Species Profile – Sponge
It was a long, 11+ hour dive yesterday on the deep-water Lophelia coral mound site about 100 miles off Jacksonville in 631 m (2070 ft) of water. There were many great video highlights including two squat lobsters tussling over a rattail fish that one of them had grabbed out of the coral, and an octopus stare down of the Jason ROV. Collected specimens included some amazing bamboo coral and a black coral, both of which are being analyzed with Carbon-13 dating to see how old they are. Some previous studies have dated corals in the Gulf of Mexico to over 1000 years old. But my personal favorite of the day was a beautiful sponge of the genus Hyalonema. One common name is the Glass Rope Sponge, which seems quite fitting for this group. The sponge looks a bit like a sunflower with a large head and a stalk consisting of a loosely twisted bundle of glass-like threads. I must admit I was not sure which end was up on this thing, and, in fact, I was wrong in my guess. Turns out the fiber mass serves as the stalk of the sponge and sticks into the soft sediments where this sponge is found. John Reed has seen similar sponges up to three feet tall with a large head nearly a foot in diameter.
John was very patient in explaining some of the basics of sponge biology and handed me an appropriately titled lab manual for me to look through, “A Simple Fool’s Guide to Sponge Taxonomy.” Of course, the initial definition was already over my head… “What is a sponge? A sedentary, filter-feeding metazoan which utilizes a single layer of flagellated cells (choanocytes) to pump a unidirectional water current through its body.” Oh, I see. Basically, sponges are animals that have specialized cells for creating a current that draws water through the sponge so they can filter out food. So I guess they could be considered the vacuum cleaners of the ocean. Our glass sponge is one of the siliceous sponges whose skeleton is made up of spicules (small needle-like structures that act to support the soft tissues of sponges) made of silica. The strands of glass stalks look like twisted optical fibers. (There has apparently been some interest in the bioengineering world in genetically engineering the stalk strands of some of these sponges for fiber optics research.)
In reading about these sponges online, I found some research that looked at the use of the stalks as substrate for other organisms (makes sense that such structures would make a great place to anchor oneself in a soft sediment habitat). A related species is used in Japan for ornamental purposes.
The intricate beauty of these deep-sea animals is fascinating, and when samples come on board (usually about 8 p.m.) there is a mad scramble to process and document them. If there is time after that we are able to photograph and really take a close look at creatures from a different realm.