144
Radioisotopic Methods for the Study of Nutrition in Aquatic Animals
20
AIM
20
A
15
15
10
10
-
1
5
••• 2
K
0
Fig.3.18. Dependence of assimilation rates of dissolved organic matter (DaM) by the
mussel Mytilus galloprovincialis on its concentration in water. 1 Of labeled protein
hydrolyzate; 2 of labeled glucose. A Absolute rates of DaM assimilation; M respiration
rate, both as I-lg C Sp.-l h-\ K initial concentration of DaM in water, mg C 1-1
boom soon faded, but the problem remains unsolved to this day: what is the
real share of dissolved organic matter (DOM) in the nutrition of aquatic
animals? Realistic evaluations done under conditions free of bacterial impact,
by estimated Cr and uptake values expressed in carbon units, have shown that
this share might be quite significant, up to 20-40% of food ration or respiratory losses, but only in animals having ciliary epithelium covering their body
or their filtering apparatus, such as some invertebrate larvae, bivalves, sabellid polychaetes, and coelenterates (Sorokin and Wyshkwartzev 1973; Sorokin
1973a, 1984, 1993; Meyer Reil and Faubel 1980). More efforts should be
addressed to this problem, and experiments should be carried out correctly.
The results of measurements should be expressed in the absolute units of
uptake rates as related to the consumers' body carbon (index of assimilation
CalC), or as the percentage ratio of the uptake rate (Ad) to the rate of respiration M: AdIM, %.
The biochemical mechanism of DOM uptake by animals possessing the
ciliary epithelium was supposed to be based upon active enzymatic transport
with the participation of enzyme permeases, which resembled the process
taking place in the intestines (Albers 1967). The latter was proved experimentally by the estimation of the isotopic dilution during uptake of labeled
sugars and amino acids by corals and clams in the presence of larger concentrations of their close biochemical analogues (Sorokin 1977a). Further experimental evidence was provided by observing how the uptake rate was affected
by DOM concentration (Figs 3.18,3.19). The corresponding curves appeared
to be similar to those by Michaelis-Menten which describe the dependence of
the rate of enzymatic reactions upon the substrate concentration. The perme-
Radioisotopic Methods for the Study of Nutrition in Aquatic Animals
20
AIM
20
A
15
15
10
10
-
1
5
••• 2
K
0
Fig.3.18. Dependence of assimilation rates of dissolved organic matter (DaM) by the
mussel Mytilus galloprovincialis on its concentration in water. 1 Of labeled protein
hydrolyzate; 2 of labeled glucose. A Absolute rates of DaM assimilation; M respiration
rate, both as I-lg C Sp.-l h-\ K initial concentration of DaM in water, mg C 1-1
boom soon faded, but the problem remains unsolved to this day: what is the
real share of dissolved organic matter (DOM) in the nutrition of aquatic
animals? Realistic evaluations done under conditions free of bacterial impact,
by estimated Cr and uptake values expressed in carbon units, have shown that
this share might be quite significant, up to 20-40% of food ration or respiratory losses, but only in animals having ciliary epithelium covering their body
or their filtering apparatus, such as some invertebrate larvae, bivalves, sabellid polychaetes, and coelenterates (Sorokin and Wyshkwartzev 1973; Sorokin
1973a, 1984, 1993; Meyer Reil and Faubel 1980). More efforts should be
addressed to this problem, and experiments should be carried out correctly.
The results of measurements should be expressed in the absolute units of
uptake rates as related to the consumers' body carbon (index of assimilation
CalC), or as the percentage ratio of the uptake rate (Ad) to the rate of respiration M: AdIM, %.
The biochemical mechanism of DOM uptake by animals possessing the
ciliary epithelium was supposed to be based upon active enzymatic transport
with the participation of enzyme permeases, which resembled the process
taking place in the intestines (Albers 1967). The latter was proved experimentally by the estimation of the isotopic dilution during uptake of labeled
sugars and amino acids by corals and clams in the presence of larger concentrations of their close biochemical analogues (Sorokin 1977a). Further experimental evidence was provided by observing how the uptake rate was affected
by DOM concentration (Figs 3.18,3.19). The corresponding curves appeared
to be similar to those by Michaelis-Menten which describe the dependence of
the rate of enzymatic reactions upon the substrate concentration. The perme-