Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Sea Spiders?!

Yes – there are spider-like animals in the ocean!

Globally, more than 1,300 species have been identified.

Yellow Hairy Sea Spider grazing on the polyps of Red Soft Coral. ©Jackie Hildering.

But, even though they are jointed-legged invertebrates (arthropods) and most do have 8 legs, they are not true spiders (arachnids) nor are they crustaceans. They are a special group of arthropods called the “Pycnogonida”. The name “Pantapoda” is also used for the group which is Latin for “all legs”, a good label as they have almost no abdomen.

“All legs” indeed. ©Jackie Hildering.


T
hey have a mouth part called a proboscis, a flexible tube that they use to mix digestive chemicals with their food and then suck it up.

Yellow Hairy Sea Spider having grazed off polyps of Red Soft Coral. Also appears to have “decorated” himself with algae. ©Jackie Hildering.

Some species have additional leg-like appendages near their mouths. Often only the male has these structures so that they can take care of the eggs by carrying them.

The species pictured here are those I see most often around NE Vancouver Island and they are only about 1 cm across. They have been given the common name “Yellow Hairy Sea Spider” (Tanystylum anthomasti).  The hairy parts are believed to help the animals feel and sense chemicals.

Yellow Hairy Sea Spiders  grazing on Red Soft Coral. ©Jackie Hildering

I have only ever seen this sea spider species on Red Soft Coral colonies (Gersimia rubiformis). As you can see in the photos, they feed (graze) on the bushy polyps of the soft coral. As defence, the polyps can retract and have stinging cells but this seems to do little to deter the sea spiders. 

One of the things I find fascinating about sea spiders is that they have a very thin external skeleton (exoskeleton) and as a result don’t need a respiratory system; they can “breath” through their skins.

Nudibranch species that also feed on Red Soft Coral include the Diamondback Nudibranch (Tritonia festiva to 10 cm) and the Orange Peel Nudibranch (Tochuina tetraquetra to 30 cm). See below. 

 

Sources:

7 Responses to “Sea Spiders?!”

    • jackiehildering

      Hello Nicole. So glad that you have an appreciation of them! I was afraid that some readers might have an “Ew” like response. Then, here you come with the first comment sharing the perspective that they are beautiful. Thank you!

      Reply
      • Nicole

        I didn’t know our waters were so beautiful …I only ever saw ..dark cold water and a few flying whales .

      • jackiehildering

        Hello Nicole, So appreciate the feedback and knowing that this is reaching students. It is such a huge privilege to have the experiences I do on and under the ocean, I want to open this window to others and it is so valuable to know that even for locals, this may be happening.

  1. Carine

    Wow I didn’t know what to expect but these creatures are pretty in their own special way! Thumbs up for the awesome pictures!

    Reply
  2. Nicole

    I think your site is awesome ..I work at a school and have shown this to students .
    Nice pictures and just the right amount of info .

    Reply

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