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Dr. Jack Randall – Hawaii’s Renowned Fish Scientist – Scuba Dives on his 90th Birthday

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This past week, as you may have heard, former President George H.W. Bush celebrated his 90th birthday by jumping out of a plane, performing his 8th skydive. But did you know that here in Hawaii, a locally well-known septuagenarian marked his 90th by scuba diving? Dr. John E. Randall, former Curator of Fishes of the Bishop Museum and member of the Graduate Faculty in Zoology of the University of Hawai’i, was taken for the dive by former student Dr. Richard Pyle from the dive boat of good friend Dr. Gordon Tribble. He even shared the dive off Waikiki with two of his grandchildren, Sandra and Sean!

Jack's 90thdive3

Dr. John E. Randall after a scuba dive with his grandchildren on his 90th birthday

Dr. Randall, or “Jack” as he is known, has led an incredibly rich and adventurous life, so the fact that he dived on his 90th birthday is actually not that surprising. As a 26-year old, Jack built and then sailed his 37-foot ketch from California to Hawaii where he earned a PhD in Zoology. He married Helen Au, also a graduate assistant in Zoology. They sailed the ketch with daughter Lori (age 2.5) to Tahiti for research on fishes with support of a research fellowship from Bishop Museum and Yale University. While an assistant professor at the University of Miami, he directed a marine biological survey of the Virgin Islands National Park, followed by four years at the University of Puerto Rico as a Professor of Zoology and Director of the Institute of Marine Biology. He returned to Hawaii in 1965 as Director of the Oceanic Institute for a year before becoming the ichthyologist at the Bishop Museum in Honolulu.

Jack’s long career has resulted in the description of 731 valid new species of fish, more than any ichthyologist in history! At 90 he continues to describe and write about fishes, and this year will publish his 14th guidebook on fishes, entitled Coastal Fishes of the Red Sea with a Russian and a German as coauthors. It includes all the fishes of the Red Sea to 200 m (total 1072 species).

More exciting however is his soon to be published memoir, Fish ‘n’ Ships! I have had the opportunity to read much of it, and while I can’t talk about it just yet, I will say that it is a page-turner. Jack has packed so many adventures (and close calls!) into his life, and he has lived through so many interesting periods in US history that I could not put it down. The book should be published before the end of 2014.

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Do Hermit Crabs Kill Snails for Their Shells?

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This is what I have wondered for most of my diving career.

The 6th edition of Ruppert/Barnes Invertebrate Zoology textbook published in 1994 seemed to make it pretty clear: “Hermit crabs always use empty shells and never kill the original occupant.”

So did the 7th edition published in 2004: “These distinctive decapods appropriate discarded snail shells for use as portable domiciles.”

Then a couple months ago I came upon this scene.

Scene 1 Old shell and new

A yellow hairy hermit crab (Aniculus maximus), in a scrappy remnant of a triton’s trumpet shell, was reaching way into the opening of a beautiful intact triton’s trumpet (Charonis tritonis) shell. What was going on in there?? Was the triton snail alive and in its home shell? Or was the shell empty? Was there another hermit crab already occupying the shell?

hermit entering triton 2

I moved the hermit crab aside and, after convincing myself that the shell was not occupied by a hermit crab, reached in and felt the snail completely retracted, with the operculum (trap door) tightly sealing the opening. Since it takes energy to hold the operculum tight, I knew that the triton snail was still alive.

So, what was the hermit crab trying to do? Clearly it was in need of a new shell because it was exposed from the rear by the broken apex of the shell. Was it just inspecting the shell to see if it was occupied? Or did it have a darker plan? Since there was no way to know, we had to continue on our dive with our questions unanswered.

When I got home I Googled “Do hermit crabs kill snails for their shells.” Many aquarists reported hermit crabs killing snails in their tanks as a common occurrence, mostly to eat the snails, but sometimes occupying the shells as well. Is this behavior a result of being held in captivity where food availability, shell availability and snail refuge options are not representative of those found in the wild? Or is this normal behavior that happens in the wild as well?

