Halloween Special: An Underwater Gravestone

Wordless Wednesday
Watery Wednesday

What: Marker placed on a reef in honor of someone who met his death there
(or so we were told).

Where: I took this photo at Ras Mohammed, near the tip of Egypt's Sinai Peninsula.

underwater marker
Happy Halloween!

Dotted Sea Slug from the Mediterranean

by B. N. Sullivan

Peltodoris atromaculataToday we present the next example of 'Exotic Underwater Nudies' -- our series on nudibranchs (a.k.a. sea slugs) from around the world. This particular nudibranch lives primarily in the Mediterranean Sea. Its usual common name is the Dotted Sea Slug. Its scientific name is Peltodoris atromaculata -- but it used to be called Discodoris atromaculata. More on this below.

We have seen this species frequently along the coasts of both mainland Greece, in the Greek islands in the Aegean Sea, and Crete. We also have seen this species in the waters around Cyprus. It reportedly exists in many other areas of the Mediterranean region as well, including the Adriatic Sea.

Let's have a look at this nudibranch. Keep in mind that the images displayed here are macro photos. This nudibranch is actually about two inches (5 cm) long. You can click on any of the photos to enlarge them. (Note: The photos on this page all were taken near Cape Sounion, Greece).

The first two photos are of the same individual. The first shows the creature at rest. You can see how it got its common name, Dotted Sea Slug. By the way, the exact pattern and shape of the 'dots' on these nudibranchs is unique for each individual. They are similar enough to recognize that individuals belong to the same species, but they are not identical.

Peltodoris atromaculatusThe second photo shows the underside of this creature. (Yes, I flipped it over on purpose so that I could photograph its underpinnings, but I then returned it to its original position before I swam away.) You can see the creature's 'foot' -- the muscular structure that it uses for locomotion -- and you can see how the mantle extends like a skirt to obscure the foot when the animal is in its normal position.

Like many nudibranchs, this species feeds on sponges. For a long time it was thought that it fed preferentially on only one sponge species, but then better and more refined methods of study revealed that it did indeed feed on at least a second sponge species, and it is possible that there may be others in its diet as well, at least occasionally.

The third photo shows the nudibranch on a sponge, Petrosia ficiformis. There is evidence that the nudie has been munching away at it for some time. These nudibranchs eat by scraping off the top layers of the sponge's tissues with their mouth parts. The scars on the sponge may eventually heal over, at least partially.

Peltodoris atromaculataNow, about the name. Regular readers of The Right Blue know by now that we like to give the scientific names of the critters we write about or show in our photos, because common names often vary from one location to the next, and certainly from one language to the next, while the scientific name is standardized: it is the same for a given species across languages and locations. When we know and use a creature's scientific name, we can be sure that we are all talking about the same thing.

Sometimes, though, the scientific name can change, too. By this I do not mean to suggest that different scientific names are used in different locations haphazardly. Instead, creatures sometimes are re-named. That is the case with the Dotted Sea Slug.

When a new species is discovered, its anatomy is carefully examined in order to classify it. In the old days, this meant dissection in a laboratory so that its organs and other structures could be assessed for how similar or different they were to those of other, known, species. This is still done, of course, but more recently -- thanks to both the accumulation of knowledge and the development of more advanced methods and instruments -- much finer details about a creature's anatomy can be determined. In short, taxonomists (i.e., those whose job it is to categorize life forms) now can identify differences that were not visible before. One animal may 'look like' another at first glance, but when their cellular structures are examined and compared, for example, we may find significant differences that set one apart from the other in important ways.

Renaming a creature is not done on a whim. Rather, it happens when important new information about a creature becomes available some time after it was originally categorized and named. Discovery of sufficient anatomical differences may lead to re-assigning the creature to a different group or, in some cases, establishing an entirely new classification for it.

As best I can tell from what I have read, at the time this nudibranch was discovered and first described, in 1880, it was classified as a Dorid nudibranch, belonging to the genus Discodoris. It was given the scientific name Discodoris atromaculata. It kept that name for more than 100 years. Then, in the late 20th century, taxonomists using more refined methods began to notice anatomical features that seemed to distinguish this species from others in the genus Discodoris, and placed it instead in the genus Peltodoris. Slowly, the literature on this species is being amended to reflect the re-naming. Meanwhile, it is possible to search on either name and come up with information about the same critter.

Confused yet? Oh dear, I thought so. Don't worry -- there won't be a test!

Smile for the Camera, Mr. Moray

Wordless Wednesday
Watery Wednesday

What: Close-up portrait of a Yellowmargin Moray eel (Gymnothorax flavimarginatus).

