Perophora annectens Ritter, 1893

Common name(s): Sea grapes, green grapes, yellow social tunicate, yellow-green creeping tunicate

Synonyms: Perophora annectens
Phylum Chordata 
Subphylum Urochordata 
Order Enterogona 
Suborder Phlebobranchia 
Family Perophoridae 
Perophora annectens, about 4 mm tall.
(Photo by:  Dave Cowles, August 2009)
Description:   These small social ascidians live as distinguishable individuals which are connected by persistent threadlike stolonsof tissue.  The vaselike individuals are only slightly taller than they are wide, and are a translucent yellowish or grayish-green.  The tunic at the basal attachment is narrower than farther up the tunic.  The pharyngeal basket has four rows of stigmata with about 24 stigmata per row.  Oral siphons are 6-lobed and have about 12 tentacles.  The atrial siphons have 5-6 lobes.  The ovary and testis are within the curve of the gut.  Individual zooids are about 2-3 mm wide x 3-5 mm tall; colony up to 10 cm or more across.  Colony may resemble a cluster of  tiny green seedless grapes.

How to Distinguish from Similar Species:  Other small local social tunicates with similar configuration such as Metandrocarpa taylori are opaque, usually orange-red or brick red (sometimes yellowish), and the tunic does not narrow at the basal attachment point. Perophora japonica (found in Japan and introduced into Humboldt Bay in California) has star-shaped flattened yellow terminal buds on the stolons that are not found on P. annectens.

Geographical Range:   SE Alaska to San Diego, CA

Depth Range:  Lower midlittoral to 30 m

Habitat:  Rocks, algae, and floats; more common on open coast.

Biology/Natural History:   The zooids of this species may be well separated, or may be fairly closely packed together or their tunics may even be partially fused together.  This species broods its larvae.  Some of the darker yellow spots on the individuals above are likely larvae.

The zooids of a colony are genetically identical, formed by budding of the stolons.  Individual zooids are hermaphroditic.  In a related species the hormone thyroxin has been shown to enhance growth of the stolons while inhibiting formation of buds, which would presumably result in a colony of individuals which are more spread out from each other.  Thiourea, on the other hand, inhibits stolon growth but stimulates bud formation.  Growth of the stolons seems to be strongly affected by local electrical charges.  In P. orientalis, stimulation of the neural ganglion alters the heartbeat.  This alteration is passed on to neighboring zooids by the blood.

This species concentrates vanadium up to 9 ppt dry weight, mainly in blood cells.

In California these colonies grow rapidly in spring, sexually reproduce in summer or early fall, and degenerate over winter.

Though small, this translucent species is excellent for studying heartbeat, blood flow, ciliary beating on the pharyngeal basket, and characteristics of stolon growth.



Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996

General References:
  Harbo, 1999
  Johnson and Snook, 1955
  Kozloff, 1993
  Lamb and Hanby, 2005
  Morris et al., 1980
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985

Scientific Articles:

Web sites:

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

Authors and Editors of Page:
Dave Cowles (2009):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)