Meet the Mantis Shrimp

Let me introduce you to one of our favorite marine creatures: the mantis shrimp. Why are they a favorite? They're cute (sort of), they're very smart (for a crustacean), and they're fun to watch. Unfortunately, they're also difficult to photograph -- more on this a little later!

The individual in the photos on this page is a Shortnose Mantis Shrimp (Odontodactylus brevirostris), from Hawaii. I know that the critter looks pretty big in these photos, but it's not. These are macro images. The mantis shrimp in these pictures was only about two inches (5 cm) long. You can click on any of the photos to see a larger view.

Despite the name, mantis shrimps are not true shrimps. I guess I don't need to explain that they are not mantises, either -- although they apparently acquired their name because they resemble praying mantises somewhat. Like crabs and lobsters and true shrimps, mantis shrimps are Crustaceans.

All mantis shrimps belong to the order Stomatopoda. Stomatopods have a number of features that set them apart from other crustaceans. Among the most notable -- and noticeable -- are their raptorial arms, and eyes that are highly evolved.

Mantis Shrimp Eyes

I've always wondered what the undersea world looks like through the mantis shrimp's eyes, because their eyes are like no other eyes. Take a look at the photos, and notice that the eyes are set at the end of stalks. Each eye is independently movable -- and they seem to move constantly, giving the critters a hyper-alert look. Each eye is trinocular, that is, each has three separate perceptual regions. This would be sort of like having built-in trifocal lenses, except that instead perceiving things at three different levels of magnification, each eye region is specialized to perceive a different kind of visual information -- but all at once.

Mantis shrimp eyes are capable of hyperspectral vision. In other words, not only can they see the visible light spectrum, like we can, but they also can see spectra of light that we cannot, including infrared and ultraviolet. Very recently it was discovered that mantis shrimps have the ability to perceive circular polarized light, too.

Raptorial Appendages

The mantis shrimp's raptorial appendages actually are legs that have evolved into claw-like arms, specialized for killing prey. There are two types: some species have thin, barbed raptorial arms that can spear prey; others have club-like raptorial appendages that smash their prey. (The mantis shrimp species in the photos is a 'smasher'.) When mantis shrimps are at rest or walking about, they keep those killer appendages folded up like closed jack-knives against their bodies, just as the creature in these photos is doing. When they go after prey, those appendages unfold at an incredible speed and they spear or whack the prey.

The spearers tend to choose soft-bodied prey like worms and little fish. The spearers are ambush predators. That is, they sit quietly and concealed until prey comes along and then they attack. In contrast, the smashers usually pursue their prey -- and that is one of the mantis shrimp behaviors we love to watch, when we get the chance.

The smashers use their raptorial arms not just to kill prey, but also to break it apart to eat. The species in the photo eats things like small crabs, and gastropod snails that live in shells. When the mantis shrimp sees one of those and goes after it, first he punches it silly, then he uses his raptorial arms to crack open the shell so that he can pick out the meat with his little forward legs, which are also specialized for that purpose.

The Star of the Puako 'Petting Zoo'

The mantis shrimp in the photos on this page lives off the coast of Puako, Hawaii in an area where we have made countless dives. When you dive in the same area again and again and again over a period of years, you become aware of things that a visiting diver probably never would notice in the course of just a few dives. One thing you learn is where all the different types of creatures live. Except for pelagics that roam the open sea, most marine creatures have a relatively small range. Once you spot where they live, you can usually count on seeing them in the same general area any time you go there. Once you know where to look, there they will be.

Puako has a wonderful fringing reef that parallels the shoreline for a couple of miles. The coral reef area is beautiful, and very accessible, but there are areas beyond the reef that are just as fascinating, if not quite so pretty. Where the seaward edge of the reef ends there is a steep slope. The top of the slope has many rocks and is still covered with quite a lot of coral, but deeper on the slope where less sunlight penetrates there is little live coral. There are more rocks, plus lots and lots of coral rubble -- lumps of dead coral washed down the slope from the reef over time. At the base of the rubble slope the terrain levels out into a sandy plain.

There is an area near the base of the rubble slope, at a depth of about 100 ft (30 meters), that we named the Petting Zoo. We called it that because it teems with small creatures. Sometimes we would go directly to the Petting Zoo, plop ourselves down in one spot, and spend the entire dive watching all the little creatures go about their business. You can learn a lot about marine creatures' behavior that way.

