Team UAB in Antarctica has been diving far and wide in the Palmer Station vicinity searching for algae laden with amphipods for our ocean acidification experiment. The hunt always yields algae but not always amphipods, much less the particular species and numbers desired for the ocean acidification experiment. The divers are sort of like Goldilocks looking for an alga that is not too big (to handle), not too small (yielding low amphipod abundances), but just right size (to fit in our special collecting bags and have good numbers of the amphipods of interest). As we swim about looking for that perfect alga, we often get distracted by other types of critters living on the seafloor. I’d like to introduce you to some of those cool creatures we have encountered – in particular those with many arms and many legs.

Palmer Station’s aquarium room includes a shallow water table that we use for sorting the myriad of algal and cool critter samples the divers collect. This sorting table is also referred to as the touch tank and we encourage station folks to regularly stop in and see what has been collected either on purpose or unexpectedly as by-catch.

Every touch tank needs a seastar and fortunately for Palmer, Antarctica boasts a great variety some of which are very common in local waters. Seastars are many-armed, usually based on multiples of five arms (also called rays) radiating from a central disk. In biology speak such a body plan is called pentamerous symmetry. The orange Perknaster aurorae pictured below has the standard sheriff badge-like 5-armed body. In fact, most of the body parts of seastars are in multiples of five, usually including the reproductive parts. See the orange ‘strings’ rising up from the body between each arm? Those are eggs being released from oviducts. More strings of eggs are floating around the star. Had we collected a male star of the same species we might have been able start a nursery – dare I say a galaxy of stars in our little touch tank universe!

And most touch tank visitors turn the star upside down and marvel at the rows of many small suction-cupped tube feet running the length of each arm. The tube feet act in unison to glide the star across the seafloor. Also on the underside of the star is its mouth. Seastars are capable to moving their stomach outside their body and around their prey to digest lunch extra-orally. Nature can be pretty gruesome, eh?! The mouth and everted stomach are seen in the middle of the central disk in the following image.

Some seastars have more than five arms but the body plan is based on five parts. Sun stars, like Labidiaster annulatus (shown below) have dozens of arms. How many do you count? This dinner plate-sized star has very rough, bumpy skin. Those bumps are attributed to thousands of tiny little pincers, or pedicellaria, which cover the upper surface serving to help defend the star or capture food. The pedicellaria of L. annulatus are like tiny bear claw traps which when disturbed rapidly snap shut. A small amphipod blundering into one would be a quick snack for the star.

A few days after we introduced the sun star to the sorting table I noticed a small pile of orange stuff in its vicinity. Curious, I siphoned up the mass to inspect with a microscope. Hmm – detached pedicellaria. Some looked like most of those in the image below, like little tiny molars. Those traps had triggered shut. A few were still open (like the one far right) but as I watched another snapped shut! How can that happen – zombie pedicellaria?! The stuff of nightmares! Pedicellaria often slough off the skin whether used or not and the star can regenerate them. New and better traps perhaps.

Another sorting tank critter possible of causing nightmares for some is a crustacean, the multi-legged Glyptonotus antarcticus. For its resemblance to the famed fossil, some refer to it as the Antarctic trilobite while others call it (with a shudder) the Antarctic cockroach. Which would you call it? With an average length of about 6 inches ‘Spike’ as he has been named, looks rather intimating. Spike is harmless though, like its more familiar land cousin the pill bug and was by-catch in an algal collection – just like a pill bug raked up in leaf litter.

Another multi-legged star of the sorting table is also an isopod and for me at least evokes happy thoughts of cartoon characters. Well, it did when I encountered it at 100 ft. This isopod, maybe Antarcturus furcatus, was perched on the edge of a big white sponge and it reminded me of the grasshopper Hop who palled around with Jiminy Cricket in old Disney cartoons. It has been dubbed ‘Peanut.’ The legs of Peanut are lined with fine hairs that collect bits of whatever flows by for the isopod to eat – passive filtration. So, it is not uncommon to see arcturid isopods perched atop sponges, rocks, seaweed with their legs stretched out into the current collecting yummies.

All of our touch tank critters are temporary station visitors and once folks have had the opportunity to meet and observe, we return them to their proper home in the ocean. In a future blog I’ll introduce you to another group of All Creatures ….

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