First record of the freshwater bryozoan Pectinatella magnifica in north-west Russia with a description of sensory structures

Abstract

Colonies of the freshwater bryozoan Pectinatella magnifica (Leidy, 1851) were found in north-west Russia for the first time. As the colonies have been observed in Vuoksi river connecting Saimaa and Ladoga lakes, most likely this is a result of the downstream migration from Finland. Details of the general morphology of P. magnifica and distribution of sensory structures on the lophophore and colony surface were studied using scanning electron microscopy. Three types of sensory structures were recorded. Two rows of presumably immobile cilia were found on the latero-frontal surfaces of tentacles, and this type is common in Bryozoa. One-two sensory cilia with bases surrounded by short microvilli were detected on the abfrontal surface of the tentacles as well as on the outer and inner surfaces of the lophophoral arms. The mechanosensory function of both these types was assumed like in other bryozoans. Sensory structures of the third type were microvillous 'knobs' situated on the colonial body wall surface. They were described for the first time in Bryozoa. Their possible photosensory function is discussed.