Scene 3 Dead triton and hermit with flesh in claws

The next day by chance we ended up diving in the same location. I had no expectation of seeing the animals again, but as we approached the ledge, there they were in exactly the same place. As we got closer though, we could see that something was different. The hermit crab still had its claws inside the opening of the shell, but not as far in as yesterday because the triton snail was protruding from the aperture – and was motionless. The hermit crab, with its claws full of snail flesh, had apparently killed the snail!

operculumLooking more closely, the operculum had small chips all around the edge, indicating that the hermit had been attempting to gain access to the snail by picking away at the operculum with its claws.

The following day when we returned to the site, all the participants were gone. Since the triton snail was dead and could no longer crawl away on its own, we theorize that the hermit crab was able to remove the dead snail, occupy the shell and carry it away.

To find out if anyone else had seen anything like this, I asked people who I knew had been diving a really long time and were known for paying particular attention to what they saw. Not surprisingly, Linda Marsh, a divemaster with over 15,000 dives in Hawaiian waters and owner of Kauai dive operation Bubbles Below, had had a similar, but more “interactive,” encounter over a period of five days.

Linda’s yellow hairy hermit crab was in an old partridge tun shell, and when she found it trying to get at a triton’s trumpet snail she actually separated them and swam the hermit crab about 100 yards away. The next day, however, it was right back on the triton snail! She separated them again on two more days, each time swimming the hermit far away, but the following day the hermit would be back on the triton, digging around the operculum. Eventually within a 24-hour period the hermit successfully killed the triton snail and she saw it occupying the triton’s shell.

With this evidence, I contacted Dr. Brian Hazlett, hermit crab expert and Professor Emeritus of Ecology and Evolutionary Biology at the University of Michigan. He was aware of only one report in the literature of a hermit killing a snail and occupying the shell. Another researcher, Edwin Iverson, also was aware of only one example in the literature.

Petrochirus diogenes Keoki

Giant Hermit Crab (Petrochirus digenes)
Photo by Keoki Stender.

The paper they cited was one published by Dr. Jack Randall (yes, world-reknowned fish biologist) FIFTY years ago. In that paper Dr. Randall described a long-term study in St. John, Virgin Islands where he and some colleagues built a fence around an elliptical area of seagrass and sand that housed numerous queen conchs they had tagged. One day they found one of their tagged conchs missing, and in its place an empty eroded queen conch shell that had not been inside the enclosure initially. Later they watched as a hermit crab, Petrochirus diogenes, attacked a queen conch, and subsequently occupied the queen conch’s shell. They determined that this species of hermit had climbed the fence, consumed one of the conchs, moved into its shell and climbed out of the enclosure, leaving its old shell behind. In total six of their tagged conchs were killed and occupied by this species of hermit crab.

Our question had finally been answered. At least two species of hermit crab (Aniculus maximus in Hawaii and Petrochirus diogenes in the Caribbean) kill snails for their shells.

 

Scene 4 showing damage to snail and chipped operculum

But one question answered invariably begs numerous follow-up questions. For me, one of these is how did the hermit crab kill the triton snail? As you can see in the photo to the left, other than a few small gouges out of the snail, there is no obvious cause of death. One possibility is that the triton snail, being forced to remain fully retracted in it shell, could not effectively circulate enough water across its gills and died from lack of oxygen. Or, the muscular tension required to keep the operculum tightly sealed could have led to anaerobic metabolism and lactic acid build-up, something that might have reached toxic levels. Either of these or the combination of them could have led to the death of the triton snail, and once the snail’s muscles relaxed, the crab could have consumed the original builder and moved into its beautiful new home.

