Functional studies aimed at uncovering the genetic and molecular mechanisms controlling neural regeneration may, in certain cases, be more tractable in the larvae due to their small size, transparency, and relatively simple body plan and tissue architecture compared to adult acorn worms.
Adult acorn worms display the same size disparity after regeneration, and this was attributed to a lack of feeding during the first week of regeneration after the anterior region, including the mouth and anterior gut, was amputated (Luttrell et al., 2016).
Reports are also rare on the abundances of these groups and acorn worms for the Eastern Tropical Pacific region.
The 1984-1987 survey: Examples of the acorn worms and brachiopods collected are included in Fig.
One gene cluster preserved for more than half a billion years is though to be linked to the development of the pharynx - the passageway linking the nasal cavity to the mouth and throat - in both acorn worms
are themselves part of the hemichordates, a group of marine animals closely related to today's sea stars and sea urchins.
"It's astonishing how similar Spartobranchus tenuis fossils are to modern-day acorn worms
, except that they also formed fibrous tubes."
"Shallow water acorn worms
live in burrows and are rarely seen, whereas deep sea species browse on the sea floor leaving spiral poo traces that resemble crop circles.
Ptychodera flava were collected monthly from September to December 2009, as well as in June 2010 and June 2011, with a shovel in the sandy beach at Chito, Penghu Islands, Taiwan (23[degrees]38'54.17"N, 119[degrees]36'14.40"E).
At present, 135 hemichordate species are described: 121 are solitary Enteropneusta, or acorn worms
; and 24 are colonial, tube-dwelling Ptero-branchia (Appeltans et al., 2012; Halanych and Cannon, unpubl.
The northwest plains were the home of deep-sea enteropneust acorn worms
. Only a few specimens, from the Pacific Ocean, were previously known to science," said Professor Monty Priede, Director of the University of Aberdeen's Oceanlab.
The largest oocytes cause an outward bulge of the epidermis but are not externalized in epidermal pouches as they are in acorn worms
of the genus Allapasus (the latter were described by Holland et al., 2012b).