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Family Teredinidae - shipworms
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Class |
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Bivalvia |
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Environment |
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Fresh : No |
Brackish : No |
Marine : Yes |
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Remark |
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Shell reduced, covering only the anterior end of a long, worm-like animal which secretes a tubular, calcareous lining inside its burrow. Shell equivalve, hemispherical to auriculate, widely gaping anteriorly and posteriorly, divided into 3 parts (an anterior slope, a median disc and a posterior slope). Anteroventral margin with a deep, right-angled notch, posterior margin often lobed. Dorsal margin more or less unrolled over the umbones, forming an umbonal reflection. Outside of valves with an umbonoventral groove. Sculpture mainly concentric, forming denticulate ridges on anterior slope. Ligament internal, reduced. Hinge without teeth. Interior of shell porcelaneous. Umbonal cavity with a finger-like apophysis to which the foot muscles are attached. An internal umbonoventral ridge corresponding with the outer groove, with a knob at both ends, on which valves rock during boring process. Three adductor muscles, scars of which are generally obscure. Anterior adductor small, on umbonal reflection; posterior large, on lobed posterior slope; ventral small. Pallial line coincident with valve margin. Accesory calcareous tube lining burrow long and vermiform, greatly varying in extension and thickness, sometimes with septa near its aperture which can be closed by a pair of paddle- or feather-like pallets. Gills elongate, of eulamellibranch type, with only 1 branchial sheet. Siphons relatively short, fused or partly separate. Foot discoidal, truncated, forming a sort of sucker protruding through anterior gape of shell. Mantle fused ventrally, except at the pedal gape, with a thickened fleshy fold (the mantle hood) covering the umbonal region of valves. The Teredinidae are highly specialized bivalves adapted for boring into submerged wood and other plant materials. FIlter-feeding animals, alternating spells of feeding on plankton with periods of utilixation of rasped wood particles, initially digested by symbiotic bacteria. Internal calcareous liningg of burrows probably preventing shipworms from intersecting one another. Mainly consecutive hermaphrodites, changing sex several times with age. Either external fertilization of numerous, small eggs hatching as free-swimming larvae with long pelagic stage, or internal fertilization of relativel few, large eggs yielding larvae with a short swimming life. SHipworms are generally well known for causing damage to shipping and harbour wooden structures. However, they are also locally used for human consumption (Ref. 348). |
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