Rock Borers and Giant Clam Shells of the Hiatellidae Family
One Giant Clam Shell of the Hiatellidae Family can be found in this website:
Cortez Geoduck Shell, Panopea globosa. A representative of the Hiatellidae Family of Rock Borers and Giant Clam Shells.
Phylogeny: Hiatella Clam Shells of the Hiatellidae Family are bivalve mollusks in the Adapedonta order. The superfamily Hiatelloidea is one of two superfamilies in this order. Hiatellidae is the only family in the superfamily Hiatelloidea. The Hiatellidae Family is fairly small, with no subfamilies, four genera, and twenty-six species. Shells in this family are also commonly known as Rock-borers, Giant Clams, Geoducks, and Hiatellids.
Description: Hiatella Clam Shells are solidly built and irregularly ovate or trapezoidal in shape. They are longer than they are tall. Most species gape at the anterior and posterior ends. In some species the only portion of the shell where both valves touch one another is along the hinge. The exterior may be smooth or sculpted with weak commarginal striae or wavy growth ridges. They have one cardinal tooth in each valve. The interior is smooth but not nacreous. The animal is larger than the shell and cannot fit entirely inside. Most species are whitish in color and have a thick periostracum. Hiatella Clam Shells are small to large in size. The largest species in the family reach 23 cm (9.1 inches) in shell length. The animals can reach 100 cm (39 inches) in length.
Habitat and Distribution: Despite their common names, Hiatella Clam Shells seldom bore into rock, nor are they all giant in size. Some species do bore into corals, rocks, mud, sponges and sand but most are “nestlers”, settling into a crevice as a larvae and then growing to fit the crevice. This produces an irregular shape, making identification of different species difficult. The longer species in the Hiatellidae Family burrow in soft substrates. Most of their body length is their siphon, allowing them to burrow up to one meter (3 feet) deep. These shells live in the intertidal zone and at depths up to 400 m (1,300 feet). Hiatella Clams are found worldwide, in polar to tropical seas. Three species from the Hiatellidae Family are found in Mexican waters.
Natural History: Hiatella Clam Shells are suspension feeders, filtering plankton from the surrounding water, by use of their siphon. They have a limited number of predators that include fish, shorebirds, marine mammals, and sea stars. The lack of predators may contribute to their long-life spans, as some species can live over one hundred forty years. Most Hiatella Clam Shell species are gonochoric, though some are protandric hermaphrodites. They reproduce sexually through broadcast spawning. Hiatella Clam Shells are edible and are commercially harvested and farmed. The name Hiatella is a combined Latin and Greek word meaning “Little Gaper”, referring to the opening at both ends.