*****************

Written by Pauline Fiene. Photos by Pauline Fiene unless otherwise credited. Mahalo to John Hoover, Dr. Brian Hazlett and Cory Pittman for discussion and insights; to Warren Blum for underwater observations, to Keoki Stender for generous use of his Petrochirus diogenes photo; and to Linda Marsh for her recounting of such a fabulous and rare multi-day encounter.

Iverson, Edwin S. 1986. Predation on Queen Conchs. Strombus gigas, in the Bahamas. Bull. Mar. Sci. 39(1): 61-75.

Randall, J. E. 1964. Contributions to the biology of the queen conch, Strombus gigas. Bull. Mar. Sci. Gulf Carib. 14: 246-295.

 

 

 

 

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How far will a moray eel travel? A Giant Moray circumnavigates Molokini Islet

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Almost every month brings a new underwater discovery that could be titled “Who Knew?” This summer a Giant Moray (Gymnothorax javanicus) has been sighted numerous times at the islet of Molokini. Although common farther west in the Pacific in places such as Indonesia, the Philippines and Australia, this eel is rare in Hawaii. So rare, that in over 26 years of diving in Hawaii this was my first sighting of this species of eel!

 

I should clarify that it was my first sighting in the wild. My first sighting was actually in the Bishop Museum’s fish collections. There, tens of thousands of little glass jars contain one of the world’s most extensive collections of fishes, thanks to the prodigious efforts of world famous ichthyologist John E. (Jack) Randall. Arnold Suzumoto, Ichthyology Collections Manager who has worked at the Bishop Museum for 38 years, guided us through the aisles and shelves containing over 100,000 fish specimens. Many, such as gobies, clingfish or wrasses, were tiny and easily fit into equally tiny glass vials. Most of the specimens, such as butterflyfish, goatfish, damselfish, etc. were small-to-medium and bottled in various sizes of glass jars. But then Arnold led us to a white plastic 5-gallon bucket sitting on the floor. This, he explained as he removed the lid, contained a specimen of a Giant Moray. But not the whole eel. This species can reportedly reach 8 feet long and weigh up to 77 pounds, rather large for the limited space in such a massive collection. So, in this bucket was just the head of a Giant Moray. And, it filled the bucket!! (*see note at end of article)

 

But on to the “Who Knew” part of the story. Beginning in June of this year, Justin Haghbin, a divemaster at Ed Robinsons Diving Adventures, spotted a Giant Moray on the back wall of Molokini.

Javanicus body Justin for blog copy

Giant Moray (Gymnothorax javanicus). Outer western slope of Molokini. Aug. 21, 2013.
Photo by Justin Highbin.

Over the next few months Giant Moray sightings continued to be made by Justin and others. But not within just a 10- or 20- or even 50-foot radius like other species of morays we have known. These sightings were sometimes a half-mile apart! So, we wondered, is it a different Giant Moray at all of these places? Or the same individual? Odds were that it was the same individual, since the species is so rare in Hawaii. But we had to know for sure.

 

Fortunately, like most animals, there are identifying characteristics if you look closely enough. The Giant Moray has tiny black spots all over its body. So, we compared the spot pattern on the right side of the face in photos taken in the three locations – on the back wall, on the outer western slope and at Enenue. As you can see, the spot pattern is identical.

composite javanicus

Showing identical spot pattern on the Giant Moray photographed a quarter-mile or a half-mile apart, depending on the route it took. Photo on left taken on Aug. 21, 2013 on the outer western slope of Molokini. Photo on right taken Sept. 18, 2013 at Enenue, the inner eastern slope of Molokini.

 

Molokini is about 0.4 miles in diameter and about 1.3 miles in circumference. Just moving from the outer western slope clock-wise around to Enenue one time is a trip of about half a mile, and it has done this several times that we know of. Then there have been several visits to the back wall, about 1/4 of a mile from the outer western slope. Added up, this eel has swum miles around the perimeter of Molokini in just the few months that we have been aware of its presence.

