Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Who You Calling “Unstable”?

Don’t you hate when people use a provocative “hook” to get you to read their material? Yes, that’s what I’ve done but I promise you, it is worth it.

While I think all of us are a little unstable right now, this blog is not about me. It’s about the astounding adaptations of a little limpet assigned the name of “Unstable Limpet” (Lottia instabilis). 

 

Unstable? This species just limpetted along on its own evolutionary path!

Most other limpet species are shaped so they can suck down securely on a FLAT surface for protection This works well because these most often graze on algae encrusted rocks. But the Unstable Limpet can secure to a ROUNDED surface.

Which rounded surface? Oh I will never forget the first time I noticed this species and realized the marvel of the adaptation. Unstable Limpets are shaped to be able to hunker down on the cylindrical stipes (stem-like structures) and holdfasts of the kelp species upon which they also feed!

Screen grab from “Invertebrates of the Salish Sea”. Caption: “The uneven edges of the shell of Lottia instabilis can easily be seen in this end and side view. The shell is shaped to fit snugly around a round stipe instead of a flat surface.”

 

I suspect that, like their flat-shelled brethren, Unstable Limpets have a specific spot to which they “home” and where their shell fits perfectly.

As is supported by others’ observations, I have found Unstable Limpets living / feeding on Stalked Kelp (Pterygophora californica) and Split Kelp (Laminaria species).

Underside of an Unstable Limpet on the stipe of kelp.

 

An individual with a lot of coralline algae growing on its shell.

I hope that this little limpet leads to you reflect anew on the wonder of the natural world around us and . . . about how being “unstable” just might mean being better adapted to the conditions you are in. It may even be of benefit in having a unique place and perspective in the world. 🙂

Below are further details about the species and an explosion of my photos documenting them.


Size: To 3.5 cm across

Known range: Northern Alaska (Kodiak) to Southern California (San Diego) from the intertidal to 73 metres depth.

Variation: Greg Jensen reports that: “Some members of this species settle on rocks, where they develop a more conventional limpet sharp and are difficult to distinguish from other limpets. This rock form was previously known as Lottia ochracea.” (Source: Jensen)

Behaviour: If touched by predatory sea star species, the Unstable Limpet “vigorously” runs away. Predatory sea star species referenced in the study are Six-Rayed Stars( Leptasterias hexactis), Sunflower Stars (Pycnopodia helianthoides), and Ochre Stars (Pisaster ochraceus ). It was unclear to me from reading a summary of the research (and being unable to find the original paper) if this response behaviour is different if the Unstable Limpet is on its “feeding scar” (a bit of an indentation in the surface of the kelp). It may be that it responds then like the Seaweed Limpet (Discurria insessa) whichusually responds to contact by elevating its shell (“mushrooming”) and rocking from side-to-side, but rarely moving away from the scar.” (Source: Snail’s Odyssey).


 

Little limpet. Long stipe of kelp.

 

This individual may have had another limpet species feeding on the algae on its shell.

I believe you can see the scars here of where the limpet has been feeding on the kelp.

 

The following photos offer additional perspectives on two of the individuals shown in photos above.

I believe you can see where this individual has been feeding and yes, thats a lovely hat of algae that is growing on the shell.

 


Sources:

  • Jensen, Gregory C, Daniel W. Gotshall, and Miller R. E. Flores. Beneath Pacific Tides: Subtidal Invertebrates of the West Coast. , 2018. Print.
  • Lamb, Andrew, Sheila C. Byers, Bernard P. Hanby, Bernard P. Hanby, and Michael W. Hawkes. Marine Life of the Pacific Northwest: A Photographic Encyclopedia of Invertebrates, Seaweeds and Selected Fishes. Madeira Park, BC: Harbour Publ, 2009. Print.
  • Homna, L. 1995. DISTRIBUTION, ABUNDANCE, AND REPRODUCTION OF THE ALGAL SPECIFIC LIMPET, LOTTIA INSTABILISMaster’s Thesis. Moss Landing Marine Laboratories, San Francisco State University. 77pp.
  • Snail’s Odyssey; Limpets & relatives – Predators & Defenses: Escape-crawling from Seastars
  • Walla Walla University. Invetebrates of the Salish Sea – Lottia instabillis

10 Responses to “Who You Calling “Unstable”?”

  1. Yvonne Maximchuk

    Jackie. O my goodness, fascinating post, fabulous, richly jewel-toned photos. Thanks so much for another exquisite journey into the magical marine domain
    Yvonne

    Reply
  2. Celia Lewis

    Beautifully designed, and I even love the name… Fascinating details of their lives, and carefully shaped shell. So much to see, to learn.

    Reply
  3. Beth Stewart

    I loved this. Its name suggests it may not be strong but just look how it so wonderfully attaches itself wherever it needs to be. Your sharing much appreciated.

    Reply
  4. Jamie

    You are absolutely correct, “about how being “unstable” just might mean being better adapted to the conditions you are in”. I think we often forget just how important it is to be able to adapt to our surrounding conditions instead of being worried about what people might think. Just like this little limpet, perhaps the “unstable” ones are who actually have had the right idea all along! Great blog!

    Reply

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