Laboratory research was done in order to study the feeding of larval Cricotopus silvestris F. in relation to characters of structure of oral apparatus. Results of the experiments are summarised and the oral apparatus morhologically described

Shilova, A.I.

English

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Sorokin, Yu. I. & Mordukhai-Boltovskaya, E. D . 1962 
A study of the nutrition of the Rotifer Asplanchna, 
with the help of Carbon14. 
B y u l l e t e n ' Insti tuta Biologii Vodokhranilishch, No. 12, pp.17-20, 
1962. 
Translated By Dr. J.W.G. Lund. 
FRESHWATER BIOLOGICAL ASSOCIATION 
December, 1962. 
Isuchenie pitaniya kolovratok Asplanchna s pomoshch'yu C14. 
The carnivorous rotifers Asplanchna priodonta Goese and A. herricki do 
Guerne are widely distributed in the Rybinsk Reservoir, and play an important 
role in the trophic connections of the organisms inhabiting it. The data in 
the literature about the question of their nutrition are extremely poor and 
refer in the main to the composition of the food. The majority of author 
consider that carnivorous nutrition, even reaching sometimes to cannibalism, 
is characteristic for Asplanchna (Skorikov 1896; Naumann 1929). At 
the same time Naumann, Lucks (1931) and Myers (1941) point out that algae are 
an important component of the nutrition of Asplanchna. 
The quantitative side of the nutrition of rotifera has scarcely yet been 
studied. Data on this question have been brought forward only in the work of 
L.A. Erman (1956), in which, however, information about the nutrition of 
Asplanchna is absent. Information about the utilisation of algae by Asplanchna 
was obtained by us as a result of opening the guts. However, partial 
swallowing by the rotifer of algae along with other food does not prove that 
the animal utilises them. Because in experiments on the nutrition of 
cyclopoids with the help of C14, (Monakov & Sorokin 1959a) it was shown that 
although they swallow protococoid algae they scarcely digest these algae at all. 
Our problem was the clarification of the question about the role of algae 
and bacteria in the nutrition of Asplanchna priodonta and Asplanchna herricki 
and also the obtaining of the quantitative characteristics of the carnivorous 
nutrition of these rotifers. The work was carried out with the aid of the 
radiocarbon method described in the works of Monakov & Sorokin (1959a, 1959b). 
For the experiments were picked out Asplanchna priodonta and Asplanchna 
herricki of the size 0.6 - 0.8 mm. As choice for nutrition were takes various 
algae, bacteria and the crustacean Bosmina longirostris. 
The algae were labelled by means of growing them in a buffered medium 
containing labelled carbonate. The bacteria for the experiments were isolated 
from the water of the Rybinsk Reservoir on a glucose medium. They were labelled 
with C14 by means of growing them up on an agar medium to which was added 
glucose with completely labelled carbon atoms, as C14. For labelling the 
2. 
Bosmina with C14 they were fed from 3-4 days with labelled Chlamydomonas 
algae. The activity of the algal and bacterial mixtures prepared for the 
experiments was 0.1 - 2.0 x 106 impulses per ml. The activity of the Bosmina 
varied within the limits of 200 - 250 impulses per specimen. 
40-50 rotifers were put here and there in small glasses with 50 
milliliters of water taken from the reservoir and filtered through a membrane 
filter. Then labelled C14 food was introduced into the glasses in such 
quantity that its concentration was somewhat higher than is observed in the 
marginal region of the Rybinsk Reservoir. After 24 hours the experiment was 
stopped. The rotifers were picked out, and in order to free their intestines 
from traces of labelled food, were planted for one to one and a half hours in 
pure water to which was added a small quantity of normal food. After the 
lapse of this time, the rotifers were transferred onto a glass in a drop of 
0.1% agar and dried. In this form they were placed under the counter for the 
estimation of their radioactivity. The radioactivity of Bosmina was estimated 
by the same method. The coefficient of self-absorption by radiation in the 
body of the dried Bosmina, which was determined by means of burning the labelled 