Molokini javanicus sightings cropped copy

Approximate locations of Giant Moray sightings at Molokini, summer, 2013.

We are not aware of reports of a moray eel traveling such distances, so we asked eminent fish scientist Dr. Jack Randall, and Dr. John McCosker, Senior Scientist at the California Academy of Sciences and moray behavior expert. Neither had heard of such long-distance movement by a moray.

Morays that we have known have remained in roughly the same location for years, possibly a decade or more, and some divers have reported that they have visited the same moray eel in the same place for at least 20 years. What would cause this Giant Moray to move around so much? Being such a rare eel in Hawaii, perhaps this individual is expending all this energy in search of a mate, something it would not have to do in areas where it is a common species.

Such discoveries are exactly the kinds of things that dive guides have a unique opportunity to document. All it takes is paying attention (and usually a camera) to document marine life behavior that has never been observed before, because while dive guides spend only a tiny fraction of their lives underwater, it is still more than most professional scientists are lucky enough to spend.

 

* the specimen at the Bishop Museum had been caught on hook and line (sharkline) off Milolii, Kona Coast of Hawaii, in Oct. 1977. It was a male 6.7 feet long and weighed 69 pounds. Information courtesy of Arnold Suzumoto, Ichthyology Collections Manager at Bishop Museum.

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Tumor disappearance in a South Maui resident sea turtle

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Any frequent Maui diver or snorkeler has witnessed innumerable green sea turtles with tumors, some as large as a baseball, and sometimes completely covering a turtle’s eyes. It’s a painful sight, even more so because these tumors are more prevalent in areas where we humans reside, and because we are most likely responsible for their suffering. Indications are that our activities on land change the nearshore ecosystem and make it more likely that turtles will contract this disease. Turtles with tumors the size of a baseball have not been known to recover. Some of these end up stranding themselves and are euthanized, or they disappear from our reefs and we just stop seeing them.

Fortunately, not all turtles are equally afflicted. Many have tumors that do not grow to such large size. And in these turtles, some individuals actually experience tumor regression or disappearance altogether.

We have been lucky to see a few of these fortunate turtles over the years, one as recently as this summer.  In 2001 Andy Schwanke began a photo catalog of turtles that we see at the places we dive. This was possible because each turtle’s face has a unique pattern of scales.

154R_Race 2002

In 2002 Juerg Grieder photographed the above turtle at Ulua Beach with small tumors in the back corners of both eyes.

154R_Race 6_27_05 edited 2

In 2005, off Kamaole, tumors were seen in the armpit and almost covering both eyes.

Race 2013 edited 2

But In July of 2013, off Wailea Point, the right eye showed no evidence of tumors. Her eyes are closed because she is resting, and we did not want to bother her just to get a photo of her eye open, but it appears as though no tumor is present.

 

This is not unusual. A 2006 master’s thesis by Joseph Spring showed that 88% of nesting females at French Frigate Shoals had tumors that were regressing. In a 1999 paper by Peter and Ursula Bennett they report a 33% regression in the turtles they monitored.

So, while not unusual, she is the first turtle we know personally (and have photographed) with a good outcome from this disease. Now we will keep an eye out for her and see if she remains disease-free. She is a huge female with an easy-to-remember scale pattern on her face so she will be easy to spot, especially because in the 11 years we have known of her, she appears to have stayed within a small area between the St. Anthony wreck and Wailea Point. If we see her again we’ll keep you posted!

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Atlas crabs in their coral homes – what goes on under there?

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As promised in my last article, there is more Atlas crab behavior to share. To recap, I had collected a few of these dead coral pieces (which I will sometimes refer to here as rocks) with their resident crabs and kept them in an aquarium for a couple days before putting them back in their neighborhood. Because they are not in ID books, I wanted to try and find out what species they were, and to learn what they are doing under there!

