Electric Eel (Electrophorus electricus)

Sometimes when I find an animal to blog about I’m surprised I haven’t written about it before. This usually leads to me frantically searching through my former posts to double- and triple-check that I have not, in fact, blogged about said animal before. Today’s animal is one of the those, the electric eel. How can I not have written about such a strange and wonderful creature yet?

Electric eels aren’t actually eels — they are knifefish (I have written about one of these, the Black Ghost Knifefish (Apteronotus albifrons)). They are so weird that they are placed in their own genus, Electrophorus. Electric eels live in fresh water, and can be found in South America, particularly in the Amazon and Orinoco Rivers. They prefer to hang out at the bottoms of rivers and swamps, and the muddier the water, the better. They like areas with lots of shade for protection, and can survive in waters with low oxygen thanks to their air breathing capabilities.

An electric eel hanging out in some foliage. Image source: http://ffden-2.phys.uaf.edu/104_2012_web_projects/Jenna_Schmidt/Electric%20Eels.html

An electric eel hanging out in some foliage.
Image source: Wikipedia

The reason electric eels are commonly thought to be eels is pretty obvious. They look almost exactly like an eel, being long and thin without the fins most fish wear so proudly. Electric eels can grow up to 2.5 metres in length, and the first twenty percent of the fish contains all of the eel’s vital organs. Though they have gills, electric eels cannot get all their oxygen from the water, and so must surface to breathe. They get about 80% of their oxygen from air breathing.

The remaining length of the eel’s body is dedicated to producing electricity. These guys are kings of electricity, with three different organs that create electricity. Using these, the eels can make both high and low voltage discharges. Electric eels can produce a shock of up to 600 volts and 1 ampere of current. Though the shocks are painful to people (and can be felt from a ways away, thanks to the conducting power of water), they are not enough to kill an adult human, thanks to the short duration of the shocks (2 milliseconds).

Electric eels are polarized - the front end is positively charges while the tail is negative. They're basically giant batteries. Image source: http://www.asknature.org/strategy/cf1aee08559245ccc321c6cb77a2479a

Electric eels are polarized – the front end is positively charges while the tail is negative. They’re basically giant batteries.
Image source: http://www.asknature.org/strategy/cf1aee0 8559245ccc321c6cb77a2479a

Electric eels use their electric powers for a number of purposes. Of course, self-defence is a key purpose; I think it would take some guts to try and eat a fish that can shock you with 600 volts. The eels also use their electricity for hunting, with low voltage shocks from the Sach’s organ to electrolocate, and high voltage shocks to stun prey. Of course, the shocks could also hurt the eel producing them, so electric eels are covered in a slimy skin that protects them from being zapped.

Reproduction in electric eels occurs during the dry season. Electric signals are used by the fish to find mates, because why be called the electric eel if you aren’t going to use electricity for absolutely everything? The female lays her eggs in a nest of saliva produced by the male. Once the eggs are laid, the male guards them against any potential predators.

I’ve always thought that electricity is super cool — if I had a superpower it would definitely be control over electricity. The fact that a fish pretty much already has this superpower makes me more than a little jealous. Maybe in my next life I will be reincarnated as an electric eel.

Cover image source: http://ffden-2.phys.uaf.edu/104_2012_web_projects/Jenna_Schmidt/Electric%20Eels.html

African Clawed Frog (Xenopus laevis)

I don’t usually picture frogs with clawed feet — I’m much more familiar with the typical webbed foot with sticky balled toes on the end. Today’s animal is one of those special frogs that decided to forego the expectations of frog society and grow claws on its feet. How exciting!

African clawed frogs are naturally found in Africa ( a big shocker, I know), particularly in the southern part of the continent. They have been introduced to a number of other places, including California, Chile, and Great Britain. These frogs favour habitats that are warm, stagnant, and covered in algae — in other words, places that are disgusting. Not only do clawed frogs like to live in these tepid, horrifying waters, but they rarely leave them, only exiting their chosen ponds when forced to migrate.

A nice picture of a clawed frog showing the claws on its back feet.  Image source: http://www.clawedfrogs.com/

A nice picture of a clawed frog showing the claws on its back feet.
Image source: http://www.clawedfrogs.com/

Though they are called clawed frogs, the claws on their feet are not the only weird thing about these frogs. They don’t have tongues, so you can also throw out the classic image of a frog happily catching insects with its long tongue. Another thing clawed frogs lack is external ears. Males grow to be about five centimetres long, while females can reach ten to twelve centimetres.  Clawed frogs have very smooth skin (the second part of their latin name, laevis, means smooth). Their front feet have no webbing, and while the back feet are webbed, they also posses the weird claws for which this animal is named, with each of the three inner toes being clawed.