On one of our visits to the Petting Zoo, we noticed this particular mantis shrimp. Some mantis shrimp species are nocturnal, i.e. they only come out at night. This species works the day shift. We first saw him when he emerged from his burrow and began scurrying about. Mantis shrimps can swim a bit. If you look at the second photo above, you'll notice that this creature has a tail not unlike that of a lobster. They can use their tails to propel themselves through the water for short distances, but their more usual method of locomotion is to run about. Notice I said run. They move quickly -- usually too quickly to get a good macro shot.

Mantis shrimps live in burrows. This one had excavated a double-ended tunnel under the sand. I have no idea what it's like inside the burrow -- we used to joke that he probably had an overstuffed chair and a TV in there for all we knew. We did notice that outside the entrance to the burrow we would sometimes see pieces of broken shell in little piles. A few times we saw the critter in the process of housecleaning -- literally throwing bits of shell out the door.

On successive visits we saw this mantis shrimp stalk and kill prey -- usually a small crab. One time we saw him smack a crab that was bigger than he was, dismember it, and drag the body to the opening of his burrow. The mantis shrimp disappeared inside the burrow for a few minutes, then re-emerged and whacked the shell of the now legless crab a couple of times to crack it open and began to dig out the 'meat' for his feast. We watched him until it was time for us to begin our ascent. He was still working on the crab when we left. When we came back a day or two later we looked for the remains. Sure enough, there was a recognizable piece of the crab's empty shell not too far away from the entrance to the mantis shrimp's burrow.

I mentioned in the first paragraph of this article that mantis shrimps can be difficult to photograph. That's because they seem to be in motion constantly when they are outside their burrows. It's not too difficult to get a shot of one peeking out of its burrow, but capturing an image of the whole animal had eluded me for years.

Then one day at the Puako Petting Zoo, this little mantis shrimp came out of its burrow and just stood there looking at us. And -- Hallelujah! -- not only did I have my camera, it was set up for macro photography. Moving as slowly as I could, not to startle the critter, I lay down on my belly on the sand at the edge of the rubble slope, and sort of inched toward the mantis shrimp. He didn't run away.

I focused carefully on his wonderful eyes and pressed the shutter release, figuring this would probably be my one and only shot. So often in underwater nature photography, the flash of the strobe startles a photo subject and it quickly leaves, so one shot is all you get. But no, not this mantis shrimp. I expected him to high-tail it to his burrow, but instead he actually came toward me a bit, stopped and turned sideways, almost posing. Now practically touching him with the end of the lens port, I took another shot, and a third.

Then he turned the other way and positioned himself as if to say, "How's this? Can you see my tail a little better now?" I shot once more, and then he finally scampered over to his burrow and disappeared inside. I did press the shutter one more time while he was in retreat, but his movements had stirred up the sand by then.

I've often wondered what it was that made that mantis shrimp decide to be such a cooperative photo model that day. I've never again had an opportunity like that.

The Cave Where Turtles Die

Back in the early 1980s, the famous ocean explorer Captain Jacques Yves Cousteau and his team made their first visit to Sipadan Island, off the coast of Borneo. They made a film about Sipadan, and one of the highlights in that film was an eerie cave in which they found many bones and skeletons of sea turtles. They had never before seen such a sight, and they were puzzled by it. At the time, they theorized that perhaps old sea turtles just went there to die.

About a decade after Cousteau's first visit to Sipadan, we went there to dive. We had heard about the legendary turtle cave, and it was one of the things at Sipadan that we wanted to see for ourselves. Since it's a potentially dangerous dive, the Sipadan Turtle Cave is restricted to experienced divers who have had appropriate training, and it is essential to go with a guide who knows the terrain inside the cave. Fortunately, we were able to make arrangements to dive the Sipadan Turtle Cave with a veteran guide who knew the cave well.

As underwater caves go, this one is not particularly deep. The entrance to the cave is in the side of a limestone wall that begins a few meters below the surface and plunges straight down to a depth of about 600 meters (about 2,000 ft.). The mouth of the cave, found at a depth of only 20 meters or so (about 65 ft.), is small and partly disguised by large soft corals.

Just inside the cave's narrow mouth is a fairly roomy chamber, where we paused to let our eyes begin to adjust to the darkness. Once we passed beyond this first chamber there was no ambient light at all, so of course the three of us -- the guide, Jerry, and I -- carried multiple lights with us on this dive.

What makes the dive tricky is the cave's interior terrain - an intricate maze of chambers connected by narrow tunnels. The tunnels are not straight: they curve this way and that -- not just left and right, but also up and down, as if the whole works had been built as a bed for a roller coaster.

