This is a follow-up to a previous blog post. Learn about different kinds of sea jellies and their unique characteristics here.
Black Sea jelly, via Wikimedia Commons
"True Jelly" reproduction
One remarkable trait of most Scyphozoans is their dual reproductive strategies. They can produce asexually by budding and sexually after a process called strobilation. The fertilized egg becomes a planula larva that quickly settles and morphs into a polyp. This polyp then becomes a strobila – almost looking like a stack of coffee filters. Each of these detaches and becomes an ephyra which then transitions into either a male or female medusa to begin the process all over again.
Jellies are beauties, adaptors, predators, survivors, neighbors...
If this year is anything like last we will see a fairly large population of jellies in the harbor pretty soon. They thrive in warmer water, but humans also play a role in helping jelly populations.
Credit: NancyHeise, via Wikimedia Commons
Overfishing – Humans can overfish the natural predators of jellies, creating a host of problems. By removing their predators, namely large fish, it allows populations of jellies to grow exponentially. Since jellies in turn eat larval fish, increased jelly populations further reduces already overfished populations.
Pollution and runoff – Pollution and runoff can cause what's known as "dead zones," areas that are severely depleted of oxygen. While these conditions are inhospitable to fish, they are a fine environment for jellies.
Invasive species – Many invasive species are introduced to oceans around the world through the ballast
waters of boats; and invasive jellies are no exception. A famous example is the comb jellies that were introduced into the Black Sea in the 1980's. They have no natural predators and have wiped out many commercial fisheries. By 2000, the total weight of the comb jellies in the Black Sea was more than 10x all the commercial fish caught there throughout the entire year.
What can you do?
There are lots of ways you can support healthier oceans, including hoofing it now and then and choosing ocean-friendly seafood. Explore ways you can LiveBlue™ at the Aquarium. Come see jellies up close and learn even more about these fascinating creatures in The Trust Family Foundation Shark and Ray Touch Tank area, opening April 15!
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