(from Norway) 274.434 Ptychodera bahamensis Spengel, 1893 115,310 Rhabdopleura
44.74'S 2.3 Antarctica Rliabdopleuridae Rhabdopleura sp.
Taxa 18S rDNA 16S rDNA HEMICHORDATA Cephalodiscidae Cephalodiscus hodgsoni KF683576 -- HI 1.3 Cephalodiscus hodgsoni EU728441 -- Cephalodiscus fumosus KF83575 -- H5.3 Cephalodiscus KF683574 -- nigrescens H12.3 Cephalodiscus gracilis AF236798 -- Cephalodiscus densus EU728439 -- Cephalodiscus EU728440 -- nigrescens Rhabdopleuridae Rhabdopleura sp.
We were able to include three 16S rDNA sequences from the pterobranch genus Rhabdopleura in our analyses, as well as 18S rDNA data from two additional Rhabdopleura and three additional Cephalodiscus taxa.
We gratefully acknowledge Jon Norenburg and Darryl Felder for providing Rhabdopleura sp.
Some enteropneust species, like Saccoglossus pusillus (Davis, 1908) as well as pterobranch hemichordates in the genera Cephalodiscus (Sciaparelli et al., 2004) and Rhabdopleura (Lester, 1988; Sato et al., 2008), retain early developmental stages in the maternal burrow or tube.
Ultrastructure of adult gonads and development and structure of the larva of Rhabdopleura normani (Hemichordata: Ptero-branchia).
Fine structure of the heart vesicle and pericardium in the pterobranch Rhabdopleura
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).
Given that the males of Cephalodiscus sibogae and all Rhabdopleura species have a single pair of arms (there are only two pterobranch genera; Atubaria is most likely a form of Cephalodiscus), the ancestral condition for pterobranchs is assumed, by parsimony, to be a single pair of arms because a single evolutionary event can account for the multiple arms in Cephalodiscus.
The entire 18S rDNA gene was aligned for all of the taxa with the exception of the Rhabdopleura normani sequence for which only the 5[prime] third of the 18S gene has been obtained.
Taxon Plumatella repens U12649 Bryozoan Terebratalia transversa U12650 Articulate Glottidia pyramidata U12647 Inarticulate Phoronis vancouverensis U12648 Phoronid Rhabdopleura normani U15664 Pterobranch Balanoglossus carnosus D14359 Enteropneust Antedon serrata D14357 Crinoid Asterias amurensis D14358 Seastar Artemia salina X01723 Crustacean Placopecten magellanicus X53899 Bivalve Branchiostoma floridae M97571 Cephalochordate Xenopus laevis X04025 Vertebrate Acanthopleura japonica X70210 Chiton Tenebrio molitor X07801 Insect Anemonia sulcata X53498 Cnidarian Sycon calcaravis D15066 Sponge