Seamounts Species Spotlight: The Jelly-Like Ctenophore

The New England Coral Canyons and Seamounts are a special area 150 miles off the coast of Cape Cod. The unique geological formations make this area a biological hotspot, attracting many unique species. This blog post in part 4 in a series that profiles some of these incredible animals.

Glowing water is not just the stuff of sailor stories and fairy tales. In tropical regions, when the briny depths appear to be glowing, it is most likely a result of bioluminescent plankton. But here in the North Atlantic, there may be another culprit: the ctenophore.

Also known as “comb jellies” and “sea walnuts,” the ctenophore is a nearly transparent floating creature frequently misidentified as jellyfish. While similar, the ctenophore is actually in a phylum of its own (lower than kingdom; higher than class). This is due to differences in ctenophores and jellyfish in how embryos develop, and the physical appearance of adult individuals. Scientists estimate there are 150 species of these jelly-like creatures, found throughout the water column and in all the world’s oceans.

Important Differentiators 

Don’t worry if you see a ctenophore in the water – unlike jellyfish, ctenophores aren’t able to sting humans. To hunt for food, some do deploy tiny stinging cells, while others can engulf prey even larger than they are!

While there is no “typical” way to describe the ctenophore’s physical features, scientists can agree on a few facts: First, ctenophores are invertebrates, meaning they have no bone structure. This makes them appear to be simply floating in the water. Almost all species are small and transparent. One exception to this rule is the beautiful and large “Venus’ Girdle.” This species can grow up to a meter in length, is pale violet in color, and is found in the Mediterranean Sea. Almost all ctenophores are bioluminescent, meaning they glow.

A ctenophore can appear to be rainbow colored because when it swims, tiny hair-like structures on the outside of its body beat together so quickly that it deflects light into tiny rainbows. These fast-beating hairs are called cilia. Cilia are found arranged in eight rows on the outside of all ctenophores.

Although the ctenophore can live in many places throughout the water column and in most habitats, benthic (seafloor) varieties are difficult to come by. This makes them very challenging creatures to study, leaving scientists with much to learn about them.

In 2013, NOAA conducted an Okeanos Explorer Program Expedition within the New England Canyons area and had the rare opportunity to view and record a number of ctenophores (and many other unique critters). Clearly, an abundance of research opportunities lay in the lively communities of the Coral Canyons and Seamounts.

This is another reason why permanently protecting unique ocean habitats is so important. Who knows – this research that may provide marine science with its next big discovery!