Where: I took this photo off the coast of Puako, on the Big Island of Hawaii.

Gymnothorax flavimarginatus[Click on the photo to enlarge.]

Divers, Cover Yourselves!

by B. N. Sullivan

diverFor the past few months, virtually all of our posts here on The Right Blue have focused on interesting species of marine life we have come to know. Feedback on those articles has been positive: our readers seem to enjoy learning about creatures that inhabit the sea. But we also have been nudged by a few readers to get back to writing about diving -- as in, "Enough with the critters, already. Get back to diving stories!"

Well, okay then. How about some tips for divers?

Over the course of a few decades of diving, we have learned a number of useful things that, for one reason or another, are not taught to divers in formal training courses. The first is a simple rule that usually does not occur to divers until after they have had a bad experience or two. Cover yourselves!

In colder water, divers must cover themselves in drysuits or heavy wetsuits in order to retain body heat. But we believe that divers should be completely covered even when diving in warm tropical locations. These days, there are plenty of lightweight dive suits designed specifically for use in warmer waters.

We see many, many divers here in Hawaii -- mostly (but not only) tourists -- who seem to think that because they are in the tropics, they should just wear a shortie suit. We see them jumping into the water with their arms and legs exposed. Worse yet, some wear no dive suit at all, donning their dive equipment right over their bikinis. Guess what happens? Sooner or later, they get wounded!

It is very easy to brush against something -- a rock, a coral head -- even when you are trying to be careful not to touch anything. Sometimes it happens because the diver is not paying attention. Other times there is a little surge, just at the wrong moment. In any case, sooner or later some part of your exposed anatomy will collide, however briefly, with something in the water, and you will get cut or scraped.

In addition to those kinds of bumps and scrapes, it happens that there are many critters in the water that can bite or sting. Some are very tiny -- stinging plankton so small that you cannot see them in the water column -- so you cannot take evasive actions. Other are big enough to spot -- jellyfish come to mind -- but even then, you run a risk of being stung. Just because you see the critters doesn't mean you can count on completely avoiding contact.

marine lifeThe best way to prevent many of these inadvertent stings and scrapes is to wear a full suit that covers you from your wrists to your ankles. Wear boots or neoprene booties inside your fins. And wear gloves.

Now, we know that many dive operators discourage or even prohibit divers from wearing gloves. We also know the reason for that: they don't want to encourage divers to pick things up or handle them, and they figure if the divers are not wearing gloves, they may be less inclined to touch things.

Fair enough, but short-sighted. There are just too many situations where the protection afforded the diver by gloves outweighs the momentary protection of the reef and its critters afforded by bare-handed divers.

We think of it like this: we're grown-ups. We know we shouldn't recklessly handle things that dwell underwater. We know that touching corals (and many other things) can damage them. We promise we won't do that -- not because our hands are bare, but because we know better.

At the same time, what happens if we are shore diving and need to grab onto rocks at our exit point? We can very easily get cuts and scrapes on our hands, that's what.

If we are diving from a boat, what happens when we need to hang onto a mooring line or an anchor chain in order to remain stationary for our safety stop? Lines and chains that have been in the water for awhile are certain to be covered with algae, hydroids, and even teeny-tiny crustaceans. If you don't believe me, just have a look at the second photo on this page -- a 1:1 macro shot of an actual mooring line, totally encrusted with an entire ecosystem of its own! Hanging onto such a line is going to disrupt some of those things anyway, regardless of whether your hands are bare or gloved. But hanging on with a bare hand will really hurt. Said teeny-tiny crustaceans will cut your hand like little razors, and if you happen to grab onto a hydroid, you will know it, believe me. They sting like a son-of-a-gun -- and you will never forget the experience!

So then, even if you don't want to wear gloves for the entire dive, do carry a pair in your pocket at all times, just in case you have to hold or grab onto something for your own safety.

Dive like grown-ups. Cover yourselves completely to protect yourselves from scrapes and stings; but at the same time, do keep in mind that being covered (and thus protected) does not excuse you from responsibility for avoiding physical contact with the reef and the creatures that call it home.

Colony of Long Red Sea Whips - Indonesia

Wordless Wednesday
Watery Wednesday

What: A colony of Long Red Sea Whips (Ellisella sp.), a type of soft coral.

Where: I took this photo in the Celebes Sea at Bunaken Island, Indonesia.

Ellisella sp.
[Click photo to enlarge.]

My previous Wordless Wednesday posts.

