Category: fish and marine creatures

Readers’ wildlife photos

June 6, 2020 • 8:00 am

During the pandemonium surrounding the entry of Honey and Dorothy’s broods into Botany Pond at the beginning of May, reader David Campbell sent me some wildlife pictures. And, as sometimes happens, I forgot to put them in the “readers’ wildlife” folder. He reminded me, and, with apologies, here are some late photos. David’s captions are indented:

Descriptions follow.  The Cannon Spring photo [last one] is not the highest quality but the situation was so unique that I thought some of your readers would be interested.

Dog Puke Slime Mold (Fuligo septica) A plasmodial slime mold that frequently occurs on mulch around plants after heavy rains.  The gross factor made it a big hit with my students when it appeared in the ornamental plantings outside my classroom.  It has no odor.  I am waiting for someone to come up with a Hairball Slime Mold.

Sailfin Catfish, Pterygoplichthys sp. Photographed in Silver Glen Springs in the Ocala National Forest of Florida.  Sailfins are exotic invasives that I have seen in a lot of springs in the St. Johns River basin.  Two species of Pterygoplichthys are found in Florida and frequent hybridization makes identification to species difficult.  Sailfin catfish are edible but they are encased in a hard, bony armor so cleaning them is difficult.  Some people simply cook them “in the shell” and peel them apart.

Blue Crab (Callinectes sapidus).  Blue crabs are anadromous, occurring in both fresh and salt water.  This one was photographed about 15 feet below the surface at the mouth of a freshwater spring in the Ocala National Forest.

Florida Gar (Lepisosteus platyrhincus) Gars look intimidating but are not aggressive toward swimmers.  This meter long fish swam over to examine me and then went back under nearby overhanging vegetation to do what gar seem to spend most of their time doing, sitting motionless in the water column.

Green Fly Orchid (Epidendrum magnoliae).  A native epiphytic orchid that is found as far north as North Carolina.  Different plants bloom at different times of the year, sometimes as late as December in Florida.  The flowers are quite small and easily overlooked but worth the effort to find.

Sidewinder (Crotalus cerastes).  Photographed in Arizona.  This is one of the smaller rattlesnakes and this individual was typically nervous and aggressive.  The right infrared sensing pit is visible forward of the eye.  Like many other pit vipers, sidewinders hunt at night and use infrared radiation from homeothermic prey in the final localization stage of hunting.

Monarch Butterfly (Danaus plexippus).  Two photos of a chrysalis, the pupa of this familiar butterfly.  These photo were taken three days after pupation.  The first photo was taken using conventional front lighting.  Clearly visible in the “skin” of the pupa are the outlines of wings, antenna, respiratory spiracles, and abdominal segmentation.  The second photo, taken during the same session, shows the chrysalis backlit.  Notice that the lower two thirds of the pupa is translucent with little or no visible structure.  Small clusters of cells are already organizing development of major butterfly organs and tissues from the products of broken down larval tissues.

Unicorn Caterpillar Moth (Schizura unicornis).  This is one of the more unusual Notodontidae caterpillars and was found feeding on an antique rose in the garden.  I moved it to a less valuable Cherokee rose where it continued feeding.  The adult is a nondescript little moth with a 25-35 cm wingspan.

Cannon Springs, Ocklawaha River, Florida.  This is a grab shot of something that is only visible for a month or two every three to four years.  Back in the 1960s the Army Corps of Engineers conceived and began construction on a barge canal connecting the Gulf of Mexico with the Atlantic Ocean, cutting across the Florida peninsula around the same latitude as Ocala.  One of the most beautiful rivers in Florida, the Ocklawaha was dammed to provide a wider and deeper channel for barges using the canal.  The resulting reservoir covered more than a dozen freshwater springs including several large ones.  President Nixon halted the canal construction before it could be finished but the dam remains and attempts to dismantle it and begin restoring the river have failed due to political resistance.

