Lumpy Crab at Florencia Bay

Earlier this week I spent two hours at Florencia Bay in Pacific Rim National Park Reserve. The beach here is sometimes overlooked by tide pool explorers heading to better known locations like the rocks at Wickaninnish Beach, Green Point or Schooner Cove.

Florencia Bay, Pacific Rim National Park Reserve
The boulders at Florencia Bay, Pacific Rim National Park Reserve are excellent for intertidal exploration.

I love poking around in Florencia Bay because access is easy and the intertidal zone is a little different from other locations in the national park. At Florencia, a field of large rounded boulders ranges in size from small chairs to love seats. Adding a few that are the size of small sheds creates a very interesting landscape and habitat. Most of the boulders are about mid-thigh height and are surrounded by sand facilitating the opportunity to look for organisms without damaging other creatures.

Lumpy Crab (Paraxanthias taylori)
Lumpy Crab (Paraxanthias taylori) often nestle in the rounded crevices on boulders in the intertidal zone.

While you’ll see many of the same anemones and sea stars that you would find elsewhere with careful searching other less common things can be found. I was examining a boulder and when I pulled the seaweed aside I noticed a small red crab nestled inside a pocket carved out of the stone. The lumpy red shell and round shape of this crab were characteristics that help identify it as a Pygmy Rock Crab (Cancer oregonensis). Notice too the hairy legs, also diagnostic for this species. The black tips of the claws are also a feature to look for (although they aren’t visible in these photographs).

Update: With a little help from Heather Holmes at Parks Canada, this crab is now correctly identified as a Lumpy Crab (Paraxanthias taylori). Particularly telling is the fact that the tips of the claws probably aren’t black (although it is difficult to see the tips considering that most of the crabs are safely hidden in bowls in the rock). Looking at the close-up photograph below, notice the bumps on the cheliped – this is a diagnostic feature of the Lumpy Crab, the Pygmy Rock Crab has smooth chelipeds. The fact that this crab isn’t listed in any of the common guide books, including Andy Lamb’s book led to a misidentification (and learning opportunity!).

Lumpy Crab (Paraxanthias taylori)
The rounded shell, bumpy texture and bumps on the chelipeds are features that help to identify the Lumpy Crab (Paraxanthias taylori).

 

The Pygmy Rock Crab is usually more active at night, emerging from its crevice or other hiding place to eat barnacles, snails, marine worms, bivalves and some green seaweeds. Males often have a harem of females and mate just after the female has moulted and its shell is soft. Apparently this crab will fold up its legs and roll like a stone when disturbed. Lumpy Crabs eat both green and red seaweeds as well as coraline algae. They are found in the middle to low intertidal zone, often hiding in rocks and crevices (like Pygmy Rock Crabs). The one that I found was so tightly wedged into its bowl that I wasn’t able to remove it, a very safe and protected space indeed!

This was my first look at a Pygmy Rock Crab Lumpy Crab. I’ll be definitely heading back to south end of Florencia Bay on the next set of good low tides in early August to see if I can find and photograph a few more!

3 comments

  1. What a gorgeous little thing. And well spotted! It’s really well camouflaged among the algae.

  2. Pingback: Dave Ingram's Natural History Blog :: Flacid

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