Purple Sea Star (Pisaster ochraceus)

One thing I absolutely loved to do as a kid was wander around rocky shores, looking for any form of life. I’d lift up whatever rocks I could to search for crabs, I’d run from tidal pool to tidal pool to peer at starfish and sea anemones. I love living in Ontario, but one thing I desperately miss is the ocean. So today I’m going to going to write about a species of sea star, to fully embrace my nostalgic mood.

Probably the most common starfish I encountered as a child were large purple ones. Unsurprisingly, these are known as purple sea stars, but confusingly are also known as ocher sea stars, since not all of them are purple. They can also be orange, yellow, red or brown. That being said, most of these guys are purple, so I’ll refer to them as purple sea stars. They have five legs, each of which can be from 10 to 25 cm long. Purple sea stars are covered in very small spines, which are no bigger than 2 mm in height.

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An example of some colour variants in purple sea stars. Image credit: D. Gordon E. Robertson

Purple sea stars live in the Pacific Ocean, from Alaska to California. Depthwise, they can be found from 90 m to the low-tide zone. They are commonly found along the coast, on mussel beds and rocky shores. Special suckers on their feet allow purple sea stars to cling to rocks with great force, so they can withstand violent waves.

Despite their harmless looks, purple sea stars are quite vicious eaters. They feed mainly on mussels, but will also eat chitons, limpets, snails, barnacles, and sea urchins. They will swallow their prey whole if they can, grabbing their meal with their tubular feet and then everting their stomach onto their prey. The digestive enzymes in the starfish’s stomachs will then liquify the victim, so it can be easily ingested.

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A purple sea star. Image credit: D. Gordon E. Robertson via Wikipedia

Mussels try and defend against starfish by clamping their shells together very tightly, but sea stars are patient hunters. Mussels need to open their shells slightly, both to breathe and to feed. The starfish then use their strong feet to pull the mussel shell further open, and insert part of their stomach into the shell, digesting the poor mussel inside. Purple sea stars have quite large appetites, with one sea star being able to eat eighty Californian mussels a year (a California mussel can reach lengths of 20 cm, so they aren’t small).

Purple sea stars breeding from May to July, with both sexes releasing gametes into the water. If all goes well, sperm and eggs meet in the ocean,  and the fertilized eggs can drift around until they hatch. Sea stars progress through a number of larval stages, and at this stage of their life the little starfish are filter feeders, relying on plankton to sustain them. Purple sea stars live to be at least four years of age, and may live much longer.

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I decided to try something a bit more abstract for this week’s drawing. I had fun with all the shapes!

Purple sea stars aren’t just pretty; they are an extremely important species. Thanks to their diet, purple sea stars help keep mussel populations under control. A loss of only a few purple sea stars leads to a drastic increase in mussel populations. When sea stars are present, the intertidal ecosystem is diverse, instead of becoming dominated by mussels. So next time you see a sea star, remember that they help keep our oceans wonderfully diverse!

Cover image source

Spotted Ratfish (Hydrolagus colliei)

A lot of fish are named after land animals — catfish, dogfish, rabbitfish, porcupine fish, kangaroo fish (that last one does’t actually exist, but I wish it did).  Today’s animal, the ratfish, seems to have gotten the short end of the naming stick. I like rats, but I don’t think I’d want to be named after them.

Ratfish belong to the family Chimaeridae, otherwise known as shortnose chimaeras. Chimaeras are an odd group of fish that have cartilaginous skeletons like those of sharks and rays. In fact, their closest relatives are sharks. Almost all chimaeras are deep water fish, and are therefore difficult to find and to study. So today I’m going to focus on one of the few chimaera species that hangs around in shallow waters, the spotted ratfish.

Spotted ratfish live in the Pacific Ocean, from Alaska to Baja California. They have been found at depths of up to 913 m, but are much more common in areas between 50 and 400 m deep. In the spring and autumn spotted ratfish tend to hang out in shallower waters, moving to deeper areas in the summer and winter. They prefer to live on the ocean floor, particularly on sandy, muddy or rocky reefs.