The bottom of the entire cave system was covered in fine, silty sand, so we had to be extremely careful to stir it up as little as possible as we went along. Once fine sand gets stirred in small spaces like that, visibility is quickly reduced to zero.

We saw and photographed the famous turtle skeletons, which we came across in several of the cave's chambers. Some were no more than disorderly piles of bones, like the first photo on this page. Others were more complete skeletons, with half-disintegrated carapaces, and goofy looking turtle skulls, like the second photo. [Click on any of the photos to enlarge.]

While Cousteau and his group conjectured that old or sick turtles may have gone there intentionally to die, our guide told us that Cousteau's original notion had been replaced more recently by a more prosaic explanation: Turtles occasionally wander into the cave system, perhaps to rest, or to hide from a predator, or maybe just out of curiosity. Then they become lost in the dark, disorienting interior of the cave. When they need to surface for a breath of air, they can't find their way out, so they drown. This explanation, while not as romantic as Cousteau's, made sense to us.

Turtles are not the only air breathing animals to have drowned in that cave. In one of the cave's chambers our guide used his light to direct our attention to a rocky ledge. There was the complete skeleton of an unlucky dolphin, which had shared the fate of the hapless turtles.

Diving in the Sipadan Turtle Cave was one of the highlights of our time at that remarkable little island in the Celebes Sea. We recently unearthed a cache of photos from our first trip there -- not just underwater photos, but some taken on the journey there, and on the island. For the next several posts, we will share some of those photos, and the tales that go with them. Stay tuned.

On a collision course with critters in the sea

This post was inspired by a comment on our Rush Hour On the Reef photo in which Chris asked, "It's probably a fairly silly question, but do you ever get run into by fish?" The short answer is, "No, not really." But we have had some very close calls.

Little fish, like the fast-swimming Fuslier Fish we showed you recently, often approach in a large school, and at a high rate of speed, but they manage to steer en masse around obstacles -- including divers -- by making high-speed turns in unison, or simply by splitting the school for a moment, with half the fish passing on each side of the diver. Once past the obstacle, the fish reunite into one school again and continue on their way.

Other kinds of small fish that form dense schools do more hovering than swimming around. Sometimes a diver will encounter a dense school of Sweepers or Glassfish hovering in an underwater canyon, or even inside a shipwreck or a cavelet. As the diver (or a large fish) swims toward the apparent wall of little silvery fish, they may scatter. More often, though, the school simply parts like two halves of a stage curtain to allow the bigger swimmer to pass through, then closes again afterward. It can be an amazing sight, and an almost dream-like experience.

In sum, smaller fish usually get out of the way of larger fish and divers, one way or another. Now let's talk about larger fish -- much larger fish.

Over the years, we have noted that the larger the animal, the more likely it will notice divers and even come close to have a look. On occasion they come very, very close.

Consider the photo at right: that's a Whitetip Reef Shark (Triaenodon obesus). I first saw this particular shark while it was about 75 feet (23 meters) in front of me. It was coming toward me at a leisurely pace, so I settled into position and aimed my camera, hoping it would come close enough for a good photo.

Through the viewfinder I watched it come closer and closer, heading straight at me now. It had spotted me, for sure.

About two seconds before I snapped the shutter for this shot I thought I might have to duck out of the way, because the shark had now picked up speed a bit and I feared it might bump into me, head on. I knew it had seen me, so it was starting to feel like a game of chicken! Then at the last moment, the shark made a sharp right turn directly in front of me and swam off (as if that had always been what it had intended to do!), avoiding a collision.

This was neither the first nor the last time that one of the larger species on the reef had intentionally come right up to one or both of us to look us over, and made a very close pass. In fact, sharks and barracudas often do this. So do large groupers, wrasses, jacks, and every kind of marine mammal we've ever been with in the water, including dolphins and whales. (Long-time readers of The Right Blue will recall our tale of close encounters with humpback whales.) But none of these cases ended in a collision, either.

On the other hand, we've had, or witnessed, quite a number of very close calls -- near-collisions with big critters in the sea. Usually this happens when two critters, or rather a critter and a diver, round a corner or swim over a rise at the same time from opposite directions, unaware that the other is approaching until they nearly collide.

