380
THE BIOLOGY OF EUPHAUSIIDS
to E. superba in Fig. 135. It is apparent from ( 1 ) estimations of the
biomass of euphausiids, (2) studies of the food of euphausiids, and (3)
the array of predators dependent upon them for their nourishment,
that euphausiids, along with the copepods, form the most important
links between the primary producers and the primary, secondary, etc.,
predators in the marine food chains.
FIQ. 135. Antarctic food chains. Heavy arrows indicate that the groups from which
they point probably constitute the main diet of the groups to which they point;
broken lines are tentative. (After Hart, 1942.)
Over and above forming a link between primary and predatory
levels of food chains, the more coastal species of euphausiids such as
Meganyctiphanes norvegica and Thysanoessa raschii, which feed on sea
bed detrital material, must effect a certain amount of recycling of
nutrients simply by lifting this material from the bottom and, during
their diurnal vertical migration, releasing faecal pellets in upper water