Leyia Johnson - Week Two

Hello All!

Pushkin

I have had so much fun this week! On both Tuesday and Wednesday morning, I finally got to don my rubber boots and go on an adventure. Alan drove Pushkin, Peter, and myself down to South Cove to go limpet tagging. This is the Northern most region that Lottia scabra, a species of limpet, live and there are only approximately two hundred Lottia scabra here; there are only approximately three hundred Lottia scabra in all of Cape Arago. On the California Coast you can find them clustered together, but this far North, since there are so few of them, they are more widely dispersed. Searching for the Lottia scabra was like the greatest I spy game or like a treasure hunt. We scrambled over rocks searching for the correct limpets. Lottia scabra are identifiable by their physical appearance and their distinctive behavior.

Tagged Lottia scabra

Lottia scabra look very similar to Lottia digitalis, a similar limpet, with shells that are mostly white and scalloped with ridges. However, Lottia scabra will have smaller ridges between the main ridges. Also, the apex, the radial center of their shells, will be pushed back about a quarter of the length of the animal. This is unlike Lottia digitalis whose apex is far forward. The juvenile Lottia scabra are a dark grey and bright cobalt blue. The juveniles also have little hooks trailing down their ridges. This makes them slightly simpler to identify than their tiny size would otherwise allow.

Lottia scabra home range:
Look closely,
you can see where the radula has
been scraping algae off of the rock.

Lottia scabra tend to prefer horizontal surfaces on large boulders; knowing this made them much easier to distinguish from the Lottia digitalis which preferred vertical surfaces. Lottia scabra, like other limpets, eat algae by slowly moving their heads back and forth and licking the algae off the rocks with their radula. A radula is a ribbon of tissue, similar to a tongue, that contains teeth. Lottia scabra also have a definitive home range. A home range is the area in which a limpet lives its adult life. Once attached to an appropriate surface, the limpet will remain in this small area for the rest of its life. During high tide, the limpet will move across the rock scraping algae off to eat. When the tide is low, the limpet has returned to its home scar. A home scar is the exact spot on the rock that the Lottia scabra returns to every low tide. If the limpet has been returning to its home scar for several years, (Lottia scabra can live to be thirty years old!), a depression in the rock can be seen around the limpet’s shell.  This depression is due to wave action eroding the rock around the limpet.

Me tagging a Lottia scabra

Once we found a Lottia scabra, Peter and I became very good at it by lunch of the first day, we would proceed to tag them. We accomplished this by mixing epoxy, placing a dab of the epoxy on the shell of the limpet, then, using forceps, taking a small plastic tag and placing it in the epoxy. Then, with a wet finger, so that the epoxy did not stick to our hands, we would smooth the tag into the epoxy and the epoxy over the shell so that wave action might not rip our tags off. If the tags stay on, we can learn more about Lottia scabra’s growth rate. If we can learn their growth rate, then we might be able to determine their longevity.

Friday, we did not spend any time in the lab considering it was the Fourth of July. Instead most people on campus went to the 4th of July picnic on Sunset Beach. The food was fantastic, the weather was warm, and the fireworks that night down on the boardwalk in Coos Bay were spectacular.

Happy Independence Day!