Every three to four years the Corps draws down the water level in the reservoir and, for a few weeks, several of the “lost” springs reappear.  Cannon is one of them.  I had planned on snorkeling here to photograph the fish and spring but I was the only human within miles and I never swim alone, especially when there is a five foot alligator sunning on the bank.  This photo was taken by holding the camera underwater as I floated nearby.  The larger of the two spring basins is in the background including the two vents where water flows out fast enough to keep the limestone clear of debris.  Also visible are several species of fish including lake chubsucker (Erimyzon sucetta), largemouth bass (Micropterus salmoides), chain pickerel (Esox niger), and bluegill (Lepomis macrochirus).  The spring is now submerged beneath four additional feet of murky brown water and won’t be visible again until at least 2023.

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Readers’ wildlife photos

February 21, 2019 • 7:30 am

We have fishes, underwater invertebrates, and one birdie today. The underwater photographs come from reader Peter Klaver, whose notes are indented (readers with marine expertise might identify the squid and the last fish).

Here are some photos and links to video clips of underwater wildlife I saw while on a scuba diving trip off the coast of Myanmar. My knowledge of Latin names is not much better than the previous time my scuba diving photos and video appeared here, so hopefully readers can again fill out the gaps and correct mistakes in the species’ Latin names.
We saw quite a few cuttlefish. They were quite big, but it’s not the giant cuttlefish Sepia apama I think, which is exclusive to Australian waters. Would anyone know which kind this is?

We even saw them in bunches together, and there is a short 3.2 MB video clip of these three here.
Lion fish, Pterois volitans, are a common site in almost any tropical reef scuba diving trip:
Moray eels are also a common sight, and they come in many different varieties.
There is a 1.5 MB video clip of the darker kind in the photo below here.

Finally, here is some fish whose name I wouldn’t know in English. You might wonder if the photo is in grayscale, but it is actually in color, see the small striped yellow fish in the right bottom corner. The pattern on the fish is just almost perfectly monochrome.

And for the ornithophiles, reader Garry VanGelderen sent one photo, but with two birds:

Here is a pic of two Red-Bellied woodpeckers (Melanerpes carolinus). Male is upper one, female the lower one.

Readers’ wildlife photos

February 5, 2019 • 7:30 am

Reader Carl Sufit sent us some nice underwater photos, and I hope we’ll have more from him and others in the future. His notes are indented:

After reading your notes from Hawaii, with various underwater images, I felt it was time to send you some of mine. Underwater photography is even harder than surface photography, and I find there are usually better photographers on most trips/boats I’m on (but they don’t send you any images!).  Anyway, I’d just about finished weeding through pix from my last trip, with some minor editing (all I’m capable of) when it was time to head off for the next one.

I’m relying on google to find Latin names. Comments on animal behavior are anecdotal and based on personal experience for the most part.

Last fall I visited Cayman Brac (one of the 2 smaller islands) for the first time, although I’d been to Little Cayman 20+ years ago, and Grand Cayman about 15 years ago.  My overall impression was that the reefs were in pretty good shape, with minimal/no coral “bleaching” and good fish life despite the scourge of invasive Lionfish.

Regarding the coral, I’ve read that Elkhorn, Acropora palmata, and its close relative Staghorn corals, are considered endangered and could be a marker of overall coral reef health.  There were some good areas of Elkhorn (as well as some destroyed by storms, as they grow in fairly shallow water):

Lionfish, Pterois volitans or P.miles:

On most dives, there were one or more Nassau Groupers, Epinephelus striatus, hanging around, and even coming toward the divers.  They didn’t seem to be waiting for us to scare up snacks (although I’ve seen that in the past on night dives, when our lights illuminated potential prey), and in fact appeared to want to be petted or stroked.  Why?  Helping clean them? (They often go to “cleaning stations” where tiny fish will pick through their mouths or scales, presumably for parasites.)  Or do they just enjoy it?   I was reluctant to take part, because, hey, you’re not supposed to touch the wildlife, but sometimes they were insistent.  Most were 2-4 ft. in length.