Bosmina, and that of the following determination. of the activity of C14 in the 
form of barium carbonate equalled 1.17. In determining the radioactivity of 
the rotifers we neglected the influence of self-absorption, in as much as the 
thickness of the layer of matter regaining after the drying of the rotifers on 
the apparatus was of an order of less than 1mg.per cm2. The activity of the 
algae and bacteria was counted on membrane filters. 
The main quantities characterising the intensiveness of the nutrition and 
utilisation were, in our experiments the amount of the organic matter of the 
food utilised per day expressed in Y of carbon per single species (Ca) and the 
percentage relationship of this quantity to the total quantity of carbon in the 
body of the animal (Cn) - index of utilisation - P These quantities Were 
calculated according to the formulae: 
3. 
where Cr is the quantity of the carbon of the marked food in Y per one impulse 
of its activity, r is the radioactivity of the animals at the end of the 
experiment with a correction for self-absorption. 
The amount of the carbon in the algae, bacteria and invertebrates was 
determined by wet combustion with the chromic mixture. In the invertebrates 
it was equal; in the body of Asplanchna to 0.7 Y carbon per specimen, and in 
the body of Bosmina to 0.36 Y of carbon per specimen. The results of the 
experiments with labelled algae and bacteria are shown in Table 1. They 
show that the algae and the bacteria cannot satisfy, even to a small degree, 
the nutrient demands of Asplanchna. Among the algae notable utilisation was 
observed only in the experiments with the big Chlamydomonads. However, these 
algae approximate in certain characteristics to flagellates, and are hardly 
ever set with in the reservoir. Other big algae Scenedesmus and Anabena, 
assail algae and bacteria are utilised much worse. The index of utilisation 
in these experiments (0.02 - 0.4) is 100-200 times less than with carnivorous 
nutrition. 
So the algae and bacteria were not normal food of the carnivorous rotifers, 
hut perhaps serve only as a source of additional elements of nutrition-vitamins. 
The main food of Asplanchna is small planktonic animals. 
In the experiment of T.H. Tribush (1960) Asplanchnas quickly died when 
feeding in pure cultures of Scenedesmus, but lived well feeding on rotifers. 
This confirms our data. In carnivorous nutrition the daily ration of rotifers 
exceeded 1.5 - 2 times the weight of their own body (Table 2). The index of 
utilisation reached 36%. This points to the high intensity of the exchange 
of the carnivorous rotifers in the presence of sufficient food. Per day the 
matter of their bodies renews itself approximately by a third at the expense 
of the utilisation of the food. In Daphnia longispina the maximum index of 
utilisation in the most favourable conditions of nutrition reached 25% 
(Monakov & Sorokin 1960). 
The utilisation of the food in feeding on Bosmina is 15-20%. These 
amounts are close to the amounts of utilisation of food in the carnivorous 
4. 
nutrition of cyclopoids (Monakov & Sorokin 1959a), and somewhat lower than the 
utilisation of algae when daphniae are feeding on them (Monakov & Sorokin 1960). 
The data about the nutrition of the carnivorous rotifers brought forward 
in our present communication once again demonstrates the great delicacy of the 
isotope method which permits one to study in short period experiments the 
nutrition of animals whose day weight scarcely exceeds 0.001 mg. The 
suitability of this method in such investigations is shown by this, that with 
its help it is possible to determine the utilisation of this or that nutrient 
object and by such a method to evaluate its true importance in the nutrition 
of aquatic animals. 
LITERATURE 
5. 


A study of the nutrition of the Rotifer Asplanchna, with the help of Carbon 14 [Translation from: Byulleten ' Instituta Biologii Vodokhranilishch, No. 12, pp.17-20, 1962]

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A study of the nutrition of the Rotifer Asplanchna, with the help of Carbon 14 [Translation from: Byulleten ' Instituta Biologii Vodokhranilishch, No. 12, pp.17-20, 1962]

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