The Channel Clinging Crab (Mithrax spinosissimus)

Channel Clinging Crab (Mithrax spinosissimus)

by B. N. Sullivan

We were on a night dive in the Turks and Caicos Islands when we came across this crab.  It is a Channel Clinging Crab (Mithrax spinosissimus), the largest species of Caribbean reef crab.

How big is he?  We estimated that this crab's carapace measured about 15 cm (6 inches) across.  If you could measure across its spread-legged footprint, however, it would easily be over to 30 cm (12 inches).

We were scanning around with our lights across a sandy area off the coast of West Caicos, when we saw this crab gallumphing along, hunting for his dinner.  I had been shooting macro photos earlier that day, but for some reason I did the night dive with a wide angle (15mm) lens on my camera.  As it turned out, that lens allowed me to get these wide angle close-up shots of this crab.

We located this crab out on the sand flat, at a depth of about 15 meters (50 feet).  I maneuvered around in the dark to position myself to intercept its path. I settled on the sand just a meter or so in front of the critter, while Jerry shone a small beam of light on it from above so that I could set up the shot.  I waited, and when the big crab was right in front of me, I snapped the shutter release.  The result is the first photo on this page.  By chance, I managed to capture him just as he began to raise one of those claws in defense!

Of course, as soon as the camera's strobe blasted the poor crab with bright light, he decided to leave in a hurry.  He 'turned on a dime' and retreated quickly, but not before I was able to capture an image of the posterior of his carapace and those wonderful, bristly, spidery walking legs!

Channel Clinging Crab (Mithrax spinosissimus), posterior view

We know this species by the common name Channel Clinging Crab, but it turns out that it has several other common names, including Reef Spider Crab, and Spiny Spider Crab, among others.  The crab's scientific name is Mithrax spinosissimus, and that designation stays the same, independent of the common name, which varies from place to place.  This crab belongs to the Majidae family and is a 'true crab' (as opposed to, say, a hermit crab).

Majidae tend to have long slender legs -- just like this example -- which is why the common names of many species in this family include the word 'spider'.  Majids also tend to have little hairs or bristle-like structures on their carapaces.  Bits of material -- algae, sponge, and so on -- attach to those hairs and act as part of the crab's camouflage.

Note that the walking legs of this species also are rather hairy, and are covered with 'stuff' while the business end of the crab -- those impressive claws -- are smooth.

Like so many reef creatures, this species forages mainly at night.  During the day, they hunker in the reefs, under ledges, and in cavelets.  Because of their size, they can't wiggle into small cervices like so many smaller species can do.  Still, they can be difficult to spot during the day, since their decorated carapaces blend so well with their surroundings.

These crabs inhabit a range from the sub-tropical western Atlantic to the Caribbean. They can be found in reef areas along the coasts of southern Florida, through the Bahamas and the Turks and Caicos Islands, and throughout much of the Caribbean.

Scarlet Hermit Crab from the Cayman Islands

Scarlet Hermit Crab (Paguristes cadenati), Cayman Islands

by B. N. Sullivan

Many small crustaceans look quite similar to one another, but it's hard to misidentify this little hermit crab.  A denizen of reefs in the Caribbean Sea, the brilliant coloring of the Scarlet Hermit Crab (Paguristes cadenati) sets it apart from other hermit crab species of that region.

These little crabs (about an inch long) inhabit old gastropod shells, and for some unknown reason, the shells they choose as their portable houses usually are pretty cruddy looking.  The one in the photo on this page is covered with a layer of coralline algae so thick that it almost looked like a stone, rather than a seashell.

Like many hermit crab species, these little guys are difficult to find during daylight hours.  At dusk they emerge from their hiding places in the reef and go about foraging for their food.  We spotted this individual during a night dive at Little Cayman island.

Most often, divers see only the crab's red legs and pale eyestalks poking out of the aperture of the shell in which they live.  This individual was cruising along across some coral, so we got to see a bit of the pretty speckled markings on its back, too.

The Scarlet Hermit Crab is a member of the Diogenidae family.  Comprised of more than 400 known species, the Diogenidae are the second-largest family of marine hermit crabs.

A Queen Conch snail, giving us the eye

Eyes and proboscis of a Queen Conch (Strombus gigas)

by B. N. Sullivan

Conch shells, like all seashells, are created by secretions from the mantle of the snail that lives inside. This happens gradually, over the snail's lifetime.  Most people have seen empty Conch shells, yet few have seen the snails that are the natural inhabitants of those large, heavy shells.  Fewer still realize that those critters have wonderful stalked eyes.

All of the snails in the family Strombidae, to which Conchs belong, have these stalked eyes.  If you come across a live Conch shell while diving, you can see the snail's eyes for yourself if you are patient.  If you pick up the shell and turn it over, the animal inside will retract into the shell almost immediately.  Set the shell down with the glossy aperture exposed and just wait.  Eventually -- say, in five or ten minutes -- the snail will extend its eyes to look around.  If you are lucky, you also may get to see its proboscis (tubular mouth), as in the photo above.

