Journal of the Marine Biological Association of the UK

Research Article

Tunicate feeding filters

Q.  Bone a1c1, C.  Carré a2 and P.  Chang a2
a1 Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, PL1 2PB, UK
a2 Observatoire Océanologique, LOBEPM–ESA 7076, BP28, 06234 Villefranche-sur-Mer, Cedex, France

Article author query
bone q   [PubMed][Google Scholar] 
carre c   [PubMed][Google Scholar] 
chang p   [PubMed][Google Scholar] 


This review discusses the structure and operation of the fine mesh ‘mucous’ feeding filters of tunicates. The function of the endostyle in producing the feeding filter and the different ways in which the filter is deployed are also described. The fine structure of the filter includes new data, and the ultrastructural dimensions of the filter mesh and filament thickness are tabulated for the different tunicate groups. Histochemical data suggest that a peptide core is surrounded by a mucopolysaccharide sheath, and endostyle gland cell histochemistry and ultrastructure indicates protein synthesis. The construction of the filter by the endostyle was first considered in ascidians, and has been updated by observations on the simpler endostyle in salps, where there is evidence that secretions of gland cells pass to the bases of a fence of cilia, there to fuse and pass off the ciliary tips as fine filaments composing the filter net. Although all filters that have been examined when deployed have a rectangular mesh, reasons are given for supposing that when formed in the endostyle they have a square mesh in which both longitudinal and transverse filaments are of similar thickness and that the transverse filaments are stretched as the filter is deployed, so becoming thinner. Finally, some ecological consequences of the filter parameters in the different tunicate groups are considered.

(Received March 20 2003)
(Accepted July 18 2003)

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