Pterobranchia


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Pterobranchia

[‚ter·ə′braŋ·kē·ə]
(invertebrate zoology)
A group of small or microscopic marine animals regarded as a class of the Hemichordata; all are sessile, tubicolous organisms with a U-shaped gut and three body segments.

Pterobranchia

 

a class of deuterastomous animals of the phylum Hemichordata. Their development and the structure of their internal organs are similar to those of the Enteropneusta. Pterobranchs are small (up to 10 mm), stationary animals that develop through budding of colonies (except for the genus Atubaria). The body consists of a proboscis, a collar, and a trunk. The collar has paired, pinnate tentacles covered with cilia. The mouth opens on the ventral side of the body, between the proboscis and the collar. The intestine is looped; the anal opening is located at the posterior end of the body and is at the same level as the mouth. Pterobranchs include only a few species, which make up the orders Rhabdopleuroidea and Cephalodiscoidea. The former are found in the seas of northern Europe and East Asia, and the latter inhabit the waters of Antarctica.

References in periodicals archive ?
Enteropneusta and Pterobranchia were recovered as reciprocally monophyletic, with strong support (bootstrap/posterior probability = 98/1.00), although the alternative hypothesis (Pterobranchia + Harrimaniidae) was not rejected by Shimodaira-Hasegawa tests (P value > 0.05).
Prior studies using 18S rDNA have recovered a Pterobranchia + Harrimaniidae clade (Halanych, 1995; Cameron et al., 2000; Bourlat et al., 2003; Cannon et at., 2009; Worsaae et at., 2012).
In combined analyses, however, Pterobranchia and Enteropneusta are reciprocally monophyletic sister taxa with good support (98/1.00).
Hemichordata (Pterobranchia, Enteropneusta) and the fossil record.
Features of this development support the recent hypothesis (Cameron et al., 2000) that the Harrimaniid worms are sister taxa to the colonial class Pterobranchia; the evidence also suggests that these taxa evolved from a worm-like ancestor with indirect development.
Molecular sequence data suggest that the harrimaniid worms are more closely related to the colonial class Pterobranchia (including the genera Rhabdopleura and Cephalodiscus), which also have paired protocoel ducts and pores, than they are to the ptychoderid worms (Balanoglossus and Ptychodera) (Cameron et al., 2000).
Cephalodiscus (Hemichordata: Pterobranchia): observations of functional morphology, behavior and occurrence in shallow water around Bermuda.
Fine structure of tentacles, arms, and associated coelomic structures of Cephalodiscus gracilis (Pterobranchia, Hemichordata).