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.

Bluespotted Fantail Ray (Taeniura lymma)

There’s something so graceful and beautiful about rays that I can’t help admiring them. I think it’s the way they move through the water, with their undulating ‘wings’ — they are such marvellous but strange creatures. I’ve written about a few rays before: the manta ray and the giant freshwater stingray, and today I’m going to talk about the bluespotted ribbontail, or fantail, ray.

Bluespotted ribbontail rays live in the Indian and western Pacific Oceans. They are found in shallow coastal waters, rarely venturing beyond 25 meters in depth. Bluespotted rays prefer to live in and around coral reefs and sandy flats, so they have places to hide during the day. The rays will also venture into intertidal zones and tidal pools.

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Aren’t these guys amazingly beautiful? Image credit: Jens Petersen via Wikipedia

These stingrays are easily recognized by the bright blue spots that cover their bodies, though they are not the only species of ray known as bluespotted stingrays. They are, however, quite distinctive, as they have more and brighter spots than other species, as well as having two bright blue stripes on their tails. Bluespotted fantail rays do not get overly large, reaching maximum widths of 35 cm. They are oval in shape, with a smooth, yellowish-green disc.

Bluespotted fantail rays are nocturnal, spending the day hidden in caves, shipwrecks, or coral reefs. At night, these guys emerge and head to the shallows, following the high tide into tidal flats in search of tasty meals. They feed on a wide variety of animals, including crabs, shrimp, fish, and sand worms. They detect their prey using electroreceptors, and trap them by pressing their discs into the ocean floor. Once the prey is caught, the rays move around until their meal is directed into their mouths, which are located on the underside of their bodies. Bluespotted rays have 15-24 rows of teeth arranged into plates, which can easily crush the shells of molluscs.

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A close up of a bluespotted ray’s eyes, which makes it look pretty creepy. Image credit: Nick Hobgood via Wikipedia

Bluespotted rays themselves are targeted as prey; both hammerhead sharks and bottlenose dolphins are known to feed on these rays. When threatened, bluespotted rays prefer to run away, swimming in zigzags to try and confuse predators. These rays have another method of defence, however — they have lovely venomous spines at the tips of their tails, which can deliver a nasty sting to anyone foolish enough to get close to them. Hammerhead sharks get around this by using their hammer-shaped heads to pin the stingrays down while they eat them.

Bluespotted rays mate in the spring and summer, when males start to follow females around. They eventually start nipping at the females’ discs, and then hold on while the pair copulate. The exact gestation period of bluespotted fantails is uncertain, but after four to twelve months females give birth to up to seven pups, which look like miniature versions of their parents.

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A quick sketch of a bluespotted fantail ray.

Bluespotted fantail rays are popular in home aquaria, in spite of their dangerous spines. They are also very difficult to keep in captivity, with many refusing to eat or dying for unknown reasons. But people still try and keep them for some reason, and the rays are also suffering from degradation of their natural habitat. They are still fairly abundant in the wild, but have been assessed as Near Threatened by the International Union for Conservation of Nature (IUCN). Hopefully these beautiful creatures can stick around for a while.

Cover image credit: Jon Hanson via Wikipedia

Garden Eel (subfamily Heterocongrinae)

Have you ever seen a garden full of eels? I picture a pretty rose garden with a bucket of slimy, wriggling eels poured all over it. It would be pretty gross. But there are actual eel ‘gardens’, and they are much more beautiful than you might think.

There are around 35 species of garden eel, organized into the subfamily Heterocongrinae. Garden eels prefer warm waters, with most species being found in the Indo-Pacific, and some in the Atlantic. These eels require sandy bottoms to burrow in, and like areas where there are lots of sea currents.

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A pair of spotted garden eels in their burrows. Image credit: Johan Fredriksson via Wikipedia

Garden eels can get as big as 120 cm in length, but most are on the smaller side. They look quite eel-like, with long, thin bodies and no obvious fins. They come in an amazing variety of colours and patterns, from white-green with pretty black spots to yellow with white stripes.

