Corals: a case study hot buttons for nutrition of corals part of BCCR hot button for prey-capture section of BCCR hot button for photosynthesis part of BCCR hot button for coral-bleaching part of BCCR hot button for mucus-net feeding part of BCCR
Corals gain nutrients and energy in 3 ways: prey capture, mucus-net feeding, and photosynthesis. Bleaching is included here because it is such an important factor in the health of corals.

This section deals with mucus-net feeding, while other topics can be accessed via the icons.

Corals: a case study: mucus-net feeding

seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of pillar coral taken from a video

"Another way that corals get nutrition is by catching organic particles in sticky mucous sheets. The mucus is moved by cilia to the mouths of the polyps. Let's look closely at this pillar coral .Hmmm! No, we can't see it moving along. We'll probably need a microscope to see it." - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize

NOTE Dendrogyra cylindrus


photograph of possible Madracis coral
Food items caught up on mucous sheets are mostly bacteria and small-sized particulate organic matter with attached bacteria. For example, the coral Madracis mirabilis consumes about 10 million water- or particulate-borne bacterial cells per square centimeter of its body surface per hour, mainly through adhesion to sticky mucus. The mucus is secreted from glands in the skin and flows in ciliated tracts to the mouth. It is sometimes so dense as to appear as a net or sheet flowing over the coral's surface. Bak et al. 1998 Mar Ecol Progr Ser 175: 285.



Madracis sp. (?) 0.2X


close view of polyps of a mound coralThe ciliated tracts move particles of edible detrital food to the mouth and also move inedible particles away from the mouth, along the tentacles to special discard points on the body. Fisk 1981 Proc 4th Int Coral Reef Symp Vol. 2: 21.

NOTE dead organic matter, in this case in small particulate form, with bacterial complement





Polyps of mound coral
sp. 2.5X

  photo collage of mucus-feeding by various Siderastrea corals and an antipatharian AntipathesThese photographs show the fine lines of mucus being moved in the ciliated tracts to the polyp mouths, contrasted with the heavier lines of mucus in rejection tracts. Photographs courtesy John Lewis, McGill University, Montreal.

Mucous nets in corals, as in starlet corals Siderastrea spp. may function more than just in feeding. Several possibilities are listed below, 5 of which have merit and 2 of which don't. Think about the validity of each, then CLICK HERE for explanations.

Mucous nets confer protection from predators.

Mucous nets aid in release of excretory wastes.

Mucous nets help to keep the colony clean.

Mucous nets assist in the removal of fecal wastes.

As in many other marine animals, mucus helps protect the colony from stressful conditions.

Mucous nets prevent settlement of colonising organisms such as larvae or plant spores onto the coral surface.

Mucous nets help to prevent fungal or bacterial infections.

NOTE excretion in biology refers to the ridding of waste products of metabolism from the body. In coral-reef invertebrates these excretions are mainly ammonium; in fishes, they are mostly urea (as in humans). Feces are not metabolic wastes; rather, they are simply undigested food matter that have never entered any metabolic pathways in the body

NOTE a cidarian polyp lacks a complete digestive tract. Without an anus, all undigested food residues must be released from the mouth. These residues should not actually be termed feces, but are done so here for convenience

seahorse dive leader for Biology of Caribbean Coral Reef website photograph of coral-reef with mucous feeding-thread being released by a snail

"Oh...! Check this out. It's another organism that feeds by use of a mucous this case, a sessile snail. It casts out single or multiple mucous threads, then hauls them in when they are full of organic goodies." - Turks & Caicos 2003

NOTE Vermicularia sp.


photograph of sessile snail, perhaps Vermicularia sp., with a large mucous feeding-net, courtesy Anne Dupont, Florida
An unusual coral-reef organism that employs mucus-net feeding is the sessile snail Vermicularia sp., sometimes called a "worm snail". It is found in association with corals and sponges, lives in a tubular shell, and feeds by means of sticky mucous threads that are extruded from the mouth region. When the net becomes heavy with particles it is reeled in and eaten. Mucus from corals and other reef organisms is thought to hang around the reef for some time, becoming entangled in other organic matter. As such it probably represents a nutritious food source for small benthic invertebrates such as crustaceans and worms, and possiby even some fishes. Photograph courtesy Anne Dupont, Florida.



Worm snail Vermicularia sp. casting its
voluminous mucous feeding-net 1X


hot button for parasitism part of Biology of Caribbean Coral Reefs website hot button for mutualism part of Biology of Caribbean Coral Reefs website hot button for commensalism topic in BCCR hot button for symbiosis quizzes section of BCCR hot button for commensalism part of BCCR hot button for symbiosis quizzes part of BCCR hot button for mutualism part of BCCR hot button for parasitism part of BCCR hot button for corals: a case study part of BCCR hot button for photosynthesis part of BCCR hot button for herbivory part of BCCR hot button for carnivory part of BCCR hot button for detritivory/bacterivory part of BCCR