These claws help the frogs feed. Clawed frogs are scavengers, eating anything that crosses their paths. If their potential meal is too big, the frogs will use their claws to rip it apart into appropriate sizes. Clawed frogs use a number of senses to detect scraps of food: their front ‘fingers’ are very sensitive; they have a very good sense of smell; and they possess a lateral line system (used to detect movement and vibrations in the water), something that is usually only found in fish.

Some African clawed frogs hanging out. Image credit: Tim Vickers

Some African clawed frogs hanging out.
Image credit: Tim Vickers

Mating in clawed frogs usually occurs in spring, but can occur at any time of the year. Males call out to females, advertising their readiness to mate. Females will then call back, using either a rapping sound for acceptance, or a slow ticking which signals rejection of the male. This behaviour of replying to a male’s call is extremely rare in the animal kingdom.

Living in arid and semi-arid conditions means that clawed frogs face the constant threat of having their homes dry up. Luckily these guys are very resilient. If their ponds dry up they will burrow underground, leaving themselves a small air hole, and stay dormant for up to a year. If things get really bad during the rainy season, the frogs will migrate, sometimes travelling long distances, surviving thanks to rain. This is quite the ordeal for the frogs, because although they are very capable swimmers, they can’t hop on land, instead crawling their way around.

The hardiness and resilience of  this frog means that it is doing quite well. It has been used in research to investigate embryonic development and to develop pregnancy tests. Once better pregnancy tests were developed, many clawed frogs were released into the wild, leading to their colonization of many areas outside Africa. Responsible science, everyone!

Cover image source: http://www.clawedfrogs.com/

Redear Sunfish (Lepomis microlophus)

I had a bit of trouble when I first saw this fish’s name — I wasn’t quite sure how to read the ‘redear’ part of the name. Every time I look at it I read it as ‘re-dear’, when it’s quite clearly supposed to be ‘red-ear’. I think the people who named this fish should have just disposed of any ambiguity and gone with red ear sunfish. One extra space won’t kill anybody.

The native range of redear sunfish is in the southeastern and central US, though they have been introduced to other parts of the United States, as well as Panama, Puerto Rico, Morocco and South Africa. These fish have been introduced for the very simple reason that people like to fish for them. Redear sunfish like warm, still, waters, and so are generally found in ponds, lakes, rivers and reservoirs.

See the bright red gill cover? It does kind of look like an ear.  Image source: Wikipedia

See the bright red gill cover? It does kind of look like an ear.
Image source: Wikipedia

Redear sunfish range in colour from green to grey or black, with lighter undersides. They have thick vertical stripes down the length of their bodies. The name ‘redear’ comes from the bright red colour that male redear sunfish have on their operculums. Females also have colourful operculums, but they are orange not red. And since the operculum isn’t actually an ear, but is instead a bony protective covering over the gills, these guys are really poorly named. They should be called ‘red-operculed sunfish’, or something like that. Though I guess it isn’t nearly as catchy. They can reach up to 43 cm, but sizes between 20 and 24 cm are more common.

Redear sunfish are known for eating molluscs and crustaceans, and are especially fond of snails. They have very strong teeth that enable them to crush the shells of snails and other creatures, such as clams. This strange diet allows redear sunfish to feed without much competition, something that should reduce the harm redear sunfish do to native fish in their introduced habitats. In fact, some think introducing these guys could be helpful to control quagga mussels, an invasive species in freshwater areas. Whether or not this is actually true I suppose we’ll find out, but based on past records of introduced species, I’m a little wary…

A male sunfish guarding the nest he has painstakingly made.  Image source: Wikipedia

A male sunfish guarding the nest he has painstakingly made.
Image source: Wikipedia

Reproduction in redear sunfish is triggered by water temperature, with mating occurring between 21 and 24 degrees celsius. Males build nests out of sand and mud, near plants so the eggs have some protection. They then set about trying to attract females, which they do by snapping their teeth together, to make a popping sound. If the female is impressed by the noise, as well as his colouring, she will lay some eggs in his nest. He can then fertilize the eggs and protect them from harm.

Despite the claims that redear sunfish don’t really hurt native fish populations, there have been declines of local fish in areas where sunfish have been introduced. I think a quick look at humanity’s track record of making smart ecological decisions should give us a bit of a warning. I don’t think the fact that the fish are fun to catch makes up for any damage they might do to local ecosystems.

