Dragonet (family Callionymidae)

I’ve loved dragons ever since I can remember loving anything. I think they’ve always been my favourite mythical creature. So any real-life animal that is named after dragons always sparks my interest. Which is how I came across today’s group of animals, the dragonets.

Dragonets belong to the family Callionymidae, which consists of 139 fish species in nineteen genera. They live in the Indian and Pacific Oceans, and enjoy hanging around in warm, tropical waters. Dragonets are bottom dwelling fish, residing on the sandy ocean floors at depths of up to 200 meters.

Dragonets, as their name implies, are not overly large fish. The largest species of dragonet reaches lengths of only 30 cm. Many species of dragonet are brightly coloured, and have wonderful patterns along their bodies. Males and females have different colour patterns, and although the fins of all dragonets are large, males are known for having particularly impressive dorsal fins.

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A very colourful mandarin fish, look for a post on these guys in the future, they’re super cool! Image source

They may look pretty, but dragonets are not friendly fish, and males are especially aggressive during courtship and mating. They will charge each another, biting the other fish’s mouth, and twist around one another. Both their large spines and bright colours are required to achieve dominance, and thus gain access to mates. Unfortunately, this comes at a cost: males are more likely to die than females, both from fights with one another and from predation, since they are easier to find, thanks to their bright and beautiful colouration.

Reproduction in dragonets begins with courtship, with both sexes (though more commonly males) displaying to one another. Displays include spreading of the fins, as well as swimming around one another. Males will also open and close their mouths, and position themselves on top of females and rub them. Once a pair has been formed, the two prepare to spawn.

To spawn, dragonets swim upwards, rising together in a semicircular pattern. They don’t move very quickly, and have to take a rest after rising about fifteen centimetres. Once they proceed to the second part of their rising swim, the dragonets start to spawn, with both sexes releasing their gametes into the water. The buoyant eggs stay floating in the water, and travel away with the current. Once spawning is done, male dragonets go back to the depths and look for more females to mate with.

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A picturesque dragonet, looking spotty and colourful. Image source

Dragonets feed on benthic organisms, primarily small invertebrates. They have large mouths, and can extend their jaws towards their prey, sucking the unfortunate victim into their mouth. When dragonets themselves are threatened, they will bury themselves in the sand, so that only their eyes are visible. Other defences depend on the species; some spines on dragonets have been reported to be venomous, while many species are able to secrete nasty tasting substances that deter predators.

Though I picked these fish as my animal for the week because of their name, they turned out to be a lot of fun to draw too. Their bright colours and pretty patterns made a lovely subject to paint. Isn’t it nice when things work out like that?

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My watercolour painting of an oscillated dragonet. I decided to highlight the splash of colour on its dorsal fin by keeping the rest monochrome.

False Catshark (Pseudotriakis microdon)

As you’ve probably noticed if you follow this blog regularly, many animals have names that make no sense at all. There are some rare species, however, that have names that are perfectly logical, and today’s animal is one of those.

When the first specimen was found, it was thought to resemble a catshark, but was subtly different enough to be placed in its own genus. Thus the name ‘false catshark’ (Pseudotriakis) was born. False catsharks are found in many places around the world, particularly around continental slopes. They live at depths of 500-1400 m, generally sticking near the ocean floor.

These sharks can get pretty big, growing to lengths of three meters. They are brown or grey in colour, which probably helps them blend into the seafloor. False catsharks have long, bulky bodies, and giant mouths. The insides of their mouths are filled with two hundred rows of teeth, but luckily these teeth are very small. Here’s where the logicalness of false cat sharks’ names get even better — the second part of its scientific name, microdon, means ‘small tooth’. I love it when things make sense!

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As a deep water species, getting pictures of live false catsharks is pretty rare. This one is pretty cool! Image credit: NOAA Ocean Explorer via Wikipedia

False catsharks are very lazy animals. In fact, their bodies aren’t really built for much action — their fins and muscles are soft and flabby. The catsharks get around this by having a very large and very oily liver. This organ can make up to a quarter of a catshark’s total bodyweight, and helps with the sharks’ buoyancy. With the aid of their livers, false catsharks can float near the bottom of the ocean without expending much energy. When they do hunt, the catsharks do actually move quickly. They prey mainly on other fish, squids, and octopi. The catsharks’ big mouths mean they can eat quite large prey.

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A picture of a false catshark showing its distinctive long dorsal fin. Image credit: CSIRO National Fish Collection via Wikipedia

Another unusual thing about false catsharks is their reproductive habits. Developing eggs feed on the yolk from their eggs, but switch to consuming ovulated eggs later in gestation. The mothers give birth to live young, usually only birthing two pups at a time. This type of reproduction is not unheard of in sharks, but is rare for ground shark species.

Though false catsharks may not be actual catsharks, I would argue they are much cooler than their namesakes. Of course, I don’t really know much about catsharks, having only written about one of them (the chain catshark). I guess there will have to be a future post on true catsharks, and then I can make an informed decision about which is better!

