Nutrition
 
  Nutrition
 
 
Detritivory/bacterivory hot buttons for nutrition part of BCCR hot button for primary productivity part of BCCR hot button for carnivory part of BCCR hot button for Corals: a case study part of BCCR hot button for herbivory part of BCCR hot button for detrivory/bacterivory part of BCCR
This part of nutrition deals with detritivory/bacterivory, that is, with coral-reef organisms that subsist on these food items. Other topics relating to nutrition of coral reefs can be accessed via the icons. The subject of bacterivory is considered here, while that of DETRITIVORY is found in its own section.
 
 

Bacterivory

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of bacteria-covered sand taken from a video

"This scum is a combination of algae and bacteria. It looks yucky, but it's quite nutritious. Bacteria surround us as we swim along. They coat the small floating particles and they're on every surface of the reef. Bacteria are eaten by reef animals as part of detritus, and the floating bacteria are a major food of sponges and tunicates. This blue tang certainly seems to enjoy its meal of scum." - Cayman Brac 2001

NOTE Acanthurus coeruleus

 
 

photograph of purple sponge photograph of bacteria and a diatom courtesy John Smit, University of British Columbia
Sponges are suspension-feeders, meaning that they strain the seawater passing through them for small organic particles. The particles, bacteria-sized or smaller, are then engulfed directly into their cells. Bacteria comprise the main diet of sponges and about 80% of them are removed on a single passage through a sponge. Photgraph of bacteria courtesy John Smit, University of B.C.

Marine bacteria coat particulate surfaces, such as detrital matter, and also float freely in the water. The large
organism on the Left is a photosynthesising diatom. 2000X

 

 

 

Branching vase sponge Callyspongia vaginalis
with direction of water flow indicated 0.2X.
The seawater is propelled out of the main chimney
openings by the combined action of a myriad of
flagellated cells lining tiny chambers within the
sponge. This causes food-bearing seawater to be pulled
in through small holes perforating the external surface

 

photograph of cyanobacteria killing a portion of the reef
Cyanobacteria, also known as blue-green algae, contain a variety of toxic chemicals and have been implicated in fish-kills throughout Florida and in outbreaks of "swimmer's itch" in Hawai'i and elsewhere. They are eaten by only a few specialist herbivores including certain opisthobranch molluscs.



 

 

Mixed growth of cyanobacteria
and algae on a dead coral 0.33X

 

 

 

photograph of opisthobranchs Steilocheilus longicauda and S. citrinus courtesy Steve Pennings, University of HoustonFew reef animals feed on cyanobacteria. However, some specialised sea hares feed solely on them and incorporate their toxins, known as malyngamides, into their flesh. Despite suggestive evidence that these diet-derived chemicals act in defense against fish predation, unequivocal scientific demonstration of this role is lacking. Pennings et al. 2001 Coral Reefs 20: 320. Photograph courtesy Steve Pennings, University of Houston.

 

 

 

Two species of cyanobacterivores Stylocheilus longicauda
(above, note long tail) and S. striatus (below, note fine
lines, just visible on "neck" region) in Guam. Only the
darker morph is found in the Caribbean region 2.5X

 
 

photograph of social tunicate Clavelina photograph of colonial tunicate Eudistoma
Tunicates subsist on bacteria and other small organic particles that they catch on a sticky mucus-net produced within an internal filtering structure known as a pharyngeal basket.


 

Colonial tunicate Eudistoma sp. 1X

 

 

 

Blue-bell tunicates Clavelina puertosecensis 0.5X. This is
a social species, where each component zooid is joined
to the next via a nutrient-communicative stolon

 

drawing showing details of feeding in a tunicateIn tunicates, seawater bearing bacteria and other food particles is pumped via the inhalent siphon into the sieve-like pharyngeal basket. A fine-mesh mucous net is continuously formed at one side of the basket and moved around the inner surfaces of the basket. As it slides along, the sticky mucous net picks up food particles and carries them to a ciliated groove on the opposite side of the pharyngeal basket. The food-bearing mucus, now in the form of a rope, is moved conveyor-belt fashion into the esophagus and then into the gut where it is digested. A salivary gland (green in the drawing) and a digestive gland (not labeled, but shown) aid in this process. Feces are released from the anus and are carried away in the water flow from the exhalent siphon.

 

 


photograph of colonial tunicate Tridemnum solidum overgrowing boulder coral Montastrea sp.A study on feeding in colonial tunicates Tridemnum solidum on the reefs of Curacao show that bacterial feeding may contribute as much as 50% of the total food-carbon needs of the species.  The bacteria are not free-floating in the seawater; rather, they are attached to larger colloidal and other water-borne particles.  These are taken in via the inhalent siphons and filtered from the seawater in the pharyngeal baskets. The balance of the nutritional needs of Tridemnum is met from consumption of of other microplankton and from photosynthetic activities of symbionts in its tissues.  Bak et al. 1998 Mar Ecol Prog Ser 175: 285.  For more on photosynthesis in tunicates and other invertebrates see FILES/NUTRITION/PRIMARY PRODUCTIVITY/INVERTEBRATES.

 

Colonial tunicate Trididemnum solidum
overgrowing mound coral Montastrea sp. 1.3X

 

 
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hot button for cyanobacteria part of BCCR hot button for phytoplankton part of BCCR hot button for invertebrates part of BCCR hot button for seaweeds/seagrasses part of BCCR