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These guys are a little strange looking…     Image source

Spotted ratfish are named for their spots, and for their long, ratlike tails. They can grow to be up to a meter in length, and females are much larger than males. Ratfish tails can make up almost half of the fish’s length, and are long and thin. Spotted ratfish have silvery-bronze skin, and are covered in fun white spots. They have big huge adorable eyes, which reflect light like those of a cat or dog.

Spotted ratfish hunt during the night, using their sense of smell to locate prey. They swim slowly above the ocean floor, looking for shrimp, worms, fish, crustaceans and sea stars. Ratfish particularly enjoy foods with some crunch to them, such as crabs and clams. They have incisor like teeth that act as grinders to help break up their yummy diet.

Spotted ratfish may be hunters, but they themselves fall victim to predators. Sharks, halibut, pinnipeds and pigeon guillemots are all known to consume spotted ratfish. Eating a ratfish is not always a pleasant experience, however. They are equipped with a venomous spine on their dorsal fin, which can cause painful wounds. The spine can also be deadly if ingested: harbour seals have died after a ratfish spine penetrated the stomach or esophagus. The lesson here: don’t eat ratfish, unless you posses spine-removal tools.

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A spotted ratfish egg sack. Image source

Breeding season in spotted ratfish occurs from spring to autumn. Female ratfish lay one or two fertilized eggs into sandy or muddy areas every two weeks or so. Egg laying can last for four to six days, which is a long time, but is necessary, considering the size of the egg sacks. Each sack is twelve centimetres long, and is basically a leather pouch. The eggs take a long time to develop and hatch, sometimes staying inside the egg case for up to a year.

Unfortunately for spotted ratfish, the appearance of their eggs, and the extensive time it takes for the eggs to hatch means that the eggs are sometimes mistaken as inanimate objects by divers. But the news isn’t all bad: the overall population of spotted ratfish is doing just fine, in part because they don’t taste that good. I guess the key to surviving in the modern world is to taste bad, and not look too pretty.

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A quick sketch of a spotted ratfish, emphasizing its big cute eye. 

Cover image credit: Clark Anderson via Wikipedia

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

Saltwater Crocodile (Crocodylus porosus)

During the past two weeks I watched all four Jurassic Park movies, so I’m in a bit of a dinosaur mood. Unfortunately, Our Wild World is a blog about extant animals, so dinosaurs are right out. I’ve decided instead to write about a species of crocodile, because they’re basically the next best thing.

The species I’m going to focus on is the saltwater crocodile, because they are super cool. Saltwater crocodiles have a broad range, and are found from eastern India to Indonesia, Australia, and even around some Pacific islands, like Vanuatu and the Solomon Islands. As their name implies, saltwater crocs can tolerate high levels of salinity, and are often found in rivers, estuaries and coastal areas. More than any other species of crocodile, saltwater crocodiles are found in the ocean; they often travel long distances in the open ocean and can spend months at sea.

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The range of the saltwater crocodile. Image source: Wikipedia 

Saltwater crocodiles are big. You definitely don’t want to meet one of them in a murky river. In fact, saltwater crocodiles are the biggest of all crocodiles and are the biggest reptiles in the world. Males can reach lengths of six to seven meters, though females only grow to a paltry three meters. The largest male ever recorded weighed 1,075 kg. Adults are a dark greenish colour, with lighter bellies. Young crocodiles have more exciting colouring, being yellow with stripes and spots on them.

Crocodiles are big (as I mentioned), and they have large, pointy teeth. Saltwater crocodiles have between 64 and 68 teeth, the longest of which can measure up to nine centimetres in length. They use these massive teeth to hunt, feeding on a wide variety of animals such as fish, turtles, snakes, buffalo, birds, wild boars and monkeys. Crocodiles are ambush predators, hiding below the water’s surface with only their backs, nostrils and eyes visible, until an unlucky victim stumbles along.

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A very fat looking saltwater crocodile. Image credit: fvanrenterghem via Wikipedia

When a prey animal does happen to wander too close to a saltwater crocodile, the crocodile strikes. They are surprisingly fast when striking from the water, using both feet and their tails to launch themselves at their prey. They can swim in bursts of 24 to 29 km/hr, so you really don’t want to be stuck in the water with a saltwater crocodile.

