Mytilimeria nuttalli Conrad, 1837

Common name(s): Sea bottle, sea bottle clam, bottle clam, bladder clam

Phylum Mollusca
 Class Bivalvia
  Subclass Anomalodesmata
   Order Pholadomyoida
    Family Lyonsiidae
Mytilimeria nuttalli found in the low intertidal in Guemes Channel
(Photo by: Dave Cowles, July 2005).  Identified with the help of Gene Coan
Description:  As a member of family Lyonsiidae, this species has 2 adductor muscle scars of similar size.  It has no hinge teeth (photo)and no chondrophore.  The shell has no radial ribs.  The umbones do not quite touch (photo).  The interior of the valves is pearly (photo).  The pallial line and pallial sinus are continuous (though often indistinct in this species).  The tips of the siphons are not bright red.  This species is fragile and nearly circular in outline or higher than long (but often deformed).  The periostracum is translucent yellowish brown.  It is usually found embedded in colonies of compound ascidians with the siphons exposed.  The shell usually cracks when dried.  The shell has fine concentric growth lines, and Johnson and Snook say it also has fine radiating lines.  Length to 4 cm.

How to Distinguish from Similar Species:  Members of most other families have hinge teeth.  Other members of family Lyonsiidae such as Entodesma navicula are longer than high (not circular in outline) and do not live in ascidian colonies.

Geographical Range:  Forester Island, Alaska to Isla Rondo, Baja California, Mexico

Depth Range:  Low intertidal to 40 m

Habitat:  Lives in ascidian colonies

Biology/Natural History:  This species is almost always embedded in compound ascidian colonies, especially Archidostoma psammion and Cystodytes lobatus.  Larve appear to settle on the ascidian colony and attach by a byssus.  The clam eventually becomes surrounded by the colony except for a narrow slit for the siphons.  The species is a hermaphrodite but doesn't spawn eggs and sperm at the same time.

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

General References:
  Harbo, 1997
  Johnson and Snook, 1955
  Kozloff, 1993
  Morris, 1966
  Morris et al., 1980

Scientific Articles:

Web sites:
Seashells of British Columbia

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

Species in this family (Lyonsiidae) have no hinge teeth.  This is the hinge on the left valve.  Notice the calcified shieldlike plate that wraps around the hinge ligament from the left valve.

The platelike shield can be more clearly seen in this photo.

The interior of the shell is pearly but the pallial line and pallial groove are difficult to distinguish.

The shell is fairly inflated, as can be seen in this end-on view of the left valve.  The shieldlike plate which wraps around the hinge ligament can also be seen.

The species has large umbones which face anteriorly.

The shell is thin, and along the ventral edges is mostly yellowish-brown periostracum.  In this view of a live individual, the thin, flexible periostracum along the ventral margin has distorted when the animal closed, forming into two nearly parallel plates.

Authors and Editors of Page:
Dave Cowles (2006):  Created original page