I study deep-corals (gorgonians mostly) but I am fascinated by all things cnidarian (sea anemones, hydroids, jellyfish, corals). These are suspension feeders that filter food from the water column, so I am also inevitably drawn to dabblings in physical oceanography, and I will try to post on these whenever I can. For now, though, I think I’ll use my first post at the new Deep-Sea News to spill the beans on some old trickery.
One thing you should know about DSN is that Craig keeps real strict rules on his definition of the deep-sea, so I work to find a way around this when something interesting pops up in shallow waters. For instance, Craig will use his (very awesome) “25 Things You Should Know” series to tell you 200m is a minimum depth cutoff for the deep-sea. However, many sea creatures (like squid) ignore this boundary, so I try to navigate through this barrier with “depth certified” asides that fly under Craig’s 200m radar. See the “extended entry” below. You’ll see more of this tomfoolery in future posts about sea turtles, whale sharks, and waterspouts.
Jellyfish are one of the most unexpected and delightful encounters in deep-sea surveys. They cast shadows on the seafloor big enough to frighten you, and fly at the video cameras to fill the frame in spectacular displays.
Jellyfish are attracted to light through primitive eyes called rhopalium, but the most deadly jellyfish, the cubozoans, have sophisticated visual systems. New research on cubomedusans investigates these elaborate eyes that can see a burning match meters away, navigate around dark objects, and actually see people.
This month’s Journal of Morphology reports visual processing and integration in a diffuse system spread throughout the rhopalium of the toxic box jellyfish Tripedalia cystophora (Skogh et al. 2006). These and other results (Nilsson et al 2005, Parekfelt et al 2005) show that a major part of the rhopalial nervous system is bilaterally symmetrical. One website reports at least 8 human deaths from box jellies. So beware, my friends, if the carnivorous sponges don’t get you, the jellyfish will.
Nilsson DE, M Coates, L Gislen, C Skogh, A Garm. 2005. Advanced optics in the jellyfish eye. Nature 435:201-205.
Parkelfelt L, DE Nilsson, P Ekstrom. 2005. A bilaterally symmetric nervous system in the rhopalia of the radially symmetric cubomedusa. J Comp Neurol 492:251-262.
Skogh C, A Garm, DE Nilsson, and P Ekstrom. 2006. Bilaterally symmetrical rhopalial nervous system of the box jellyfish Tripedalia cystophora. J Morph. 267: -13911405