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It's a Jelly-Eat-Jelly World





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Posted by Merry on May 08, 2012 at 16:09:38:

Ho-hum. Another descent along the anchor line and there’s nothing in the water except these darn sea gooseberries. I’m not asking for much – a large comb jelly, perhaps a fried egg jelly, anything larger than a quarter. At only 5/8”, the abundant and ever-so-common sea gooseberry, Pleurobrachia bachei, doesn’t usually promise thrills and chills. But this day is different.

Propelled by 8 ciliated comb rows, sea gooseberries troll the water dragging 2 retractable tentacles. When fully extended, fine side-branches on the tentacles have specialized cells which adhere to fish larvae, copepods, eggs, and small crustaceans. My camera occasionally captures some of the larger copepods, which are barely visible to the naked eye.

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The interior of the little gooseberry is pretty straightforward. Right next to the aboral anus (they have multiple anuses) is the balancing organ, or statocyst Even jellies need to know which way is up.

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A pharynx fairly stuffed with prey.

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Facing the prospect of nothing else to photograph, I continue snapping away at any Pleurobrachia that will cooperate. A spinning marble catches my eye. Wait, I’ve never seen a gooseberry do anything other than pulse along mostly upright. This one makes a crack-the-whip type of maneuver and plops a tentacle right on top of its mouth. Removing prey from the sticky tentacles must be an interesting trick.

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Here comes a plucky gooseberry that looks like it bit off more than it can chew. Oh boy, it snared a Beroe comb jelly.

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Wait a minute, who’s eating whom? Beroe species are famous for biting into or engulfing prey as large as they are. This young Beroe is devouring the sea gooseberry one mouthful at a time. Note the bites already inflicted.

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What a treat to witness the food chain in action!



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