The Giant Barrel Sponges, Xestospongia muta, were impressive. Wikipedia says they can live thousands of years, and seeing some that were 6 ft/2 meters long, I can believe it.  (Homo sapiens aqualungis and vase sponge, Niphates digitalis? in background):

We were able to see what most divers love, sea turtles and octopus. Hawksbill, Eretmochelys imbricata (I think, or could it be a Green Sea Turtle??):

This octopus, presumably a Caribbean Reef Octopus, Octopus briareus, was out in the open in broad daylight, somewhat unusual, as they’re mostly nocturnal hunters and should be wary of lurking groupers, for whom they’d be a good meal. Their rapid color changes are quite impressive.

And as you liked the humuhumu in Hawaii, here’s one of its Caribbean cousins, a Queen Triggerfish, Balistes vetula: 

 

Readers’ wildlife photos (and videos)

January 29, 2019 • 7:45 am

Peter Klaver sent us something we don’t see here often: underwater photographs—and there are some videos as well. Peter’s captions and notes are indented.

Included below are 5 full sized scuba diving photos and 5 smaller preview pictures of movie clips. With each preview picture connected to a video, I’ve provided the url of the movie clip to link to on the Delft University server, where I put the website of the holiday Rachel Wilmoth and I had ( http://dutsm1219.tudelft.net/Africa2018/ ).
From Tofo and Vilanculos in Mozambique we did scuba diving and snorkeling and saw really beautiful underwater wildlife. I do pretty terrible in my knowledge of the Latin names of the animals; hopefully some readers can fill in the gaps and correct my mistakes.
This is a lion fish, Pterois:

Here is a leopard shark, Triakis semifasciata, lying on the bottom:

Here is a fish whose name I don’t know:

This was a large stingray, suborder Myliobatoidei, I guesstimate it spanned well over a meter wide:

And this is a close-up of a grouper, subfamily Epinephelinae, resting on the bottom.

We snorkeled with a whale shark, Rhincodon typus, that was scooping up plankton near the surface (movie here).
I think these are bigeye snappers, Lutjanus lutjanus, but I’m not 100% sure (movie here):
Turtles (Chelonioidea?) were almost a common site in the Two Mile Reef off the coast near Vilanculos (movie here).
I think these are reef sharks (Carcharhinus) but I’m not sure (movie here).
And finally I don’t know what the fish species in this shoal is (movie here).

 

The bizarre anglerfish: first video of their equally bizarre mating

March 22, 2018 • 11:30 am

You’ve surely heard of the bizarre anglerfish. There are actually many such species in the order Lophiiformes, but the most famous are the deep-sea species with fearsome teeth who attract their prey with a luminescent lure. (All anglerfish are carnivorous.) Here’s a picture of ten such species from Wikipedia:

Their huge mouths and distendable stomachs enable them to eat prey twice their size: a useful adaptation in the deep sea, where prey are few and far between. And the reproduction of some species, as shown in the stunning video below, is totally bizarre (see this Mental Floss piece for more information). Males are tiny, and weren’t even known to exist until many females had been caught, many afflicted with “parasites”. Scientists eventually realized that the parasites were actually males whose bodies had become permanently fused to the female. That’s a good mating strategy because finding a female in such sparse populations is a real problem. But it’s almost unique in animals.

When males are born, they have to find a female, and they do so by homing onto her using both her light and species-specific pheromones. Such males can’t feed, and don’t get mature gonads until they attach to a female. When a male does that, he secretes an enzyme that dissolves his head and the female’s body wall, allowing the pair to fuse right down to joining their blood vessels. The male remains attached to the female for life, and can spawn repeatedly until she dies (how the male releases sperm when the female produces eggs is something I haven’t yet found out). As I used to tell my students, to their great delight, “the male anglerfish is simply a parasitic sack of gonads—much like undergraduate men.”

