The Byssal Apparatus in the Pacific Mussel, Mytilus trossulus (Bivalvia, Mytilidae), from the Sea of Japan

In the commercial Pacific mussel species, Mytilus trossulus, from the Sea of Japan, features of the morphological structure of the byssal apparatus, byssal threads, and pedal groove are studied. Steps in the process of byssal threads formation and characters of the morphological structure of the byssal groove related to this process are described in M. trossulus. The byssal apparatus is shown to consist of a root, a stem, and byssal threads, the latter in cross section being ellipsoid in shape. A byssal thread consists of a corrugated proximal part located immediately behind the cuff and is one-third of its length, and a relatively smooth and flexible distal part taking up two-thirds of the thread length and ending with an attachment disk at the distal end. On the surface of the attachment disk, three reinforcing cords are situated. The morphological features observed in these structures are discussed in terms of the spatial distribution of mytilids in marine coastal zones, a successful habitat of M. trossulus being rocky shores with active wave activities.

Automated summary

The morphological structure of the byssal apparatus, byssal threads, and pedal groove in the commercial Pacific mussel species, Mytilus trossulus, from the Sea of Japan, have been studied. The process of byssal threads formation and the morphological features of the byssal groove related to this process are described. The spatial distribution of mytilids in marine coastal zones is discussed with a focus on rocky shores with active wave activities being a successful habitat for M. trossulus.