Another scenario for close scrapes occurs when a diver inadvertently startles an animal, and the animal reflexively attempts to escape the scene. Once, while diving with a good friend and a visiting diver, we took the visitor to a place where we knew Whitetip Reef Sharks went to rest. The spot was a sheltered cavelet in the face of an underwater cliff. We approached carefully from below the cavelet and quietly positioned ourselves so that we could peek inside. My friend shined his light onto the ceiling of the cavelet, so that the light reflected down just enough for us to see two sharks 'sleeping' inside. The visitor, wanting to get a better look, shined his light straight into the cave, right into the face of one of the sharks. The shark startled and shot out of the cavelet like a missile, grazing my friend's head on the way, and knocking off his dive mask in the process.

On another occasion, Jerry and I passed below a ledge where drowsy sharks sometimes lolled. I was in the lead, with Jerry following just a meter or two behind me. As best as we can reconstruct what happened, we think my exhaled air bubbles must have passed by a shark on that ledge and disturbed it. It was another 'missile launch' situation, but this time the shark swam between Jerry and me, and as it did, it passed right in front of Jerry's face. Reflexively, Jerry's arms shot forward and he shoved the shark. This shocked the poor shark even more, and it sort of jack-knifed sideways. By this time I had turned around, and now the shark went berserk, probably thinking we were trying to corral it. It swam around frantically in a very tight circle for two or three revolutions (like a puppy chasing its tail) before it saw its opening and catapulted itself from between us and went careening down the reef. We stared after it until we could no longer see it, our hearts pounding from the unexpected excitement on an otherwise tranquil and leisurely dive.

Here's one more photo from a near-collision we had with a large stingray. From a technical point of view, it's a lousy shot, but I'm posting it anyway because it has such an interesting story.

We were on a deep sandslope, where I was shooting macro photos of small creatures that inhabited the nooks and crannies of a large, irregular rock. We were both crouched over the rock, engrossed in the task. Jerry looked up briefly, just in time to see an Amberjack swimming up the slope, heading right toward us. Jerry nudged me and pointed toward the Amberjack. I turned my head to look, and noticed that there was another, darker creature moving along the sand, beneath the Amberjack. In one of those 'lightbulb' moments of comprehension, we instantly recognized that we were witnessing a rare sight: a large deep-dwelling stingray species hardly ever seen by divers. Even though my camera was set up for macro, I whirled around and snapped this one shot, just as the Amberjack veered away, and the stingray sort of skidded to a stop, touching me, but just barely.

What looks like snow in the photo is light from my camera's strobe, reflected on sand particles that the stingray and I had stirred up at that moment. An instant later the big stingray did an urgent about face, stirring up a huge cloud of sand particles as it quickly retreated back to the depths.

In case you are wondering about the stingray, it looked to be about 1 to 1.5 meters across. It is either a Hawaiian Stingray (Dasyatis brevis) or a Brown Stingray (Dasyatis latus), but the photo is not clear enough to determine which it is with certainty. Both are known to inhabit deep sandy areas in Hawaii. They are uncommon around reefs, so they are rarely seen by divers. This was one of only three or four encounters we have had with one of these stingrays in all our years of diving in Hawaii, and this was the only time I got to photograph one.

Have you ever seen a pregnant shark?

Someone we know saw a TV program about sharks, and learned that while some shark species lay eggs, others give live birth. He asked us, "Have you ever seen a pregnant shark?"

Yes, we have seen pregnant sharks, and I even managed to photograph one. At right is a photo of a pregnant White Tip Reef Shark (Triaenodon obesus) that I took at Sipadan Island, off the coast of Borneo. She looks like she is about ready to pop! [Click on the photo to enlarge.]

This species is known to breed in the Autumn and Winter. The gestation period is thought to be about five months. Whitetip Reef Sharks give birth to litters of two or three pups.

As soon as the pups are born they are on their own. The mama shark does not look after the pups in any way.

As a comparison, here is another photo, taken on the same dive. This second photo shows a human observer with a White Tip Reef Shark that is not pregnant. As you can see, individuals of this species are rather slender and sleek -- torpedo-shaped. The poor pregnant female above looks ungainly in contrast.

By the way, this location at Sipadan was a shark-lovers' paradise. We had never before (nor have we since) seen so many sharks in such a small area.

There were big sharks, little sharks, and medium sized sharks of assorted species. There were sharks swimming, and sharks lying on the bottom resting, sometimes lined up in rows like parked cars.

And there was one pregnant shark!

Crinoids - Also Known As Feather Stars

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!

Crinoids 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.

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

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.

