The Exotics Guide

Corbula amurensis Image 3

Corbula amurensis from San Francisco Bay. Note the dark fouling on the upper one-third or so of the shell that had protruded from the mud.

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Corbula amurensis Image 2

A block of mud containing Corbula amurensis from the bottom of San Francisco Bay.

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Corbula amurensis Image 1

Corbula amurensis from San Francisco Bay.

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Corbula amurensis (Schrenck, 1861)

OVERBITE CLAM, ASIAN CLAM, AMUR RIVER CLAM, BRACKISH-WATER CORBULA

  • Kingdom: Animalia
  • Phylum: Mollusca
  • Class: Bivalvia
  • Subclass: Heterodonta
  • Order: Myoida
  • Superfamily: Myoidea
  • Family: Corbulidae

Corbula amurensis is a tan, white or yellow clam, up to about 25 mm long. It lives partly buried in the sediment, with its hind third or half exposed above the surface. This is often colonized by small organisms and stained brown, in contrast to the clean, buried portion of the clam. The umbo—the hump at the center of growth—is at the hinge or upper margin of the shell and evenly centered between the front and hind ends, giving the shell the overall shape of a broad isosceles triangle.

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Mya arenaria Image 10

Mya arenaria shells washed up on a beach at Point Pinole, in the northern part of San Francisco Bay.

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Mya arenaria Image 9-dug from hole

23 Mya arenaria that were dug from a shallow, one-foot-square pit (along with 37 other clams) on the east shore of San Francisco Bay.

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Mya arenaria Image 8-young

A young Mya arenaria from San Francisco Bay, with siphons protruding from the hind end.

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Mya arenaria Image 7-interior view

Interior view of the same valve, with the head end to the right, showing the shelf-like projection (1), muscle scars (2), the pallial line (3) and the deep indentation in the pallial line (4) that outlines the pouch that held the retracted siphons.

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Mya arenaria Image 6-closeup

Closeup of the shelf-like projection.

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Mya arenaria Image 5-largest of valves

The largest of the valves from the previous image, showing the shelf-like projection and the shell interior. The shell is about 10 cm long, and the head end is to the left.

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