A piece in Science by Katie Langin describes the filming of the first pair of mating anglerfish, made at 800 meters near the Azores by Kirsten and Joachim Jakobsen in a submersible (shown in the video below). They followed the 16-cm animal (about six inches long: the size of an American dollar bill) for 25 minutes, and later identified the species as Caulophryne jordani, or the “fanfin angler”, which has a worldwide distribution.

The short video below, put out by the AAAS, shows several interesting features:

  • The long whiskers of the females of this species, which likely act as feelers. These structures appear to glow like the bioluminiscent “lure,” but the researchers aren’t sure whether the glow of the whiskers is intrinsic or merely reflections from the submersible.
  • The male seems to move his body about independent of the female
  • The female uses little energy swimming, and appears to mostly drift around. That’s probably an energy-saving adaptation in a food-poor environment. After all, why swim when you have nowhere to go, and when your prey comes to you?

Have a gander of one of the world’s truly bizarre creatures, and one of the marvels of natural selection.

h/t: Matthew Cobb

Readers’ wildlife photos

January 31, 2018 • 7:45 am

We have some New Zealand pictures from reader Michael Hannah, whose notes are indented. Hannah is an associate professor of paleontology and evolution at the School of Geography, Environment and Earth Sciences at Victoria University of Wellington.

Numbers 1 – 6 were all taken at Pukaha Mt Bruce sanctuary–  I know you visited there on your NZ trip. Most animals were confined to cages so they were easier to photograph. Numbers 7 and 8 were taken at the NZ fur seal colony at Cape Palliser, on the southern coast of the Wairarapa – about 2 hours drive from Wellington. I’ve also thrown in a couple of photos from a fishing village that the road to Palliser passes through called Ngawi. There are no wharfs: boats are pulled in and out of the water by rusty old tractors – some of which are highly decorated!

1.) Antipodes parakeet – Cyanoramphus unicolour:

2.) Kākā – Nestor meridionalis. This is the north island version of the infamous Kea; it’s not quite as brightly coloured.

3.) Korimako – New Zealand bellbird ( Anthornis melanura):

4.) Tui – (Prosthemadera novaeseelandiae)  one of my favourite birds – noisy, aggressive – but with the most beautiful feathers.  [JAC: note the white feathered “parson’s collar”.]

5.) Tuatara – (Sphenodon punctatus):

6.) Longfin Eel –  (Anguilla dieffenbachia). Once a major food source for Māori, but now in decline. Theses had gathered to be hand-fed by visitors to the sanctuary.

7.) and 8.) Young Kekeno – New Zealand fur seals. It was a hot day and everyone was sleepy. Some just wanted to float, neatly folded in a convenient rock pool.

Here are the tractors used to drag the boats out of the water in Ngawi. Those crazy Kiwis! Wikipedia says this:

Ngawi has more bulldozers per capita than anywhere else. The bulldozers are used to haul fishing boats into and out of the water as there is no wharf or other access to the ocean other than the beach, which can be notoriously rough at times.

The location has a large population of fur seals, and is popular not just with commercial but recreational fishermen. The best fish to catch are Paua (a type of abalone which is prized for its iridescent shell as well as the flesh), crayfish (also known as rock lobster), and cod. The place is popular with all types of fishermen, including spearfishers.

 

Poor Nemo!

February 15, 2017 • 10:00 am

by Matthew Cobb

Here’s a gorgeous photo of clownfish, which just won the photographer, Qin Ling of Canada, an award in the Behaviour category at the Underwater Photographer of the Year competition (click to enlarge) – you can see all the winners here.

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Ling’s photo is entitled ‘Your home and my home’. Look closely at these Nemos. Look at their mouths. Those little eyes peeking out. They are not drawn on, as PCC(E) first suggested, nor are they Photoshopped. And they are not babies. They are isopods (like pillbugs or woodlice), which are parasitic. They eat the fish’s tongue, and then replace it, sitting in there, presumably getting first dibs on the food as it comes in. They occasionally turn up on people’s dinner plates when folk order fish and get a crustacean chaser.

