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Effects of temperature and fasting on the rate of sinking of Hydra oligactis 1
Author(s) -
Schroeder Lauren Alfred,
Reeder Patricia S.
Publication year - 1979
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1979.24.6.1092
Subject(s) - lernaean hydra , biology , tentacle (botany) , zoology , dry matter , ecology , anatomy , microbiology and biotechnology
Sinking rates of Hydra oligactis Pallas reared at 10°, 15°, and 25°C were determined in a water column at 10°, 21°, and 26°C after fasting intervals ranging from 24 to >500 h. The rearing temperature ( T r ), water temperature during sinking ( T w ), duration of fasting ( F t ), and body conformation ( H c ) (i.e. body length, tentacle length, and tentacle orientation) all significantly correlated with sinking rate. The linear regression model: sinking rate (cm· s −1 ) = 0.684 − 0.0323 H c − 0.00055 F t − 0.00959 T r + 0.00711 T w accounted for 85% of the observed variability. Hydra density (g·cc −1 ) was inversely related to rearing temperature and decreased from 1.030 g·cc −1 for animals reared at 10°C and 1.025 for those reared at 25°C to a plateau of 1.017 g·cc −1 for both rearing temperatures after 200 h and 80 h of fasting for hydras reared at 10° and 25°C. Hydra size also was inversely related to rearing temperature ranging from >100 µ g (dry wt) per single hydra at 10°C to 30 µ g dry wt at 25°C. Hydra size decreased with fasting to <10 µ g dry wt. Changes in hydra density and surface area:volume ratio account for 80 and 97% of the change in sinking rate of fasting hydras reared at 10°C and 25°C. Hydras are especially susceptible to planktonic existence during spring and fall turnover and may become dispersed throughout lakes, but during summer stratification the increased sinking rates would significantly reduce the potential for their lateral transport in the epilimnion.