Three Amazing Animals From Curator Mark Siddall

On Exhibit posts

Mark Siddall, one of the co-curators of the new exhibition Life at the Limits took a surprising turn away from medical school when, while researching blood parasites in college, he found himself more interested in the delivery system—leeches—than in the bodies they invade.

Mark Siddall photo

His passion for these bloodsuckers and protozoan parasitology in general has taken him from the Amazon to Africa. In addition to his role as curator in the Division of Invertebrate Zoology, Dr. Siddall enjoys a reputation as an “expeditionary gastronomist”—game to try live grubs, sea urchin gonads, and seaweed custard in the field.

Siddall chose a few of the more interesting species he’s worked with, as well as one featured in Life at the Limits, which visitors can learn more about at the exhibition.

Early in his career, Siddall was struck by the “incredible life cycle” of the parasitic worm Ascaris lumbricoides. Humans get infected when worm eggs, passed through feces, contaminate food. The eggs hatch in the host’s small intestine, penetrate the intestinal wall, and then hitch a ride to the lungs in the blood stream. Once in the lungs, they cause irritation, which leads the infected person to cough, bringing the worms up the trachea and into the esophagus. The precocious parasites are swallowed, returning to their roots in the small intestine, where they grow into adults. “That’s just amazing!” says Siddall. 

The adult form of the parasitic worm Ascaris lumbricoides.  © CDC Division of Parasitic Diseases

The adult form of the parasitic worm Ascaris lumbricoides.

© CDC Division of Parasitic Diseases


Dr. Siddall is currently studying Ozobranchus, a group of leeches that feeds on the blood of turtles. Ozobranchus margoi targets green sea turtles (Chelonia mydas) and Ozobranchus branchiatus are found in a variety of sea turtles, primarily loggerheads (Caretta caretta). Like other blood-feeding leeches, these parasites open a wound and deliver an anticoagulant to prevent blood clotting. An Asian species, Ozobranchus jantseanus, is highlighted in Life at the Limits for its ability to survive a 24-hour dunk in liquid nitrogen. 

A flying fish photographed just after leaping out of the water.  © NOAA

A flying fish photographed just after leaping out of the water. 

© NOAA


Siddall’s favorite vertebrate in the exhibition? The flying fish (family Exocoetidae) found in tropical and subtropical areas of the Pacific, Atlantic, and Indian Oceans. Flying fish have large pectoral fins—and in some species, enlarged pelvic fins as well—that act as “wings,” allowing them to leap up and glide above the water. “I’ve seen them in Raja Ampat, Indonesia,” says Siddall. “They were streaking across the water behind our boat. Wicked fast!”

A version of this article originally appeared in the Spring issue of our Member magazine Rotunda