The snail in an upended Conch shell has the ability to right itself, but to do so takes quite a bit of effort on the part of the critter.  So, if you do handle one or set it aperture side up to try and catch a glimpse of the eyes, please do return it to its natural aperture-down position before you leave it.  The photo below shows the snail's eye peeking out of the shell as it moves along the sand in its normal position.

The creature in the photos on this page is a Queen Conch (Strombus gigas), a species common to the Caribbean. I photographed this one during a night dive off the north coast of Cayman Brac.

An eye peeks out as a Queen Conch snail crawls along the sand

The Spiny Puffer's Message: You can't touch this!

Spiny Balloonfish (Diodon holocanthus)

by B. N. Sullivan

You can't touch this... and you definitely can't swallow it!

That is the message that fishes in the Spiny Puffer family attempt to transmit to potential predators.  While other creatures defend themselves from predators by fleeing, or hiding, or with camouflage, members of this family (Diodontidae) inflate themselves.  In addition, evolution has armed these guys with another feature: rigid spines all over their bodies that are erected when the fish inflates.

The Spiny Puffer's spines actually are like specialized scales. When the puffer is not inflated, most of the spines lie more or less flat against the skin, but when the skin stretches during inflation, the spines go upright.

Ain't nobody gonna swallow these babies!

Puffers are not very streamlined even when they are not inflated, so they are not fast swimmers.  Once they inflate they really are ungainly.  Their little pectoral fins will flutter, but they don't attain much in the way of forward motion.  To survive, they rely entirely on making themselves look unappealing as prey.

When a Spiny Puffer is molested or feels threatened, it opens its mouth and draws sea water into its stomach.  The stomach is capable of expanding greatly -- so greatly that the stomach and its watery contents can virtually fill the whole fish, squishing the rest of its organs up against its backbone.  Its skin is stretchy, too, which also helps it to expand like a balloon.

Both fish pictured in this post are partially inflated.   Each was pottering along in a shallow reef area when we spotted them.   In each case, Jerry shined his light on the fish so that I could approach and aim the camera for a close-up of the Puffer's cute face and interesting eyes.  But these are touchy critters, and that was enough to induce them to begin to inflate, so in each instance I snapped two frames and retreated before they freaked out.

Some divers intentionally harass or even try to grab puffers, just to see them inflate.  This is quite a mean thing to do.  Remember, inflation is a defense.  If the fish begins to inflate, that means it is alarmed.  If it puffs out to its maximum, it is really scared!  This behavior may be amusing to divers, but it really stresses the poor fish.

If you see a puffer and it begins to inflate, move away from it to let it know you are not a threat.  Don't terrorize the puffers!

Spotted  Porcupinefish (Diodon hystrix)

Both of the Spiny Puffers on this page are Caribbean species.  I photographed them on two separate night dives in the Cayman Islands.  To give you an idea of their size, each of these individuals was approximately 12-14 inches (30-35 cm) in length.

Hermit Crab with Bright Blue Eyes

by B. N. Sullivan

This is the White Speckled Hermit Crab (Paguristes punticeps), a Caribbean species of the Diogenidae family.  Adults of this species grow to a length of  3 to 5 inches (about 8 to 13 cm).  These reef dwellers inhabit empty gastropod shells, tail end first, so you won't normally get to see the crab's full length.

Without the artificial light produced by the camera strobe, these crabs look dark brown with white speckles.  It's also difficult to make out those wonderful bright blue eyes without artificial light and a macro lens.  But that's why macro photography was invented, right?

Jeepers, creepers -- where'd he get those peepers?!

One of the most noticeable morphological features of this species: both of its claws (chelipeds)  are approximately equal in size.  More commonly, the claws of hermit crab species are of different sizes -- typically the left claw is larger than the right.

All of the images on this page are of the same individual, photographed during a night dive at a site known as Cumber's Caves on the north shore of Little Cayman island.

Oh, Baby! A juvenile Scorpionfish

by B. N. Sullivan

See that little fishie in the photo at right?  It's a juvenile scorpionfish -- species unknown.


We came across this little guy in the Red Sea during a night dive at a place called Tiran Island,   in the Straits of Tiran.  (For those of you who may be a bit foggy on Red  Sea geography, the narrow body of water that separates Egypt's Sinai Peninsula from Saudi Arabia is known as the Straits of Tiran. That is also where the Gulf of Aqaba joins the rest of the Red Sea.)


We were there to photograph other critters -- which we did --  but once we spotted this little baby, it became the highlight of our dive.  I was kneeling on the sand, fiddling with camera settings.  Jerry shined his light onto my camera so that I could see what I was doing.  In the periphery of the pool of light, we saw something move.  That something was partially covered with sand, but it had some colorful bits sticking out of it.  It looked a little bedraggled, but we recognized that it was a tiny fish.  Those colorful bits turned out to be its tail and pectoral fins.  

