Nutrition
 
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Carnivory hot buttons for carnivory part of Biology of Caribbean Coral Reefs website hot button for zooplanktivore part of BCCR hot button for spongivore part of BCCR hot button for corallivores & other cnidivores part of BCCR hot button for gorgonivores part of BCCR hot button for benthic invertebrate-eaters part of BCCR hot button for piscivores part of BCCR
This part of carnivory deals with corallivores & other cnidivores, that is, with coral-reef organisms that eat corals, and with coral-reef organisms that eat cnidaria other than corals, for example, hydroids, sea anemones, fire corals, and others. Other topics relating to carnivory can be accessed via the icons.
 
 

Carnivory: corallivores & other cnidivores

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of parrotfish scrapings on boulder coral

"These surface scrapings on the boulder corals are made by grazing parrotfishes. They may be after the surface algae, or even the algal symbionts in the coral's tissues. There is some thought that they may be territorial markings but, if that's so, what we see here seems like overkill." - Little Cayman 2003

NOTE Montastrea sp.

 
 

photograph of boulder coral scraped by parrotfishesParrotfishes bite at corals for food or as a by-catch in their quest for encrusting algae. If the bite-patches are separated from one another, it is known as "spot-biting"; if the patches are joined, it is known as "focused-biting". The resulting white patches are obvious from several meters photograph of boulder coral scraped by parrotfishesdistance and are thought possibly to serve as territorial markers. Miller & Hay 1998 Oecologia 113: 231; Bruckner et al. 2000 Coral Reefs 19: 50.

"Focussed- biting" marks on
boulder coral Montastrea sp. 0.1X




"Spot-biting" marks on
boulder coral Montastrea sp. 0.2X



  Scientists in the Florida Keys have identified the culprit that creates circular white lesions on elkhorn coral Acropora palmata. It is the honecomb cowfish Acanthostracion polygonius, shown in the act in the photographs below. The fish sucks for a moment on the coral surface and removes a ring of tissue, leaving polyps within the ring intact. The action creates no apparent mechanical damage to the coral skeleton, and the wounds seem to heal within a few weeks. The authors are uncertain whether the fish is actually feeding on the coral tissue, or whether the marks just result from the fish’s general foraging behaviour. Williams & Bright 2013 Coral Reefs 32: 651. Photographs courtesy the authors.
 
No. 1 in a series of photos showing a honeycomb cowfish Acanthostracion polygonius sucking at and leaving a ring-shaped mark on the surface of an elkhorn coral Acropora palmata No. 2 in a series of photos showing a honeycomb cowfish Acanthostracion polygonius sucking at and leaving a ring-shaped mark on the surface of an elkhorn coral Acropora palmata No. 3 in a series of photos showing a honeycomb cowfish Acanthostracion polygonius sucking at and leaving a ring-shaped mark on the surface of an elkhorn coral Acropora palmata No. 4 in a series of photos showing a honeycomb cowfish Acanthostracion polygonius sucking at and leaving a ring-shaped mark on the surface of an elkhorn coral Acropora palmata
 
 
seahorse dive leader for Biology of Caribbean Coral Reef website photograph of scrapings on corals made by parrotfishes

"Oh, oh! What's this? Somebody's clumsy flipper... I guess, or...a predator taking bites, maybe. Based on the way the finger corals are broken, I guess it could be biting...hard to tell though." - Little Cayman 2003

NOTE Porites porites

 
 


photograph of a parrotfish's beak-like mouthThe teeth of parrotfishes are fused into a beak-like structure for scraping off algae. Additional pharyngeal teeth grind the mixed coral and algal food, and the food moves through an essentially stomach-less gut before being discharged as a plume of sediments. Who is the guilty party in the photograph on the Right? Judging by the volume of feces involved, it is likely to have been the redtail photograph of a redtail parrotfish Sparisoma chrysopterum recently defecatingparrotfish swimming to the left of the photo. The sergeant-majors are omnivores whose diets include mixtures of anthozoans, tunicates, copepods, algae, and small fishes. They are neither big enough, nor are their diets so calcareous, to have produced such a large fecal plume.