The photography judge said:  “Six eyes all in pin-sharp focus, looking into the lens of the author … this was one of my favourite shots of the entire competition.”

Isn’t nature wonderful?

*********

JAC: Let me add two references and two videos.  You can read Carl Zimmer’s take on these parasites at National Geographic, or Wikipedia’s entry on Cymothoa exigua, the “tongue-eating louse,” which appears to be the only species that does this.

Here’s a video, which has only one photograph:

Here’s another video with photos; it claims that this is the only case in which one organism replaces another organism’s body part:

The oldest living vertebrates? Greenland sharks could live 300-500 years

August 12, 2016 • 8:45 am
The Greenland shark (Somniosus microcephalus), a little known species, rivals the white shark in size. According to Wikipedia, individuals can be as long as 7.3 m (24 ft) and weigh more than 1,400 kg (3,100 lb). Here’s what they look like:
5-greenland-shark1
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 They are mostly fish-eaters, swim slowly for a shark, and live in the area below:
1280px-Somniosus_microcephalus_distmap
 They have poisonous flesh, laced with neurotoxins that aren’t lethal to humans but can make sled dogs temporarily unable to stand. Although they’re carnivores, they haven’t been reported to attack humans. They do, however, eat large animals, though perhaps only after the animals are dead. As Wikipedia notes:
Greenland sharks are some of the slowest-swimming sharks, which attain a maximum swimming speed about half the maximum swimming speed of a typical seal. Therefore, biologists have wondered how the sharks are able to prey on the seals. Greenland sharks apparently search out seals and ambush them while they sleep. Greenland sharks have also been found with remains of polar bear, horses, moose, and reindeer (in one case an entire reindeer body) in their stomachs. The Greenland shark is also known to be a scavenger, but to what extent carrion (almost certainly the origin of the reindeer) figures into the slow-moving fish’s stomach contents is unknown. It is known that the species is attracted by the smell of rotting meat in the water.
The other day I saw some click-baitish post about this shark saying: “This shark eats polar bears!” They didn’t mention that the bears might already have been dead.

It’s been reported from mark-release-recapture studies that the sharks grow only about 1 cm per year (due, no doubt, to their cold habitat), so their large size suggested to some scientists that they might be very old. This suggestion was supported by a new paper in Science by Julius Nielsen et al.  (reference below, access probably not free). Using a unique method of dating these sharks, they found that they could be up to 500 years old, attaining sexual maturity only after 150 years. That makes them the longest-lived vertebrate on record, far longer-lived than the previous recordholders, Aldabra tortoises and bowhead whales—a bit more than 200 years each. (See the bottom for the longest lived animals that we know about.)

The way that Nielsen et al. aged the sharks (they sampled 28 females between 2011 and 2013) was to use radiocarbon dating on the proteins in the eye nucleus, whose center forms when the shark is still a fetus. (Note: the sharks weren’t killed for this study: they were “by-catch”, accidentally caught in fishing nets.)

It turns out that nuclear bomb testing in the 1950s and 1960s created a spike in radioactive carbon (carbon 14) that was absorbed into the marine environment, and then into animal proteins, so you can see a spike in the amount of radioactive carbon occurring in specimens caught beginning around 1960 (figure from the paper):

F1.large
(from paper): Fig. 1 Radiocarbon chronologies of the North Atlantic Ocean. Radiocarbon levels (pMC) of different origin (inorganic and dietary) over the past 150 years are shown. Open symbols (connected) reflect radiocarbon in marine carbonates (inorganic carbon source) of surface mixed and deeper waters. Solid symbols reflect radiocarbon in biogenic archives of dietary origin. The dashed vertical line indicates the bomb pulse onset in the marine food web in the early 1960s.

