The Function of the Heart-Body in Polychaetes

A series of cladistic analyses assesses the status and membership of the taxon Polychaeta. The available literature, and a review by Fauchald & Rouse (1997), on the 80 accepted families of the Polychaeta are used to develop characters and data matrices. As well as the polychaete families, non‐polychaete taxa, such as the Echiura, Euarthropoda, Onychophora, Pogonophora (as Frenulata and Vestimentifera), Clitellata, Aeolosomatidae and Potamodrilidae, are included in the analyses. All trees are rooted using the Sipuncula as outgroup. Characters are based on features (where present) such as the prostomium, peristomium, antennae, palps, nuchal organs, parapodia, stomodaeum, segmental organ structure and distribution, circulation and chaetae. A number of analyses are performed, involving different ways of coding and weighting the characters, as well as the number of taxa included. Transformation series are provided for several of these analyses. One of the analyses is chosen to provide a new classification. The Annelida is found to be monophyletic, though weakly supported, and comprises the Clitellata and Polychaeta. The Polychaeta is monophyletic only if taxa such as the Pogonophora, Aeolosomatidae and Potamodrilidae are included and is also weakly supported. The Pogonophora is reduced to the rank of family within the Polychaeta and reverts to the name Siboglinidae Caullery, 1914. The new classification does not use Linnaean categories, and the Polychaeta comprises two clades, the Scolecida and Palpata. The Palpata has the clades Aciculata and Canalipalpata. The Aciculata contains the Phyllodocida and Eunicida. The Canalipalpata has three clades; the Sabellida (including the Siboglinidae) Spionida and Terebellida. The position of a number of families requires further investigation.

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“…Circulation is closed (Wirén 1885: 15-17). Heart body is present (Picton 1899;Kennedy & Dales 1958). …”

Section: Sperm Morphology No Interpolation Of Mitochondria (Mchugh Amentioning

confidence: 99%

“…Circulation and heart body. Closed circulation with heart body (Meyer 1887; Mesnil 1899; Picton 1899; Kennedy & Dales 1958).…”

Section: Sperm Morphology No Interpolation Of Mitochondria (Mchugh Amentioning

confidence: 99%

Cladistics and polychaetes

1997

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“…Segmental organs mixonephridia (Goodrich 1945); first pair excretory; others gonoducts; only few anterior pairs present. Circulatory system closed (Wirén 1885); heart body present (Kennedy & Dales 1958). Aciculae absent.…”

Section: Ampharetidae Malmgren 1866mentioning

confidence: 99%

“…Segmental organs mixonephridia; a single anterior pair excretory; others more posteriorly gonoducts (Meyer 1887;Goodrich 1945). Circulatory system closed; heart body present (Mesnil 1899;Kennedy & Dales 1958). Aciculae absent.…”

Section: Cirratulidaecarus 1863mentioning

confidence: 99%

Polychaete systematics: Past and present

1997

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In this paper, we first demonstrate the historical background for the current unsatisfactory state of systematics of the polychaetes. We then briefly discuss our knowledge of internal and external structures. A review of the polychaete families makes up the third section; 81 families are treated in detail. Five families have been recently synonymized with others, and six families are too poorly known to be sufficiently characterized. Fossil polychaetes are briefly mentioned, with specific attention to problems associated with incorporating them in recent systematics.The traditional separation in 'errant' and 'sedentary' polychaetes has increasingly become recognized as being unsatisfactory; however, the current trend towards grouping the polychaetes in many orders without specifying the relationships among the orders, is no more satisfactory. The lack of consistent morphological information is a major source of uncertainty. Intensive morphological studies should remove terminological ambiguities and alleviate some of the problems.

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“…The functions of the heart body in polychaetes are the secretion of blood pigment, the sequestration of foreign material, and possibly mechanically ensuring the flow of blood or performing a valvular function (Kennedy and Dales 1958;Braunbeck and Dales 1984;Fransen 1988). In terebellids, the heart body is formed by an invaginated wall of the dorsal vessel and contains cells similar to the chloragogen cells outside of the vessel (Kennedy and Dales 1958).…”

Section: Structure and Functioning Of Circulatory Systemmentioning

confidence: 99%

Ontogenetic development and functioning of the anterior end of Cossura pygodactylata Jones, 1956 (Annelida: Cossuridae)

2015

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Juvenile and adult Cossura pygodactylata Jones 1956 from the White Sea were studied using confocal laser scanning microscopy, light microscopy, scanning and transmission electron microscopy. Transformations of the anterior musculature and digestive tract during ontogenesis were investigated. The early juveniles were shown to be lecithotrophic; their pharyngeal cavities were not connected to the intestines, which contained yolk granules. The juveniles bore prototrochs, which are used for movement, although juveniles had parapodial musculature similar to that of the adults. The juveniles presumably inhabit the upper semi-liquid layer of the silt. The muscles of the prostomium and circumbuccal complex change dramatically during ontogenesis. The ultrastructure of the buccal tentacles is redescribed. The tentacles consist of outer ciliated epithelial cells and an inner cylinder formed by epithelio-muscle cells. The blood sinus is situated between the central cylinder and the epithelium. Both juveniles and adults have developed circulatory systems. The whole dorsal vessel forms the heart with walls that consist of cells with circular cross-striated muscular fibres. The inner lumen is occluded by the heart body which is formed by a single row of cells that are tightly pressed together and connected by adherens junctions along their anterior and posterior surfaces. They contain granules and vesicles and bear numerous processes on the outer surface. The heart body most likely has a secretory haemopoetic function. A hypothetical mechanism of protraction and retraction of the buccal tentacles is suggested, and the participation of muscle contraction and relaxation in these movements is described. It is proposed that the protraction of the tentacles is provided by cell rigidity and increases in the blood volume in the tentacles blood sinuses. The development of the circulatory system is likely related to the need to keep the tentacles exposed during feeding while the anterior part of the body cavity is filled with muscle cell processes and there is no coelomic liquid flow. The proposed mechanism of feeding inside the sediment contrasts with that of surface feeding suggested by Tzetlin (Mém Mus Natl Hist Nat 162:137-143, 1994).

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The Function of the Heart-Body in Polychaetes

Cited by 52 publications

References 14 publications

Cladistics and polychaetes

Cladistics and polychaetes

Polychaete systematics: Past and present

Ontogenetic development and functioning of the anterior end of Cossura pygodactylata Jones, 1956 (Annelida: Cossuridae)

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