A new deep-sea species of epibenthic acorn worm (Hemichordata, Enteropneusta)

Abstract

Individuals of an enteropneust, Tergivelum baldwinae n. gen., n. sp. were videotaped at a depth of about 4 km in the eastern Pacifi c and collected by a remotely operated vehicle. Th e living worms range in length from 9 to 28 cm and are dark brown anteriorly and beige posteriorly. Th e proboscis is shaped like a shallow dome, indented on either side by a laterodorsal fossa housing a prominent proboscis nerve. Th e collar comprises a thin transverse crest dorsally and two laterally projecting lips on either side of the mouth ventrally. Th e mouth is oriented parallel to the substratum and is fl anked by large left and right buccal muscles (contrasting with the rudimentary musculature elsewhere in the body). Th e respiratory pharynx of the trunk extends far anteriorly so that much of it lies dorsal to the mouth opening. Th e gill bars are not joined by synapticles. Th e laterodorsal body wall at the anterior extremity of the trunk extends as two conspicuous fl aps (back veils) that run posteriorly as unattached coverings over the anterior 30-50% of the trunk. On either side of the midline, the body wall of the trunk is extended as a narrow lateroventral fold. Within

An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata, Enteropneusta) with Asexual Reproduction by Paratomy

“…Torquaratoridae is likewise well supported in all analyses, and includes considerable diversity, despite their late discovery [5], [77].…”

“…The sampling includes members from all described families, and a large diversity of the recently discovered Torquaratoridae [5], [77]. We only used nearly-complete 18S rRNA sequences, with the exception of rhabdopleurids, for which no complete 18S rRNA sequences were available.…”

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

“…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.…”

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

“…In all, these photographs and collections included three distinct morphotypes in addition to the ones described, suggesting that substantial undocumented enteropneust diversity existed in the deep sea [6]. The feeding behaviour of an animal with the most common morphotype was described from time-lapse camera images [12] and the species was later described [7]; however, it could not be placed in a family because of the phylogenetic uncertainty within Enteropneusta. Here, we (i) show that enteropneusts are common and diverse in the deep sea, (ii) provide a phylogenetic framework for Hemichordata based on ribosomal DNA, (iii) show that some deep-sea enteropneusts use the water column to move between feeding sites (figure 1a-c), and (iv) provide individual species densities and habitat characteristics.…”

“…Hemichordates are a critical component in any study of early chordate evolution [1][2][3], yet relationships within the phylum remain unresolved [4,5], diversity is poorly known [6][7][8][9] and our perception of enteropneusts as coastal infauna needs revision. Other than a single species described from Challenger material [10], enteropneusts were unknown in the deep sea until 1965 when a specimen was photographed at the head of its distinctive faecal trace (but not collected) [11].…”