Thylacodes decussatus, commonly known as the decussate worm shell, is a marine gastropod mollusk belonging to the family Vermetidae. These fascinating creatures are distinguished by their unique tube-like shells that are often found attached to rocks, corals, and other hard substrates in shallow coastal waters.
Description & Characteristics
Thylacodes decussatus exhibits a characteristic tube-shaped shell that is typically white or pale gray in color. The shell is often covered in a layer of algae and other marine organisms, giving it a mottled appearance. These shells can grow to a maximum size of around 5 centimeters in length. The shells are generally straight or slightly curved and often have a series of distinct ridges or “cross-bars” that run perpendicular to the length of the shell, giving it a characteristic “decussate” appearance. The name decussatus itself refers to this unique crossed pattern.
Habitat and Occurrence
Thylacodes decussatus is typically found in shallow coastal waters, specifically within the intertidal zone and subtidal zones. They are most commonly encountered in rocky reefs, coral reefs, and other hard-bottom habitats. This species is particularly prevalent in the Indo-Pacific region, including areas like the Red Sea, the Indian Ocean, and the Pacific Ocean.
Taxonomy
Thylacodes decussatus is classified within the Gastropoda class, which encompasses a wide array of mollusks including snails, slugs, and sea hares. It belongs to the Littorinimorpha order, a group characterized by their coiled shells, and the Vermetidae family, which is known for its tube-dwelling members. The family Vermetidae includes several other worm shell species, each with its own unique morphology and ecological niche.
Feeding
Thylacodes decussatus is a suspension feeder, meaning it relies on capturing food particles suspended in the water column. These particles are typically phytoplankton, small algae, and other organic debris. The worm shell uses its specialized feeding apparatus, which includes a feathery structure called a “lophophore,” to filter and collect these particles from the surrounding water. The lophophore acts like a tiny net, trapping food as water flows through it.
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