Journal Entry

When it is a sea spider, of course. Yesterday's benthic ROV dive produced a beautiful array of animals both on the screen and in the collection canisters. One of the highlights were multiple sea spiders (Phylum Arthropoda, Subphylum Chelicerata, Class Pycnogonida). Interestingly, the guts of sea spiders extend out to the ends of the claws, and males carry the eggs. Normally quite small, sea spiders in the Arctic and Antarctic can be much larger than in warmer waters. In the photos below, notice the very large proboscis that is used to suck up food, including sea anemones. It can be difficult to gauge size of organisms based solely upon their appearance in the video feed shown on the television. As you can see in photos of me holding one of the sea spiders, the specimens collected cover my hand.

Sea spiderHere is an image of a sea spider seen via the ROV camera. Water depth was around 900 meters. Sea spiderI am holding the same sea spider. Notice the difference in screen color versus "real" color. Photo courtesy of Michael Aw.

Here is an image of the ROV collecting arm in action. The arm has a vacuum apparatus as well as a pincer-like claw.

ROV armThe ROV arm in action. The tube-like structure on the right works by vacuum. Sea starThis is a closeup image of the sea star shown with the ROV arm. Depth approximately 900 meters.

Question of the Day

Question: What does the term "arthropod" mean?

Comments

Wed, 07/27/2016 - 05:02

Judy Fahnestock

Great journal Sandi! What a beautiful colored sea spider! Is there a proportion of size difference that you see between creatures like the sea spider in arctic vs. tropical waters when it comes to size difference? 2:1? or more? And when you say the "guts" of the sea spider extend all the way out--is that their intestines? Just curious!

Thu, 07/28/2016 - 16:40

Sandra Thornton

Thanks, Judy. Yes, I am referring to intestines. This is not to imply, however, that defecation occurs through the ends of the claws. I asked one of the scientists on board - Dr. Dhugal Lindsay - for help with your size question. According to Dr. Lindsay, there isn't a specific proportion that can be applied across species. He said the average differences for each species would be so wide that the averages would not be meaningful. Dr. Lindsay also said that these kinds of size differences may also be observed in depth layers. For example, deep ocean versus shallower waters. According to Dr. Lindsay, "So little is known; that's why we are here."!