The authors found that the highest amounts of radioactive carbon were found in the eye nuclei of smallest sharks, which were presumably born about 50 years ago. They also did radiometric dating of the eye nuclei of the other sharks, which were born before the pulse and could be dated using conventional methods. Because once the eye nuclei are formed in utero the proteins (and the carbon they contain, derived from the environment at that time) do not change further, forming in effect, biological artifacts that can be dated just like ancient wooden artifacts.

The analysis was a bit more complicated than this, but you can read the paper and its references for details.  The upshot is that there’s opportunity for error—not only in the radiocarbon dating itself, but in their use of Bayesian statistics, which requires prior assumptions about age and growth rate.

Given this, the authors are still confident that their estimates are pretty accurate within the error limits shown. The figures that everyone wants to know are in bold (my emphasis):

The model estimated asymptotical total length to be 546 ± 42 cm (mean ± SD), a size matching the largest records for Greenland sharks, and the age estimates (reported as midpoint and extent of the 95.4% probability range) of the two largest Greenland sharks to be 335 ± 75 years (no. 27, 493 cm) and 392 ± 120 years (no. 28, 502 cm). Moreover, because females are reported to reach sexual maturity at lengths >400 cm , the corresponding age would be at least 156 ± 22 years (no. 19, 392 cm) (table S2). Amodel was 109.6%, demonstrating that samples are in good internal agreement, implying that the age estimates are reliable.

The error limits put the upper age limit of the biggest shark as 512 years and the lower limit at 272 years, with the point estimate at 392 years. That means the shark was estimated to have been born in 1624, and could have been born as early as 1504 (that’s 60 years before Shakespeare was baptized). The Guardian says this about the point estimate of the oldest female:

But not everyone is convinced that Greenland sharks can live for four centuries. “I am convinced by the idea of there being long lifespans for these kinds of sharks, [but] I take the absolute numbers with a pinch of salt,” said Clive Trueman, associate professor in marine ecology at the University of Southampton.

Trueman agrees that it is possible to get a record of the early life of a vertebrate from eye lens proteins. However, the fact that the proteins in the centre of the eye lenses, and hence the carbon-14 within them, came from nutrients taken in by the shark’s mother adds a number of uncertainties to the calculations, he says.

Campana says while the approach taken by the researchers is sound, he remains unconvinced that Greenland sharks live for almost 400 years. But, he adds, “future research should be able to nail the age down with greater certainty.”

2.) Is this the longest lived animal? No, not by a long shot. Sponges and corals, which are animals, can live millennia, with some Antarctic sponges estimated at 10,000 years old. However, for animals we’re more familiar with, the record longevity known with reasonable certainty is held by a clam. As I mentioned in 2013, a specimen of the ocean quahog Arctica islandica—a clam nicknamed “Ming”—was snatched from the sea floor off Iceland and dated at 507 years old using growth rings. Pity that the heartless scientists killed it, for who knows how long it might have lived? Like the shark above, this is a cold-water organism. Cold environments can put physiological limits on growth rates by slowing down metabolism, and that might have something to do with extreme longevity. Who knows?

To close, here’s an email exchange I had with Matthew about this paper:

Matthew:  And why don’t most vertebrates live for a long time anyway, Mr Professor?

Me: Antagonistic pleiotropy? How the hell do I know?

Matthew: He he. The more you know, the more you realise we know nothing about anything.

Me: Nothing about anything? Not how many hydrogen atoms in a normal water molecule? Not when we split off from the ancestors of chimps? Not how old the universe or the Earth are?

Matthew: You know what I mean. Don’t be a curmudgeon

 

h/t: Hempenstein
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A day at the Aquarium

December 29, 2015 • 2:00 pm

by Greg Mayer

My Okinawa correspondents spent Boxing Day at the Okinawa Churaumi Aquarium, and sent me a bunch of pictures. The aquarium is a sprawling complex on the coast in northwestern Okinawa, and includes large areas of gardens and park land, and a recreation of traditional Okinawan homes and buildings, as well as the aquarium proper.

