‘Flatworms’
Convolutriloba retrogemma (flatworms)
Music, Video, and Aquarium
2010 Morphologic Studios

The flatworms (Convolutriloba retrogemma) featured in the video are shown at 3x normal speed. They each range from 2-4mm in total length.

These particular flatworms harbor symbiotic zooxanthellae in their thin tissue and utilize the excess sugars they create as their primary energy source. Packets of zooxanthellae can be seen as the tiny, red-brown dots along the back of flatworm. Their reliance upon this photosynthesis requires that these flatworms bask in sunlight like little photovoltaic cells, and enables them to live without a developed digestive system.

In the wild, this species can be found in the shallow water of protected lagoons and around mangroves. Reproduction is accomplished asexually via fission, in which the flatworms literally split into two. This strategy enables exponential population growth in optimum conditions. They are the preferred prey of several species of larger flatworms and sea slugs; animals that can tolerate their toxic bodily fluids.

While it appears that the flatworms just glide along like magic carpets, they are actually propelled by invisible cilia (flapping filaments) that slide them across a thin layer of mucous laid over whatever surface they happen to be upon.

Upon close inspection of flatworm-to-flatworm interaction, it is apparent that these flatworms do not like making direct contact with each other. If they do, they react as if stung. It seems that this reaction prevents the worms from piling on top of each other in an effort to gain the best solar power. Instead, they jockey for position until they each find a place in which to ‘park’ themselves, like sunbathers on a crowded beach.

‘Sally Lightfoot’
Percnon gibbsi crab amongst Anemonia bermudensis anemone garden
Music, Video, and Aquarium
2010 Morphologic Studios

The sally lightfoot crab (Percnon gibbsi) is an agile maneuverer on the rocky shores of the Caribbean. These crabs are particularly well-suited to life on craggy limestone rock in shallow water. The rockwork is the result of sea urchins eroding the limestone as they rasp off the algae growing on the surface. The cumulative erosion by sea urchins over many years creates a jagged network of fissures and channels through the solid rock. The sally lightfoot crab’s pancake-flat body allows it to scuttle beneath the protective spines of a nearby urchin at a moment’s notice. Anemonia bermudensis sea anemones like the ones seen in the film can also be common on the rocks in this surf-washed zone. The sally lightfoot’s nimble legs allow it zig-zag harmlessly between the tentacles of these stinging animals. Between the crab’s eyes you’ll notice a pair of fast-flitting antennae that detect the ‘smell’ of food in the water. The turbulence of the environment requires accurate detection and nimble response.

‘The Florist’
Leptopsia setirostris (Decorator Crab) scavenging amongst a Zoanthus polyp garden
Music, Video, and Aquarium
2010 Morphologic Studios

Once again we return to observe a cryptic red decorator crab (Leptopsia setirostris); this time living upon, and decorated with, zoanthid polyps (Zoanthus sociatus), close cousins to both sea anemones and corals.  Zoanthus in Latin literally means ‘animal flower’.  The species name sociatus refers to the fact they these flower animals live socially in dense groupings of identical polyps.

Decorator crabs demonstrate a remarkably prescient instinct to be able process the information required to successfully camouflage themselves to match their preferred habitat.Unlike the typically fast-scuttling crabs of the mainstream, decorator crabs move at a deliberately slow pace to reduce being noticed.

This particular decorator crab species boasts a brilliant red exoskeleton that it has disguised with the zoanthids.  The crab has carefully nipped individual zoanthid polyps from a larger colony and placed them upon its carapace (back) where they attach down on their own and continue growing.  My experience suggests that it takes at least two days for a polyp to begin attaching down to new substrate.  I have yet to observe the crab going through the whole process of zoanthid ‘decoration’, but clearly it is a very patient animal.

The crab uses it’s small claws to pick at and remove pieces of detritus between the polyps.  The animal nature of the zoanthids becomes especially apparent when the movements of the crab cause the polyps to close up in reaction.   If you look carefully at the bottom right of the screen you’ll notice the periodic movements of a barnacle that these zoanthids are growing upon.  Zoanthids are commonly called ‘sea mat’ due to their rubbery, encrusting morphology. They live together in interconnected colonies of cloned polyps, slowly expanding their colonies outward; growing over shells, in-between coral heads, and across shallow tide pools.

