Aplacophorans: The fuzzy little Mollusk you don’t know

mollusc copybiogallery-ImageF.00062Cute and cuddly may not be the first words you would to describe a Mollusk. A group whose name literally means “soft-bodied” in Latin. However, the approximately 300 species of aplacophorans are quite cute. These cylindrical mollusks lack the shells of their brethren but rather are covered in small calcified spicules that given them a fuzzy appearance.   Most of these cute little buggers are no longer than couple of inches but some can top out at a full foot in length.

aplacophora_smCompared to other mollusks aplacophorans are quite simple and different. So different that at one time they were thought to be sea cucumbers. Not until1987 were the officially classified a mollusk.   The head of aplacophorans is pretty simple and lack eyes and tentacles. The have single opening, called a cloaca, in which the excretory and reproductive systems both empty. One hole to rule them all if you will.

Most of the species live either crawling around in or on top of the seafloor sediment.  Depending on the group of aplacophorans, these little guys are either fierce hunters of cnidarians, or in contrast, grazerspicking bits of good out of the sediment.


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The simplicity suggests the aplacophorans are the ancestors to all other mollusks. However, a fossil found in 2012, Kulindroplax, tosses this idea aside. This fossil aplacophoran contained plates like chitons, another group of mollusks. This suggests aplacophorans evolved from a shelled ancestor as opposed to all other mollusks originating from an ancestor without shells.

Well the great granddaddy of mollusks or not you cannot deny their cuddliness.  Although this pink one does look a bit like a fuzzy penis.

Dr. M (1798 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (http://deepseanews.com/), a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.


One Reply to “Aplacophorans: The fuzzy little Mollusk you don’t know”

  1. They all look like penises LOL but in that regard, their resemblance is only vague compared to the penis worms. They are all put to shame by Atretochoana eiselti. a caecilian. I’m sure you know what it is, but if you don’t an image search should make it clear that when it comes to penis mimics it’s the champ.

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