Effect of temperature on growth, mortality, reproduction, and production of adult Lymnaea obrussa Say (Mollusca:Gastropoda) Page: 4 of 37
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MATERIALS AND METHODS
Specimens of the pulmonate gastropod mollusk, Lymnaea obrussa Say,
were collected on April 5, 1973 at 12*C from a pord on the Energy Research
and Development Administration Reservation near Oak Ridge, Tennessee,
U.S.A. The pond has a surface area of about 800 m2 and a maximum depth
of about 3 m. Annual temperature variation is relatively small. Pond
temperatures varied over a rare of about 12 to 23C for the years 1972-
1973. The population of L. obrussa is limited to the area very near shore
(< 50 cm depth) where the pond plants Ludwigia sp. and Elodea sp. and
their associated periphytor. dominate the flora. The water temperature
of this area is more variable than the rest of the pond. Maximum daily
variation for the period from April through August 1973 was 5.5*C; the
mean was 2.1*C.
Snails were acclimated in the laboratory at a rate of less than 1*C
per day to a series of constant or varying test temperatures. The con-
stant temperatures were 10, 15, 20, 25 and 30*C. The varying regimes
included the natural field temperature in the pond (F), mean daily field
temperature (F), and temperatures exceeding F by 5 (F+5) and 10*C (F+10).
The latter three regimes were maintained in the laboratory. Field tem-
perature was monitored using temperatures recorders in cages placed beside
the experimental cages in the pond. Each noon ;1200 hours) the mean field
temperature for the previous 24-hr period was estimated from the tempera-
ture recording. Regime F was then set at the estimated mean field tem-
perature for the next 24-hr period, and +5. and F+10 were set appropri-
ately. Mean temperatures for the total period of observation were obtained
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Mattice, J.S. Effect of temperature on growth, mortality, reproduction, and production of adult Lymnaea obrussa Say (Mollusca:Gastropoda), article, January 1, 1975; Tennessee. (digital.library.unt.edu/ark:/67531/metadc878762/m1/4/: accessed July 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.