Halloween Special: An Underwater Gravestone

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.

Happy Halloween!

Dotted Sea Slug from the Mediterranean

by B. N. Sullivan

Today 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.

The 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.

Now, 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

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.

[Click on the photo to enlarge.]

Divers, Cover Yourselves!

by B. N. Sullivan

For 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.

The 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.