Proceedings of the Conference on Primary Productivity Measurement, Marine and Freshwater: 1961 Page: 180
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marchicus can make use of about half the nitrogen in Nitzschia closterium. Calanus was
reported by Bond to have a proteinase activity at a pH as low as 3.5. This is quite contrary
to the observations made by Hasler (1935) on the fresh water crustacea Daphnia magna and
Daphnia pulex, which have trypsin-like enzymes. Hasler (1937) extended his work to a study
of the dipeptidase, aminopolypeptidase and carboxypolypeptidase activities of Daphnia, Poly-
phemus, Diaptomus and a fresh water Calanus. It is not known to what degree his observa-
tions may apply to marine species.
There is general agreement that there are amylase enzymes present in the various ani-
mals studied but very little cellulase activity, (von Dehn, 1930; Bond, 1934; Hasler, 1935;
Fish, 1955a; Huang and Giese, 1958). The absence of cellulase activity may also be inferred
from the absence of attack on many plant cell membranes (ref. e.g. Gibor, 1956). Whole plant
cells often pass through an animal gut unharmed, or if the content of a plant cell is digested
it is only after having first passed out through pores in the cell wall. One cannot generalize,
however, as Conover (1960) noted that Thalassiosira decipience passed unchanged through part
of the gut of Acartia tonsa and then quite suddenly disintegrated. Calanus and other animals
cannot digest alginic acids (Bond, 1934; Huang and Giese, 1958). However, vast more work is
necessary before we can reach any satisfactory conclusions.
In particular we know next to nothing about the role played by intestinal micro-flora in
the gut of planktonic crustacea (Huang and Giese, 1958).
There is probably a similarity between the diet of Calanus and many other members of the
marine planktonic crustacea, with a good correlation between growth and egg laying and the
overall abundance of phytoplankters (Marshall, 1924; Marshall et al, 1934; Digby, 1950; and
Marshall and Orr, 1952). Studies using radioactive carbon by Marshall and Orr (1955a) and
Lasker (1960) support the view that efficiency of phytoplankton utilization by crustacea is very
high when the concentration of plant cells in the surrounding water is optimum. Skeletonema
costatum is generally agreed to be an excellent diet.
All of the diatoms tested in feed trials by Marshall and Orr (1952 and 1955b) were found
to be good food for Calanus finmarchicus although some were better than others. The two
dinoflagellate species used were also satisfactory as was the coccolithophore Syrascosphaera
carterae. On the other hand a marine Chlorella, the cryptomonad Hemiselmis rufescens and
the Chrysophycean Dicrateria were very poor foods. Conover (1960) has recently added to our
knowledge of the feeding of zooplankters using twelve species taken mostly from below 100 m.
He characterized the animals as to whether or not they were herbivores or carnivores and
tested the abilities of the herbivores to utilize species of diatoms in pure culture, most of
which were readily digested. Bacteria were present so we do not know to what extent they pro-
vided critical growth factors. Corner (1961) measured the intake of carbohydrate, lipid and
protein by Calanus helgolandicus from natural sea water. The organism ingested organic mat-
ter in preference to inorganic material in the same sample.
It is known that animals will show some discrimination when feeding on algal species with
different nutritional values. There is even marginal evidence that a Calanus can be "condi-
tioned" to favour one species more than another (Harvey, 1937).
Only by using bacteria-free cultures of both plant and animal can the true food value of a
phytoplankter for a given zooplankter be correctly evaluated. There are regrettably few such
studies. The classical work of this type is by Gibor (1956) who showed that there were very
real differences in food value between various species of phytoplankton. Although a single
species (Monochrysis lutheri) provided a balanced diet for Tigriopus (27 generations) it was
generally necessary for several different species to be eaten together if the full growth and
development of the animal was to be attained (Shiraishi and Provasoli, 1959a and 1959b).
Provasoli et al, (1959) have given a useful list of algal diets for Artemia salina and Tigriopus
japonicus, only a few of which were wholly satisfactory.
(c) Phytoplankters, as food for lamellibranchs
A certain amount of work has been done on the dietry requirements of lamellibranchs,
mainly mussels, clams and oysters, because of their direct economic importance. These180
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Doty, Maxwell Stanford. Proceedings of the Conference on Primary Productivity Measurement, Marine and Freshwater: 1961, report, 1962?; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc784222/m1/192/?q=food+rule+for+unt+students: accessed July 5, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.