The Leaf Scorpionfish

Meet the Leaf Scorpionfish (Taenianotus triacanthus). This little fishie is one of the smallest members of the Scorpionfish family. This fish family, Scorpaenidae, gets its name from the venomous spines that most of the fishes in the family bear. (Regular readers of The Right Blue will recall our posts about the Turkeyfish/Lionfish -- another member of the same family.)

The Leaf Scorpionfish gets its name from its appearance. When you see one in its natural environment, it really does look like a leaf, rather than a fish -- until you spot its eye! Members of the Scorpaenidae family tend to be "lie-and-wait" predators. They tend to stay still in one spot until their prey happens past, and then they pounce very suddenly. They rely on camouflage so that they can blend into their surroundings, making it easier for them to surprise their prey.

The bodies of Leaf Scorpionfish are laterally very flat, which certainly contributes to their leaf-like appearance. This little fish not only looks very much like a leaf, it also behaves like a leaf! If you stay still and watch one for awhile, you'll see the little guy rock back and forth every once in awhile, just as a leaf or a stray piece of seaweed would do if it had settled on the reef. This, too, seems calculated to trick potential prey.

The Leaf Scorpionfish is a small species -- maximum length is about four inches (10 cm). They come in lots of colors -- yellow, reddish, purple, brown, pale pink, and off-white. They often have blotches, which enhance their camouflage, and they sport little fleshy appendages on their heads and chins that look like little weeds growing on them.

The photos on this page show examples of some of the color variations of the Leaf Scorpionfish. Despite the range of colors, they are all the same species. (Click on the photos to enlarge.)

The first photo on this page shows a purple Leaf Scorpionfish. You can see that this individual has a lot of blotches. If you see a scuzzy-looking Leaf Scorpionfish, he's probably getting ready to molt, which they do periodically. Soon after they molt they look much less blotchy. Sometimes the color looks a bit different after molting, too.

The second photo is a 1:1 macro shot of a Leaf Scorpionfish that we watched over a period of many months. In the second photo, you can see the little fleshy appendages on the fish's chin quite clearly. It's all part of the disguise.

We've noticed that when one of these fish finds a good spot on the reef, they tend to stay put in the same small patch of real estate for a long time. Once one is located, it's a safe bet that a diver will be able to return to the same spot again and again, day after day, month after month, and see the same little fish. Good dive guides know this, and that is why they can reliably lead divers and underwater photographers to a Leaf Fish almost at will.

The final photo on this page shows one more color variety. This yellow Leaf Scorpionfish is perched on a coral head. We have noticed that smaller Leaf Scorpionfish often tend to hide in the coral this way, while the larger ones seem to prefer a spot on a rocky bottom. We don't know why this is so, but we surmise that the little ones may feel safer in the coral, since it affords them some protection. They can hunker down if there's a lot of surge, for instance.

I took all of the photos on this page at Puako, Hawaii, at depths ranging from less than 20 feet (6 m) to about 125 ft (38 m).

Nephtheid Soft Corals - Pale Pastels

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

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.

Broccoli Coral

This is the second in a series of posts intended to showcase the many colors and shapes of soft corals in the taxonomic family Nephtheidae.

In the first post I mentioned that these corals appear in a countless array of colors. Most grow as tree-like structures having a stem, or stalk, with many branches. Near the ends of the branches are clusters of polyps which open like tiny flowers when they are feeding. When the polyps are closed, they look like little beads.

In fact, when the polyps are retracted, these corals -- especially the greenish colored ones -- resemble broccoli plants, and "Broccoli Coral" is one of the common nicknames given to this type of coral. One look at the photo here, and you'll understand why. (Click on the photo to enlarge.)

Although this kind of coral can resemble broccoli in appearance, it definitely is not a plant. It is a colony of animals -- the coral polyps. The polyps arrange themselves in bundles at the ends of the rubbery stalks. Each polyp has exactly eight short, feathery tentacles. In order to feed, the polyps open and close their little tentacles, grabbing tiny nutrient particles that are suspended in the water.

Many Nephtheid coral colonies contract during daylight hours, making them look a bit shrunken and withered. They expand to feed at night, plumping themselves out and extending all of their little tentacles like bouquets of flowers at the tips of their stalks. For this reason, many of the best photos of these corals are taken during night dives.

I took the photo on this page in the Red Sea, during daylight hours. You can see that the polyps are tightly shut. In tomorrow's "Wordless Wednesday" post, you'll see some macro photos of this same variety of soft coral.