Atlas crab eating square

Even though the crabs were in a foreign environment (a small aquarium) they quickly started moving their dead coral homes around. Next, they all began picking at whatever they could find on their or their neighbor’s rock. Using their big claws (chelipeds) they picked at the rock and put whatever they were getting in their mouth.

One other cool thing that the video showed was the amount of current that the crab generates to move water across its gills. As divers we don’t even notice this underwater when looking at a crab. We see all the appendages moving up by its face, but we don’t see the current. Because the bottom of the tank was clean, the current was very apparent when the few pieces of debris by the crab’s mouth were blown out of the way. Crabs create this current to force water over their gills so they can “breathe.” Normal water movement is not enough.

(In this photo an Atlas crab is picking something edible off of the rock. You can see some of the debris that is flying around due to the current the crab is producing with his head appendages. You can see video of the crab feeding here).

By chance I had collected one rock occupied by a male and two others by females. That made for some interesting interactions. When put in the same tank they probably began communicating chemically right away. Then the male began performing his courtship duties which included intermittent vibrating of his large claws and some of his other legs. The vibrating could have been sending a vibrational signal to the female, and, once they were in contact, a tactile signal as well. They both flapped their abdomens and then slowly they inched into their mating position which is basically belly to belly – with 20 major appendages to keep out of the way in the process. It was kind of excruciatingly too intimate to watch, but I posted the video here. After about fifteen seconds  they suddenly separated and bolted to their separate holes. In the photo below the male crab on the right is just beginning to reach for the female on the left. It took them another whole minute to even get into position.

Male and female reaching

Atlas crab with eggs

The other female crab that I had brought in was carrying a batch of well-developed cranberry colored eggs, and she could not come out of her hole fast enough to begin aerating them. The developing embryos inside the egg capsules require oxygen which diffuses through the egg capsule membrane, so she must keep water moving across them or the embryos will suffocate.

The female that I watched spent most of her time vigorously flapping her abdomen open and closed, and the eggs that were attached to it were agitated along with it. She also periodically moved her claws and legs through the eggs to clean them. All the while she was creating a current in the water by moving her head appendages which helped to aerate the eggs too.

(In this photo from the video, the female Atlas crab’s abdomen is fully extended as she opens and closes it to move water around the eggs and to keep them aerated).

Also while I was videoing, a juvenile Atlas crab emerged from one of the rocks “operated by” an adult. It is likely that juveniles live in coral pieces that are carried by the adults. Do they leave and find their own piece of rubble once they are mature, or do some wait in line to take over the existing coral if the resident crab is an aging individual? Do they remain in the same rock their whole lives, enlarging the hole as they grow or do they try on different unoccupied rocks or trade/fight for already occupied rocks?

And, what do they eat? Do they mostly scavenge underneath their coral homes and supplement their diet with what grows on their  homes? Do they “farm” the algae and organisms growing on their home coral by picking off undesirable species and allowing desirable species to grow?

What a world of their own these little crabs have underneath their dead coral pieces… so many unknown details of their lives.

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Atlas Crabs Move Their World

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Atlas crab thumbnail

 

In Greek mythology, Atlas was the Titan
condemned by Zeus to hold up the celestial sphere.

 

 

 

 

dead meandrina with crab-Kamaole 3

Trail made by an Atlas crab (Actumnus obesus) moving its coral home.

Have you seen a kind of scruffy drag mark on top of the sand, only to find what looks like a rock or piece of coral rubble at the end of it? I’d seen these for years and every time I turned one over all I saw was a perfectly circular hole in the rock that dog-legged out of sight, making whatever was in there difficult to see. I assumed it was a kind of crab, but it wasn’t until a few months ago that I collected some of these coral pieces to observe in a holding tank.

The little crab that inhabits this coral rubble isn’t in popular Hawaii ID books, so it took the help of several people in the islands and on the mainland to match this crab with its name. It turns out to be Actumnus obesus Dana 1852, and – even though it is found throughout the Indian and West-Pacific Oceans – it was first collected and described from Maui! In 1852!