NOTE the fecal plume is in the 5 o'clock position; the other "plumes" visible are exhaust bubbles from two SCUBA divers positioned in centre-left of the photo

Redtail parrotfish Sparisoma chrysopterum
and sergeant majors Abudefduf saxatilis 0.15X

 
 
seahorse dive leader for Biology of Caribbean Coral Reef website photograph of 4-eye butterflyfishes feeding

"Here's a pair of foureye butterflyfishes busily eating. I wonder what they found that is so good to eat?" - Bonaire 2003

NOTE Chaetodon capistratus

 
 

Parrotfishes eat corals by scraping them with their specialised beaks, but other reef fishes selectively eat coral polyps and have their own specialised feeding adaptations. Mouth morphology of fishes can tell a lot about what they eat. The accompanying photographs show examples of different fishes and their feeding specialisations, including four-eye butterflyfishes that selectively nip off coral polyps.

 
photo collage of mouths of various fishes showing adaptations for  different types of feeding, mostly carnivory
 

histogram showing dietary preferences of 4-eye butterflyfishes in St. CroixAlthough specialised for nipping off coral polyps for food, foureye butterflyfishes Chaetodon capistratus eat other types of prey. Observation of 85 individual fishes over 85h in St. Croix showed the following allocation of bites (see histogram), out of 2325 bites total. Neudecker 1985 Proc 5th Int Coral Reef Symp Vol 5: 415.

NOTE it is interesting that butterflyfishes often often eat polyps from coral species that regenerate quickly; hence, are behaving more like a parasites

  histogram showing preferred coral prey of 4-eye butterflyfishes in St. CroixOf several coral species eaten by the St. Croix butterflyfishes, the preferred ones are shown here.
 
 

photograph of pokadotted hermit crab Phimochirus operculatus courtesy John Lewis, McGill University
Other motile invertebrates including hermit crabs, sea stars, shelled snails, nudibranchs, and worms may also eat coral polyps. Hermit crabs that inhabit coral heads may actively prey on the coral’s tissues.  This is evidenced by damage seen on the epidermal tissue of the coral as well as presence of zooxanthellae in the guts of the hermit crabs.  Gilchrist 1985 Proc 5th Int Coral Reef Sympos 5: 211.  Photograph courtesy John Lewis, McGill University, Montreal.

 

 

Polkadot hermit crab Phimochirus operculatus
often crawl on corals and may eat the polyps 4X

 
 

photograph of sea star Linckia guildingii
Some Caribbean sea stars prey on corals, as do crown-of-thorns sea stars in the Indo-Pacific region. These sea stars feed by extruding their stomachs and digesting the soft coral-tissue in situ. 

 

 

 

 

Coral represent a good part of the diet of
a comet sea star Linckia guildingii 0.6X

 
 

photograph of nudibranch Dondice occidentalis courtesy Anne Dupont, Florida
Several species of aeolid nudibranchs eat hydroids and sea anemones. The stinging cells (nematocysts) of the prey do not deter the snails because, for reasons not fully understood, they remain undischarged on their passage through the gut of the predator. Many aeolid species can incorporate their prey's undischarged nematocysts into special sacs at the tips of their distinctively coloured cerata. When aggravated, the nudibranch forcefully expels these in its own defense. Photograph courtesy Anne Dupont, Florida.

NOTE this topic is considered in more detail at DEFENSES OF INVERTEBRATES: CHEMICAL: SNAILS, CEPHALOPODS, & CRABS


An aeolid nudibranch Dondice occidentalis crawls on its hydroid food.
The undischarged nematocysts are shunted into sacs contained in the
light-coloured tips of the cerata. The snail is facing to the left.
Visible are a pair of slender oral tentacles at the front, followed
by a pair of rhinophores, and then the numerous cerata 4X

 

photograph of pleurobranchid Berthellina quadridensAnother coral-eating opisthobranch is the sea slug Berthellina quadridens. A researcher at the University of Amsterdam notes that it only feeds at night, is shy of light (as from light-wielding SCUBA-divers), and secretes acids thought to be used in defense. Consumption of mound corals Montastraea spp. by Berthellina is doubly jeopardous for the corals, first, in loss of polyp tissue, and second, in overgrowth of the wounds by filamentous turf algae. Vermeij 2010 Coral Reefs 29: 1047. Photograph courtesy the author.