A little fish with a big job

This is an enlarged photo of a little bitty fish --but he's a little fish with a big, important job. Meet the Hawaiian Cleaner Wrasse (Labroides phthirophagus).

These little fellows -- only two to four inches long as adults -- make their living by keeping other fish clean. They are an important part of the reef community.

The little cleaner wrasse stakes out a spot on the reef, usually near a prominent coral head. He hovers above the coral in a head-up posture and wiggles. That's the cleaner wrasse equivalent of turning on a neon sign that says "OPEN."

Other fish come as clients to the cleaning station to be rid of bits of old scales, dead skin, and small parasites that they may have acquired. The client fish swims up to the cleaner wrasse and stops. The cleaner wrasse approaches and gives his client a once over, looking all for extraneous bits, which he then pecks off. This service can take anywhere from a moment, to several minutes, depending on how big the client is -- and how scruffy!

Here's a photo of a Hawaiian Cleaner Wrasse servicing a Spotted Puffer (Arothron meleagris) at Puako. [And yes -- in case you were wondering -- the Spotted Puffer is a first cousin to the Stripebelly Puffer that we showed you a number of weeks ago. They belong to the same genus.]

These cleaning stations serve pelagic (open ocean) fish as well as reef fish. It's not unusual to see animals like sharks, manta rays, and large jacks waiting their turn at busy cleaning stations.

Once a cleaning station is established, it will exist for a long time -- even for years -- in the same spot. Client fish learn where it is, and return to it again and again. The busier cleaning stations may have several cleaners at work -- much like a barber shop with multiple chairs.

Some fish that don't clean other fish full time, do become cleaners from time to time. An example that comes quickly to mind are the several species of fish that clean turtles here in Hawaii. It happens that turtles' carapaces sometimes get covered with a film of algae. Certain fish that are primarily algae-eaters will clean the turtles' shells -- not because they are trying to clean them but because they like to eat the algae, regardless of whether it's growing on a rock, on a coral head, or on the back of a turtle.

Several species of shrimp also make their living cleaning other animals on the reef, and they act as dental hygienists as well. It's not at all uncommon to see a toothsome moray eel -- jaws agape -- with a little cleaner shrimp busily pecking about inside the eel's mouth. (Moray eels don't floss!)

We've played with both the cleaner wrasse and the shrimp to see if we could get them to work on us. The wrasses rarely seemed very interested in us, save for occasionally snipping at Jerry's whiskers. The cleaner shrimp are another story entirely. They'll readily crawl around on our hands, pecking at our cuticles, for example. And by the way, that REALLY tickles!

The cleaner wrasse in the photos on this page is endemic to the Hawaiian Islands. That is, it is native to our waters and exists naturally only here. But, it has close relatives in other parts of the world that look very similar, and which serve the same function in their own locales.

Turkeyfish or lionfish? Different name, same critter

Several days ago I put up a couple of photos of a Hawaiian Turkeyfish -- as a sort of tongue-in-cheek reference to American Thanksgiving. 'Turkeyfish' is a common name for this fish -- but it is not the common name. In some circles, the same creature is called a 'Lionfish.'

Some of the readers who commented on the previous post seemed to know this, and found my Turkeyfish label to be a bit confusing. Unfortunately that is one of the problems with identifying things in nature by their common names: the names are not standardized. That is why I always include the scientific name (when I know it!) as well as the common name for the marine life in the photos I post on The Right Blue. Scientific names do not vary.

The angle of the photo on this page might give a little better clue as to why this fish might have earned either of its common names. It has this habit of spreading its spiny fins when it is disturbed, a display that must have reminded someone either of a turkey's tail, or a lion's mane. That seems to be the origin of both common names for this fish and its kin.

The scientific name for this fish is Pterois sphex. It belongs to the Scorpionfish family (Scorpaenidae). A characteristic shared by the fish in this family is that they possess venomous spines. This is their defense against being gobbled up by larger predators.

This particular species is endemic to the Hawaiian Islands. In other words, it is native to Hawaii, and it is not found elsewhere naturally. There are other fish of the genus Pterois elsewhere in the world. They all look quite similar, but close examination will reveal some clear distinctions among the species.

These other fish in the genus Pterois also are referred to as Turkeyfish or Lionfish, depending on geographical location and who's doing the talking or writing. At least one leading ichthyologist (fish biologist) prefers to apply the name Turkeyfish to the genus Pterois, and the name Lionfish to a different Scorpionfish genus, but most people seem to use the two common names almost interchangeably.

