The feeding rate of Daphnia magna was studied by measuring the radioactivity of animals fed on pure cultures of Escherichia coli, Saccharomyces cerevisiae, Chlorella vulgaris, and Tetrahymena pyriformis labeled with radioactive phosphorus. Below a certain concentration of each food, the feeding rate is proportional to concentration of food. Above that concentration, feeding rate is independent of concentration. Starved animals, when placed in a nonlimiting concentration of food, behave temporarily as if it were limiting and for a few minutes filter at the maximum rate. Although the maximum volume of the various foods eaten in unit time is not the same, it is probably determined more by digestibility than by size of the food cells.
Filtering efficiency of Daphnia magna is independent of the size of food cells between 0.9µ3 and 1.8×104µ3.
Log‐phase Chlorella vulgaris was not observed to inhibit feeding, but senescent cells caused Daphnia magna to decrease the filtering rate and its maximum feeding rate.
The feeding behavior of Daphnia magna was studied in relation to the effect of animal size, water temperature, and light intensity. D. magna were fed on pure cultures of Chlorella vulgaris and Saccharomyces cerevisiae labelled with radioactive phosphorus.As size of D. magna increased over the range 1.25 mm to 3.54 mm, both maximum filtering rate and maximum feeding rate increased. The relation between the increase of filtering rate and the increase of maximum feeding rate is such that the "incipient limiting level" (the external level above which there is no limiting effect of food supply) also increases as size of Daphnia increases. The feeding rate of D. magna was studied over the temperature range 5 °C to 35 °C. The temperature optimum for feeding was approximately 24 °C.Feeding rate was also studied under conditions of total darkness and at light intensities of 100, 300, 500, 1,000, 3,000, and 10,000 ft-c. Illumination from total darkness to 1000 ft-c did not appear to affect the feeding rate of D. magna.The results of this investigation are discussed in relation to previous studies of filtering rates of other Crustacea.
feed in^ regulation h?' the plan ktunir rr11IiL+wri1li Pnpkri 1 7~nffrm war; srtrdied it1 incrrasing r -n r~r e n t~~t i o n s r l i tmcl Ior>ds: Chlnrrllfl r-rrlyoris arid Sort hnronz.vce.~ cermisine. Dirtxt ohr~rraiinn st~~rlies shrrw t h ;~~ Iticdi~le ratc i s propcrrtinr~;il ICI conrclltration of food only belnn. a 'crilic~l COIITI'III~:L t ion'. ;\bnrr this cririrnl val~ut further iricrencc in mnrc~~tr:xtio~~ ol Imrl II,~R little trr ncl rtttrt or1 f~eding rate. Dopknis m-as shosll to ycqulatc rnllr=r.ti(>n . i r~t l i~~~t -s~i o n or lrrnrl I>v dcrre.i<-in^ pun~pin!: n t e and r e j c c~i n~ excess Food from t h r Fnocl Ernow. The :irnol~~tt of food prrqelit in thc aninr:11s' ~L I t prior to an cxprrirnc~~ t alsn nilects feeding clip u i Dnphrrra in foorl susperl.;ions < l h o l~ the critical rr>nrrritratiotl, Krstllts shoii-that xnirl~alh, prefed at n very Iuw r:ite (1110 n~asimutn ratc) rlo, Inr n short time, Yeed nlnrt. rapidly illnr~ those prufrrl a t thc ~r~auinttlni rate. 'l'hcnr results arc colisirlc.terl ill relation to i hnsc oi R~t h e r ;l~u! kiylcr for free-s\\+i.irrlmi~lg Daphnin magna.
Simple and straightforward vaccination strategies implemented in LTCFs over a short period of time can have a significant impact on vaccination rates. Collaborative efforts between state PROs and LTCFs enhance implementation of these strategies and can result in the achievement of national vaccination objectives. Standing orders appear to be one intervention effective in sustaining successful vaccination efforts. Regardless of the specific interventions employed, PROs played a significant role in facilitating vaccination program development and intervention implementation.
Radioactive tracer studies of the ingestion and cycling of iron by Daphnia magna showed that about 60% of the iron was present as gut contents. Daphnia assimilated iron at the rate of 3.8 × 10−3 μg per milligram dry weight per hour. After feeding on 59Fe-labeled Chlorella for an extended period the animals assimilated only 1.3% of the ingested iron. Excretion and assimilation rates were similar.The feeding time required to pack the animal's gut was 2.5 h. The use of the time of initial loss of radioactive gut contents through defecation as an indicator of a full gut is questioned.The biological half-life of 59Fe in Daphnia is divisible into two components, a short-lived fraction (2.5 h) caused by replacement of gut contents and a longer lived component with a half-life of about 65 h.
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