No. 50–Delightful Delicate Drifters

I’ve always been fond of alliteration as in the above title line. And it is, as you will see, definitely, demonstrably, descriptive… Okay, Okay, that was a bit of a reach.

After three recent columns dealing with dreaded, dangerous and sometimes deadly drifters; the DDDs of this month’s piece are benign and beautiful.

One day in the spring of ’92, the North Street Aquarium had just opened the previous October; I was on one of the floating docks at the Downtown Marina preparing to haul water for tank changes. I had learned early on to come for water as near high tide as possible as nearly full five gallon buckets weigh around 35 lbs and it’s no fun hauling them up a steep ramp.

I was on my knees with bucket poised to plunge when a nearly transparent aberration just a few inches beneath the surface and the size of a guinea hen egg went drifting by. Whoa… what in the world is that was my immediate novice naturalist reaction as the outgoing tide carried it beyond reach.

The initial disappointment of not having reacted fast enough to scoop the creature up was soon allayed by the appearance of several others in the quickening current. Three were collected that morning and I remember sitting in front of their tank enthralled with their beauty and grace and that night being treated to a delightfully surprising light show.

Full of questions I went next day to the USCB library where my now longtime friend, Ellen Chamberlin, directed me to a section were I found a several hundred page tome, one of the few with photos and drawings, on marine invertebrates. The index was no help as it was mostly Greek to me (actually Latin), so I fanned through and turned pages until there it was in all its glory… Mnemiopis leidyi.

M. leidyi is a ctenophore (the “c” is silent), one of approximately one hundred species in the phylum Ctenophora. The common name is comb jelly and while they do share some characteristics with the cnidarians of previous columns, they are not jellyfish.

Comb jellies, unlike jellyfish, have bilateral symmetry which means they have a front and rear end whereas jellyfish have only tops and bottoms. With a few exceptions they propel themselves with rows of cilia rather than muscle contractions and, except for possibly one new species now under study, lack stinging cells.

Like jellyfish, the comb jelly’s basic structure has an epidermis, a gelatinous mesoglea and endodermis. The diversity of variations on a theme within a phylum containing so few species is, however, surprising. Some have a pair of tentacles used for “fishing”, some like our M. leidyi are spherical while others laterally compressed like Beroe (ba-ROE-ee) ovata which is also found here. Some have even evolved with a jellyfish-like medusa shape. They inhabit coastal, open ocean and deep sea environments.

Ctenophores may be observed locally from spring through fall if you’re patient. The trick is to have a vantage point within a few feet of the water’s surface when the tide’s not running full tilt. I’ve found the half hour or so on either side of high tide to be optimum for catching a glimpse of these easy to miss creatures.

Many of you who throw cast nets have most likely seen what remains of their delicate selves as small masses of clear jelly dripping through your nets. That had been my experience. In all the years before the “what in the word is that?” morning, I simply knew them as jelly balls without a thought as to what a jelly ball was.

Next month we will explore these interesting creatures further and address how, while benign in it’s home environment, M. leidyi became a scourge thousands of miles from Port Royal sound.