Showing posts with label marine life. Show all posts
Showing posts with label marine life. Show all posts
Tuesday, August 5, 2008
Friday, August 1, 2008
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.
Tuesday, July 29, 2008
Sunday, July 27, 2008
Marine Mammals in The Right Blue
Marine mammals are warm-blooded animals that either live all or most of their lives in the sea, or make their living in the sea. Marine mammals we have had the pleasure to observe up close, and in some cases to dive with, include several species of Cetaceans -- i.e., whales, dolphins and porpoises -- and some Pinnipeds, such as seals.
Here is a directory of articles about marine mammals on The Right Blue:
Sunbathing at Kaikoura - Dec. 10, 2007
Male Fur Seals at Taiaroa Head - December 17, 2007
Tales of Whales: Humpbacks in Hawaii - January 20, 2008
Tales of Whales: Vocal Visitations - January 21, 2008
Tales of Whales: Close Encounters with Humpbacks in Hawaii - January 24, 2008
PHOTOS - Cetaceans:
Humpback Whale (Megaptera novaeangliae), photo by Lou Herman - Pacific: Hawaii
PHOTOS - Pinnipeds:
New Zealand Fur Seal (Arctocephalus forsteri), female, basking on the rocks - Pacific: New Zealand
New Zealand Fur Seal (Arctocephalus forsteri), 3 photos, male, swimming on the surface near shore - Pacific: New Zealand
Monday, July 21, 2008
Sea Birds in The Right Blue
The young girl in the photo at right is watching a Little Blue Penguin (Eudyptula minor). The little bird, which had been injured, now lives in a managed colony of rescued penguins at the Antarctic Center, Christchurch, New Zealand. We visited the Antarctic Center in December of 2007.
We sometimes forget that sea birds are classified as marine life, and that they play important roles in marine ecosystems. We don't have too many photos and stories about sea birds on The Right Blue, but here they are:
New Zealand's Little Blue Penguins - December 8, 2007
Taiaroa Head on the Otago Peninsula - December 13, 2007
PHOTOS:
Little Blue Penguins (Eudyptula minor) - Oamaru, New Zealand
White-faced Heron (Ardea novaehollandiae) - Kaikoura, New Zealand
Royal Albatross (Diomedea sanfordi) - Taiaroa Head, New Zealand
Sunday, July 20, 2008
Sea Turtles in The Right Blue
We have noticed that our readers really seem to like stories and photos of sea turtles. In fact, the story called The Cave Where Turtles Die, which we published in June of 2008, has received more traffic than any other single story on The Right Blue since the blog's inception! (Fortunately, most of our turtle stories are not so grim as that one was.)
Here is a directory of articles about sea turtles in The Right Blue:
- Puako's shoreline: Tidepools and turtles - September 25, 2007
- Meet Myrtle the turtle - October 5, 2007
- Myrtle's special spot on the Puako reef - October 6, 2007
- Loggerhead sea turtles need further protection - November 15, 2007
- The Cave Where Turtles Die - June 16, 2008
- Sipadan Turtle Cave: The Video - June 24, 2008
Here is a directory of sea turtle photos in The Right Blue:
- Loggerhead Turtles (Caretta caretta), three photos - Atlantic: France
- Green Sea Turtles (Chelonia mydas), basking on the rocks - Pacific: Hawaii
- Myrtle, the Green Sea Turtle (Chelonia mydas), close-ups - Pacific: Hawaii
- Green Sea Turtle (Chelonia mydas), swimming with diver, and resting on the reef - Pacific: Hawaii
- Green Sea Turtle (Chelonia mydas), close-up, on the coral - Pacific: Hawaii
- Green Sea Turtle (Chelonia mydas), swimming just under the water's surface - Pacific: Hawaii
- Green Sea Turtle (Chelonia mydas), survivor of a shark attack - Celebes Sea: Pulau Sipadan
- Hawksbill Turtle (Eretmochelys imbricata), swimming underwater - Red Sea: Tiran Straits
- Hawksbill Turtle (Eretmochelys imbricata), resting on a reef - Celebes Sea: Pulau Sipadan
Monday, July 14, 2008
WW #42 - The Right Blue's 1st Birthday Review
Not-Quite-Wordless, Special Tuesday/Wednesday Edition
The Right Blue celebrates its first birthday on July 15, 2008. To mark the occasion, we thought we'd post some of our favorite underwater photos this week and next, as a review. All of these have appeared as illustrations to our articles over the past year, but have not appeared before as Wordless Wednesday images.
We know that some Wordless Wednesday visitors only come to see the images, not the articles, but just in case you'd like to read the stories, too, we're including a link to the article where each photo first appeared. We hope you enjoy these photos -- all of which are Bobbie's original work.
Please leave a comment to tell us which one you like the best.
* * * * *
Tuesday, July 8, 2008
Tuesday, July 1, 2008
BNSullivan.jpg "Blue Spotted Stingray (Taeniura lymma) at Pulau Sipadan")
Tuesday, June 24, 2008
Tuesday, June 17, 2008
Monday, June 16, 2008
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.
Tuesday, June 10, 2008
Monday, June 9, 2008
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.
Tuesday, June 3, 2008
Monday, June 2, 2008
Fusilier Fish: Speed Demons of the Reef
This is a Right Blue photo essay on Fusilier Fish (Caesionidae). These fish, which move about a tropical reef in large schools, always seem to appear suddenly and out of nowhere. In unison, they zoom first one way, and then another, at speeds that can make your jaw drop, doing precision turns that leave those watching in awe. For divers, encountering a school of Fusilier Fish always is exhilarating. I hope this series of photos, which I took in quick succession, will give our readers a sense of what it's like to encounter a school of Fusilier Fish.
Here they come.
Then they do an about face.
Then they circle back again.
And then they're gone!
[Click on any of the photos to enlarge.]
Tuesday, May 27, 2008
Tuesday, May 20, 2008
Sunday, May 18, 2008
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!
Tuesday, May 13, 2008
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