Sea Cucumber (class Holothuroidea)

Are there stranger animals than sea cucumbers? Probably. But as a whole, sea cucumbers are bizarre and silly animals that definitely deserve a blog post. They are so oddly shaped, and look like they shouldn’t be a successful group of animals. But there’s a lot going on in these sea vegetables, and they are definitely successful.

Sea cucumbers make up the class Holothuroidea, which contains over 1,700 species. They are found worldwide, but are particularly abundant in the Asian Pacific Ocean. Sea cucumbers vary in their habitat preferences, but most species are benthic, or bottom-dwelling. They tend to be particularly abundant in deep waters, and make up 90% of the macrofauna at depths greater than 8.9 km.

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A massive and neat-looking sea cucumber. Image credit: Leonard Low via Wikipedia

The size of sea cucumbers ranges from a paltry 3 mm to a massive 3 meters in length. Most sea cucumbers are somewhat cucumber shaped, though others can be nearly spherical and still more can be long and snake-like. There are some odder varieties as well, but I’ll get to them later. As members of the phylum echinodermata (which includes starfish and sea urchins), sea cucumbers have five-fold symmetry, though this is not nearly as obvious as it is in starfish. The radial symmetry in sea cucumbers occurs lengthwise, so if you were looking at one head on (if you assume these guys have heads), you’d be able to see it.

The mouths of sea cucumbers are usually pretty easy to spot, as most species have bunches of tentacles coming out of them. The shape and size of the tentacles are dependent on the cucumber’s diet, but most species can retract the tentacles rapidly in the case of any threat. Sea cucumbers are usually scavengers, feeding on detritus and particles that fall to the ocean floor. Many sea cucumbers sift through sandy sea floors, and excrete a lovely homogenized product that helps shape the ecology of the ocean bottom.

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A lovely picture of a sea cucumber’s mouth. Image credit: Drow_male via Wikipedia

Though most species of sea cucumber tend to stay on the ocean floor, not all do. There are some that are capable of making ‘jumps’ in the water, because their bodies’ densities are about the same as the water around them. Of course, propelling yourself into the water with no control isn’t such a good idea, so these species have special appendages  that help them ‘swim’ — such as umbrellas or lobes.

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One species of ‘jumping’ sea cucumber, which looks nothing like a cucumber. Image source: Wikipedia

Jumping sea cucumbers may have reasonable escape methods from predators, but more sedentary species have to have different ways of protecting themselves. Many species are toxic to all but the most specialized predators, and some actively dispel a toxin into the water that can kill nearby predators. Other species can expel a bunch of sticky threads from their body that entrap attacking predators.

Sea cucumbers are used both in cuisine and in traditional medicines, particularly in the Asian markets. Some species have been threatened by over-fishing, and others are grown in aquaculture farms.  I don’t know why someone would want to eat one of these guys — they don’t look very appetizing. Still, I’m not much of a seafood fan in general, so I’m not the best judge. I think I’ll stick to nice green land cucumbers.

Cover image credit: Hans Hillewaert via Wikipedia

Atlantic Wolffish (Anarhichas lupus)

Any animal named after wolves is automatically awesome. Think about it: wolf spiders (terrifying but undeniably fierce), aardwolves (adorable!), and now, the atlantic wolffish. This fish, as you will see, is one bizarre animal.

Atlantic wolffish are found in the Atlantic Ocean, along both the eastern and western coasts. They favour cold waters, and are found as far north as the Davis Strait. They survive in these icy waters thanks to a natural antifreeze in their blood. How cool would it be to have blood that can’t freeze? Maybe I should make a superhero with that power… Wolffish rarely venture father south than Cape Cod, presumably because things are too warm down there. Wolffish are bottom-dwellers, and particularly like rocky areas, where they can hang out in crevices.

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Some wolffish hanging out in a nice protected rocky nook. Image source

If you’re named after a wolf, you have to something fearsome about you. Atlantic wolffish definitely meet this criterion. They can grow to lengths of a meter and a half, and weigh up to 18 kilograms. But their size isn’t even the most intimidating part about wolffish. No, the most terrifying (and most wolfish) thing about Atlantic wolffish is their teeth.

Atlantic wolffish have very strange teeth for fish. First of all, each jaw has up to six huge fangs. Then on the top jaw there’s three rows of teeth specifically designed for crushing. The fish also have some lovely molars, and a number of serrated teeth all over their throat. In summary: wolffish have a crapload of teeth.

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A side view of a wolffish’s teeth. Pretty scary stuff. Image source: Wikipedia

So what do wolffish need these ridiculous teeth for? Thankfully they don’t use them to eat people. They don’t even eat other fish, instead using their powerful jaws and rows of teeth to crush the shells of molluscs, crustaceans and echinoderms. Wolffish help control the populations of sea urchins and green crabs, which is important for ecosystem health.

The uniqueness of wolffish isn’t limited to their blood and teeth. Unusually for fish, Atlantic wolffish practice internal fertilization. Males also stick around and help protect the eggs for up to four months. During this time, males are so dedicated to their children that they barely eat. Wolffish have some of the largest fish eggs in the world, at 5.5 to 6 mm in diameter.