NOTE this species is a pleurobranchid opisthobranch and is quite rare in Caribbean waters


The opisthobranch Berthellina quadridens on its feeding
patch, a mound coral Montastraea faveolata. Note that
the slug is consuming both polyps (clear yellowish areas)
and algal-containing epithelial tissues (brown areas)

 

photograph of coral-eating snail CoralliophilaSo, really, how much damage can a few gastropods do to a coral? Well, actually quite a lot. Studies in Haiti have shown that a single snail Coralliophila abbreviata can eat 16 sq cm of coral tissue per day, and this can be made worse by subsequent feeding activity of butterflyfishes who come to investigate the wounded coral. Brawley & Adey 1982 Bull Mar Sci 32: 595.

NOTE in areas of Barbados Coralliophila abbreviata commonly feeds on mound corals Monastrea annularis and is capable of consuming up to 9 sq cm of tissue in 24h.  Ott & Lewis 1972 Can J Zool 50: 1651.

 

The coral-eating snail Coralliophila sp. apparently lacks a radula and,
instead, releases an enzymatic secretion into the coral and then pumps
up the semi-digested tissues with its muscular proboscis 2X

 

A study in the Florida Keys shows that this same snail species Coralliophila abbreviata feeding on patches of elkhorn coral Acropora palmata can cause tissue loss of about 3 sq cm per day. When the snails are removed over a 2mo experimental period, tissue loss continues but at a significantly lower rate (see histogram). The predator-caused tissue loss is an added stress to the corals, whose numbers in the study area have already been seriously reduced by winter kills, bleaching, photograph of snails Coralliophila abbreviata feeding on staghorn coral Acropora palmatahurricanes, and disease. Miller 2001 Coral Reefs 19: 293. Photograph courtesy Brian Silliman, Duke University, NC coolspeciesinteractions. histogram showing effects of carnivorous snails Coralliophila abbreviata on tissue loss in prey staghorn corals Acropora palmata

NOTE three branches of each of 6 colonies are assigned a different treatment. In the “snails-present” treatment, some 2.5 snails on average are maintained on each of 6 branches. On the 6 “snails- removed” branches,
all snails are removed weekly, but
about 20% crawl back in the between times. Thus, corals in this treatment
still lose tissue to predation. No snails are present on the 6 "snails-absent" branches

Denuded patches are created by snails
feeding on, in this case, staghorn
coral Acropora cervicorni 0.5X

 
Coralliophila snails in the Caribbean actually have variable feeding habits depending upon species. For example, C. abbreviata described in the foregoing accounts consumes all soft tissues and causes considerable colony mortality. Coralliophila clathrata, in comparison, lives in association with zoanthids Palythoa spp. and consumes mucus from the host’s skin. Members of a third species, C. caribaea (shown here), extend their probosces into the mouths of polyps of mound corals, e.g., Montastrea cavernosa, and suck out their contents. If the inner parts of the corals’ gastrovascular cavities are not being consumed, then
in this case the snails are behaving more like a parasite than a predator. Martin
et al. 2014 Coral Reefs 33: 1017.
photograph of coral-feeding snails Coralliophila caribaea photograph of snail Coralliophila caribaea feeding on a mound-coral polyp
Coral-eating snail C. caribaea resting on a mound coral 3X The snail sucks out contents of M. cavernosa polyp with its proboscis
 
 

Studies in Barbados show that bristleworms/fire worms Hermodice carunculata alternate between diets of fire corals and gorgonians, with a photograph of bristleworm Hermodice carunculata on a gorgonianpreference for late-afternoon feeding on fire corals. Lewis & Crooks 1996 Bull Mar Sci 58: 853.