So what makes garden eels different from other types of eel? Do they cultivate beautiful gardens of seaweed and other aquatic plants? Well, not really. You see, in these gardens, the eels themselves are the plants. Garden eels have a very peculiar way of living. They dig burrows in the soft, sandy ocean floor, stick their heads out, and then simply wait. The lovely ocean currents bring the eels drifting bits of food, and the eels rarely leave their burrows. They tend to live in colonies, so all the eel heads swaying in the currents look a lot like a garden.

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A bunch of garden eels hanging out. From far away a colony looks like sea grass. Image source

Digging a burrow with your tail isn’t the easiest task – but garden eels have a pretty good way of doing it. The eels make themselves rigid, and then shoot into the ground tail first. Their tails are covered by hard skin, so the eels don’t get injured. Garden eels also secrete a substance that cements the sides of their burrows, so they don’t cave in. When threatened by predators, garden eels simply slip down into the safety of their little homes.

While an on-land garden full of eels might not be a very pretty sight, the underwater ones must be quite spectacular. If I didn’t have a fear of diving in oceans, I would definitely try and go see some garden eels. I’ll have to settle on looking at pictures.

Cover image source

Merten’s Carpet Anemone (Stichodactyla mertensii)

I don’t recall ever being stung by a sea anemone, but I’ve heard it can be pretty nasty. Still, anemones are fascinating creatures, and they look quite cool with all their tentacles waving about with the currents. The only anemone I’ve written about was the Cloak Anemone, which forms a partnership with hermit crabs. Today’s anemone is an entirely different type, choosing to live a more sedentary life.

Rocky, coral areas are the preferred habitat for Merten’s carpet anemones, which live in tropical waters in the Indo-Pacific Oceans. They don’t like to live in very deep water, usually hanging out around depths of one to twenty metres. Merten’s anemones like rocky areas because these allow the anemones to hide their bodies in crevices, only exposing their mouths to the dangers of the open ocean.

A really beautiful picture of a Merten's anemone and some fishes. Image source: http://www.messersmith.name/wordpress/tag/stichodactyla-mertensii/

A really beautiful picture of a Merten’s anemone and some fishes.
Image source: http://www.messersmith.name/wordpress/tag/stichodactyla-mertensii/

Merten’s carpet anemones are the largest sea anemones in the world. They can reach staggering proportions of over one metre in diameter. That’s a little ridiculous for a sea anemone. Other than their size, Merten’s anemones are a bit boring, having no bright fun colours that other anemones flaunt. I guess these guys decided to forgo colourful creativity in favour of getting really, really large. They are different shades of green, yellow or cream.

The tentacles of Merten’s anemones are also fairly unimpressive. They are relatively short, only being about a centimetre or two long. The anemones use these tentacles for protection from predators. I know, it’s weird that things would want to eat an anemone, but there are animals that try. Predators of Merten’s carpet anemones include other anemones, sea stars, and some types of fish.

Here's a Merten's anemone all folded up. Image source: http://animal-world.com/Aquarium-Coral-Reefs/Mertens-Carpet-Anemone#Habitat: Distribution / Background

Here’s a Merten’s anemone all folded up.
Image source: http://animal-world.com/Aquarium-Coral-Reefs/Mertens-Carpet-Anemone#Habitat: Distribution / Background

These sea anemones can be aggressive, but they also share their large bodies with a number of different organisms. Some of the most visible of them are anemonefish and damselfish, which hide in the anemones’ tentacles for protection. Other, less obvious partners are the symbiotic zooxanthellae that the anemones require to survive. These algae provide the anemones with most of their food, and in exchange are protected by the anemones’ tentacles.

Some anemones look really neat, but they are a little terrifying thanks to all those nasty tentacles they have. I cannot even imagine seeing a meter-wide anemone. I think something like that could haunt my dreams, so it’s a good thing I have no intention of diving in any ocean, let alone the Indo-Pacific.

Cover image source: Brocken Inaglory via Wikipedia 

Giant Clam (Tridacna gigas)

I’m trying very hard to think of a mollusk that is as impressive as the giant clam. It’s pretty difficult to do. These guys are just so massively amazing. There’s definitely something to be said for animals that are really, really, big. It’d be better if they had faces, but no animal is perfect.

