Functional morphology and feeding behavior of Streblospio benedicti and S. shrubsolii (Polychaeta: Spionidae)

Abstract

The functional morphology of the feeding palps and prostomium of the spionid polychaetes Streblospio benedicti and S. shrubsolii was studied. Three functional groups of cilia of the feeding palps were found on both species — frontal cilia, latero-frontal cirri and lateral cilia. Frontal cilia line the food groove and transport food particles to the pharynx, and have been reported for all spionid polychaetes except species of the genus Scolelepis. Laterofrontal cirri deflect particles onto the frontal surface and have been observed in several spionid genera including Paraprionospio, Streblospio, Polydora and Dipolydora. Lateral cilia beat in continuous metachronal waves creating lateral vortices that potentially entrain suspended particles, and are known in Paraprionospio and Streblospio. The two species of Streblospio did differ in the distribution of prostomial papillae. These papillae are eversible and thought to function in particle selection as particles on the pharynx come in contact with the papillae. Prostomial papillae were restricted to the peripheral surface of S. benedicti and were widely scattered on all surfaces of the prostomium of S. shrubsolii. A conical tentaculate structure occurs between the branchiae of the first setiger of S. benedicti, but only a low raised elevation is present on S. shrubsolii.