Byssus Sentence Examples
The foot has a byssus gland on its posterior surface.
In many Lamellibranchs a gland is found on the hinder surface of the foot in the mid line, which secretes a substance which sets into the form of threads - the so-called " byssus " - by means of which the animal can fix itself.
A very few have the power of swimming by opening and shutting the valves of the shell (Pecten, Lima); most can crawl slowly or burrow rapidly; others are, when adult, permanently fixed to stones or rocks either by the shell or the byssus.
The glochidium quits the gillpouch of its parent and swims by alternate opening and shutting of the valves of its shell, as do adult Pecten and Lima, trailing at the same time a long byssus thread.
This byssus is not homologous with that of other Lamellibranchs, but originates from a single glandular epithelial cell embedded in the tissues on the dorsal anterior side of the adductor muscle.Advertisement
In them the foot has a flat ventral surface used for creeping, as in Gastropods, the byssus gland is but slightly developed, the pleural ganglia are distinct, there is a relic of the pharyngeal cavity, in some forms with a pair of glandular sacs, the gonads retain their primitive connexion with the renal cavities, and the otocysts are open.
In the allied genus Cyclas, a byssus gland is formed in the foot and subsequently disappears, but no such gland occurs in Pisidium.
Anomiidae.-Foot small; inferior (right) valve of adult perforated to allow passage of the byssus.
Anomia; byssus large and calcified; British.
Placuna; byssus atrophied in adult.Advertisement
Trigoniidae.-Shell thick; foot elongated, pointed in front and behind, ventral border sharp; byssus absent.
Lima; members of this genus form a nest by means of the byssus, or swim by clapping the valves of the shell together.
Ostraeidae.-Foot much reduced and without byssus.
Astartidae.-Shell concentrically striated; foot elongate, without byssus.
Tellinidae.-External gill-plate directed upwards; siphons separate and elongated; foot with byssus; palps very large; ligament external.Advertisement
Scrobiculariidae.-External gill-plates directed upwards; siphons separate and excessively long; foot without byssus.
Foot reduced and without byssus.
Mactridae.-External gill-plate directed ventrally; siphons united, invested by a chitinous sheath; foot long, bent at an angle, without byssus.
The foot is a muscular mass without cuticle or skeleton, excepting certain cuticular structures such as the byssus of Lamellibranchs and the operculum of Gastropods, which do not aid in locomotion.