Okinawa Charaumi Aquarium
Okinawa Churaumi Aquarium

It reminded me, as I’m sure it did many of you, of the Sausalito Cetacean Institute. That’s Ie Shima island in the background.

Okinawa Churaumi Aquarium
Okinawa Churaumi Aquarium

One of the main attractions at the Aquarium is the Kuroshio Sea Tank. It’s enormous.

Kuroshio Sea Tank
Kuroshio Sea Tank

When my correspondents told me they were going to the Aquarium, they mentioned something about “whale sharks”, but I didn’t query them further. It turns out the Aquarium actually has whale sharks (Rhincodon typus), the world’s largest species of fish!

A whale shark
A whale shark

And not just one!

Two whale sharks
Two whale sharks

Although whale sharks are, for sharks, specialized feeders– they feed on plankton– they are “typical shark” shaped.

Sharks are cartilaginous fishes (Chondrichthyes), which are of two main types: the Holocephali, comprising the ratfishes and chimaeras (we’ve mentioned them here before at WEIT), and the Elasmobranchi, comprising sharks and rays. Most people have a good idea of what sharks and rays look like. Here are some more typical sharks (I don’t know what species– any shark people out there?) Note that the gill slits are on the side of the head; the fellow in the middle is male, as you can tell by the large claspers medial to the pelvic fins.

Typical sharks
Typical sharks

And here’s a typical ray (again, no ID). Note the flattened shape, and the spiracles (whitish bits) behind the eyes– these are the vestigial first pair of gill slits. The flat body of the ray is mostly the greatly enlarged pectoral fins.

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A ray

Most people also know the manta ray (Manta birostris). It’s a little unusual for a ray, being pelagic and filter feeding, so the mouth is at the front tip of the body– and, it’s got those crazy cephalic fins or “horns”, from whence it gets the alternative vernacular name “devil fish”. Do note that the gills are on the bottom of the head.

A manta ray
A manta ray

There is more diversity among sharks and rays than most people realize. Sawfish, which look a lot like sharks with a saw strapped to their snout, are actually rays, but shouldn’t be confused with the similar looking saw shark, which is a shark. There are also angel sharks, which look a lot like rays, and guitarfish, which are rays that look a lot like sharks– in fact, more shark-looking than angel sharks.

I’ve never seen either angel sharks or guitarfish in any aquarium, and thus was delighted to find that Okinawa Churaumi has guitarfish (which, remember, are rays). Here’s a guitarfish surrounded by three sharks, with a typical ray off to the right (and a shadowy form below and to the right). If you look carefully, you can see the spiracle (again, whitish looking) on top of the head, behind the eye.

A guitarfish with three sharks (one only a tail), a typical ray, and a menacing black hulk).
A guitarfish with three sharks (one only a tail), a typical ray, and a shadowy form below and to the right.

In the following picture, we get a really good view of why it’s a ray. Note that the gill slits are on the bottom of the head, as is the mouth (the latter is typical, but not diagnostic, of rays). And, the pectoral fin is joined seamlessly to the head– at a point above, in fact, of the gill slits (which is why the slits are on the bottom of the head). The spiracle, already spatially distant from the other gill slits in sharks, is thus, in rays, separated from the other slits by the interposition of the enlarged pectoral fin.

The underside of a guitarfish's head
The underside of a guitarfish’s head

In the next (and last) picture, note that the dorsal, caudal, and pelvic fins all are at least passably shark-like, but that the enlarged pectoral fin is being flapped for locomotion in the manner of a ray. (Also, it’s a male– you can see the free distal ends of the claspers below the second dorsal.)

A guitarfish swimming along the bottom.
A guitarfish swimming along the bottom.

More on the Okinawa Churaumi Aquarium tomorrow.