Awesome Rostrum!
Today is Flat Shark Friday on Twitter (#flatsharkfriday). It's a day when all the worlds ray and skate experts, and people who just like those flat, cartilaginous fishes post cool things about these "flat sharks". Yes, they aren't sharks, but whatever...sometimes it's more about the fun than being exact!
So, for #flatsharkfriday lets talk a bit about sawfish...because they are a ray, even if most people would mistake them for a shark.
Their body looks very shark-like but you can tell they are a ray from their flattened head with a very distinctive ray mouth and gills on the bottom with spiracles behind their eyes that are used to draw water past their gills beneath.
The most distinctive thing about sawfish is their rostrum. That nose-like rostrum has teeth sticking out from the sides but it's far more than that. In fact, that is what I'd like to talk about most in this post.
Awesome Rostrum!
There is still some debate about how sawfish use their rostrum. It used to be that people thought sawfish used it mostly to root around in mud and sand to find crustaceans and other things. But, recent research has also shown that they are more active predators as well. Using a side-to-side motion they have been shown to kill and eat fish. There's a great National Geographic article here talking about that research.
But sawfish spend a lot of time in murky water, and their eyes aren't that great. So how do they find their prey anyway? That awesome rostrum also has tons of nerve endings. In these pictures from my work you can see the tiny pores where sawfish have electroreceptors that help them sense the slight electricity created by fish or other prey. The tip of the rostrum is coved in these pores, and there is a distinct pattern down each side of the top of the rostrum as well.
Also, in my own work I've noticed that there is huge variation in the wear on the teeth of sawfish that are relatively the same size. Some have long, relatively unworn teeth. Others have just nubs that have been almost worn away. Others are pitted and brown like the water has been corroding them. I can't help but think that these differences are related to behavior and habitat...hopefully our chemical work will help us narrow down where each fish was and what habitats they experienced. There is SO much to learn about these fish!!
Oh Baby!
The other thing that is just wild about sawfish is that they give birth to live young. And...those young are born with the saw, and that saw has tiny but VERY sharp teeth attached! That is wild!
They are able to do this because the teeth of each baby is covered in a gelatinous layer that protects the teeth, and more importantly, protects the mother from those teeth. This video actually shows sawfish babies being born! Wow!
Oh, AND...those babies might be from one father, or multiple fathers...OR...they could be from no father at all!!
What?? Yep, I said that right. Sawfish have been shown to be parthenogenic. They can become pregnant without the sperm from a male. This actually isn't all that uncommon among animals, but it's still pretty wild. There's a good article about this research here.
Sawfish amaze me because they are just such weird, amazing, and cool looking creatures. But more than that, there is still so much to learn about how they live their lives. I'm really hopeful that with this crowdfunding campaign we can start the process of learning just a little more about sawfish migration, and add to what we know about this amazingly cool fish.
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