Some people who commented on the previous post mentioned that they thought they had seen this fish in a saltwater aquarium, presumably away from Hawaii. They may indeed have seen this species, or they may have seen one of its similar-looking cousins -- one of the other fish of the same genus that I mentioned above.

I don't know a whole lot about the fine points of the aquarium trade, but I do know that Turkeyfish/Lionfish are valued as "ornamental fish" and are collected for sale to aquarists. In fact, the population of these fish on our coasts has been depleted noticeably over the years as commercial fish collectors scooped them up in large numbers to sell.

The individual fish in the photo on this page (and in the previous post) has lived in the same small patch for years, along with a handful more of the same species. These fish do not have a very wide range, so once a diver discovers where they live, they can reliably be found in more or less the same spot day after day, and -- with luck -- year after year.

We know this to be true in more than a theoretical sense. Along with our friend Dan, we dived the same stretch of coastline at Puako, Hawaii several days a week for years, and we came to know where all of the permanent residents lived. We know precisely where these Turkeyfish/Lionfish live -- but we're not telling.

Loggerhead sea turtles need further protection

Over our lifetime of diving and being around the ocean, we have had close encounters with many sea turtles. We like sharing our sea turtle stories and photos, and we know that readers of The Right Blue like them, too. We've told our readers about Green sea turtles (Chelonia mydas) in Hawaii (including a special Green sea turtle named Myrtle), and yesterday we featured a Hawksbill turtle (Eretmochelys imbricata) that we had encountered in the Red Sea. Today we'd like to introduce you to another species of sea turtle.

Meet the Loggerhead (Caretta caretta). While there are populations of Loggerhead turtles around the world, the North Atlantic Loggerheads are genetically distinct from other populations. They are an important part of the marine ecosystem along the coasts of the southeastern United States, yet many marine scientists believe that they are on the brink of extinction.

In the past, Loggerheads were actively hunted for their meat, and their eggs were gathered as food. Today the species is protected internationally, although major threats to their survival remain. Loggerheads are most at risk from commercial fishing activities, and from degradation of their nesting grounds.

Loggerhead sea turtles become entangled in gill nets, and get caught in trawls and scallop dredges. Like all sea turtles, Loggerheads are air breathers, so they must surface from time to time in order to breathe. Entanglement in fishing gear prevents them from surfacing, so they drown. Turtles that do not drown outright often are injured in the process of struggling to escape fishing gear.

Fisheries that employ long-lines -- gear that consists of hundreds of baited hooks on a single line to catch fish -- also inadvertently catch Loggerheads. Long-line fishing is efficient, and is probably less ecologically damaging than trawling or dredging (in terms of 'by-catch'). Nevertheless, no one has yet discovered a method to eliminate the danger of long-lining to the sea turtles who are attracted to the bait, and who end up swallowing large steel fishing hooks along with that bait.

In the United States, there are Loggerhead nesting beaches along the Atlantic coast, particularly in North and South Carolina, Georgia, and Florida. Loggerheads also nest on beaches of States bordering the Gulf of Mexico, from Florida to Texas. Sadly, the number of nests on these beaches is declining, and in the case of Florida, the number of Loggerhead nests has declined by about 50% over the past decade -- a startling figure!

An explosion of beachfront development is partly to blame. Some coastal areas are simply being eliminated as nesting grounds as housing and commercial activities encroach on them. Other nesting areas are being damaged by pollution, and disturbed by human and motor vehicle traffic. Turtles swimming in populated areas also are more at risk from collisions with boats.

Today two conservation organizations, Oceana and the Center for Biological Diversity, have petitioned the Federal government of the United States to strengthen protection for North Atlantic Loggerhead turtles. They are urging the National Marine Fisheries Service, the agency responsible for protecting Loggerheads in ocean waters, and the U.S. Fish and Wildlife Service, the agency responsible for protecting turtles on land, to change the designation of these Loggerheads from "threatened" to "endangered" under the U.S. Endangered Species Act.

In addition to the threats from commercial fishing and degradation of nesting areas mentioned above, these conservationists also believe that climate change is now impacting the survival of Loggerheads. As summarized in a press release issued by Oceana and the Center for Biological Diversity:

Many marine biologists fear climate change will stress loggerhead sea turtle populations even further. Climate change can cause severe storms, erosion and sea level rise, all of which can affect sea turtle nesting on beaches. Rising temperatures caused by climate change may alter the timing or location of nesting or may increase the number of female turtles, because the sex of the hatchlings is temperature dependent. Climate change may also affect sea turtles by altering ocean currents and migration routes. Finally, ocean acidification caused by rising carbon dioxide levels breaks down the shells of preferred turtle prey, such as mollusks and crustaceans, and could alter turtles' food supply.