‘The Lynx Nudibranch’
Phidiana lynceus (Lynx Nudibranch) on Spondylus americanus oyster
Music, Video, and Aquarium
2010 Morphologic Studios

Last week we spent a moment making eyes with the oyster (Spondylus americanus). This week we’ll spend a moment with a diverse community of animals and plants that have colonized the upper shell of the very same oyster. Towards the left of the frame is a small colony of flower-like animals known as hydroids. Hydroids are most closely related to jellyfish, but instead remain attached to the reef their whole lives (unlike a jellyfish). But, like the jellyfish, hydroids can pack a powerful stinging punch. The brown, daisy-like creatures seen growing here on the oysters’s back are one such type of hydroid, Myrionema amboinense. This hydroid species derives its brown coloration from the symbiotic zooxanthellae (dinoflagellate ‘algae’) stored in its tissues. The ability to gain nutrition from both prey capture and photosynthesis, allows these hydroids to grow and colonize quickly. The sting from these hydroids is considerably more powerful than that of most corals. The gray, lumpy knobs on the back of the oyster shell are zoanthid polyps, close cousins of the sea anemones. However, these zoanthids are no match against the powerful sting of the hydroids. The zoanthids have all but acknowledged defeat by the encroaching stingers by simply closing up; effectively handing over control of the oyster shell to the hydroids.

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‘Oyster Vision’
Spondylus americanus oyster
Music, Video, and Aquarium
2010 Morphologic Studios

Here we look into the face of the thorny oyster (Spondylus americanus).  Unlike most shallow-water oyster species, the thorny oyster is a solitary creature that lives permanently cemented to the deeper coral reef.  Its fleshy mantle is adorned with sepia-toned psychedelic camouflage that can vary widely from one individual to the next.   The rim of the mantle is lined with dozens of eyes that stare out into the depths.  These eyes are quite simple, only detecting changes in light that might suggest an incoming predator.  If a threat is detected, the oyster will quickly snap its two shells together, sealing the animal inside with its two powerful adductor muscles.  It is the adductor muscle that people eat when they eat ‘oysters on the half shell’.  Oysters are filter feeders, spending their time siphoning water through gills that strain out particulate matter. As seen in the film, the oyster periodically expels waste and water with a quick contraction of its adductor muscles.

In the second installment (next week) we will explore the upper shell of the oyster and the community of organisms that has colonized it.

‘Transparency’
Unidentified shrimp on unidentified Ricordea polyp
Music, Video, and Aquarium
2010 Morphologic Studios

In the second installment of the ‘Unidentified Ricordea Shrimp’ series we find the (previously featured) unidentified Ricordea shrimp upon an unusual host.  While it is is most certainly on a Ricordea polyp, we are not convinced that it is in fact Ricordea florida. Over the years, we have noticed several key morphological and physiological differences that suggest that there are two genetically distinct morphs of Ricordea florida. For practical purposes, we have been referring to the morph of Ricordea seen here (under 470 nm light) as ‘inshore ricordea’…

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‘The Arrow Crab’
Stenorhynchus seticornis or ‘Arrow Crab’ guarding a cave entrance
Music, Video, and Aquarium
2010 Morphologic Studios

Take a moment to look into the compound eyes of the arrow crab (Stenorhynchus seticornis)… If NASA is looking for a robot capable of navigating rocky planetary terrain, the arrow crab would be a perfect organism to model it after. In the video we look down the sharp, pointed rostrum (‘nose’) of an arrow crab as it appears bobbing in space. In reality, its spindly, spider-like legs are holding it anchored like a sentinel, guarding the opening of a small cave.

Arrow crabs are an abundant species on Floridian reefs, living perched near cracks and crevices in coral heads where they can retreat if threatened. Their pointed rostrum, triangular body, and protruding eyes gives this crab the appearance of a predatory lizard fish that can dash away at a moment’s notice. Instead, the arrow crab is rather slow moving, relying on the fact that the paucity of meat inside the spiny, twig-like exoskeleton of the arrow crab makes it unappetizing to a would-be-predator. This unique anatomical configuration likely explains their abundance in the wild.

Like other decapod crustaceans, the arrow crab has 10 legs (8 walking legs, and 2 pincers or ‘chelipeds’ properly). However, if you look carefully, you’ll notice that this particular crab is missing the last leg on the right side of its body. Fortunately, crustaceans are capable of regrowing amputated legs. Only a few hours after it was filmed, this arrow crab molted, and as if by magic, regenerated its tenth limb.