Echiura and Sipuncula

Storch, Völker

doi:10.1007/978-3-642-51593-4_21

Cited by 31 publications

(4 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The nature of this cuticle can be such that microvilli are present and secrete a network of fibres (in part collagenous where identified to date). This form of cuticle is found in the Clitellata (Richards 1978(Richards , 1984, Polychaeta (Richards 1978(Richards , 1984, Pogonophora (Southward 1993), Sipuncula (Storch 1984;Rice 1993) and Vestimentifera (Gail1 et al 1991;. In the Echiura, preliminary analysis indicates that a collagenous cuticle is present (Storch 1984;.…”

Section: Cuticlementioning

confidence: 98%

“…This form of cuticle is found in the Clitellata (Richards 1978(Richards , 1984, Polychaeta (Richards 1978(Richards , 1984, Pogonophora (Southward 1993), Sipuncula (Storch 1984;Rice 1993) and Vestimentifera (Gail1 et al 1991;. In the Echiura, preliminary analysis indicates that a collagenous cuticle is present (Storch 1984;. Such a cuticle is absent in the Platyhelminthes and Nemertea, where microvilli and a glycocalyx may be present but there is no collagenous matrix (Rieger Zoologica Scripta 24 1984;.…”

Section: Cuticlementioning

confidence: 99%

See 1 more Smart Citation

The articulation of annelids

1995

View full text Add to dashboard Cite

The aim of this paper is to assess the monophyly of the Annelida. Also, recent cladistic analyses of metazoan taxa, using a variety of data, have shown incongruities with regards to annelids and associated taxa that should be resolved. The Platyhelminthes is selected as the taxon to root our minimal length trees and polarise our characters in a parsimony analysis; ingroup taxa being Mollusca, Nemertea, Sipuncula, Echiura, Pogonophora, Vestimentifera, Euarthropoda, Onycho‐phora, and the groups most commonly regarded as true ‘annelids’, the Clitellata and Polychaeta. We use 13 characters and a total of 33 states. This results in 18 minimal length trees of 23 steps. The consensus tree has the topology (Platyhelminthes (Nemertea (Sipuncula Mollusca (Echiura (Polychaeta (Vestimcntifera Pogonophora) Clitellata (Euarthropoda Onychophora)))))). The name Articulata is applied to the Clitellata, Euarthropoda, Onychophora, Pogonophora, Polychaeta, and Vestimentifera. The Vestimentifera is the sister group to, or more likely a clade within, the frenulate pogonophores, and the name Pogonophora is retained for this group. In half of the 18 minimal length trees, the traditionally formulated Annelida, i.e. Polychaeta and Clitellata, is paraphyletic if the Pogonophora are excluded. In the remaining minimal length trees, a monophyletic Annelida cannot be formulated. The name Annelida should not be used unless relationships within the Articulata are resolved to show it is a monophyletic taxon. The taxon name Articulata, originally formulated to include the Annelida and Arthropoda by Cuvier, is defined as the clade stemming from the first ancestor to show repetition of homologous body structures derived by teloblastic growth with a pygidial growth zone (segmentation) and longitudinal muscles broken into bands. The Articulata is considered, on current evidence, to consist of four monophyletic groups; the Arthropoda, Clitellata, Polychaeta, and Pogonophora, though the latter group may be a clade of polychaetes. If this is shown, the Pogonophora should revert to the original family name Lamellisabellidae Uschakov, 1933. An indented classification reflective of the cladistic pattern is provided. Other recent hypotheses about metazoan systematics arc analysed.

show abstract

Section: Cuticlementioning

confidence: 98%

Section: Cuticlementioning

confidence: 99%

The articulation of annelids

1995

View full text Add to dashboard Cite

show abstract

“…the cuticle shows layers of fibrils perpendicular to one another, whereas the fibrils are irregularly arranged in larvae of Golfingia species (Rice, 1976). The epidermis in adult sipunculids is generally composed of cuboidal cells with deep basal infoldings (Storch, 1984). Within the trunk region the microvilli of the supporting cells do not pierce the cuticle.…”

