Defenses
 
column spacer Defenses
 
 
Invertebrates hot buttons for invertebrate defenses part of BCCR hot button for behavioral defenses part of invertebrate defenses in BCCR hot button for toxic chemicals part of invertebrate defenses in BCCR hot button for structure part of invertebrate defenses in BCCR
The topic considered here relating to defenses of invertebrates deals with behaviour. Other invertebrate defenses are accessible via the icons.
 
 
seahorse dive leader for Biology of Caribbean Coral Reef website photograph of staghorn corals taken from a video "As we swim over this nice growth of corals we see lots of fishes, but only rarely do we see small motile invertebrates, like crabs and snails. They're around, but hiding away in crevices until nightfall." - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize.
 
 

Invertebrate defenses: behaviour

hot buttons for behaviour part of BCCR

Behavioural defenses in Caribbean invertebrates are many and varied, but are generally encompassed in the icon-topics shown.

This "hide away" part of invertebrate behavioral defenses includes hide away (as within a shell or crevice) and minimise contact with predators, topics considered here, and SMOKE SCREENS, and CAMOUFLAGE, considered in their own sections.

 
 

Invertebrate defenses: behaviour: hide away

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of queen conch Strombus gigas taken from a video

"Queen conches are probably the biggest snails we'll see on our dive. This one is in its shell, but you can see the horny operculum at the back, which closes over the shell opening after the animal pulls inside. " - Turneffe Island, Belize. Video courtesy Andy Stockbridge, Belize.

NOTE Strombus gigas

 
 

photograph of queen conch Strombus gigas showing eyes, foot, and operculum
At the first sign of danger a snail will withdraw into its protective shell, pulling in the operculum for protection. The operculum is made of a tough, horny proteinaceous material and, in a conch, does double duty as a "hatch-cover" and locomotory device. Note in the video that follows how the operculum is used as a kind of lever to lurch along the sand surface, a movement referred to as the "strombid leap".

When partially withdrawn, a conch's eyes are often just visible, as in the photograph here. What it is seeing if anything is not known. The eyes are well developed, positioned on highly extensible stalks, and are extended out when crawling. Still, like other gastropod eyes, they likely just sense dark and light.

The largest shell in the Caribbean region, the queen
conch Strombus gigas, peeks out from the safety of
its shell. From left to right, the structures visible are:
a pair of eys, part of the foot, and the operculum 0.5X

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of conch taken from a video "Conches have multiple uses for their opercula. Fighting conches use theirs to poke with, while all conches can lurch along useing the operculum as a locomotory lever." - Little Cayman 2002
 
 

photograph of 2 auger shells Terebra taurinus
When pulled into its thick and heavy shell, a flame auger Terebra taurinus would seem to be well defended against predators. So, who are the predators of flame-auger shells? Well, we don't know but, by considering the modes of feeding of some common potential predators, we can get a pretty good idea which of them might be able to break through an auger's defenses .

0.33X

 
photo array of possible predators of flame augers Terebra taurinus
  cartoon of an auger shell buried in sand during the daySo, even an auger shell tucked away deep inside its thick-walled shell with an operculum as a protective hatch-cover likely isn't fully protected from predators. However, flame-augers likely avoid contact with many potential predators by being nocturnally active. They usually stay buried in sand-mud during the day.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a tubeworm taken from a video "It's hard to sneak up on a tubeworm. When the worm perceives danger, perhaps by water vibration or shadows, it quickly pulls in." - Aruba 2004
 
 


Speed of conduction along a nerve fiber increases with its diameter, and those in tubeworm are amongst the largest known in the animal kingdom. The worm photograph of tubeworm Sabellastarte magnifica with tentacles expandedpulls into its tube far enough that a fish could bite off the top of the tube and still not reach the worm. However, even if the photograph of tubeworm Sabellastarte magnifica with tentacles withdrawnworst should happen and the worm gets its head bitten off, it can grow a new one. It can do this several times in succession, in fact, but each new one is smaller than the preceding one.

 

A tubeworm Sabellastarte magnifica with tentacles out and expanded and then withdrawn 0.6X

 

photograph of Christmas-tree worm Spirobranchus giganteus with operculum visibleChristmas-tree worms not only withdraw quickly, but a calcareous operculum is pulled in after the double tentacle-crowns are tucked away. The hard operculum is further adorned with protective antler-like structures.

 

 

 

 

Christmas-tree worm Spirobranchus giganteus
showing tentacles, operculum, and protective antlers 3X

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of Caribbean reef fishes "We're down here peering into this crevice checking for motile invertebrates. Hmmm! Not much here, except for maybe a few squirrelfishes...at least, not that we can see. Maybe the inverts are even deeper inside." - Bonaire 2003
 
 

Invertebrate defenses: behaviour: minimise contact with predators

 

photograph of boulder coral Montastrea sp. with polyps just emerging
A strategy of minimising contact with predators is a rather obvious one, and can be as simple as a potential prey organism being active when its predators are not. Many invertebrates have evolved nocturnal behaviour, perhaps in response to the presence of hunt-by-sight daytime predators. For example, the polyps of many species of corals emerge only at dusk or later, and this is the time that potential predators such as butterflyfishes are resting.

 

 

 

Boulder coral Montastrea sp.
with polyps just opening 5X

 

 

  Motile invertebrates more active at night include...
 
photo collage of coral-reef invertebrates generally active at night and hiding during the day
 

photograph of a tiger-tail sea cucumber Holothuria thomasi feeding at nightTiger-tail sea cucumbers Holothuria thomasi generally hide away beneath rocks and in crevices during the day. At night they extend their bodies to a meter or more from their hiding spots to search for organic detrital food. The organic bits are picked up on pad-like sticky tentacles that work over and between the surface particles.

 

 

 

 

0.6X

 

photograph of a crowd of lobsters Panulirus argus under a rockMultiple occupation during daytime of single dens by night-feeding spiny lobsters may not be a strategy for protection from predators but, rather, a consequence of too few habitats. Studies in Florida show den-sharing to be correlated with lobster density and scarcity of habitats, but not with lobster size, moult frequency, or density of predators. Chidress & Herrnkind 1997 Mar Freshw Res 48: 751.

 

 

A crowd of spiny lobsters Panulirus argus 0.25X

 
 
Let's hear from the crevice-dwellers:: cartoon 1 in series of 5 showing life in a crevice for a Caribbean coral-reef invertebrate
cartoon 1 in series of 5 showing life in a crevice for a Caribbean coral-reef invertebrate cartoon 1 in series of 5 showing life in a crevice for a Caribbean coral-reef invertebrate
cartoon 1 in series of 5 showing life in a crevice for a Caribbean coral-reef invertebrate cartoon 1 in series of 5 showing life in a crevice for a Caribbean coral-reef invertebrate
 
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