This next photo shows how the little fish looked when we first saw it lying on the sand.  Not quite two inches (5 cm) long, we knew it was some kind of fish, and that it probably was a juvenile.  But a juvenile what??


Jerry slid his gloved hand under the little critter, picked it up,  and held it out to me.  We shined our lights on it to get a better look, when all of a sudden it wiggled, then fluttered, launching itself from the palm of Jerry's hand into the water column like a fledgling bird leaving its nest.


Luckily, I was able to snap a few frames of the fish as it glided back down to the sand (see first photo).  By this time we were both quite sure it was some kind of scorpionfish, based on its overall shape, but to this day we do not know which species.


Our best guess is that it is a baby Bearded Scorpionfish (Scorpaenopsis barbatus), a species that is plentiful in that area of the Red Sea.  The adults have an overall shape similar to the juvenile we saw and photographed that night.  We have shown the photos of the juvenile to a number of people who know something about Red Sea fishes, but so far no one has been able to identify it with certainty.   If any readers of The Right Blue happen to know the identity of this juvenile, please do let us know.


For reference, here is a photo of an adult Bearded Scorpionfish from the Red Sea.  This specimen was photographed in the central Red Sea at Little Brother (Brothers Islands), where it was trying its best to blend into the reef scenery.

Stalking the wily night critters: Hinge-beak shrimps

by B. N. Sullivan

Imagine that it's just after dark.  You jump off the stern of the boat into the water and descend to the reef.  You switch on your light and sweep the beam  left and right to get your bearings.  You see little blinking red lights all over the place. What the...??

Don't be alarmed.  Aliens have not landed and dispersed on the reef.  What you probably are seeing are reflections from the eyes of tiny critters called Hinge-Beak Shrimps.  All of the shrimps in this family have big googley eyes that reflect when a beam of artificial light is shone on them.

These creatures of the night are little guys, usually between 3 cm to 5 cm (1.25 in to 2 in) in length. They hide all day -- who knows where?  At night they come out to feed,  often in large numbers, but they're not easy to find then either.  Oh, you definitely will see those blinking red lights I mentioned, but if you try to find the actual critter behind the pinpoint of red light you will be unsuccessful much of the time.  These critters are extremely shy, so as soon as you get near -- piff! -- they're gone!

I had wanted to photograph one of these critters for years before I finally managed to do so.  I succeeded in capturing the macro image you see on this page by concentrating very, very hard on where one of those red dots of light seemed to be, then switching off my light and sneaking up to the presumed spot.  In this instance, the tiny red light  seemed to be coming from a pencil urchin, so I assumed the shrimp was hiding among the urchin's thick spines.  I  knelt down very close to the urchin while Jerry shone a small light beam near to it, but not on it, giving me just barely enough light to set up the shot.  I pressed the shutter release and  voilà! Gotcha!

Now, about that funny name, Hinge-beak shrimp.  Shrimps in this family (Rhynchocinetidae) have a beak-like rostrum that can bend.  In fact, the name Rhynchocinetidae actually means 'movable beaks'.  Other kinds of shrimps do not have this feature.

We first encountered these shrimps in the Caribbean Sea where the dive guides called them Red Night Shrimps.  It turns out that the shrimps' bodies are mostly red, but that name referred to the red glow from their eyes at night.  We have since seen species from this family almost everywhere we have dived around tropical reefs at night: Caribbean, Red Sea, Hawaii, and throughout the Indo-Pacific region.  Each locale seems to have its own common name for the creatures in this family.  We think the name Red Night Shrimps really suits them, so that is what we like to call them.

The Armored Division: A Ridgeback Slipper Lobster from Hawaii

What: Ridgeback Slipper Lobster (Scyllarides haanii); length about 20 in (50 cm).
They're edible, but taking them in Hawaii is limited to a state-regulated season.

Where: I took these photos during a night dive at Paniau Cove, Puako, Hawaii.

Click on the photos to enlarge.

Tiger Cowries: The largest cowries in Hawaii

by B. N. Sullivan

Tiger Cowries (Cypraea tigris) have several claims to fame in Hawaii. Two of those claims have to do with their size. The third claim to fame has to do with a traditional use for the shell. (More on that in a bit.)

Tiger Cowries live on tropical reefs in a wide range of places throughout the Indo-Pacific region. They can be found as far west as the Red Sea and the Indian Ocean, and as far south as the tropical shores of Australia. They live as well along the coasts and islands of southeast Asia, and in many locations in the tropical western Pacific. Hawaii is the northeastern-most place on the globe where Tiger Cowries are found.

Tiger Cowries are the largest of the many species of cowries found in Hawaii. Not only that, those in Hawaii grow larger than Tiger Cowries found anywhere else in the world. In Hawaii, Tiger Cowries can grow to nearly 15 cm (about 6 in). Elsewhere, they rarely grow bigger than 10 cm (about 4 in).