The Blue Dragon, a Solar-Powered Nudibranch

by B. N. Sullivan

Pteraeolidia ianthinaThis is the third article in our series on 'Exotic Underwater Nudies', i.e., nudibranchs. We began the series last month with the Spanish Dancer, exceptional for its large size and unique swimming behavior. Next we presented the lovely Gold Lace nudibranch, a species endemic to Hawaii. Today we'll take a look at a very different kind of nudibranch -- different both in form, and in how it makes its living.

Meet the Blue Dragon (Pteraeolidia ianthina). This is one of a handful of nudibranch species that is, in effect, solar powered. I know what you're thinking: A solar-powered sea slug? How is that possible?

It happens in a round-about way. The Blue Dragon is carnivorous. It eats hydroids -- stinging organisms that are related to corals. The hydroids are colonized by zooxanthellae -- microscopic plants. As plants large and small are known to do, the zooxanthellae convert energy from sunlight into sugars through the process of photosynthesis.

So, the Blue Dragon eats hydroids, which contain zooxanthellae in their tissues. The Blue Dragon is one of several nudibranch species that has evolved a method of extracting the zooxanthellae from the hydroids it eats and storing them in its own body. Once in place in the nudie's tissues, the zooxanthellae continue to produce sugars via photosynthesis, thus nourishing the creature that has now become their new host. In this way, the Blue Dragon qualifies as a solar powered nudibranch.

Zooxanthellae are found in the tissues of many marine animals, including corals. In fact, it is the presence of zooxanthellae that give corals their colors. The same is true for the Blue Dragon nudibranch. The coloration of this species varies, partly due to the concentration of zooxanthellae that a given individual carries in its tissues. Juveniles of this species are a nearly transparent white. Only as they mature and accumulate zooxanthellae in their tissues do they take on their characteristic color.

Pteraeolidia ianthinaThe Blue Dragon stores zooxanthellae in its cerata -- those fluffy looking bits that cover its body. In fact, one hypothesis about the Blue Dragon's form posits that the cerata may have evolved in order to provide more surface area for the zooxanthellae to inhabit. More surface area means more space for zooxanthellae, as well as a greater likelihood that they will be exposed to the light they need for photosynthesis.

Speaking of sunlight, as you might expect, the Blue Dragon nudibranch works the day shift on the reef. It needs to be exposed sunlight so that its zooxanthellae can produce nutrients. Not only is this creature seen most frequently during daylight hours, it also tends to dwell at shallower depths than some other nudibranchs. Naturally, there is more sunlight available at shallower depths than in deeper water.

About the photos on this page: In the photo at the top of the page, you can see how the cerrata are arrayed along the entire length of the Blue Dragon. Zooxanthellae are stored in the cerata. The bottom photo is a 1:1 macro of the head of a Pteraeolidia ianthina. The feathery looking bits protruding upward from its head are its rhinophores, the organs that sense 'smells' in the water. The animal uses its rhinophores to locate food, much like a mammal on land would use its nose. The striped appendages facing forward are oral tentacles, which act like 'feelers' so that the nudie can pinpoint where the food is, by touch.

Each photo shows a different individual. The photo at the top was taken at Siapadan Island, off the coast of Borneo. The bottom photo was taken near Manado, Sulawesi Island, Indonesia.

Napoleon Wrasse in the Abstract

Wordless Wednesday
Watery Wednesday

What: The first two images are abstract macro shots of the scales and a fin of a
Napoleon Wrasse (Cheilinus undulatus).

The third photo is for context, so that you can see the patterns as they appear on the fish.

Cheilinus undualtus

Cheilinus undualtus

Cheilinus undualtus

Click on any of the photos to enlarge.

For more about the Napoleon Wrasse, click here.

Fish Tales: Encounters with the Napoleon Wrasse

by B. N. Sullivan

Imagine that you are on a dive boat in the Red Sea. The boat has just tied up to a mooring at a place called Jackson Reef in the Tiran Straits. All geared up, you jump off the stern platform of the boat and begin your descent. As you drift down gently through the water column, something off in the distant blue catches your eye. At first all you can make out is a hulking shape that looks vaguely like a Volkswagen beetle, and it is moving toward you. As it lumbers along, the shape tilts this way and that, and as it gets closer you are able to make out pectoral fins, big eyeballs, and huge fat lips. You realize it's definitely not a Volkswagen; it's a great big fish - A Napoleon Wrasse.

Cheilinus undulatusEarlier this week, for Wordless Wednesday, I posted a photo of a Napoleon Wrasse. Readers commented on the size of the fish, on its shape, and on its prominent eye.

These guys definitely are big: adults usually are close to four feet in length, although I read somewhere that there have been reports of older males of the species occasionally reaching a length of about six feet. Females tend to be smaller. In any case, they are said to be the largest species in the Wrasse (Labridae) family.

