The function of the spines in Murex (Murex) pecten Lightfoot and related species (Prosobranchia: Muricidae)

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Spines of Murex pecten are strong, solid and sharp-pointed and are developed along the varix of the body whorl and along the anterior canal at each aperture. Three such rows of spines develop on each whorl. Primary spines are large and parallel to the substrate; secondary spines are smaller, nearly perpendicular to the substrate and are best developed along the anterior canal; tertiary spines which are small and inconspicuous, occur at the bases of primary whorl spines. Anteriorly the primary and secondary spines form a cage-like structure. Spines grow by a rapid proliferation of mantle tissue which folds into a C-shaped cross section initially, fills in the spine and is resorbed again. The shell probably grows in relatively short bursts between varices, followed by prolonged periods of no growth at each varix stage. This arrangement of spines is not as well developed in related species, but in all it is precise and involves too complex a growth pattern merely to be decorative.
The spines are generally interpreted as being protective. The precise pattern of three rows of spines per whorl ensures that the shell always adopts a stable orientation with one row mid-dorsal and vertical. The anterior cage provides a protected area for the head and tentacles within which the snails may feed unmolested. In Murex pecten, where the cage is best developed, it could be used to contain prey. These functional inferences should be tested by observations of the snails in their natural habitats.