Hawaiian Tiger Cowries occur in reef areas at depths from about 4 m to 40 m (about 10 ft to 130 ft). This depth range is another thing that sets them apart from Tiger Cowries found elsewhere. Outside of Hawaii, the species usually is found only in shallow waters, including the inter-tidal zone.

Snorkelers and divers sometimes get to see these shells during the day. Tiger Cowrie shells are very beautiful: they are white or creamy ivory, and covered with irregular dark spots. The spots are mostly brown, but some individuals have a mixture of brown and bluish gray spots. The elaborate pattern of spots on each shell is unique.

The snails usually stay tucked up inside their shells during the day and forage at night, so you have to find one after dark to see evidence of the gray snail that lives inside. At night the animal emerges and crawls along the reef, carrying its shell on its back.

The first photo on this page is a head-on shot of a Tiger Cowrie snail poking out of its shell. If you look closely, you can make out the snail's proboscis and tentacles. It uses these organs to 'sniff' for food and gather it into to its mouth. Tiger Cowrie snails are herbivores -- that is, they eat seaweed and algae.

As the snail moves along to graze at night, it extends its mantle up over the shell. The mantle, with its prickly looking papillae, acts like camouflage when it covers the shell. The snail secretes a mucus that not only facilitates sliding the mantle over the shell, it also keeps the surface of the shell polished and shiny, looking like glazed china or porcelain.

In the second photo on this page, the snail is just beginning to slide its mantle up the side of the shell. In the third photo, the mantle has extended almost completely.

Now, about that third claim to fame. Tiger Cowrie snails are a favorite food of octopus. This was a fact well-known to traditional Hawaiian fishermen, who made lures from Tiger Cowrie shells to attract 'tako' (as octopus is called here in the islands).

Some Hawaii fishermen still use these lures to fish for tako. Writer Jim Rizzuto, well-known in Hawaii for his books and newspaper columns about fishing, discusses these lures and explains how they are made in his book Fishing Hawaii Style, Volume 2 (Honolulu: Hawaii Fishing News, 1987). He notes that the local Tiger Cowrie shell "is easy for the tako to see and is irresistible."

If you would like to try your hand at making a traditional tako lure from a Tiger Cowrie shell, here is a a link to a document from the University of Hawaii at Hilo that tells how to do it: Create a Hawaiian Tako Lure (11-page 'pdf' file).

About the photos: All of the photos on this page are of the same individual. I took these photos during a night dive at Paniau, at the southern end of Puako reef, which is on the western coast of Hawaii's Big Island. Click on any of the photos for a larger view.

Exotic Underwater Nudies - The Spanish Dancer

by B. N. Sullivan

Among the marine invertebrates that divers are likely to encounter in tropical and subtropical waters, some of the most colorful are the nudibranchs (pronounced NOOD-i-brank). These are marine gastropod snails without shells. These molluscs are also known as sea slugs -- a non-scientific term -- but divers and marine scientists alike often refer to nudibranchs by the short-form nickname "nudies."

Nudibranchs are wonderful subjects for underwater macro photography, because most of them are small and very colorful. We have encountered an assortment of nudies literally everywhere we ever have dived, and I have photographed many of those. We thought our readers would like to see and learn about some of the nudies we have come to know, so we decided to run a series on The Right Blue, featuring various 'exotic underwater nudies' (and you all can thank Jerry for coming up with the playful series title!).

To introduce the series, today's featured nudibranch is the Spanish Dancer (Hexabranchus sanguineus). This is the largest nudi we have ever encountered, and some say it is the largest nudibranch in the world, period, growing to a length of up to 40cm (about 15 in). The first three photos on this page are of the same individual Spanish Dancer, photographed during a night dive in the Red Sea. We estimate that it was roughly a foot long (30 cm). When these guys are flattened out on the reef, or crawling on the sand, they look a bit like red doormats!

We chose the Spanish Dancer to introduce our series about nudies because it is large (for a nudibranch) -- and since it is large, it's easier to see its most important external organs. The first photo on this page is a head-on shot of a Spanish Dancer. The two things sticking up are not horns, they are the critter's rhinophores.

Rhinophores are sensory organs that work much like our noses do. They sense 'smells' in the water. Nudies use their rhinophores to locate their food. (Spanish Dancers eat sponges, by the way.) They probably sniff out potential mates with their rhinophores, too.

You might notice that the critter does not seem to have any eyes. Nudies do have eyes of a sort, but no eyeballs. Instead they have little sensory specks embedded on their skin that sense light and dark, but that's all. So, you could conclude that their rhinophores actually are their most important sensory organs.

The name 'nudibranch' means "naked gills," and in the case of the Spanish Dancer, the gills are not only naked, they can't be retracted. Many species of nudies are able to retract their gills into a pouch on their back, but the Spanish Dancer's gills are always exposed. The second photo on this page is a macro image of the Spanish Dancer's six beautiful tree-like gills. The genus name of this creature, Hexabranchus, refers to the presence of six gills.

