Detritus is also generated by the bottominhabitants themselves as they die. The detritus is used by bacteria andby the many types of microscopic animalsthat live between the sediment particles,the
interstitial
animals, or
meiofauna
(see “Life in Mud and Sand,” p.283).Larger benthic invertebrates also feedon detritus. They are mostly burrowing
deposit feeders
(Fig. 13.6). Polychaetesare the most diverse group of deposit feed-ers in the soft sediments of the shelf. Trumpet (
Pectinaria;
Fig. 13.6
f
) and bam-boo worms (
Clymenella;
see Fig. 12.11
h
)are deposit-feeding polychaetes that in-habit tubes they build from sediment par-ticles. Lugworms (
Arenicola
) and otherslive in burrows. These polychaetes andother worms eat detritus and other organicmatter by collecting it with their tentaclesor by ingesting sediment and extractingfood from it.Some sea urchins are uniquely adaptedto live as deposit feeders on soft bottoms.Heart urchins (
Spatangus
) have abandonedthe round shape of most urchins, becom-ing more streamlined with shorter spinesthat lie flat (Figs. 13.6
e
and 13.7). Sanddollars (
Dendraster
) are almost completely flat and have very short spines (Figs. 13.8and 7.45
b
). They typically feed on detritusand use mucus to carry particles to themouth. Other deposit feeders among the