Although it belongs to the class of arthropods,
It is a different classification from the spiders we commonly know.
The most important characteristic of sea spiders
Genetically, there is no ‘abdomen’, that is, no stomach.
There is only a small tail that can be considered a vestigial organ of the stomach.
The reason is
In the HOX gene family (a collection of genes that regulate physical development)
This is because the Abdominal-A (abd-A) gene (a gene involved in the formation of the abdomen of arthropods) has disappeared.
Due to the nature of sea spiders, which do not have gills or lungs,
Breathe through your entire skin
There is a theory that this is because it evolved to reduce the abdomen, which has a small surface area to volume ratio.
Therefore, sea spiders do not have internal organs in their abdomen.
It’s all on my legs
Some people call it a walking intestine.