After posting my blog yesterday, I decided to do a little more research on the life cycle of the moon jellies in Puget Sound or elsewhere. I didn't find much in my natural history books, marine life field guides, or on the Internet. So I sent an e-mail to David Jamison, one of the marine biologist who conducts the popular public Pier Peer events at Boston Harbor Marina. (David, you may recall, also wrote weekly column on creatures of Puget Sound for The Olympian.)
I asked David what he knew about the summer aggregations of moon jellies. Here is his reply:
As to the moon jellies, they do tend to gather into groups Budd Inlet every August and Sept which is about when they begin to die off. They also occur in groups in other areas of Puget Sound. This is not a new phenomena as I have seen them do this for over thirty years that I have been in the local area. There can be hundreds to thousands of individuals.I have not found a satisfactory explanation for the aggregations. Some have said there is a reproductive reason as there are both males and females swimming at the same time, however they breed from the spring through the summer with the young growing in special areas of the swimming bell of the adult till the fall when the young move off to hard surfaces to form a polyp. Others have said it is due to their method of swimming against water flow during the day. Some have implied that they can orient relative to compass directions when they swim.
Thank you David for this satisfying and humbling reply. To think that this "lower" life form--spineless, simple, and seemingly passive--could orient itself to the North, South, East, or West is remarkable given that a large percentage of homo sapiens seem unable to point to the North when asked or navigate their way out of their driveway without a GPS unit!
How marvelous that these abundant, relatively common, and easy to observe jellyfish still hold mysteries and perhaps the upper hand on methods for finding mates.
NOTE: The next Pier Peer is October 23, from 8-9:30 p.m. These events are very popular; space is limited (isn't it always?) reservations are required. Go to: People for Puget Sound to reserve before it's too late!