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College of Food, Agricultural, and Environmental Sciences


Smart Stuff with Twig Walkingstick: Seahorse Manure (for the Week of April 5, 2009)

April 5, 2009

Q. Dear Twig: How do seahorses go to the bathroom?


A. Seahorses are fish. You probably know that. So they go to the bathroom like other fish do. Food goes into the mouth, to and through the intestine, then the food that isn't digested and absorbed there goes out the anus ("AY-nuss") as feces ("FEE-seez") — usually, in this case, small pellets.

Seahorses actually have an inefficient digestive system, says the "Biology of Seahorses" Web page of a group called Project Seahorse. "Food passes through rapidly and is often excreted in a partially digested state," says the book Seahorses by Frank Indiviglio.

Seahorses get rid of urine as well. It's made up of water and of filtered-out waste from the blood. It goes from the kidneys, into the urinary bladder, then out the urogenital ("yer-oh-jen-ih-tull") pore. That part's next to the anus; together they make up the vent. The vent is on the front of a seahorse (the bottom of a regular fish), above the tail and, if a male, the brood pouch.



P.S. Another way? They raise their fin, ask the teacher, then swim down the hall and turn right.



Ba ha ha ha ha ha heeeee! Get it? Raise their fin? That's so finny I forgot to laugh.

Thanks to Elise of Lakeville Elementary School, Lakeville, Ohio, for this week's question.

"Seahorses have an extremely reduced stomach, a characteristic found in many fishes that, like them, feed continuously on small prey." So says the "Seahorse Anatomy" Web page of the Scripps Institution of Oceanography, La Jolla, Calif., Check it out: It lets you roll your cursor over a seahorse to see the parts inside.

Project Seahorse:


About This:

"Smart Stuff with Twig Walkingstick" is a weekly feature for children (ages 9+; 4th grade reading level) about science, nature, farming and the environment. Online at

Brought to you by your scientific friends at The Ohio State University — specifically, at the Ohio Agricultural Research and Development Center (OARDC) ( and with Ohio State University Extension ( OARDC and OSU Extension are the research and outreach arms, respectively, of Ohio State's College of Food, Agricultural, and Environmental Sciences.

Written by Kurt Knebusch of OARDC and OSU Extension. For details, to ask Twig a question, and/or to receive the column free by mail or e-mail, contact Kurt at CommTech, 1680 Madison Ave., Wooster, OH 44691;; (330) 263-3776.

Kurt Knebusch