Once the crocodiles have an animal in their strong jaws, it is either swallowed whole, or, if it is too large, the crocs drag their prey underwater and drown it. Crocodile teeth are not made for shearing, so crocodiles rip chunks of meat off their prey by rolling in the water while gripping the prey to twist off pieces of flesh, or by jerking their heads to remove hunks of tasty meat.

If you do end up getting bitten by a saltwater crocodile, good luck getting away; saltwater crocodiles have the highest bite force of any animal, measuring a maximum of 16,414 N (which I’m guessing is a lot). Part of the bite strength of saltwater crocodiles comes from the design of their jaw muscles; they can clamp down extremely hard, but have weak muscles when it comes to opening their jaws. Apparently a few layers of duct tape is sufficient to hold a crocodile’s mouth shut. The tricky part, of course, is getting the duct tape on the crocodile in the first place.

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Saltwater crocs can breach out of the water to try and catch food, so don’t think you’re safe just because you’re in a tree. Image credit: Matt via Wikipedia

Saltwater crocodiles breed during the wet season, from September to October. Though they often live in saltwater, saltwater crocodiles move to fresh water to breed. Males are very territorial in general, but are especially aggressive during the breeding season, chasing away any other males that encroach on their territory.

Female saltwater crocodiles lay between 40 and 90 eggs in mounds placed on river banks and shores. The eggs are laid raised from the ground, to prevent them from being washed away during floods. The eggs hatch after around three months, at which point calls from the young prompt the mother to help unearth the eggs. She then carries the hatchlings in her mouth to the water, and stays with her brood for a few months. Very few survive to adulthood, and those that do disperse at eight months of age. Sexual maturity is reached when crocodiles are 10 to 16 years old, and these remarkable reptiles can live to be over 70 years of age.

Because saltwater crocodiles are highly valued for their meat, eggs, and skin, this species was once hunted extensively. They have since come under protection in most of their range, and have made great recoveries. Thankfully they are not currently endangered or threatened, but habitat destruction is a concern for these magnificent beasts.

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My drawing for the week (I apologize for the poor quality of the image – I’m away and do not have access to my scanner) – this is all you would see of a crocodile hiding in the water. 

I’d like to say a few last things about the saltwater crocodile. First, they are big, with large teeth, and are territorial and aggressive. So yes, they can and do eat people who come into their waters, so watch out. And secondly, even though these guys are giant man-eaters, you shouldn’t hate them, because not only are they very cool, they are also supposed to be very intelligent. They have extensive means of communication, can learn tasks quite quickly, and track the migratory patterns of their prey. So don’t hate saltwater crocodiles, and definitely don’t swim with them.

Cover image credit: Djambalawa via Wikipedia

American Lobster (Homarus americanus)

I’ve never been much of a fan of lobster meat. I like it for the first few bites, especially dipped in butter, but then the meat gets way too rich and I get sick of it. While I might not be a fan of the meat, I do think lobsters are pretty cool animals, and it’s about time I wrote about them on here.

There are lots of different species of lobster, but I’m going to focus on the American lobster, as it is the species most people are probably familiar with. American lobsters live off the east coast of North America, from Labrador to North Carolina. They can be found in shallow or deep water, though they are more common in deeper areas. Lobsters like rocky areas, where there are lots of places for them to hide. They are nocturnal, spending the day inside their burrows, and coming out at night to feed.

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The range of the American lobster. Image source: Wikipedia

American lobsters are the largest of all lobsters, and are also the owners of the title World’s Heaviest Arthropod. They can reach maximum lengths of 64 cm, and weigh over 20 kg. Most American lobsters are a greenish blue colour, but there are numerous colour morphs, such as bright blue, yellow, orange or albino. You might be familiar with bright red lobsters — but live lobsters are usually not that colour. The pigments that give lobsters their normal colour break down when they are boiled, resulting in the bright red, ready-to-eat colour.

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A blue lobster. The chances of finding one are about one in two million. Image credit: Dan Dorothy via Wikipedia

American lobsters have ten legs, four pairs of which are small used for moving. The fifth pair are the most fun, extending into great big claws that are supposed to have the juiciest meat. You may not have noticed when you were digging into a lobster, but the two claws are asymmetrical. One is bigger than the other, and has rounded bumps; the smaller claw has sharp, small teeth. The functions of the two claws are quite different: one is used for crushing (the bigger claw), and the other is used for cutting.