For comparison, have a look at the photo of two Risbecia pulchella nudibranchs that we posted recently. You can see their rhinophores and their gills quite clearly, but notice that the gills on this much smaller species are not nearly as elaborate as those on the Spanish Dancer.

You might be wondering how the Spanish Dancer got its common name. If you ever saw one of these creatures swimming underwater you would know the answer immediately.

While Spanish Dancers can crawl along surfaces just like any other snail, they have an alternative means of locomotion as well. They can launch themselves into the water column, and 'swim' for short distances by flexing their bodies rhythmically to achieve an undulating motion. The white ruffled margin of their mantle usually is tucked in when they are crawling or at rest, but when they swim, it is exposed. The visual effect is reminiscent of the swirl of a female flamenco dancer's skirt, thus the name Spanish Dancer.

The third photo on this page shows a Spanish Dancer nudibranch as it swam, with its lovely mantle ruffle fluttering this way and that. I have to say, though, that still photos are insufficient to illustrate this behavior. I don't shoot video underwater, but I did manage to find a brief Spanish Dancer video on YouTube, which I will post tomorrow.

Nudibranchs reproduce sexually. They line up side by side to mate, and then lay eggs in a ribbon-like mass. Some nudibranch species lay eggs as a flat ribbon. Others, the Spanish Dancer included, attach the edge their egg mass ribbons to solid surfaces in a spiral pattern. The Spanish Dancer's egg mass is easy to recognize. It is distinctive in that the ribbons are comparatively wide, and once set down in a spiral, they look like a reddish ruffled rosette.

The first photo below shows a Spanish Dancer's egg mass rosette. The second photo below is a macro image that shows the texture.

The Yellowline Arrow Crab (Stenorhynchus seticornis)

by B. N. Sullivan

One of my favorite macro photography subjects on Caribbean reefs is the Yellowline Arrow Crab (Stenorhynchus seticornis). At first glance, these creatures resemble pointy-headed, long-legged spiders. The way they skitter around on those long legs also lends to that first impression.

Once you see a good macro photo of the Arrow Crab, however, you will notice some features that you would never see on a spider. First there is that elongated pointy head, with the goofy eyes protruding on either side. Next you will notice that their legs are jointed, and their 'knees' are a bright yellow color. At the end of each of their forelegs is a little claw. The claws are violet, making them look as if they've just come from the nail salon.

Yellowline Arrow Crabs are abundant throughout the Caribbean, but they are very small, and they are sometimes hard to spot during the day. They tend to find resting spots in nooks and crannies where they stay put during daylight hours. They actively forage at night, so they are quite easy to find on night dives when they are roaming around the reef looking for a meal. By the way, they are carnivores, but you don't have to worry about getting chomped by an Arrow Crab. They eat tiny worms and other itty-bitty animals that populate coral reefs.

They don't seem to be afraid of divers -- even divers with bright lights and cameras -- so once you locate an Arrow Crab, it is fairly easy to photograph it. They don't spook when the camera strobes flash, so the photographer usually will have plenty of time to take a number of shots of a given individual.

I photographed the Yellowline Arrow Crab on this page during a night dive at Little Cayman. This is a 1:2 macro shot. The creature is only about two inches (5 cm) long.

Sexy Stuff on the Reef - Ruby Brittle Stars Spawning

by B. N. Sullivan

Our favorite Caribbean dive destination is the Cayman Islands. In particular, we like to stay on Cayman Brac. From there we can make day trips by boat to dive at Little Cayman, in addition to diving the many excellent sites around Cayman Brac itself.

In fact, one of our favorite night dives anywhere is a site on the north coast of Cayman Brac known as Radar Reef, which reportedly got its name from a landmark visible to boats offshore -- the antennas at a nearby telecommunications facility.

You don't need to hire a boat to dive Radar Reef at night, since it is easily accessible from shore. There is a boat ramp at the shoreline end of Kirkconnell Street at Stake Bay. Some concrete steps alongside the boat ramp lead right into the water, making it incredibly easy to enter and exit the water.

Some undersea communications cables come ashore nearby, and the trick is to locate the cables where they lie on the sandy bottom near the boat ramp, and then follow them offshore to the reef. (They're actually quite easy to spot.) At the end of the dive, you simply follow the cables back to shore again. It's next to impossible to get lost there, as long as you keep the cables in sight.

We've been to Cayman Brac a number of times, and while there, we always do a few night dives at Radar Reef. The area is well populated with small creatures, so it is a macro photographer's paradise. Particularly plentiful are critters that only come out at night. One of those is the Ruby Brittle Star (Ophioderma rubicundum), which forages only at night and hides in crevices in the reef during daylight.

Just before 7 PM one dark August evening, we waded into the water next to the boat ramp, located the cables, and swam out to Radar Reef. Fortunately I had set up my camera for macro photography in anticipation of the small critters we expected to see. Still, we had no idea what an amazing sight we were about to chance upon.

