Myzostomida: a link between trochozoans and flatworms?
Proc Biol Sci
; 267(1451): 1383-92, 2000 Jul 22.
Article
en En
| MEDLINE
| ID: mdl-10983821
ABSTRACT
Myzostomids are obligate symbiotic invertebrates associated with echinoderms with a fossil record that extends to the Ordovician period. Due to their long history as host-specific symbionts, myzostomids have acquired a unique anatomy that obscures their phylogenetic affinities to other metazoans they are incompletely segmented, parenchymous, acoelomate organisms with chaetae and a trochophore larva. Today, they are most often classified within annelids either as an aberrant family of polychaetes or as a separate class. We inferred the phylogenetic position of the Myzostomida by analysing the DNA sequences of two slowly evolving nuclear genes the small subunit ribosomal RNA and elongation factor-1alpha. All our analyses congruently indicated that myzostomids are not annelids but suggested instead that they are more closely related to flatworms than to any trochozoan taxon. These results, together with recent analyses of the myzostomidan ultrastructure, have significant implications for understanding the evolution of metazoan body plans, as major characters (segmentation, coeloms, chaetae and trochophore larvae) might have been independently lost or gained in different animal phyla.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Platelmintos
/
Factor 1 de Elongación Peptídica
/
Anélidos
Límite:
Animals
Idioma:
En
Revista:
Proc Biol Sci
Asunto de la revista:
BIOLOGIA
Año:
2000
Tipo del documento:
Article
País de afiliación:
Bélgica