Section: Comparative Morphologymentioning

confidence: 99%

Comparative structure of the epidermis in polychaetes (Annelida)

Hausen

2005

Hydrobiologia

View full text Add to dashboard Cite

The polychaete epidermis generally consists of a single layer of supportive cells, gland cells and sensory cells. Except for the latter, this paper reviews the recent literature on the annelid epidermis, focussing on the mentioned cell types and the cuticle. The annelid epidermis is compared to that of Sipuncula, Echiura and Myzostomida. Supportive cells predominate in the polychaete epidermis. They show a high structural diversity even within single specimens. Ciliated cells are usually multiciliary and only two cases of monociliary epidermis cells are known. Unambigous epithilio-muscle cells are only described in feeding palps of a Magelona species. Secretory cells release a large number of gland products and some of them are essential for tube secretion. Rather pecularities of the cells and its arrangement within glands than the ultrastructure of the secretions is useful for phylogenetic considerations. One of the main components of the cuticle is collagen. Recent studies indicate that annelid cuticular collagen differs in several aspects from collagen of the connective tissue and might be of interest for systematics.

show abstract

“…It has found general acceptance in most textbooks (Kaestner, 1965;Fretter and Graham, 1976;Barnes et al, 1988;Brusca and Brusca, 1990;Ghirardelli, 1991;Pechenik, Undoubtedly, echiurans show strong morphological homologies with annelids, a number of which were described as early as 1880 by Hatschek. They include the nearly identical mode of development by spiral cleavage (Newby, 1940) as well as the formation of a typical annelid-like trochophore larva during ontogeny in both taxa (Baltzer, 1932), the development and ultrastructure of chaetae (Storch, 1984;Pilger, 1993), the structure and organization of the blood vascular system (Clark, 1969), and the development and ultrastructure of spermatozoa (Franzén and Ferraguti, 1992). Additional support for a close relationship was found in the analysis of the nucleotide sequence of the "elongation factor 1␣" (McHugh, 1997).…”

mentioning

confidence: 99%

Are Echiura derived from a segmented ancestor? Immunohistochemical analysis of the nervous system in developmental stages of Bonellia viridis

Hessling¹,

Westheide²

2002

Journal of Morphology

154

105

View full text Add to dashboard Cite

Despite several unquestionably homologous characters with Annelida, the Echiura have generally been considered to form a distinct taxon due to apparent lack of segmentation: neither in the body cavity nor in any other structures of the adult animals have clear signs of a metameric organization been observed. However, it must be considered that this lack of segmentation could represent a secondary condition and that Echiura are derived from segmented ancestors. An immunohistochemical analysis visualized with confocal laser-scanning microscopy (cLSM) shows the development of serially repeated units in the nervous system of Bonellia viridis. This organization corresponds to the metameric ganglia typical of Annelida. Antibodies against the neurotransmitters serotonin (5-hydroxytryptamine) and FMRFamide label distinct subsets of neurons. Their perikarya are arranged in discrete repetitive units in the ventral nerve cord of different larval stages. Labeling of neurotubuli using antibodies against different tubulin isoforms provides additional support for the metameric character of the nervous system. Contrary to previous descriptions, the peripheral nerves extending from the ventral nerve cord into the body wall musculature are paired and are evenly distributed; their arrangement corresponds to that of the serotoninergic perikarya. Morphological and neurochemical differentiation of the nervous system clearly proceeds from anterior to posterior, indicating the occurrence of a posterior growth zone. The serial ganglionic organization of the nervous system of Articulata is generally regarded as having evolved in conjunction with repetitive muscular units, in particular with the formation of typical annelid segments. Therefore, these results are interpreted as an indication that Echiura are derived from segmented ancestors and thus support the systematic inclusion of the Echiura within the Annelida.

show abstract

Echiura and Sipuncula

Cited by 31 publications

References 23 publications

The articulation of annelids

The articulation of annelids

Comparative structure of the epidermis in polychaetes (Annelida)

Are Echiura derived from a segmented ancestor? Immunohistochemical analysis of the nervous system in developmental stages of Bonellia viridis

Contact Info

Product

Resources

About