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Behaviour, Setal Inversion and Phylogeny of Sabellida (Polychaeta)
Author(s) -
KNIGHTJONES PHYLLIS
Publication year - 1981
Publication title -
zoologica scripta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.204
H-Index - 64
eISSN - 1463-6409
pISSN - 0300-3256
DOI - 10.1111/j.1463-6409.1981.tb00495.x
Subject(s) - biology , inversion (geology) , phylogenetics , zoology , evolutionary biology , paleontology , genetics , gene , structural basin
The path taken by the faecal groove, following two right angle bends, appears inefficient in Sabellidae. It fits well with the thoracic folds of serpulids and follows a gentle spiral in caobangiids, but only in spirorbids is it of obvious adaptive value, being suited to life in a coiled tube. The associated setal inversion is not necessary for locomotion, which does not depend wholly on setal leverage, except in the smaller Fabriciinae where long‐shafted uncini also thrust actively against the elastic tube wall. The collar setae of spirorbids and some serpulids thrust anteriorly, giving some backward movement, but such motion is mainly by body contraction. Short uncini are virtually passive, engaged by opposing setae acting as distance pieces. Some broad bladed setae have a hollow structure around a central core. Pick‐axe setae of Sabellinae may have developed to counteract the thrust of respiratory peristalsis. This is not seen in spirorbids and serpulids, the thoracic folds of which are a sufficient respiratory supplement to the tentacles. — Numbers of thoracic segments in Sabellidae range from 1 to 16, and the abdomen becomes vestigial in some Fabriciinae. Abdominal inversion is important to spirorbids but not to sabellids, which are more varied. It seems that the former are archaic and the latter had a coiled ancestry. Sabellariids also show abdominal inversion suggesting a distant relationship with Sabellida.