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THE BIOLOGY OF EUPHAUSIIDS
and amplification, do suggest several concepts of feeding of euphausiids
which support the impressions gained from analyses of stomach contents,
previously described. First, there is the possibility that preference may
be shown for a particular food organism at a particular time and place.
Lasker obtained evidence that E. paci3ca may become conditioned to
feeding on one type of organism and neglect other acceptable organisms
which are less desirable. A period of adaptation to a new, but suitable,
food was often detected when the diet of the experimental animals was
changed. Certainly, there is evidence that Meganyctiphanes norvegica
in the sea sometimes feeds almost exclusively on one class of organism
(e.g. dinoflagellates) even although other organisms are available and
some are known to be dominant items of the diet at other times.
Much more experimental work of the type done by Lasker is required
to elucidate similar problems in other species. For instance, some light
might be thrown on the use of the elongated thoracic limbs present in
species of Tessarabrachion, Thysanoessa, Nematoscelis, Nematobrachion,
and Stylocheiron. Lasker suggests that Euphausia pacijica can detect
and capture prey at a distance of 1.7-2.0 cm in the dark, but detection
and capture at greater distances are less efficient. Nothing is known
about the mechanisms of detection and capture. It may be that
euphausiids are sensitive to changes in pressure effected by movement
of a prey organism but this whole field requires investigation because
it might equally be a form of chemoreception which is used.
Much work remains to be done on the physiology and biochemistry
of euphausiids, and it is hoped that more attention will be paid to their
physiology.
THE BIOLOGY OF EUPHAUSIIDS
and amplification, do suggest several concepts of feeding of euphausiids
which support the impressions gained from analyses of stomach contents,
previously described. First, there is the possibility that preference may
be shown for a particular food organism at a particular time and place.
Lasker obtained evidence that E. paci3ca may become conditioned to
feeding on one type of organism and neglect other acceptable organisms
which are less desirable. A period of adaptation to a new, but suitable,
food was often detected when the diet of the experimental animals was
changed. Certainly, there is evidence that Meganyctiphanes norvegica
in the sea sometimes feeds almost exclusively on one class of organism
(e.g. dinoflagellates) even although other organisms are available and
some are known to be dominant items of the diet at other times.
Much more experimental work of the type done by Lasker is required
to elucidate similar problems in other species. For instance, some light
might be thrown on the use of the elongated thoracic limbs present in
species of Tessarabrachion, Thysanoessa, Nematoscelis, Nematobrachion,
and Stylocheiron. Lasker suggests that Euphausia pacijica can detect
and capture prey at a distance of 1.7-2.0 cm in the dark, but detection
and capture at greater distances are less efficient. Nothing is known
about the mechanisms of detection and capture. It may be that
euphausiids are sensitive to changes in pressure effected by movement
of a prey organism but this whole field requires investigation because
it might equally be a form of chemoreception which is used.
Much work remains to be done on the physiology and biochemistry
of euphausiids, and it is hoped that more attention will be paid to their
physiology.