‘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.

‘The Fire Coral’ Pt. 1
A feeding Balanus sp. barnacle encrusted by Millepora alcicornis
Music, Video, and Aquarium
2010 Morphologic Studios

Millepora alcicornis, or fire coral, is not actually a true coral, but a hydrocoral.  Hydrocorals are colonies of hydroids that secrete a shared limestone skeleton, making them more closely related to jellyfish than true corals. Here in Florida, fire coral is extremely abundant on our reefs where they serve as the underwater equivalent of a sunburn to unsuspecting divers. Skin contact with fire coral will result in immediate burning pain, followed by an itchy welt that can last for several days. 

Fire coral is frequently found encrusting over neighboring corals, starting from the bottom and slowly killing the coral until the colony is completely encased in living limestone.  Because fire coral contains symbiotic zooxanthellae (like most tropical stony corals), they are capable of fast growth rates that help build a coral reef. Upon close inspection of fire coral, the stinging polyps can be seen as needle-like projections.  At even closer magnification, grape-like bunches of stinging nematocysts can been seen protruding along the polyps’ length.  These polyps are retractable, and when an edible food particle is captured, it can be drawn back towards one of the many mouths that dot the surface of the colony. In the video we see a colony of barnacle shells (Balanus sp.) that have been encrusted by fire coral.  Unlike the corals though, the barnacle can continue to live beneath the veneer of fire coral.

Barnacles are most commonly found living in the inter-tidal zone where they live periodic lifestyles of low tide rest and high tide activity. When immersed in water, the barnacle feeds with legs specialized for feeding called cirri. The cirri are covered with comb-like filaments that rake the water for passing plankton.  If a particle is caught in the cirri, it is drawn back to the animal’s mouth and eaten.  When barnacle larvae settle out of the floating plankton themselves, they permanently affix themselves to a life-long location. Barnacles have a special ‘cement gland’ under their bodies that produces an impressive proteinaceous adhesive that holds the animal firmly, in spite of the heaviest of waves.  A series of calcareous plates (commonly six) form a turret that protects their soft bodily tissues from predators. Despite their simple appearance, barnacles are in fact crustaceans, like shrimp, crabs, and lobsters.

‘Lima scabra’
The tentacles and mantle of a Lima scabra file clam filter feeding
Music, Video, and Aquarium
2010 Morphologic Studios

Lima scabra is a common resident on Floridian and Caribbean reefs where it can be found wedged in crevices, with only its long tentacles extending out into the water column. Usually these tentacles are crimson red (as seen in the specimen above), although they are occasionally white in color. Lima scabra can grow to about 3.5 (9cm) inches long.

Like most bivalves, Lima scabra is a filter feeder. It siphons water in through its fleshy mantle (seen in the video), and strains any edible particulate matter before pumping the water back it out. It holds itself semi-permanently in place through the use of ‘byssus threads’. The threads are formed by a viscous protein secretion that cures instantly upon contact with seawater. These byssus threads have captured the attention of bio-engineers who seek to replicate their strong adhesive properties for industrial applications. However, if the clam comes under attack from a predator, it is capable of detaching and swimming away. They can move surprisingly quick; swimming in fast, jerky movements, propelled by the repeated snapping-together of its shell.

‘Corynactis viridis’
The feeding of a Corynactis viridis corallimorph
Music, Video, and Aquarium
2010 Morphologic Studios

This past week we finally received our long awaited Corynactis viridis from our good friend Dr. Yvan Perez at the Institut Méditerranéen d’Ecologie in Marseilles, France. I collected these polyps this past June while diving in the Mediterranean, and Dr. Perez has been culturing them in his lab in the interim. Laurent Foure, the current curator of the Noumea Aquarium in New Caledonia, also collected us several stunning morphs from a different Mediterranean location before he left for the South Pacific.

