Deep-Sea Ghost Sharks: Why They Grow Teeth on Foreheads
Here’s a breakdown of the provided text, focusing on the key facts:
Main Topic:
the text discusses a recent discovery about ghost sharks (specifically the spotted ratfish, Hydrolagus colliei). Researchers have found that the “tenaculum” – a strange appendage on the forehead of male ghost sharks - contains teeth that are structurally similar to shark teeth and likely evolved from teeth originally in the mouth.
Key Findings:
* Teeth on the Forehead: Male Spotted Ratfish have a forehead appendage (tenaculum) covered in tooth-like structures.
* True Teeth: These structures are not simply tooth-like scales (denticles) like those found on shark skin. Thay are genuine teeth, connected to the teeth in the mouth.
* Evolutionary Origin: The tenaculum likely evolved from teeth that where originally located in the mouth, and over time, the appendage shortened but retained the ability to produce teeth.
* CT Scans: CT scans were used to analyze the structure of the tenaculum and confirm the presence of true teeth.
Researchers Involved:
* Gareth J. fraser (University of Florida)
* Karly Cohen (Washington)
* Michael Coates (Chicago)
Publication:
The study was published in the Proceedings of the National Academy of Sciences.
Images:
The text includes descriptions of two images:
- A juvenile Spotted Ratfish.
- A CT scan of an adult male Spotted Ratfish showing the frontal clasper (tenaculum).
In essence, the article highlights a engaging evolutionary adaptation in ghost sharks, revealing a unique and unexpected use of teeth.