Spiny Softshell Turtle (Apalone spinifera)

When I think of turtles, a very familiar image comes to mind: a hard, armour-like shell, four little limbs sticking out of it, and a cute little head at the front. But not all turtles are built equally. Some are not so cute, some have long legs, and some even have soft shells. This is what really throws me off — what’s the point of having a shell if it’s soft? Well a number of turtles have decided to go this route, and I’ll be talking about one of them: The spiny softshell turtle.

Spiny soft-shell turtles live in North America, and are generally found in the central and eastern parts of the continent, from northern Mexico to Ontario and Quebec. They are a freshwater species, living in bays, rivers, lakes, and ponds. The preferred habitat of spiny soft-shell turtles are open areas with some vegetation, sandy or muddy bottoms, and sandy shores for nesting.

Don't you think these guys look silly? I think they look silly.  Image source: http://www.cheloniophilie.com/Fiches/Apalone_spinifera.php

Don’t you think these guys look silly? I think they look silly.
Image source: http://www.cheloniophilie.com/Fiches/Apalone_spinifera.php

Spiny softshell turtles are some of the biggest freshwater turtles in North America, reaching 48 cm in length. Males are smaller than females, only attaining lengths of 24 cm. The spiny part of the softshell’s name comes from spines at the front of their shell. Soft-shell turtles have long, pointy noses that make them look super weird. They are dark coloured, with two yellow stripes bordering the edges of their shells.

Courtship in softshell turtles is pretty simple: males just nudge females’ heads in the water, and if he does it right they mate right then and there in the water. The females then lay their eggs on sandy banks near the water, in shallow holes. The eggs hatch in the early fall, though sometimes eggs incubate over winter and hatch in spring.

Softshell turtles are pretty good hiders, as you might imagine from a turtle that is basically the same colour as a muddy pond bottom. Often caught basking in the sun during the day, soft-shell turtles quickly dive beneath the water and bury themselves in the sand, hiding themselves extraordinarily well. The only thing you’ll see of a hiding spiny softshell turtle is its head. And if you wait for the turtle to come back up, you may be waiting for a long time — softshell turtles can breathe underwater through their skin.

There's just something about their pancake-like shell and silly nose that makes me chuckle.  Image source: http://www.mwparc.org/photo/?6

There’s just something about their pancake-like shell and silly nose that makes me chuckle.
Image source: http://www.mwparc.org/photo/?6

The soft shell in these turtles in not unique to this species: there is an entire family of softshell turtles, whose leathery, pliable shells have earned them the title. The shell is softest at the sides, and bones beneath the centre of the shell still provide protection for the turtle. The softness of the shell, on the other hand, gives turtles greater mobility in the water and on land.

So while having a soft shell may seem counter-intuitive for a turtle, there is actually a reason for it. Especially if you can just hide from predators at the bottom of lakes. Still, I don’t think I’d want that nose, no matter what type of shell I had.

Cover image source: http://www.mwparc.org/photo/?6

Black Ghost Knifefish (Apteronotus albifrons)

Is there another species of fish that has a more badass name than the black ghost knifefish? I doubt it. The combination of ‘black’, ‘ghost’, and ‘knifefish’ just make me think of some kind of underwater ninja. Which, in a way, the black ghost knifefish almost is. At least, they’re sneaky and hang around in the dark all the time. That’s what ninja do, right?

Black ghost knifefish are found in South America, from Venezuela to Paraguay. These are freshwater fish, and prefer waters that are fast moving, with sandy bottoms. Knifefish like areas with lots of vegetation and good places to hide.

Black ghosts adopt this slanted posture when searching for prey. It looks silly.  Image source: http://www.recipeapart.com/black-ghost-knife-fish/

Black ghosts adopt this slanted posture when searching for prey. It looks silly.
Image source: http://www.recipeapart.com/black-ghost-knife-fish/

Black ghost knifefish are black, with two white markings on their tails. Some fish have a white stripe that runs from the tip of the snout along the back. They are long and slender (hence the ‘knife’ part of their name), and can grow to a maximum of 50cm in length. Knifefish have one long fin on their undersides, and use this fin to move, waving it back and forth to propel themselves around.

To act more like ninja, black ghosts are only active at night. However, it’s pretty difficult to navigate streams that are thick with vegetation in the middle of the night, so black ghost knifefish have developed some senses to help them get around. Three particular systems are useful for this night-loving fish: active electrolocation, passive electrolocation, and lateral line sensing (found in most fish).