 

It always surprises me that people found things like this without SCUBA so many years ago. During the United States Exploring Expedition of 1838-1842, ship naturalists onboard the Albatross dredged these crabs “south of Molokai and near Lahaina.” It makes sense that these crabs were collected during the Maui part of that worldwide expedition as they are very common at diving depths along Maui’s leeward shore. The relatively protected leeward coastline of Maui and the fine sand allow the crabs to easily crawl around in search of food without getting thrown around by surf.

 

crab in rock for blog 5

A coral nodule turned over to see the Atlas crab in its hole.

When Actumnus obesus was described, it was noted to have a deep, convex body  (thus, the species name obesus, meaning fat) and short, stout claws. But since the dredgers did not see the crab in its natural environment, there was no description of how it used those adaptations. It wasn’t until over 100 years later that Melbourne Ward reported that another species of Actumnus excavated a burrow in a dead coral piece and then moved the coral from place to place.

Since then, two other species of Actumnus have been reported to exhibit similar behavior (some of them using pieces of coral that are still alive) (Johnson et. al., 2008), and now we’ve learned that Actumnus obesus is the fourth Actumnus species known to do so.

 

 

With the crabs in their little holding tank and me looking up at them while lying comfortably on my back beneath it, I was able to spend hours watching and videoing the crabs move about. Each crab would emerge from its hole, position its legs and claws and then abruptly thrust its claws and next two pairs of legs at the bottom of the tank propelling its coral piece rearward (while holding the coral with the last two pairs of legs). It was such a surprise! I had expected them to drag the piece of dead coral (like a hermit crab drags its shell), not pop it up off the bottom in spurts. Now the deep body and the large claws make sense – they are used to heft their home around!

You can see what I saw here: http://www.youtube.com/watch?feature=player_detailpage&v=OblcmLs2jsQ

To understand this feat a little better, I weighed one of the crabs and one of the average-size coral pieces. With the crab (wet) at less than a gram and the coral (dry) at 76.5 grams, the crab is lifting more than 150 times its own weight. That equates to a 150 pound person lifting 11 tons!

 

claw close-up

The granular surface of the claws is used to rasp a hole in the coral nodule.

 

Their deep body houses the muscles necessary for the large claws to do the heavy lifting. That makes sense. Now, how do they make that hole in the coral?

You can see that the carapace and the claws are covered with tiny pointed granules like the teeth on a rasp. Using their claws (and possibly their carapace) they excavate the perfect size hole in their coral home, and are presumably able to enlarge the hole as they grow.

The extreme ease with which they slip into and out of their hole is another example of nature’s perfection. Who knows how many more adaptations they have for their life within and underneath their coral homes?

 

In addition to watching their means of coral transport, I was also fortunate to see a female emerge from her rock and aerate her eggs, a male crab scraping material off of the rubble and eating it, and a pair of crabs perform a courtship ritual and get into their mating position. It was a warm and dry front-row seat to their precious world underneath their coral homes. I will post more descriptions and videos of their private lives soon.

 

Thanks to Cory Pittman and John Hoover for help with identification research and to Peter Castro for examining the photos and identifying this crab as Actumnus obesus Dana 1852. It is figured in Edmondson, C.H. (1962) Xanthidae of Hawaii. Occasional Papers of Bernice P. Bishop Museum, 22(13), 215-309 [p. 290, figs. 27a, 28a].

Johnson, Peter R., Davie, Peter J. F., Neil, David T. and Fellegara, Ida (2008) Excavation, habitation and transportation of massive corals by the crab Actumnus setifer (Crustacea: Brachyura: Pilumnidae) in Moreton Bay, Queensland. Memoirs of the Queensland Museum – Nature54 1: 261-271.

Ward, M. 1942. A new genus and eight new species of Brachyura from Mauritius and the Chagos Archipelago. Mauritius Institute Bulletin 2: 39-48.

 

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