Polychaetes have evolved feeding larvae numerous times
Abstract:'Trochophore' is commonly used to designate larvae with opposed-band feeding and a particular set of ciliary bands. The trochophore has been proposed to represent the ancestral larval form for a group of metazoan phyla as well as for the Annelida. The name trochophore is also often applied to larvae that do not conform to the above definition. A cladistic analysis of spiralian taxa (with special reference to polychaetes), based on a suite of adult and larval characters, is used to assess whether the trochophore (sensu stricto) is a plesiomorphic form for Spiralia or taxa such as Polychaeta. The results favor the conclusion that the trochophore, if defined as a feeding larval form using opposed bands, should not be regarded as plesiomorphic for Spiralia, or any other large taxon such as Polychaeta. The trochophore is therefore re-defined as a larval form with a prototroch. This broad definition covers a wide variety of larvae, and matches the current usage more accurately than the restricted term. The evolution of feeding larvae in a more general sense is also assessed. It is concluded that lecithotrophy is the plesiomorphic condition for polychaetes and that feeding larvae have evolved multiple times. This conclusion is supported by the fact that among polychaete larvae there a number of different feeding mechanisms. Some of these novel feeding modes have yet to be adequately described.
Document Type: Research Article
Publication date: July 1, 2000
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