Active electrolocation involves the fish emitting an weak electrical signal, which allows the black ghost to locate objects from the disturbances in the signal. Passive electrolocation lets the fish sense electric signals from other sources, such as another knifefish. The fish have two different receptor organs for each of these senses. Finally, the fish’s lateral line detects changing movements and vibrations in the water.

The electric signals generated by knifefish aren’t just used for navigation; after all, why develop such a cool ability if you aren’t going to use it for more than one thing? Knifefish also use electricity to communicate — and these communications can be quite complex. Each species of knifefish (yes, there is more than one) uses a different frequency of signal, and within species signals vary with gender and age. Female black ghost fish have higher frequency signals, while subordinate fish gradually lose signal frequency when in the presence of dominant fish.

Black ghost knifefish are quite common as pets - probably because they look so cool.  Image credit: Derek Ramsey via Wikipedia

Black ghost knifefish are quite common as pets – probably because they look so cool.
Image credit: Derek Ramsey via Wikipedia

So though they may not be actual ninja, there’s no denying that black ghost knifefish are super cool. After all, they talk via electricity. Oh, and the ghost part of their name originates from the belief that the souls of the dead hang out in these fish. Maybe they try and communicate with us via their electrical signals. Spooky stuff.

Cover image credit: Erik Sviland

Mary River Turtle (Elusor macrurus)

As this blog has clearly demonstrated, there are some very odd looking animals out there. As far as turtles go though, I think the Mary River turtle takes first prize. This turtle actually looks like one of the Koopa Kids from the Super Mario games. Here’s a picture just in case you have no idea who the Koopa Kids are:

On the left, Iggy Koopa, and on the right, a Mary River turtle.  Photo credit: Chris Van Wyk

On the left, Iggy Koopa, and on the right, a Mary River turtle.
Photo credit: Chris Van Wyk

Mary River turtles are named after the river they inhabit: the Mary River in Queensland, Australia. This is the only place that these turtles inhabit. The Mary River turtle prefers areas of the Mary river that are fast-flowing, with a steady supply of oxygen. They are partial to areas with some kind of shelter, such as underwater logs or rock crevices. During flooding, Mary River turtles move upstream, heading to eddies or backwaters where the flow isn’t quite as fast. Once water speeds return to normal the turtles return to their normal habitats. Mary River turtles are quite unique; they are placed in their own genus, and are one of the only remaining turtles from a very ancient evolutionary lineage.

These turtles are quite big, having a shell size of over 35 cm. They are usually dark brown or black, with a grey underbelly. They have very long tails compared to other turtles, with tail length exceeding 7 cm. One notable feature is Mary River turtles’ barbed chins, which makes them look quite tough. To add to their punk-rock look, Mary River turtles sometimes have algae growing on their heads, presumably to assist with camouflage.

Another interesting feature of Mary River turtles is the bursae located on their cloacae. The cloaca is the turtle’s way of expelling urine, faces, and reproducing. The bursae located on the Mary River turtle’s cloaca act like gills, allowing the turtle to absorb oxygen from the water. They can’t get all their oxygen this way, however, and so still surface to breathe with their lungs every once in a while.

Mary River turtles have very large back legs and streamlined shells, making them exceptionally good swimmers.  Image source: https://www.pinterest.com/pin/235031674275220025/

Mary River turtles have very large back legs and streamlined shells, making them exceptionally good swimmers.
Image source: https://www.pinterest.com/pin/235031674275220025/

Mary River turtles nest on sandy banks of the Mary River. Females are faithful to particular banks, and many turtles will use the same nesting site. One bank had evidence that over 100 females used the site to lay their eggs. Females lay 12-25 eggs per season, and usually lay from October to November. Once the eggs have hatched, the young turtles have a long road ahead of them: it takes around 25 years for a Mary River turtle to reach maturity.

Until the 1990s, the Mary river turtle was not actually classified as a species. It was being sold in the pet trade, under the Common Saw-shelled turtle. Though biologists were curious about the strange turtle, they could not formally describe it, because the pet traders would not reveal the source of the turtles. Legal trade in the species was banned in 1974, but scientists still could not locate the habitat of the Mary River turtle. It wasn’t until 1994 that adult specimens were found in the wild and the species was named and classified.

All and all, I think I have to declare the Mary River turtle one of my favourite turtle species. It’s just weird enough, with an interesting history and the right amount of silliness in its appearance. It’s my kind of turtle, that’s for sure!

Cover image credit: Chris Van Wyk