The Ostia
The ostia are the water canals within the gill.
![](http://danhornbach.org/wp-content/uploads/2022/11/ostia-polysem.gif)
1. An SEM of the ostia of the gill of Polymesoda carolinana. Approximate magnification of the original photo – 420x.
![](http://danhornbach.org/wp-content/uploads/2022/11/ostiadetail-polysem.gif)
2. Detail of #1.
The ostia are the water canals within the gill.
1. An SEM of the ostia of the gill of Polymesoda carolinana. Approximate magnification of the original photo – 420x.
2. Detail of #1.