We decided to tell our readers about Loggerhead sea turtles today in support of this effort by Oceana and the Center for Biological Diversity to recruit greater protection for these magnificent animals. For more information, please visit the Sea Turtle pages on the Oceana website.

We have crossed paths with very few Loggerheads over the years. As a result, we had no photos of Loggerheads in our personal collection to use for this article. All of the photos accompanying today's post came from external sources. The nice Loggerhead portrait near the top of the page came from Wikimedia Commons, and the photos of the Loggerhead with the fishing hook in its mouth were supplied by Oceana. We thank the donors of these photos for allowing us to publish them on The Right Blue.

Some of the factual information in this article was derived from Oceana's report, Climate Change and Commerical Fishing: A One-Two Punch for Sea Turtles (12 page 'pdf' file), and the Loggerhead Sea Turtle 5-year Review, published in August of 2007 by the U.S. National Marine Fisheries Service, and the U.S. Fish and Wildlife Service. (67 page 'pdf' file)

Tips for diving in blustery weather

Over the years we have learned a lot of things about diving that are seldom taught in training courses. One of the things we have learned from experience is that the conditions on the surface are not always indicative of conditions beneath the surface, and vice versa.

For example, on a day that is very windy and blustery, surface conditions can be problematic or even dangerous, while conditions a few meters below the surface may be completely calm. A brisk wind can turn the surface into a froth, generate choppy swells, and create or enhance surface currents. In short, the surface of the sea is not a pleasant place to be when it's very windy.

Most wind-driven waves and surface currents extend only a meter or two below the surface, thus as divers descend they are very likely to find calmer conditions. Our first tip, then, is to advise divers entering the water on a blustery day to descend as quickly as possible to get below the choppiness and surface current. Regardless of whether you're entering the water from the shore, or from a boat, if a strong wind is blowing and the surface is choppy, plan ahead of time to get below immediately and wait for your dive partner(s) there, not on the surface.

When divers are underwater on a blustery day, they can look up and see the wind whipping across the surface -- just like in the photo on this page (taken at Puako, Hawaii) -- and sometimes the wind actually can be heard from below, too. Our second blustery weather diving tip is this: If you look up and see that it is windy on the surface, try to surface as near to your boat or shoreline exit point as you possibly can. In blustery conditions, do not plan on making a surface swim at the end of your dive. Swimming through chop and swells will tire you, and if there is a surface current as well, it may carry you away from where you want to go.

In fact, when we dive in very windy conditions we consider the rough surface to be the equivalent of an 'overhead environment.' The term 'overhead environment' commonly refers to a situation in which there is literally a barrier overhead preventing the diver from making a direct ascent to the surface. The usual examples are diving in cave, or inside a shipwreck. In the case of extremely rough surface conditions the barrier is not a physical one in the same sense -- you won't bump your head on it! -- nevertheless, we plan the dive as if there were a physical barrier. We consider that a direct ascent to the surface in those conditions is not an option, and we plan the dive accordingly.

In summary, when the surface conditions are extremely rough, it is unwise (to put it mildly) to be on the surface anywhere but right beside your boat, or within wading distance of your shoreline exit point. Descend immediately when entering the water, and don't surface until you are right at your boat or your shoreline exit point.

Fire coral: Another view

After the previous post about fire coral was published, Jerry asked, "Why didn't you include a picture that shows what the whole thing looks like, instead of just some macros? You know, so that divers and snorkelers will know what fire coral looks like before they get too close."

I had to admit, I was remiss in not including such a shot. The photo at right is Jerry's choice to show fire coral as divers and snorkelers are likely to see it. (Click on the photo to enlarge.)

The fire coral species shown here is Millepora dichotoma. Like several other fire corals of the same genus, it tends to have whitish tips while the main structure of the colony has some color. Those of you who have been following this blog for some time could probably guess that this photo was taken in the Red Sea as soon as you saw those bright orange fishies. I've mentioned several times that these little fish, called Scalefin Anthias (Pseudanthias squamipinnis), are ubiquitous in the Red Sea.

We'd also like to note that the background color of this photo is pretty close to The Right Blue!