THE PRODUCTION O F MARINE PLANKTON
183
example, Ceratium is apparently not taken. Sinall nanoplankton flagellates can also be consumed, though these must probably exceed 2-3p
diameter; a small species such as Nannochhis may not therefore be
retained. Marshall and Orr have also studied the problem of the suitability of phytoplankton species as nourishment, using oviposition as a
criterion. Thus, while all diatoms appeared to be useful as food, only
some flagellates were satisfactory. For example, diets of Dicrateria,
Hemiselmis and Chlorella apparently did not contribute to egg production. Beklemishev (1 954) found that the copepads Calanus spp. , Metridia
spp., and Eucalanus consumed mainly diatoms in northern Pacific
waters; larger cells were definitely crushed by tbe mouth parts. In more
southern latitudes, more flagellates, dinoflagelltrtes and coccolithophores
were also eaten, and this was probably true during the summer months
in more temperate waters.
With small copepods such as Pseudocalanus, Parmalanus, Tenma,
and Acartia, the diet appears to be rather similar, mainly diatoms and
certain flagellates (cf. Gauld, 1951; Raymont, 1959; Raymont, 1963),
but differences exist. Thus Conover (1956) has suggested that although
Acartia feeds on a wide variety of phytoplankton, the setae are rather
coarse so that Acartia tends to be a ‘‘wasteful” feeder. More interesting
differences arise however with species such aEs Centropages, Labidocera
and Anomalocera which appear to be at least partly carnivorous.
Anraku and Omori (1963) confkm that certain calanoid species differ in
their feeding habits. They examined the mou1;h parts of the calanoids
and made feeding experiments using diatoms, animal food (Artemia
nauplii), and a mixture of the two. Results showed that whereas
Calanus Jinmurchicus was essentially herbivorous, Acurtia tonsa,
Centropages hamatus and Centropages typicus were essentially omnivorous, with Centropages apparently preferring animal food. LabicEocera
was almost entirely predatory, and this applied even more strongly to
Tortanus discaudatus (cf. Kaymont, 1963). Gauld (1964) agrees that
Anomalocera and Labidocera are essentially carnivorous, and that
Centropages, Temora and Acartia take some animal food. This problem
of differences in the food eaten, even in one group of zooplankton animals, applies particularly to deep-living speoies. Thus Beklemishev
found that deep living copepods such as Caidius and Uwtanus consumed large diatoms, and Conover (1960) has shown conclusively that
Calanus hyperboreus, though a deep-living species, is essentially herbivorous. On the other hand, other deep-water species such as Bathycalanus and Eucheirella are in all probability partial carnivores, and
Euchaeta, Scottocalanus, Megacalanus, and Valdiviella, amongst others,
are almost certainly carnivores. Perhaps even essentially herbivorous
species may take some animal food when food h3 scarce.
183
example, Ceratium is apparently not taken. Sinall nanoplankton flagellates can also be consumed, though these must probably exceed 2-3p
diameter; a small species such as Nannochhis may not therefore be
retained. Marshall and Orr have also studied the problem of the suitability of phytoplankton species as nourishment, using oviposition as a
criterion. Thus, while all diatoms appeared to be useful as food, only
some flagellates were satisfactory. For example, diets of Dicrateria,
Hemiselmis and Chlorella apparently did not contribute to egg production. Beklemishev (1 954) found that the copepads Calanus spp. , Metridia
spp., and Eucalanus consumed mainly diatoms in northern Pacific
waters; larger cells were definitely crushed by tbe mouth parts. In more
southern latitudes, more flagellates, dinoflagelltrtes and coccolithophores
were also eaten, and this was probably true during the summer months
in more temperate waters.
With small copepods such as Pseudocalanus, Parmalanus, Tenma,
and Acartia, the diet appears to be rather similar, mainly diatoms and
certain flagellates (cf. Gauld, 1951; Raymont, 1959; Raymont, 1963),
but differences exist. Thus Conover (1956) has suggested that although
Acartia feeds on a wide variety of phytoplankton, the setae are rather
coarse so that Acartia tends to be a ‘‘wasteful” feeder. More interesting
differences arise however with species such aEs Centropages, Labidocera
and Anomalocera which appear to be at least partly carnivorous.
Anraku and Omori (1963) confkm that certain calanoid species differ in
their feeding habits. They examined the mou1;h parts of the calanoids
and made feeding experiments using diatoms, animal food (Artemia
nauplii), and a mixture of the two. Results showed that whereas
Calanus Jinmurchicus was essentially herbivorous, Acurtia tonsa,
Centropages hamatus and Centropages typicus were essentially omnivorous, with Centropages apparently preferring animal food. LabicEocera
was almost entirely predatory, and this applied even more strongly to
Tortanus discaudatus (cf. Kaymont, 1963). Gauld (1964) agrees that
Anomalocera and Labidocera are essentially carnivorous, and that
Centropages, Temora and Acartia take some animal food. This problem
of differences in the food eaten, even in one group of zooplankton animals, applies particularly to deep-living speoies. Thus Beklemishev
found that deep living copepods such as Caidius and Uwtanus consumed large diatoms, and Conover (1960) has shown conclusively that
Calanus hyperboreus, though a deep-living species, is essentially herbivorous. On the other hand, other deep-water species such as Bathycalanus and Eucheirella are in all probability partial carnivores, and
Euchaeta, Scottocalanus, Megacalanus, and Valdiviella, amongst others,
are almost certainly carnivores. Perhaps even essentially herbivorous
species may take some animal food when food h3 scarce.