COMB JELLIES
Maybe the best description of this month’s beach animal is to say “they are practically
invisible!” I’m talking about Comb Jellies. They are so clear that you barely notice them when
they are washed up on the wet sand. And when they are in the water, you pretty much don’t see
them at all. A Comb Jelly is a fragile, gelatinous, gooey, clear glob; but it is a living animal. They
are pretty much overlooked when washed up and will appear only as a small, thin, flat, clear
round area lying on the wet sand. It might be as small as a nickel to as large as a sand dollar. If
you haven’t ever found one, don’t worry, most folks never notice them.
If you do find one that has washed ashore and lying in the wet sand, the best way to examine
it is to carefully place it in a small, clear plastic bag with a little seawater. Back in the water,
the Comb Jelly will retain its normal shape. You will still have to look carefully to see it because
it is so clear and transparent. But you should be able to notice that it is generally shaped like
a football with 8 lines running along its body, like the seams on a football. Each of these lines
is actually a row of tiny comb-shaped structures having microscopic hair-like cilia forming the
“teeth” of each comb. These comb-like structures are called “ctenes.” (The “c” is silent.) And the
scientific name for Comb Jellies is thus Ctenophores. Sometimes it’s possible to see the waves
of movement of the microscopic cilia along the rows, and you may get lucky to see them make
a moving rainbow of color due to the tiny cilia diffracting the sunlight.
Although they are gelatinous, Comb Jellies are not true “jellyfish” but rather belong to their
own minor group in the animal kingdom. They don’t have tentacles like real jellyfish, and the two
26 TYBEE BEACHCOMBER | NOV 2018
species that we get around here don’t have any tentacles at all. Using the rows of tiny cilia to
glide through the water, they eat microscopic plankton. Most Comb Jellies live in the deep sea far
from shore, but we get a couple of species in our near shore waters. One is the football shaped
“Sea Walnut,” and the other is shaped more like a cup with a rounded bottom.
To me, one of the most interesting things about Comb Jellies is their ability to produce flashes
of bioluminescence, or flashes of light. Lots of deep sea animals produce bioluminescence for a
variety of reasons. And since our inshore Comb Jellies are kin to their deep water relatives, they
retain this characteristic. Ours will produce flashes of turquoise blue light along their comb rows.
If it is a dark night and the water is calm, it’s possible to see occasional flashes produced by
Comb Jellies in the near shore water. If you’ve got one in a bag of seawater, set in the bathroom
sink, and then later that night, with it totally dark, give the bag a shake. You might get a miniature
light show!
Dr. Joe Richardson (Ph.D. Marine Sciences) is a retired marine science professor with 40 years
of research and teaching experience along GA, the southeastern coast and Bahamas. Besides
research, he conducts Tybee Beach Ecology Trips (www.TybeeBeachEcology.com) and frequently
posts pictures of their findings on his Tybee Beach Ecology Trips Facebook page.
Beach Walks
with Dr. Joe
By Dr. Joe Richardson
/(www.TybeeBeachEcology.com)