Once we arrived at the reef, in about 45 feet (14 m) of water, we shined our lights around on the coral heads to look for photo subjects. I spotted a Ruby Brittle Star almost instantly. I photographed it, and then noticed there was another of the same species very close by. As I was preparing to photograph the second one, I noticed a third, and then another and another.

Jerry was right beside me, but shining his light on a different coral head. I finished taking a photo, and he nudged me to look where he was shining his light.

There we saw more Ruby Brittle Stars -- lots more. Dozens and dozens of these critters seemed to be appearing out of nowhere, converging on the reef. They were literally draping themselves all over the coral, the sea fans, and the sponges growing on the reef. We had never seen so many Ruby Brittle Stars in one place at one time. We both had the feeling that something was going on, but we didn't know what.

I took a few more photos, and then we began to notice that some of the brittle stars appeared to be standing up. We had never seen this behavior before, but here they all were, standing up on their tippy-toes, raising their disc-shaped bodies off the corals or sponges where they had been resting flat a few moments earlier. They were beginning to look like so many miniature footstools.

Now completely fascinated, I shot frame after frame of what to us was a novel behavior. Then all of a sudden, the critters -- still balancing on the tips of their rays -- began to eject clouds of tiny red beads into the water. It took just a few seconds for the realization to hit us: these brittle stars were spawning!




As soon as they finished expelling spawn, the brittle stars ceased their peculiar uplifted posture and dropped back down into their more usual flat position, rays extended around them. Some individuals were entwined with others, but now they all just lay there. With their spawning orgy over, the brittle stars became immobile. They seemed totally spent -- in more ways than one!

We noticed little else on that dive, and I never did photograph anything but the Ruby Brittle Stars that night. I was shooting film, and I very quickly shot the entire roll of 36 frames, all the while thinking what incredible luck it was that brought us there to just the right place, at just the right time, to witness this amazing mass spawning event.

The photos on this page all were taken during that one night dive at Radar Reef. These photos are 1:2 macros. To give you an idea of the actual size of these creatures, the body disc of the Ruby Brittle Star is about a half inch (1.3 cm) across.

I have reduced the size of some of the photos on this page so that they all would fit into the text. You can click on any of them to see a larger view. In particular, you may want to look at the enlarged view of the 4th and 5th photos, so that you can see the red spawn more clearly.

Caption: "Was it good for you??"

Swing yer partner, do-si-do...

What: Caribbean Spiny Lobsters (Panulirus argus)

Where: I took this photo of the 'dancing' lobsters during a night dive
off West Caicos, in the Turks & Caicos Islands.

[Click photo for larger view.]

My previous Wordless Wednesday posts.

Bubble Coral

by B. N. Sullivan

We have displayed a lot of photographs of reef scenes on The Right Blue. Reefs are formed by corals. The stony corals in the order Scleractinia are the reef-building corals that secrete calcareous skeletons for their polyps, which accumulate over time to become the hard framework of reefs.

We have posted quite a few photos of different kinds of soft corals, ranging from 'broccoli coral' and other Nephtheids to sea fans. Soft corals generally are more colorful and showy, and so they often are more attractive subjects for photography, but without hard corals, there would be no coral reefs. Until now, we haven't really focused much on stony corals, so we thought it was time we introduced some of the more interesting ones to readers of The Right Blue.

Some hard coral colonies form massive lumpy structures that look much like rock. Other stony corals form into fingers, pillars, antler-like branches, or even structures that look like plates. The ridged ones commonly referred to as 'brain coral' belong to the stony coral group, too.

One of the more unusual-looking stony corals we know about is Bubble Coral, an organism in the family Caryophyliidae. The first photo on this page shows a large colony of Bubble Coral on a reef in the Red Sea. If you click on the photo to enlarge it, you will see clusters of what look like bubbles -- thus the common name. Those bubbles, or 'vesicles' as they are properly called, are little balloon-like structures with rubbery skin that inflate during the day.

At left is a macro photo of the vesicles. The species in these photos, Plerogyra sinuosa, is quite common in the Red Sea. Usually it is found on steep slopes or on the vertical walls of underwater cliffs at depths of about 15 meters (50 feet) to about 40 meters (130 feet). I shot the first two photos on this page at Ras Mohammed, a well-known reef at the tip of the Sinai Peninsula.

I took the third photo on this page during a night dive off the coast of Tiran Island, which is situated at the mouth of the Gulf of Aqaba. Although we are not 100% certain, we believe that the organism in the photo is Bubble Coral of the same species as the photos above. Unfortunately, we did not get to return to the same spot in daylight to verify that this was indeed Plerogyra sinuosa.

At night, Bubble Coral looks very different than it does during daylight hours. The Bubble Coral's vesicles deflate, exposing its tentacles and its mouth.

In the photo at right you can see what appear to be the partially deflated vesicles, as well as the little tentacles. The tentacles can sting.

By the way, the vesicles of this species usually are whitish, often with striations of grey or very pale blue. They are translucent, and can look slightly opalescent. We have seen Bubble Coral elsewhere with a golden or greenish tinge. Next time we'll show you some more Bubble Coral, this time from Indonesia. The Bubble Coral we saw there had some 'extras' that led us to think of it as Bubble Coral Plus.