They are heavy-bodied, and weigh several hundred pounds. Because of their bulk, they usually lumber along, but make no mistake - they are capable of very quick speeds, too, at least over short distances.

Their eyes are large, and each can move independently. The eyes protrude and rotate in a way that might remind you of the ball turret on a World War II B-17 aircraft (without the gunner). When they are close to you, they tend to tilt to look at you with one eyeball, much as a chicken would.

The common name, Napoleon Wrasse, arises from the prominent bump that protrudes from the foreheads of fully grown adults, giving them a profile that is reminiscent of Napoleon Bonaparte with his hat. Another common name for the fish is Humphead Wrasse -- take your pick -- but in either case, the scientific designation for the species remains the same: Cheilinus undulatus.

Cheilinus undulatusThese fish can live for thirty years or so, and they seem to have long memories. When we first began to dive in the Red Sea a few decades ago, dive guides there sometimes would entertain their clients by hand feeding boiled eggs to the Napoleon Wrasses. After awhile, once everyone finally realized that this was not an ecologically sound thing to do, this practice was banned.

Unfortunately, no one sent a memo to these fish to tell them not to expect boiled egg handouts from divers. For years after the practice of feeding them boiled eggs had stopped, the Napoleons still converged near dive boat moorings as soon as they heard the sound of the boats' engines approaching. There they would lurk until they spotted divers descending, at which point they would approach the divers at quite close range, hoping for a free snack.

Sometimes the Napoleons would do more than wait. If a diver reached into the pocket of his vest for any reason, the Napoleon would quickly swim right up to that diver in anticipation, sometimes nudging the diver with those great big fat lips. We've heard countless of stories of divers who had to physically push a Napoleon away from them repeatedly before the fish finally got the message that they had no eggs to hand out.

In an extreme case that we actually witnessed, a friend who was diving with us lost an important piece of gear to a Napoleon, and almost lost his hand as well.

For the benefit of our non-diving readers, let me first explain that these days, scuba regulators (the device that reduces the pressure of the compressed air in the cylinder so that it can be breathed) usually have two second stages, i.e., the part that includes the mouthpiece. The primary one will be used by the diver to breathe underwater. The secondary one, though fully functional, is a back-up. As such, it is usually attached to the diver's vest by a clip or similar means, or stuffed into a pocket.

So then, on this particular dive, the clip that usually held our friend's back-up second stage had broken. Rather than let the device trail behind him, he held it at waist level, cupped in his two hands, as he swam. Now, these devices come in a wide variety of colors. Our friend's happened to be white. (Can you see what's coming?)

Cheilinus undulatusAlong came a Napoleon. It saw the round white shape cupped in our friend's hand and apparently mistook it for an egg. First the fish swam back and forth excitedly around our friend. Then it nudged him. Annoyed, our friend put out one hand to push the aggressive fish away. At that instant, the Napoleon lunged and snapped the white regulator out of our friend's other hand -- or tried to. The regulator was attached to a hose, of course. When the Napoleon bit, the hose partly detached and it began to froth like crazy from the rapidly escaping compressed air. That scared the fish, which went zooming past us with our friend's glove hanging from its mouth!

That was the end of that dive: time to initiate emergency procedures. A fourth diver who was with us immediately handed off his back-up second stage to our stricken friend so that he could breathe. Meanwhile, Jerry swam around behind him to turn off the valve on his cylinder, stopping the uncontrolled flow of air. Then, with the two divers sharing air, we all swam back to the boat.

Once on board, we inspected the damage. The hose had to be replaced, and although the white second stage that had been bitten probably could have been repaired, our friend announced immediately that he would replace it -- with a black one! No one ever saw the glove again, but our friend was happy enough to have relinquished it, since he still had his hand.

By the way, we have seen Napoleons elsewhere -- especially in the waters around Malaysia and Indonesia -- but only the ones in the northern Red Sea were so bold. The ones we saw in other places tended to keep their distance from divers. Apparently they had not been fed by divers. In fact a dive guide in Indonesia told us that Napoleons had been a favorite target of spear-fishermen there until quite recently; thus, they had learned to be wary of humans underwater.

About the photos on this page: Each image shows a different individual Napoleon Wrasse, and each was photographed on a different dive. I took all three photos in the Red Sea: the top photo was taken at Jackson Reef in the Tiran Straits; the other two photos were taken at Ras Mohammed, near the tip of the Sinai Peninsula. And in case you are wondering, the Napoleon in the third photo is not about to bite the leg of the diver on the left. It's an optical illusion created by the wide angle lens. The wrasse actually was positioned between the two divers.