Diversification of acorn worms (Hemichordata, Enteropneusta) revealed in the deep sea

Abstract

Enteropneusts (phylum Hemichordata), although studied extensively because of their close relationship to chordates, have long been considered shallow-water, burrowing animals. The present paper more than doubles the number of enteropneust species recorded in the deep sea based on high-resolution imaging and sampling with remotely operated vehicles. We provide direct evidence that some enteropneusts are highly mobile-using changes in posture and currents to drift between feeding sites-and are prominent members of deep, epibenthic communities. In addition, we provide ecological information for each species. We also show that despite their great morphological diversity, most deep-living enteropneusts form a single clade (the rediagnosed family Torquaratoridae) on the basis of rDNA sequences and morphology of the proboscis skeleton and stomochord. The phylogenetic position of the torquaratorids indicates that the group, after evolving from near-shore ancestors, radiated extensively in the deep sea.

An Externally Brooding Acorn Worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian Arctic

“…Coleodesmium karaensis n. gen. n. sp. is genetically most closely related to another new species that was originally designated "genus C" by Osborn et al (2012). Gross morphology, as seen on remotely operated vehicle video fig.…”

“…The amplification and sequencing of partial 16S and complete 18S rDNA were according to Osborn et al (2012). The sequences from the Kara Sea enteropneust were approximately 500 base pairs of 16S rDNA (GenBank KC907711) and about 1700 base pairs of 18S rDNA (GenBank KC907710).…”

“…Class Enteropneusta Gegenbaur, 1870. Family Torquaratoridae Holland et al, 2005 (as re-diagnosed in Osborn et al, 2012).…”

“…The latter are Torquarator bullocki Holland et al 2005Holland et al (1901, Tergivelum baldwinae Holland et al, 2009 (3952 m), Allapasus aurantiacus Holland et al, 2012bHolland et al, (2994; Tergivelum cinnabarinum Priede et al, (2493, Allapasus isidis Priede et al, 2012Priede et al, (2622, and Yoda purpurata Priede et al, 2012Priede et al, (2622. Smith et al (2005), Holland et al (2005Holland et al ( , 2009Holland et al ( , 2012b, Anderson et al (2011), Osborn et al (2012), and discussed the ecology of torquaratorid enteropneusts. All known members of the family have been found living epibenthically on the surface of the deep-sea floor, although some individuals of Allapasus aurantiacus are known to burrow shallowly.…”

Evolutionary crossroads in developmental biology: hemichordates

“…(B)Hemichordate phylogeny with limited representation of the pterobranchs and enteropneusts, showing the relationships between lineages containing the most commonly studied hemichordates, Ptychodera flava (Ptychoderidae), Saccoglossus kowalevskii (Harrimaniidae) and Rhabdopleura compacta (Pterobranchia), along with the deep sea family Torquaratidae [based on published data (Cameron et al, 2000;Winchell et al, 2002;Cannon et al, 2009;Osborn et al, 2012)]. PRIMER Development 139 (14) placement, and their position as the sister group to the hemichordates and echinoderms remains controversial (Hejnol et al, 2009;Lowe and Pani, 2011).…”