Giant clams can be found in tropical areas of the Indo-Pacific Ocean. They like to hang out in coral reefs, especially shallow waters less than twenty meters from the surface. As far as what kind of substrate these jolly clams like, sandy places or coral rubble are the best.

You can't tell, but it's big.  Image source: Nick Hobgood via Wikipedia

You can’t tell, but it’s big.
Image source: Nick Hobgood via Wikipedia

Giant clams are pretty big. One might even call them giant. Not me though. They do get to be up to considerable sizes, with some clams reaching 1.5 m in length. In addition to their size, giant clams can also be fairly colourful, with their mantle being green, yellow or brown and covered in iridescent blue, purple or green spots. Apparently giant clams are like those body builders who can’t touch their shoulders because their muscles are too big — once a giant clam reaches their full size, they are too big to close their shells completely.

Reproduction in giant clams is pretty simple: the clams squirt eggs and sperm into the water, and hope that the gametes meet the excretions from other nearby clams. The clams are hermaphroditic, meaning one individual can produce both eggs and sperm, but a clam cannot self-fertilize. To increase the chance that other clams will release sperm and eggs at the same time, giant clams use a chemical called the spawning induced substance that synchronizes fluid ejection from neighbouring clams.

Young larvae spend their time floating around the ocean searching for a suitable spot to settle down. By one week of age, the little clam starts to test out potential living spaces, moving around until the perfect location is found. I guess if you spend your whole life in one spot, you want to make sure it’s a good one.

Feeding for animals that don’t move can be a bit of a problem; waiting for enough plankton to drift by is not very efficient. Giant clams have a solution for this — they host algae inside their shells that provide the clams with the majority of their diet. The clam will open up during the day to provide the algae with enough sunlight to go properly. Younger clams have a large portion of plankton in their diet, but adult giant clams cannot survive without their algae friends.

Because they are large and interesting, people have hunted giant clams for both food and for the pet trade. This has severely reduced giant clam numbers, but aquaculture efforts are in place to preserve the species. Hopefully this can keep these big guys around for a while!

Cover image source: http://www.mindanaotours.com/giant-clam-sanctuary-camiguin/

Flying Gurnard (Dactylopteridae)

I’m not really sure how I picked this fish out — whether I was drawn towards it because of the strange name (gurnard just sounds really funny) or because of the actual traits of the fish, I don’t remember. But it was flagged on my list of animals to blog about, so here we go.

Flying gurnards belong to the family Dactylopteridae, which contains two genera and seven species. They are also known as helmet gurnards, as they can’t actually fly (or glide) like true flying fish can. They are found mostly in the Indo-Pacific, though one species lives in the warmer areas of the Atlantic. Adult flying gurnards hang out at the bottom of the ocean, often ‘walking’ along the sea floor with their pelvic fins.

A flying gurnard with its 'wings' folded in.  Image source: Wikipedia

A flying gurnard with its ‘wings’ folded in.
Image source: Wikipedia

Flying gurnards are quite beautiful fish. Their most notable characteristic is their greatly enlarged pectoral fins, which can be spread out to look like wing (hence the ‘flying’ part of their name). They use these great and often brightly coloured fins to escape from predators — the wings let the fish move quickly, as well as making gurnards look bigger than they actually are. The heads of flying gurnards are covered with hard, armour-like scales (hence the ‘helmet’ alternative name).

See how pretty they are when they have their fins spread out? Image source: Wikipedia

See how pretty they are when they have their fins spread out?
Image source: Wikipedia

These fish hunt bottom-dwelling crustaceans on the sea floor, walking along the bottom until they encounter some tasty meal. Apparently gurnards have a well-developed swim bladder, which has a muscle attached to it that may be able to drum against the bladder, creating sounds. To what purpose these sounds may be used, I do not know.

In fact, it seems that not a whole lot is known about flying gurnards. Unfortunately it appears that these fish aren’t valuable enough, interesting enough, or endangered enough to attract research. It’s a real shame, because what little we know about them is pretty neat.

Cover image source: http://www.diverosa.com/Lembeh%202006/IL2-024%20Flying%20gurnard,%20Dactyloptena%20orientalis%202.html