Kaburakia excelsa Bock, 1925 

Common name(s) Giant flatworm, Giant leaf worm

Phylum Platyhelminthes
 Class Turbellaria
  Order Polycladida
   Family Stylochidae
Kaburakia excelsa, about 9 cm long.  Found under a rock on Sares Head, Rosario Bay
(Photo by: Dave Cowles, June 2003
Description:  This giant flatworm has a band of eyespots along the entire margin of the body (may not be visible except in transmitted light), plus on its pair of short, blunt nuchal tentacles (picture), at the bases of the tentacles, and in the region of the brain.  Its gut outline follows the multi-branching polyclad pattern.  The color is tan with small spots or streaks of dark brown dorsally, lighter tan with few if any spots ventrally (picture).  Has no suckers on the ventral surface.

How to Distinguish from Similar Species: This species if far larger than any other species in this area, and is one of the largest in the world.  Most other flatworms in this area are up to only about 3 cm long.  Polyclads are the only group of flatworms in our area that get larger than microscopic size.

Geographical Range:  Sitka, Alaska to Newport Harbor, CA

Depth Range:  Mid-intertidal to subtidal.

Habitat:  Among mussels and under rocks, sometimes on pilings or on boat bottoms among fouling organisms.

Biology/Natural History:  The tentacles are just in front of the brain and can be retracted.  This animal is negatively phototactic.  The margins of the body wrinkle as the animal moves (see photo above).  Will eat mussel tissue in the laboratory.  In Washington, gravid individuals can be found in March.  150-160 golden yellow eggs are laid individually in capsules, in a tight-packed monolayer or bilayer on rocks.

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Dichotomous Keys:

Kozloff, 1987

General References:
O'Clair and O'Clair, 1998
Morris et al., 1980
Kozloff, 1993

Scientific Articles:

General Notes and Observations:  Locations, abundances, unusual behaviors, etc.:
This species is uncommon.  In many summers of intertidal study I have found only one and a colleague had found none.

This photo of the anterior end as the animal tries to climb the side of the bowl shows the nuchal tentacles and the dorsal and ventral pigmentation.

Authors and Editors of Page:
Dave Cowles (2004):  Created original page