I have a shark question! Why are different shark tails different shapes? What makes it good to have a symmetrical tail for a great white while cat sharks have the little lobe type tail thingies?
I think that this might constitute more than one question, lol.
About 'dem shark tails
Shark tails, like most things, evolve depending on things like environment, diet, hunting, general physiology and so on. So, in this case, sharks can have different shaped tails because they need a different shape for... swimming faster (Mako shark), stunning prey (Thresher sharks), fast take off for escape (Angel sharks), and so on.
Shark tails are like the propellers on a boat. Some boats need larger propellers because they're big, some because they need the speed, and some need asymmetrical ones for whatever reason. The same goes for shark tails.
The lifestyles of some sharks mean that they have to have long tail lobes (top and bottom), a longer top lobe, or a longer bottom one. This physiological variation can be seen pretty clearly in Thresher sharks compared to Great Whites compares to Angel sharks.
[source: shark-world]
The caudal fin aka the tail, affects thrust, velocity, and speed when swimming. Some sharks can't swim all that fast (though don't be fooled into thinking they're slower than you are in the water: they're not) while others can shoot off like a pop-rocket suddenly with a flick of their tail. Some sharks use their tails for communication (shark body language yoooo) though the Cookiecutter shark, which I talked about here, is one of the few with bioluminescence in their tails that they use to communicate and attract prey for- ya know- dinner.
Anyway. The caudal fins of sharks can be categorised into several groups, depending on different evolutionary purposes of the tail adaptations.
1. Typical sharks: the upper lobe of the tail is longer than the lower and has a little upward angle. Great White sharks and Threshers have tails like this.
- Note: not gonna lie, when I see the shape of a Great White's tail, i can't not see the way Kermit's mouth opens comically wide as not being dissimilar.
[source: blogspot]
2. Fast swimming sharks:
these tails are crescent shaped with the upper lobe extending further out, but not too much (not up, out as in horizontally when looking at a side-ways view of the shark) with a little divot in the bottom of the top lobe. The picture below shows what I'm trying (badly) to describe. Fast-swim sharks tend to be open ocean kind of swimmers, so having a good caudal fin that lets you swim at a decent speed without costing you too much energy is *insert ok-fingers emoji*.
[source: github]
3. Benthic (heh, ben afflick thicc) sharks:
the top lobe of the tail is angled slightly and pretty darn long compared to the bottom lobe. They don't turn all that quick or swim all that fast, but they tend to also swim more like eels with the wiggles rather than the loooooong swish like a Great White. These kinds of sharks spend a lot of time on the ocean floor so they're basically the Carpet And Ground Sharks Of The Ocean and have tails suited to that lifestyle.
Note: Houndsharks are Benthic. As are Nurse Sharks, hence the image below showing the eel-like tails they have.
[source: Shark Research Institute]
4. Cirrhigaleus and Squalus genera sharks:
the names sound very fancy and Academic but they essentially mean the Dogfish shark category. Interestingly male and female dogfish have slightly different tail shapes. Female dogfish tails are a little... uh puffier I guess. The images below show a male (1) and a female (2)
[source: image 1, male dogfish]
[source: image 2, female dogfish, shark trust]
You can see that the female's tail is smoother, with less sharp definition like the males. They're still the same species though. Dogfish.
Now, interestingly enough, the longer upper lobe of a dogfish's tail doesn't slow it down. It can still swim fast, still rack up some speed quick, and maneuver well. This is because the spine of the dogfish extends through the top lobe at a lower angle than the lobe itself (you can see that in the pictures).
If you've read my other Shark Facts asks, you'll have probably seen the recent one about Great Whites and their dorsal fins being designed in way that makes them more rigid the faster they swim. If you haven't then it's here. Anyway, the same sort of logic applies. More rigid top lobe, the better it is for fast swimming.
5. Angel Sharks:
last on our list of shark tail types, we have Angel sharks. Honestly, these sharks have a larger bottom lobe than they do an upper lobe because they tend to be the I'm Going To Sit Here And Not Move For A Lifetime Then Shoot Out From Beneath You And Eat You. These shark tails allow the sharks that have evolved them to have a higher percentage of speed/velocity/acceleration in situations where they need to haul ass quick.
You can see the bottom lobe of the tail of the Australian Angel Shark is larger than the top lobe in the image below. They look, honestly, not unlike a ray but with a thicc tail instead of a needle of death (if you're a stingray, that is). You can definitely tell that sharks and rays are related when sharks like these exist, can't you.
[source: wikipedia]
What makes it good to have a symmetrical tail for a great white while cat sharks have the little lobe type tail thingies?
Okay so, I think you can guess what the answer to this specific question is if you've managed to read all the droning on I've done above. If not, then cool, I'll cliff-notes this shit.
1. Great White sharks need tails for speed and agility in the ocean, but also tails that aren't like the Basking Shark because they also go into shallow waters.
2. Cat sharks (my bae's) are ground sharks. Great Whites are not ground sharks. Tail differences are expected.
3. The image below shows you the differences in a Catshark's tail and a Dogfish's but you can see how it's considerably flatter on the top lobe than a Great Whites is. This is because, like Dogfish, Catsharks hunt specific types of prey (small fish, crabs, basically the stuff of the shallows/mid-depth waters of the world)
[source: wildlifeonline]
Basically, the differences can only truly be summed up with the following images.
Great Whites:
[source: knowyourmeme]
Catsharks (when threatened, I shit you not):
[source: memegenerator]
I hope this has been informative, educational, mildly entertaining and, as always, made you love sharks more.
After all, statistically speaking, sharks aren't the deadliest thing in the ocean to humans. Australian Box Jellyfish exist after all. As do Coral Reef snakes. Blue-Ringed Octopus. Pufferfish. And Stonefish.... so yeah.
A shark might bite ya, but it's not gonna kill ya like a pufferfish might just for the hell of it.
The ocean is a hellscape and we evolved outta that shit a couple million years ago, why we wantin' to go back in there, huh. Apologies I've been watching Casual Geographic on youtube, the whole "no ocean swimming advised, it deadly" vibes be spreading
