Posted by: lauraearly | March 7, 2011

The adventures of Hermy Dermy and Jelly Belly

Living in the sand or mud between the tides can be quite the adventure. This area, called the soft intertidal, provides a very dynamic environment for its inhabitants. Part of the day they could be flooded with salt water, but in a few hours would be high and dry. Most animals are adapted to live either in the water, or out of the water–not both!

From Bunche Beach, we walked and waded through the intertidal zone to meet some of the super-creatures that deal with these interesting circumstances and to figure out how they do it.

First, we encountered Jelly Belly. Jelly Belly was actually not a single organism, but a sac of eggs rooted into the sand by a marine worm. Seven-year-old Cami’s nickname for the gooey-looking egg case was much more flattering than “sea snot,” which you might also hear it called. The jelly-like substance the eggs are suspended in helps keep them moist if they happen to find themselves out of the water. Stepping gingerly through the water, we saw several Jelly Bellies stuck in the sand, swaying with the gentle movement of the water.

 

Jelly Belly (worm egg case) in a sample jar.

Hermy Dermy (hermit crab) tries to take refuge in the sand.

Shortly after Jelly Belly, we met Hermy Dermy. Unlike Jelly Belly, Hermy Dermy was on the move. A small hermit crab in a bubble shell, Hermy was able to scurry around, but quickly retreated into the shell when a giant hand came down upon it. Hermit crabs are also common residents of the intertidal zone, and they are able to move in and out with the tide to some degree. All crabs use gills to breathe oxygen from the water, so as long as their gills stay moist they are able to survive out of the water. As we carried Hermy Dermy around in a shell filled with wet sand, he started to sink down into that small amount of sand. Later while digging on a small exposed sandbar, we discovered that even when the sand isn’t covered by water, it’s just below the surface, so that burrowing animals can retreat further into the sand until the water returns.

King's crown pulls its body into its shell when out of the water.

King’s crown conchs were a sharp contrast for our feet from the soft sandy bottom, but we discovered that they have some superpowers of their own. Like other gastropods, king’s crown conchs have a special door called an operculum attached to their muscular foot. They can pull their entire body and a little bit of water into their shell and seal it off with the operculum until they are in the water again. The operculum can also act as a shield from predators.

These are just a few critters that have developed ways to live in and use the constantly changing intertidal. What other amazing adaptations have you encountered in the soft intertidal?

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