Crinoids - Also Known As Feather Stars

by B. N. Sullivan

In the previous post, about our final dives on the wreck of the Zenobia, I mentioned that we saw crinoids inside the shipwreck. As I wrote that, I realized that many readers, and especially non-divers, probably had never seen or even heard of crinoids. They're strange creatures, and I was hard pressed to describe them for that story, so I thought it would be a good idea to show readers of The Right Blue what a crinoid looks like.

The photos on this page show a crinoid known as Klunzinger's Feather Star (Lamprometra klunzingeri), a species found commonly in the Red Sea. This is not the species we saw inside the Zenobia, but these photos should work well to illustrate what a crinoid is like.

Crinoids belong to the same phylum (Echinodermata) as sea stars and urchins. The phylum name means "spiny skinned" and most members of the phylum do have some kind of spiny structures on their outer coverings.

The crinoids have feathery arms, which are jointed. They can (and do) bend every which way. The arms have rows of protrusions, called pinnules, which run the length of the arm, making them resemble feathers. The crinoids catch their food by extending their arms like a fan. Bits of plankton are caught on the pinnules.

These creatures also have a set of appendages, called cirri, that serve as feet. They can move along on the cirri a little bit, but they also use their feathery arms to propel themselves. Sometimes they bend their arms down in a sort of arc, and use them like extra legs to skitter across sand or other flat surfaces. They use their cirri to hold on tightly to whatever they decide to perch upon.

There are teeny tiny hooks on their ends of the cirri, which help them to grab onto their perch. We have seen these actually puncture a sponge enough to leave a scar. I should also add that, on occasion, we have attempted to move a crinoid from one location to another. It's fairly easy to put a gloved finger next to a crinoid's little feet, and nudge it to perch there. The trouble comes in getting the crinoid to release its hold on that gloved finger again!

Some crinoids, including the species pictured here, are nocturnal creatures. They fold themselves up into a ball and hide in crevices in the reef during daylight hours. They usually emerge from their hiding places at dusk, and situate themselves on a favorite perch -- on coral, a large sponge, a sea fan -- wherever they can anchor themselves well. Then they unfold their feathery arms and feed all night, returning again to their hiding places at first light.

Nocturnal crinoids are sensitive to light. When they are exposed to a bright light, they immediately begin to fold in their arms. For this reason, it is sometimes difficult to photograph them in their full glory, with all their arms completely outstretched. Crinoids are fairly plentiful on many reefs, so they are relatively easy to find during night dives. However what often happens is, we shine our lights around and spot a lovely crinoid, but as soon as it senses the light beam it begins to curl up. So, we switch off our lights and wait. Eventually the crinoid will unfold again, but then the photographer is lucky to get more than one or two shots before the light from the camera's strobe prompts the crinoid to fold into itself again. It takes patience to photograph crinoids.

The two photographs on this page were shot in quick succession. In the first photo, the crinoid's arms are fully extended. (Take note of its little cirri, hanging onto the coral it has chosen as a perch.) In the second photograph, the crinoid already is reacting to the light emitted by the flash during the first shot, so it's beginning to curl up. I photographed this crinoid during a night dive in the Red Sea, off the coast of Egypt's Sinai Peninsula. [Click on the photos to enlarge.]

Do Not Disturb: Sleeping Fish

by B. N. Sullivan

We all need our rest, and so do the fish in the sea. Fish don't sleep exactly like we do. For one thing, they don't have eyelids, so they can't close their eyes. Nevertheless, most fish we know about do take their rest for some part of the day or night, on a fairly regular schedule.

Some fish -- especially pelagics -- hunt at night, and rest during the day. Most reef fish are very busy during the day, so they rest at night. They stop moving about and enter a sleep-like state. While they are resting, they are generally sluggish and not very alert. We try our best not to startle them or disturb their rest during our night dives.

Some fish lie on the bottom to rest, while others hang motionless in the water column. Small fish, in particular, often hide while they are in their somnolent state so that their predators can't find them and eat them. Staying out in the open to rest definitely would give their predators an unfair advantage. In the first photo on this page, a tiny fish called a Pygmy Toby (Canthigaster pygmaea) has snuggled itself amongst corals and sponges to "sleep."

In the second photo, a small fish has chosen to settle into a stand of fire coral to takes its rest. We're not sure what species of fish this is, although the shape suggests that it is some kind of Damselfish.

In addition to hiding, another strategy that many fish use to discourage predation while they rest is to change color. Their color may darken or become mottled during periods of rest, helping them to blend in with their environmental background.

Some species of Parrotfish hide themselves by spinning a slimy cocoon around themselves. The mucous cocoon is secreted from an organ in the head of the Parrotfish. (Sorry, I don't have a photo handy.) It is thought that, in addition to hiding the fish, the cocoon also masks the animals' scent, making it harder for predators to locate them.