Corynactis viridis is an archetypal corallimorph species found all along the cold, rocky coastlines of Western Europe. Its distribution across the Mediterranean is much more sporadic and considerably less common. They are frequently referred to as ‘jewel anemones’, which is a misnomer, as they are not anemones despite their superficial resemblance. Typically, polyps range in size from about 3-10mm in diameter and can be found in a seemingly limitless number of color morphs. What they lack in individual size, however, they make up for in colonial dominance. It is not uncommon for colonies to completely carpet large areas, frequently rocky outcrops and vertical surfaces. As these colonies are comprised of clones, this carpet will be of uniform coloration, creating the illusion of a singular connected organism. Multiple color morphs will often be found living in close proximity, creating a technicolor patchwork of tiny individuals. Their colors are often vibrant with fluorescent accents. Unlike most of our tropical corallimorphs, C. viridis are non-photosynthetic, relying entirely on the capture of plankton by their sticky tentacles. At the end of each tentacle is a small ball known as an acrosphere; a tell-tale characteristic of all non-photosynthetic corallimorphs.

In this video a single Corynactis viridis polyp (about 8mm in diameter) is seen capturing and digesting tiny plankton as they flow past in the current. As the tentacles capture food, they retract towards the animal’s mouth, located at the center of the polyp. The mouth is likewise transformable; capable of extending, expanding, and enveloping food items. The total elapsed time was roughly 12 minutes and sped up 1200% in order to demonstrate the hydraulic muscular contractions and contortions that the polyp goes through while feeding. 470nm LED light is used to highlight the fluorescent orange ring around the outer diameter of the polyp.

‘Preener’
Mithraculus cinctimanus crab on Ricordea florida corallimorphs
Music, Video, and Aquarium
2010 Morphologic Studios

Shown above is a 1cm Mithraculus cinctimanus, commonly known as the banded clinging crab. Typically this species is known to live in association with a variety of Caribbean sea anemone species. However, several years ago we noticed that juvenile and sub-adult banded clinging crabs seemed to prefer the protection amongst Ricordea florida polyps in the wild. When they are small, like this one,  the carapace (shell) of the crab is nearly entirely covered by a fuzzy red algal camouflage. As they get larger (up to 25mm) they lose much of this hairy coat, revealing a striking white and maroon patterned exoskeleton.

The video shows the crab alternating between preening its own algae covered carapace and the fluorescent tentacles of the Ricordea florida on which it lives.  It is possible that the crab may ingest some of the polyps’ mucus as an occasional food source.  The video was sped up considerably (9x). At normal speed the polyps appear static, but at this speed the regular hydraulic undulations and contractions of the R. florida polyps are clearly visible.

‘Cleaner’ Pt. 2
Periclemenes pedersoni shrimp on Ricordea florida corallimorphs
Music, Video, and Aquarium
2010 Morphologic Studios

Here a 2 centimeter Periclemenes pedersoni shrimp is seen perched on its host colony of fluorescent orange Ricordea florida corallimorphs. Pederson’s shrimp are native to Floridian and Caribbean waters, and are found in symbiotic association with a variety of sea anemone and corallimorph species. Pederson’s shrimp live amongst the tentacles of these animals, immune from their sting. They act as ‘cleaners’ of much larger fish. The shrimp wave their antennae and swim in a characteristic swaying motion to signal that they are ‘open for business’. Fish seem to learn and remember the specific location of these ‘cleaning stations’, returning as needed for service. When not removing parasites from fish, these shrimp will forage for bits of food amongst its host’s tentacles and spend time preening itself, as can be observed in the video. Pederson’s shrimp form monogamous mated pairs that will live together on same host. These shrimp are quite territorial, fighting fiercely with its own kind if another Pederson’s shrimp tries to take up residence on its anemone or corallimorph. If an ‘unmated’ shrimp tries to take up residence too close to an established territory, the invader will usually be dissuaded through threat displays and physical harassment.

Pederson’s shrimp are closely related to the spotted cleaner shrimp (Periclimenes yucatanicus) featured last month.

Jared McKay (left) and Colin Foord (right) of MORPHOLOGIC; self portrait.

During the night of Saturday, December 5th we displayed a video projection at the Art Basel Miami Beach satellite Moksha Art Fair. The subject of the the film was a Entacmea quadricolor sea anemone (right) and it’s corresponding reflection (left).