Unfortunately wolffish have fallen prey to overfishing, particularly by bottom trawlers that ruin the rocky habitats wolffish love. This isn’t just bad news for the wolffish, but also for the ecosystems they maintain by eating sea urchins and crabs. Lets hope these odd fish get some protection, so we can keep admiring their strangeness.

Cover image source: Wikipedia

Longnose Sawshark (Pristiophorus cirratus)

I don’t think it would be very much fun to have a saw as a mouth, but at least one animal in this world thought it was a good idea. It would make sense that this animal is a shark. After all, sharks try their best to be as terrifying as possible, and what’s more intimidating than a shark with a saw on its face?

Longnose sawsharks live in the waters around Australia, in the Indian and Pacific Oceans. They can be found in both coastal areas and in the open ocean, though they prefer spaces with sandy bottoms. Sawsharks are usually found at depths below 40m.

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These sharks look so ridiculous… Image source: http://dantania.blogspot.ca/2013/08/dante-vs-nature-27.html

The most characteristic and recognizable feature of the sawshark is its giant snout. Sawsharks can grow to be 1.37 meters long, and their snouts can make up 30% of that length. That’s a pretty big nose! About halfway down this impressive noggin are two barbels, which help the shark feel its way around the ocean. The sawlike appearance of the sharks’ noses is due to their protruding teeth, which are arranged in an alternating long and short pattern. Sawsharks are a boring combination of yellow, grey, and brown. Though these colours aren’t very flashy, they do help the sharks blend in with the ocean floor, giving them some protection against predators.

Those vicious and undoubtedly strange snouts do serve a purpose — they are used for hunting. The sharks swim close to the ocean floor, their barbels sensing the sandy bottom, and their ampullae of Lorenzini detecting any electric fields made by nearby prey. Once they have found a tasty morsel, the sharks slam it with their snouts, immobilizing the victim.

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Another great picture of a longnose sawshark and it’s impressive nose. Image source: http://www.nhmsharksandrays.co.uk/the-fish.html

Longnose sawsharks are slightly unusual for sharks in that they often form schools. They breed every two years, and give birth to 3-22 live young. You might think that it would be incredibly painful to give birth to sharks that have rows of sharp teeth sticking out of their snouts, and you would be right. Thankfully, sawsharks have a solution to this — when the young are born their teeth are folded in, and only straighten out after they’ve left their mother’s belly.

The conservation story of the longnose sawshark is a happy one. They were once classified as Near Threatened, but have recently been downgraded to Least Concern. Protection from fishing has helped these sharks tremendously, and these days they seem to be doing quite well.

Goatfish (family Mullidae)

Goats are funny creatures. So any fish named after our silly ruminant friends automatically gains some of that hilarity. That’s why when I was browsing through the endless realm of the internet this morning, looking for a fish to write about, the goatfish leapt out at me.

Goatfish comprise the family Mullidae, which contains six genera and fifty-five species. They are found in tropical waters, usually around reefy areas. Goatfish can live in the Atlantic, Pacific, and Indian Oceans, as well as in the Mediterranean and Red Seas. They are benthic fish, meaning they tend to stay on the ocean floor, but prefer shallow areas where they don’t have to venture deeper than 100 m.

A bluestriped goatfish sporting some nice barbels.  Image credit: Graham Short via http://www.fishesofaustralia.net.au/home/species/595

A bluestriped goatfish sporting some nice barbels.
Image credit: Graham Short via http://www.fishesofaustralia.net.au/home/species/595

Like goats, goatfish come in a wide variety of colours. Unlike goats, goatfish can rapidly change their colour (side note: how cool would it be to have a colour-changing goat?!). The fish will change their colour depending on what they are doing; a fish resting on the bottom will have a different colour than a highly active fish. Goatfish sometimes swim with other species of fish, and will change their colour to match that of the schools they swim with.

Goatfish are bottom feeders, using two barbels that protrude from their chin to sweep the ocean floor for any edible meals. They will eat pretty much anything, which is where the ‘goat’ part of their name comes from. Once they’ve found a tasty animal, goatfish dig their heads into the sand, ingesting both the prey and a ton of sand. The food is swallowed while the sand is expelled through the fish’s gill covers.

A whitesaddle goatfish foraging for some food.  Image credit: Divervincent via Wikipedia

A whitesaddle goatfish foraging for some food.
Image credit: Divervincent via Wikipedia

Goatfish don’t just use their funny barbels for foraging; they are also involved in courtship behaviour. Male goatfish will waggle their barbels at females to attract their interest. Females lay eggs in the open water, where they float until hatching. Their behaviour doesn’t change much after hatching, with the little goatfish simply dancing with the currents until they reach 5 cm in length, when they go to the bottom and start acting like real goatfish should.

In many countries, goatfish are caught for human consumption, and have been for quite some time. In ancient Rome goatfish were highly valued thanks to their colour-changing abilities: fish would be served still alive, and as they died the poor goatfish would go through a number of colour changes. I think I’d be put off by food that changed colours before my eyes, but the Romans loved it.

Cover image source: http://www.zoochat.com/1821/manybar-goatfish-paurpeneus-multifasciata-287419/