NOTE common names for H. carunculata include bristleworms, fire worms, and bearded fire worms, relating to its appearance with the setal bristles extended and to their stinging nature. In BCCR the common name used is simply the one used by a certain author whose work is being considered

 

 

Bristleworm Hermodice carunculata
crawls on a gorgonian. 1.25X

 

 

 

 

photograph of a colony of fire coral Millepora complanata  In St. John, U.S. Virgin Islands, fire worms Hermodice carunculata can make short work of even large areas of fire coral Millepora complanata. The damage is compounded by rapid infestation of the feeding lesions by crustose coralline algae Neogonolithon sp. Witman 1988 Bull Mar Sci 42 (3): 446. Photograph courtesy the author.

 

 

Note that many of the branch tips of this colony
of Millepora complanata are lopped off and white
which, according to the author, is suggestive of consumption
by fire worms. Based on this, is it possible that the
unusual appearance of the finger corals in the VIDEO
above may also represent bristleworm depredation?

 

histogram showing daily feeding activity of bristleworms Hermodice carunculata on fire corals Millepora complanata
On fringing reefs in Barbados, bristleworms Hermodice carunculata may gang up on fire corals Millepora complanata with greatest feeding activity (90%) occurring in mid- to late-afternoon. The data shown here are obtained from observations made on 6 Millepora clumps ranging in size from 0.4-4.5 square meters over a 20d period in Apr-May using SCUBA and surface snorkelling. Lewis & Crooks 1996 Bull Mar Sci 58: 853.

  drawing of gut morphology of a fire worm Hermodice carunculataAnother study in Barbados on reef flat-inhabiting bristleworms Hermodice carunculata provides information on diets through analyses of gut contents and, for those with an interest in such things, details of gut structure and function. Gut contents include identifiable remnants of snails, polychaetes, and algae, suggesting a mainly carnivorous diet but with some herbivory. Additional evidence of zooxanthella cells and empty nematocyst capsules of the type found commonly in reef corals confirms that corals are consumed (see first entry for fire worms above). The digestive tract is comprised of 5 main parts (see drawing): a buccal mass containing muscle fibres and secretory glands that can be extruded from the mouth through expansion of a muscular pharynx, an esophagus, a long intestine, and a posterior anus. When feeding, the buccal mass wraps itself firmly around, for example, a prey coral, and digestion ensues. The resulting liquid slurry is sucked back into the gut by pharyngeal contractions. Marsden 1963 Can J Zool 41: 165.
 


Tests in Curacao on feeding behaviour fireworms Hermodice carunculata of different ages on coral recruits (spat) provide unexpected results. Gametes from several corals, but notably mound corals Montastraea faveolata, were collected and larvae cultured in the laboratory to 2-21d-old spat. The tiny spat were then offered to fireworms of small, medium, and large size (see photos below). Unexpectedly, only the smallest-sized worms ate the spat, with the largest-sized worms ignoring the spat but readily eating adult corals. This shift in preference with age has interesting implications with respect to the role that fireworm predation plays in recruitment in coral-reef ecosystems. Wolf & Nugues 2013 Coral Reefs 32: 227. Photograph courtesy the authors.

NOTE known as an ontogenic (age) shift in diet

 
series of photographs showing partial consumption of a mound-coral spat Montastraea faveolata by a fireworm Hermodice carunculata
 

Feeding by Hermodice carunculata on a 3mo-old coral spat involves enlarging and everting the buccal mass over the prey. Muscular action and secretion of digestive enzymes break down the coral tissue and the soft slurry is ingested. By 4min after the initial attack shown here, two-thirds of the spat is consumed, and the fireworm moves away

 

photograph of a bristleworm Hermodice carunculata feeding on an orange cup-coral Tubastrea coccineaIn Curacao bearded bristleworms Hermodice carunculata also feed on brain corals Diploria spp., orange cup-corals Tubastraea coccinea, and several others.  The worms prefer decaying to living tissue, and are often found sheltering within algae, such as the green Halimeda spp., that itself colonises open wounds on the coral.  This creates a synergism, where the worms nibble on dying coral beneath the algae, creating more dead tissue, and ultimately more habitat for algae and thus photograph of brain coral Diploria strigosa and encroaching green alga Halimeda sp.more protective shelter for the worm. Wolf & Nugues 2013 Ecology 94 (8): 1667. Photograph on Left courtesy Alexander Wolf, University of Bremen.


