Summary: To get a thorough understanding of the Aba aba join Kiersten for a look at this amazing fish’s anatomy.
For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean
Show Notes:
“Gross Anatomy and Histological Features of Gymnarchus niloticus (Cover, 1829) from the River Niger at Agenebode in Edo State, Nigeria,” by M. O. Agbugui, F. E. Abhulimen, and H. O. Egbo. International Journal of Zoology, Volume 2012, Issue 1, June 19, 2021. https://doi.org/10.1155/2021/3151609
“Studies on the Biology of Gymnarchus niloticus in Lake Chad: Age Determination and growth; Meristic and Morphometric Characters,” by V. O. Sagua. https://aquadocs.org
Music written and performed by Katherine Camp
Transcript
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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.
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Kiersten - Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.
This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.
I can’t believe we are half way through Aba aba already, but here we are at episode five. The fifth thing I like about Gymnarchus niloticus is their anatomy. Up until now, we’ve talked about some of the very interesting parts of the Aba aba’s body, but in this episode we’re going to talk about the Aba aba’s anatomy as a whole.
If we start from the inside out, we already know that the Aba aba has a bony skeleton as it is classified as a ray-finned fish which has an internal bony skeleton. That is going to include a skull, elongated with small sharp teeth in the lower jaw and a bony tongue. Last week we discovered that bony-tongues fish have teeth in their tongues, but Gymnarchus niloticus is an exception to this. Instead of having teeth in the tongue they have teeth in both the lower and upper jaws. Their bony tongue is used to hold prey still for easier swallowing.
The teeth, though sharp, are not triangular, but peg-shaped. They look like a flat-head screwdriver bit that fits into a power drill. The lower mandible is rounded and is deeper than the upper. The upper jaw does have teeth, as well. The upper jaws teeth are also peg-shaped. The bottom jaw teeth number around 24 teeth while the upper jaw has only 10 to 12. There is only one row of teeth on both jaws. The structure of the jaw gives the Aba aba a perpetual smirk.
Let me inject a funny story here as it pertains to the teeth of this amazing fish. As you know, listeners, I worked with an Aba aba at the zoo and one day, I was cleaning the algae off the glass of his tank. This was a precarious job and typically entailed two people, one to clean the glass and one to watch where he was in the tank. Well, this day we were all busy but the algae on the glass had become a bit more unsightly than we liked so I said I would clean it alone. That was the day I got bit by an Aba aba.
It was a bit more startling than terrifying, I must say, as he caught me off guard hiding in the plastic plant nest he’d built in the center of the tank. I thought I knew where he was but he got my upper arm as is it slipped below the water line just next to the nest. A scary sucking sound ending with a pop and a sting told me I’d just been bitten. He tagged me on the underside of my upper arm just below my armpit. It didn’t hurt much, or bleed that much either, it felt more like a scrapped knee, but the bite was wicked cool. It looked like a dotted circle and I hoped it would scare, because that would have been one heck of a scar to talk about later, but it healed up perfectly fine with nothing left to show for the exciting moment.
I had a hard time finding research that described the internal skeleton of the Aba aba fish, with the exception of one study detailing the number of vertebrae. With ten specimens examined the number of vertebrae averages about 117 from the base of the skull to the tip of the tail.
Internal organs include the typical fish guts with research paying particular attention to the gastrointestinal tract. The GI tract consists of long and longitudinally organized organs. I mean they have a long tubular body so this makes a lot of sense to me. It begins with a tubular oesophagus, followed by a long tubular stomach, two pyloric ceaca, and straight intestine, and the cloaca. The intestine is neatly folded and compacted to sit nicely within the fish.
A single lung arises from a slit in the right side of the pharynx which is on the right side of the fish. The lung and pharynx are held together with sheaths of connective tissue and blood vessels.
Let’s move to the external anatomy of this fish. Beginning at the head, we have a two nostrils for intake of oxygen. The eyes are next and are relatively small. Aba aba fish do not depend heavily on eyesight. Continuing toward the tail of the animal we come to the gills next. There are four sets of gills on the left and right sides. The gills are small and bony with prominent gill arches, 11 gill rackers, and 63 pairs of fused gill filaments. One operculum, the gill covering sits over the gills to protect them with a slit opening to allow water to pass over the gills.
The head has no scales but there are small cycloid scales on the entire body. Cycloid scales are round, smooth edged scales that overlap. To tell you the truth, the scales on the Aba aba are so small it’s hard to see them. It gives the impression of a smooth skinned fish.
The one fin is the dorsal fin and it runs the length of the top of the fish from behind the head to the also the tip of the tail. The very end of the tail is blunt and lack a fin. There are no hard spines in the fin and is the main means of propulsion. The fin flows in a serpentine motion allowing the Aba aba to move forward and backwards very quickly. That’s how he tagged me!
To summarize, Aba abas have a long slender body with no scales on the straight head, no caudal fin, anal fins, or pelvic fins. The long dorsal fin extends down the entire body from the head to the end of a blunt tail. No spines in the fin. The entire body, not including the head is covered in small cycloid scales.
Inside the mouth we have peg-shaped teeth on the top and bottom of the jaw with a bony tongue. Small nostrils and eyes adorn the head. That is the Aba aba in a nutshell.
I hope it paints a good picture of this extraordinary fish for you because my fifth favorite thing about Gymnarchus niloticus is its anatomy.
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Join me next week for another exciting episode about the Aba aba.
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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.
