baited traps usually contained more Tisbe than unbaited ones. A spatial distribution of Tisbe was also identified within the study area, i.e., a greater catch was recorded from deeper waters outside the bay. A significant positive correlation between the number of Tisbe trapped and sediment organic content was identified. Simultaneously, Tisbe catches corresponded negatively to the median grain size of the substratum, implying that the distribution of scavenging Tisbe is inversely related to sediment physiography in Lobster Bay.
THE EFFECT OF DELAYED FERTILIZATION IN SOME SPECIES OF THE GENUS TISBE (COPEPODA, HARPACTICOIDA)
Delay in fertilization of the females of Tisbe dobzhanskii from Anzio.T. holothuriac from Ponza, and T. clodiensis from Venice and Ponza was found to affect the sex-ratio of these populations.The degree of the influence depended largely upon the lateness of fertilization and, thus, upon the biology of the species.Especially in T. dobzhanskii shifting of the sex-ratio in favor of males was highly significant. In the other populations it was less evident, but still significant. If the delay of fertilization was too great, the females were no longer able to produce viable offspring.In addition to the shifting of the sex-ratio towards males an increase of offspring per family was observed.The possible adaptive nature of the phenomenon is discussed.