Styela montereyensis

Stalked Tunicate, Monterey stalked tunicate, Long-stalked sea squirt

Phylum Chordata
 Subphylum Urochordata
  Class Asidiacea
   Order Pleurogona
     Suborder Stolidobranchia
      Family Styelidae
Styela montereyensis observed at Cape Flattery, Wa    11 cm in length
Photo taken by Brandon White 7/08/02
Description:  Body elongate and cylindrical, supported on a thinner stalk about equal to body in length.  The overall length occasionally exceeding 25 cm in calm habitats but more often 8-15 cm in exposed sites.  Siphons close together at distal end; the oral siphon recurved (pointing to the side or downward) and the atrial siphon straight (pointing upward).  Tough, leathery tunic with prominent longitudinal ridges and grooves running the entire length of animal otherwise relatively smooth.  Yellow to dark red brown, often fouled with debris and other organisms in harbors but clean in wave swept areas.

How to Distinguish from Similar Species:  Can be easily confused with Styela clava.  It can be distinguished by the facts that Styela clava has the following (a) tunic usually bearing conspicuous tubercles, (b) tunic often with irregular longitudinal wrinkles but never with regular ridges and grooves along entire body representing thick and thin regions of test, and (c) both siphons straight, the oral siphon not recurved toward base of stalk.

Geographical Range:  Vancouver Island to Baja, California.

Depth Range:  Low intertidal zone to about 30m

Habitat:  Fairly Common, firmly attached to solid substrata in calm to very rough waters.  In the Pacific Northwest it is mainly found in the outer Straits and open coast, but rarely in inland waters.

Biology/Natural History:  Although they just look like slimy sacs, tunicates or sea squirts, are more closely related to humans than any other invertebrate group. This is because larval tunicates have several chordate structures - including a nerve chord and a notochord. These are later lost in most adult forms. Two openings are found on the tunicate: the buccal siphon (water comes in) and the atrial siphon (water goes out). Sea squirts got their name because a gentle squeeze will cause water to shoot out of their atrial siphon! The sedentary adult forms can either be solitary or colonial. A cool fact about tunicates is that they have a long, tubular heart that contracts in two directions!
Breeding and larval settlement occur in the summer. Study of the developing eggs shows that the inner follicle of the oocyte provides the test cells that are enclosed with the ovum inside the chorion. Both eggs and sperm are shed to the sea. In natural situations the larvae settle best on surfaces that have been underwater at least several months. In metamorphosing larvae the tail collapses, as is characteristic in members of the suborder Stolidobranchia, by contracting of the notochord itself, not (as in Aplousobranchia) by contraction of the caudal epidermis  This species may store vanadium (to about 36-40 ppm dry weight) in its tunic.  On the open coasts of Washington and Vancouver Island this species often has the copepod Pygdelphys aquilonaris in its branchial sac.

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Dichotomous Keys:
Flora and Fairbanks, 1966
Kozloff, 1987, 1996
Smith and Carlton, 1975

General References:
Brown and Rovetta, 1996
Brusca and Brusca, 1978
Gotshall, 1994
Harbo, 1999
Hinton, 1987
Kozloff, 1993
Morris et al., 1980
Niesen, 1994
Niesen, 1997
Ricketts et al., 1985
Sept, 1999

Scientific Articles:

General Notes and Observations:  Locations, abundances, unusual behaviors, etc.:

The name Styela means "pillar".

An individual from San Simeon, CA.  Photo by Dave Cowles, April 1997

This individual is under a rock at Cape Flattery.  Photo by Dave Cowles, July 2005

Authors and Editors of Page:
Brian Catelli (2002):  Created original page
Edited by Hans Helmstetler 11-2002