Snails Meets Snail in Kwajalein Atoll - Observation of the Week, 4/12/22

Our Observation of the Week is this Marble Cone Snail (Conus marmoreus) eating a Chocolate Spotted Auger Snail (Terebra subulata) in the Marshall Islands! Seen by @uwkwaj.

The uwkwaj iNat account belongs to Scott and Jeanette Johnson, and Scott wrote back to me for this week’s blog post. “I guess we have been interested in nature as far back as both Jeanette and I can remember,” says Scott. Growing up in Los Angeles, Jeanette would seek out insects in her backyard and Scott sought out snakes, turtles, and frogs in a nearby pond in New England. “But what focused each of us on marine life was moving to Kwajalein Atoll in the Marshall Islands,” he explains.

In my case, my parents dragged me out there when I was 8 years old, and I immediately became fascinated by the water and reefs surrounding these small islands. Some years later, Jeanette and I returned to Kwajalein and spent the next 30 years diving and documenting [the atoll’s] marine life. Permanently living in an area gave us a more complete overview of the reefs and animal populations that come and go than sporadic expeditions ever could. While my main focus was mollusks, particularly nudibranchs, we are interested in and photograph anything that gets in front of our cameras. Unfortunately, we were also witness to the decline in health of the reefs. In all my years out there, I did not see any sign of coral bleaching until 2009, when Kwajalein had its first recorded episode. It happened again in 2013, 2014, 2016 and 2018, with more coral failing to recover each time. I fear that our documentation of the marine life of the Marshall Islands might turn out to be just a record of what used to be there.

Scott has mostly shot underwater video since 1994, and the image you see at the top of the page is a still from footage he took in 2009. 

For years we mostly dove the coral rich lagoon pinnacle reefs or the steep seaward drop-offs, but after a while discovered that lagoon sand flats bearing dense fields of Halimeda and other algae were surprisingly diverse, and the Halimeda patches became some of our favorite sites. Sand dwelling mollusk species such as cones and augers were abundant. I came across this particular scene of a Conus marmoreus sucking the animal out of a Terebra subulata in the sand around one such algae patch.

Famously venomous, cone snails are all predators that immobilize their prey by injecting toxins via their harpoon-like radular tooth, then consuming them. Marble cones seem to specialize in eating other mollusks. Chocoloate spotted auger snails are also predatory and venomous, using a similar venom delivery mechanism to that of cone snails. However, they predate marine worms.

Scott and Jeanette (Scott middle, Jeanette below) joined iNaturalist just over three years ago and have since added nearly eight thousand observations. The oldest photos are Scott’s, taken from his time as a graduate student in Hawaii and as a research staff member at the Mid-Pacific Research Lab at Enewetak. Most of the photos since the mid-90’s are Jeanette’s.

“Although I knew it existed and had looked at a number of species there,”  says Scott, 

I became more aware of iNat when a researcher asked me to post my images of a Marshall Islands endemic anemonefish there so they could be referenced in a paper in preparation. That made me realize that iNat would likely be a great way to make our observations more widely available and would almost certainly have a greater longevity than our own website on Marshall Islands marine life. I find it very useful as a means to compare variation within a species across its range; I’ve always been interested in biogeography and how and where species are distributed.

- Scott and Jeanette’s website can be found here.

- PBS’s Deep Look has a great video breaking down cone snail predation.

- Check out the remarkable observations Scott and Jeanette have posted from their archives!

- This paper goes over the potential benefits and drawbacks of using conotoxins in pharmacology.

- Speaking of Hawaii, check out this old Observation of the Week, documenting a crab that’s found a curious to place to call home.

Posted on April 12, 2022 05:47 PM by tiwane