Both of the images on this page were captured during night dives in the Red Sea, along the coast of the Sinai Peninsula.

Nephtheid Soft Corals - Pale Pastels

by B. N. Sullivan

In the past several posts, we've been displaying images of soft corals of the Nephtheidae family. To soothe any damage we may have inflicted on our readers' retinas with yesterday's collection of corals with fiery colors, today we're presenting images of Nephtheid corals in pale pastel colors.

By the way, the species of a Nephtheid soft coral cannot be determined merely by looking at the colors. Corals of a particular species in this family may come in a variety of colors.

All of the corals on this page, as well as on yesterday's post, belong to the genus Dendronephthya, but we're not certain of the species. In fact, I have been told by a marine biologist friend who studies these corals, that the only reliable way (short of DNA analysis) to identify a species of Dendronephthya is by examining certain internal structures, called spicules, with a microscope. In other words, it's next to impossible to reliably determine the species in the field.

For our purposes, we don't mind that we can't be sure of the exact species. When it comes to soft corals, we have been more concerned with collecting images of the different color varieties than with precise species identification. We're content just to know that these are Nephtheids.

At first glance, the more brightly colored varieties certainly are impressive, but we think there is something appealing about the pastels, too. The paler colors suggest a certain fragility, perhaps.

The stalks of almost all of these corals are somewhat translucent. But take a look at the macro image at right: The stalk is nearly transparent! (To see even more detail, you can click on any of the photos on this page to enlarge.)

Some of the corals in this family have greenish coloration, making them resemble plants. A common nickname for those varieties is Broccoli Coral. Other Nephtheid soft corals are sometimes referred to as Carnation Coral. The series of images below may give you an idea of why they acquired this common name.

I took all of the photos on this page while diving in the Red Sea, at reefs along the Sinai Peninsula. I hope you enjoy them.

Nephtheid Soft Corals - Fire in the Night

by B. N. Sullivan

This past week I began a series about soft corals in the Nephtheidae family, arguably some of the most beautifully colored marine life on the planet. I mentioned that these corals come in a wide variety of colors, and that while they sometimes look like plants, they are in fact colonies of small animals -- coral polyps -- that arrange themselves in bundles on a stalk or stem.

I have a big problem with these corals: There are so many wonderful colors and varieties that I can't stop taking pictures of them!

The colors range from pastel pale, to richly saturated, to just plain knock-your-eyes-out. Today, we'll show you a few that we call "Fire in the Night" -- brilliant reds, oranges and golds.

I took all of the photos on this page during night dives in the Red Sea. These Nephtheid varieties feed mostly at night, so that is when they are plumped up and looking their best, with their feathery tentacles extended like flower petals. Click on any of the photos to enlarge and see more detail.

The first photo on this page is a a soft coral that had attached itself to the underside of a ledge. This bright red and yellow color combination is, to me, the prototypical "Fire in the Night" color. In case you are wondering, that is not an official name; it's just our name for this color variety.

Next is a macro shot of that same coral. You can see that it is the tentacles of the polyps that are bright red. The stalk itself is relatively pale. Those bright yellow bits on the surface of the stalk are sclerites -- hard structures that help it to hold its shape when it is plumped up. They serve a purpose similar to battens in a sail. They also pose a lighting problem to photographers, since they tend to be more reflective than the rest of the coral.

This next variety is a little less fiery than the one above, but is definitely bright and rich. We call this "Golden Glow." This time it's the stalk and sclerites that are golden, while the tentacles on the polyps are almost white.

A similar variety is the one we call "Hot Peach." It has a yellowish stalk, and bright yellow sclerites, but the flower-like polyps are a rosy pink. The combination of the yellows and pinks make it look quite "peachy," we think.

We'll wind up today with a macro shot of the "Hot Peach" color variety. According to my dive log, this image was captured just after dusk. The photo clearly shows that the tentacles were not fully retracted, but not yet fully extended, either.

These corals are not exactly easy to photograph. First of all, they don't need bright sunlight to prosper, so many of them live in deep water, or under ledges and overhangs, or inside cavelets. So, first the photographer has to find them.

Secondly, since these corals are bushy and branchy, they have many planes, and it's difficult to choose a point of focus. Also, since some parts -- especially those calcareous sclerites -- are more reflective than other parts, lighting them evenly can be a challenge.

Shots like the ones on this page were taken at night. Often there is virtually no ambient light underwater at night. So, the photographer (and her helpful dive companion) must locate the subjects to photograph by shining their handheld searchlights this way and that. It helps a lot if the team already has done at least one thorough survey of the area during daylight!

Next, the photographer composes the shot in light provided by a submersible flashlight. Underwater strobes only light a relatively small area -- so the photographer really has to get in close. Meanwhile we have to mind our buoyancy, depth, elapsed time, and our air supply, among other technicalities. But somehow it all comes together, at least some of the time.

Next time we'll show you some paler specimens of Nephtheid soft corals from our photo collection.