Macrofauna – Sieve Pickings
(^) Composition of deep-sea macrofauna is characterized according to major zoological
groups in Table 13.1. The big players among macrofauna are polychaetes, segmented
annelid worms with clusters of spines and often flaps (parapodia) along the sides.
They are usually over half of both the individuals and the biomass in a screening.
Polychaetes belong to more than 80 mostly distinctive families, with many
modifications in lifestyle, particularly feeding mode. The simplest polychaetes are
very like the familiar earthworm, which is an oligochaete. Modifications on that basic
body plan are most pronounced at the head, which is constituted of a conical
prostomium segment ahead of the mouth and a seta-less peristomium behind it. The
peristomium often bears eye spots, even image-forming eyes, and sundry palps or
tentacles that assist in feeding in a variety of ways. In some (e.g. cirratulids), the
tentacles reach out and gather sediment or food toward the mouth, in others (e.g.
serpulids) they are shaped like feathers and form extensive filtering fans. The anterior
esophagus in many families (e.g. glycerids) can be everted to grasp food, then
retracted to ingest it. These proboscides can bear stout, recurved spines in predatory
forms or be coated with mucus to which organic particles will adhere. Polychaete size
varies widely in shallow bottoms, where some species are tiny and the largest forms
can exceed a centimeter in diameter and several decimeters in length. In progressively
deeper bottoms, however, size diminishes in practically all families.
Table 13.1 The numerical percentage composition of macrofaunal taxa of deep-sea,
soft-bottom communities.
(After Hessler 1972.)