Brain coral Diploria
strigosa
with encroaching
green alga Halimeda sp. 1X

 

 

Bearded fire worm Hermodice carunculata eating a polyp of
an orange cup-coral
Tubastraea coccinea 1.75X

 
  photograph of bristleworm Hermodice carunculata  
Bearded fire worm Hermodice carunculata
crawling on and perhaps eating a
mound coral Montastrea sp. 1.75X
 
 
 

photograph of carpet anemone Stichodactylus helianthus
In Glover’s Reef, Belize carpet anemones Stichodactyla (formerly Stoichactis) helianthus are preyed upon by amphinomid polychaetes (bristleworms, fireworms) Hermodice carunculata. The worms seem oblivious to the nematocyst stings from their prey, but do sting in return as bristles penetrating the anemone can be seen. The anemone responds by releasing its pedal attachment and floating away with the worm still attached by its everted buccal mass. As this area of the reef is often subjected to heavy wave action, the pair may be washed away and the worm eventually dislodged. Although seemingly a good defensive strategy, detachment by the anemone is not known to be followed by re-attachment. Other worms may be attracted by feeding smells, leading to pack feeding. Lizama & Blanquet 1975 Bull Mar Sci 25 (3): 442.

NOTE the authors think that a kind of “pre-digestion” begins at the site of this attachment, with the partially digested slurry being sucked in by contractions of the worm’s pharyngeal musculature

 


Two individuals Stichodactyla
helianthus
apparently worm-free 1X

 
  Other cnidarians have their own special kinds of predators. A few examples are shown here:
 

photograph of a bubble-raft snail Janthina with its prey chondrophore Porpita stranded on the shore
Chondrophores, a type of hydrozoan, are pelagic and have highly toxic nematocysts, but are eaten by equally specialised bubble-raft snails.

 

 

 

 

Chondrophores Porpita porpita float at the ocean surface and
are preyed upon by bubble-raft snails Janthina janthina. The
snail is buoyed up on a raft formed from mucous bubbles

 

 

  photographs of a Portuguese-man-of-war Physalia physalis and its predator, the pelagic opisthobranch Glaucus atlanticusThe pelagic opisthobranch Glaucus atlanticus eats Portuguese-man-of-wars Physalia physalis and selectively incorporates the undischarged nematocysts of its prey into special sacs in the tips of its cerata for use in its own defense. Photograph of Physalia courtesy Cindy Young, Vancouver and of Glaucus courtesy Carol Lalli, Victoria.
 

Hawksbill turtles Eretmochelys imbricata generally eat sponges, but in areas of the Dominican Republic various cnidarians, including corallimorphs and zoanthids are highly preferred along with sponges. Leon & Bjorndal 2002 Mar Ecol Progr Ser 245: 249.

 
photo collage of alternate prey (in addition to sponges)
 

photograph of leatherback turtle Dermochelys coriacea attacking a jellyfish, courtesy Todd Jones and Mike SalmonAs adults, leatherback turtles subsist on pelagic cnidarians including jellyfishes, siphonophores, and chondrophores. Even the hatchling and juvenile leatherbacks eat nothing but gelatinous zooplankton. Feeding observations courtesy Todd Jones; hotograph courtesy Mike Salmon.

 

 

 

 

 

Nine week-old leatherback turtle Dermochelys coriacea attacks
a moon jelly Aurelia aurita. With a powerful stroke of its
flippers, the turtle launches itself at the prey and, with jaws
agape, slices a mouthful from the moon-jelly's body 0.2X

 

 
 

photograph of spadefish with cleaner-fishes courtesy Anne Dupont, Florida
Spadefishes in shallow waters complement a diet of polychaetes with hydroids, sea anemones, and sometimes algae. In the open ocean they prefer to eat jellyfishes. Hayse 1990 Fish Bull 88: 67. Photograph courtesy Anne Dupont, Florida.

 

 

 

 

After a presumed nice meal of jellyfishes, a pair of
Atlantic spadefishes Chaetodipterus faber is cleaned
by a few cleaner gobies Elacatinus sp. 0.25X

 
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