Lobsters start out as very small animals, weighing less than a tenth of gram upon hatching. They grow through a series of moults, which begin with the lobster reabsorbing the minerals that harden the shell. This makes the shell soft, so that the lobster can break through it. The softness of the shell also allows the lobster to take in water, which makes it swell in size. The new shell then hardens, and the moult is complete. A lobster can grow 10-15% in size during each moult. To reach the minimum legal catch size, American lobsters go through 25-27 moults.

Moulting serves another very important function for lobsters: females can only mate within 48 hours of a moult. The females lay their eggs between a month and fifteen months after fertilization. during this time, sperm is stored inside the females, and the eggs are fertilized as they leave the females’ bodies. Lobsters can lay between 3,000 and 75,000 eggs, depending on their body size. After the eggs have been laid, female lobsters carry them under their tails until hatching, for about ten to eleven months. The survival rate of young lobsters is very small, with only one in one thousand reaching the juvenile stage.

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A female lobster carrying eggs. Her tail is notched to mark her as a breeding female. Image source: Wikipedia

Though lobsters are a popular food animal, they are currently not threatened. This is in part due to the strict regulations that protect lobsters from overfishing. Lobsters under 8.3 cm must released, and in some areas lobsters over 13 cm cannot be caught, to keep breeding males alive. If a lobster is caught carrying eggs, a notch is put in her tail, and notched animals cannot be sold or caught. These regulations ensure a large breeding population, key to the survival of lobsters.

While there are many tragic stories about overfishing in our oceans, it seems like lobsters are doing pretty well, which is great news!

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A fun silhouette I did of a lobster! 

Cover image source: Wikipedia

Crocodile Icefish (family Channichthyidae)

Almost by definition, animals that live in and around Antarctica have to be bizarre. After all, you have to be pretty strange to want to live in frigid temperatures year round. Today’s group of animals, the crocodile icefish, are specialist fish that are particularly fond of cold waters.

There are sixteen species of crocodile icefish, all of which are found in the Southern Ocean. They range from Antarctica to southern South America, staying in waters that stay between -1.8 to 2.0 degrees Celsius year round. Because of the increased oxygen content in cold water, lower temperatures are key to icefish survival.

Icefish can reach lengths of 25 to 50 centimetres, so they get to be reasonably sized. They have protruding snouts and distinctive spiny dorsal fins. Crocodile icefish don’t have super flashy colouration; they are light coloured with darker patterns, such as stripes or blotches covering their bodies.

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A crocodile icefish – they look a little funny, don’t they? Image credit: marrabbio2 via Wikipedia

One of the strangest things about crocodile icefish is the lack of hemoglobin and red blood cells in their blood. Because of this, icefish have colourless blood, which must look very strange. They are the only known vertebrates that lack hemoglobin.

So how to these fish survive without the oxygen-carrying protein hemoglobin? Well, they have much larger blood vessels and bigger hearts than other fish. Crocodile icefish have blood volumes that are four times as large as other fish, and their hearts’ outputs are five times greater. Icefish also have very spongy ventricles in their hearts, which means the organ can absorb oxygen from the blood they pump. All these adaptations means blood flows in large quantities at low pressures, allowing oxygen dissolved in the blood plasma to be absorbed by the body.

You may think, then, that icefish have evolved a more efficient way of living without haemoglobin, but that is not the case. In fact, although icefish can live without hemoglobin, the lack of it is not adaptive. The reason these traits evolved when they were not adaptive is that crocodile icefish evolved in a very unique environment.

The steadily cold waters of the Antarctic allow for very high concentrations of oxygen in the water. There is also limited competition in Antarctic waters — many species of fish went extinct millions of years ago, and ocean trenches and current keep icefish populations relatively isolated.  Thus, a deleterious trait that would have resulted in the extinction of the species anywhere else has been able to persist in crocodile icefish, and this unique species is the end result.

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My drawing of a crocodile icefish. I haven’t worked in pencil for a very long time, so this was fun! 

I love writing about animals that live in extreme environments; they are always some of the coolest creatures around. The fact that icefish can survive without one of the most important proteins in our bodies is crazy. The world is truly full of amazing creatures.