Pogonophora (Annelida): form and function

Abstract

Pogonophora, also known as Siboglinidae, are tube-dwelling marine annelids. They rely on endosymbiotic chemoautotrophic bacteria for nutrition and their anatomy and physiology are adapted to their need to obtain both oxygen and reduced sulphur compounds. Frenulate pogonophores are generally long and slender, sediment-living tubeworms; vestimentiferans are stouter, inhabitants of hydrothermal vents and cool seeps; and moniliferans or sclerolinids are very slender inhabitants of decaying wood and sulphidic sediments. The anatomy and ultrastructure of the three groups are compared and recent publications are reviewed. Annelid characters are the presence of chaetae and septa, concentrated at the hind end. The adaptations to a specialised way of life include, in particular, the chitinous tube; the anterior appendages that function as gills; the internal tissue called the trophosome, where the endosymbiotic bacteria live; and the blood vascular system that transports oxygen, sulphide and carbon dioxide to the trophosome.

Systematics, evolution and phylogeny of Annelida – a morphological perspective

“…1C, F). Among these Siboglinidae are the most obviously segmented, when the often-missing posterior part of the body was found (Webb, 1964;Southward, 1988;Southward et al, 2005). Only subtle traces of segmentation have been found in developmental stages of echiuroids and sipunculans whereas in adults all signs of segmentation are absent (Hessling and Westheide, 2002;Hessling, 2003;Wanninger et al, 2005;Kristof et al, 2008).…”

Direct Evidence That Extracellular Giant Hemoglobin is Produced in Chloragogen Tissues in a Beard Worm, Oligobrachia mashikoi (Frenulata, Siboglinidae, Annelida)

“…The intravasal body is regarded as homologous to the heart body (Dall and Pell, 1970). Considering the results of these previous studies, one can conclud that in Frenulata, as in other polychaetes, earthworms, and Vestimentifera, hemoglobin synthesis takes place in tissues originating from chloragogen and/or the heart bodies (Southward et al, 2005).…”

Geophysical and geochemical controls on the megafaunal community of a high Arctic cold seep

“…This species is also the only animal seen at the site that could 10 possibly be a seep obligate species. However, the generalist lifestyle of frenulates (Hilário et al, 2011;Southward, 2000;Southward et al, 2005) and the debate around the consideration of O. haakonmosbiensis as a separate species from the fjord frenulate Oligobrachia webbi (Meunier et al, 2010), means that it is possible that, despite the cold seep setting, the entire pingo community consists solely of background benthic species, regardless of whether community members are chemosynthesis based or conventionally heterotrophic. Nonetheless, the animals at the study site appear to take advantage of, 15…”

“…All frenulates have obligate, nutritional symbiotic associations with bacterial endosymbionts (Fisher, 1990;Hilário et al, 2011;Southward, 1982;Southward et al, 2005) and molecular data and electron micrographs suggest that thiotrophy is the dominant metabolic mode for symbionts of O. haakonmosbiensis (Lösekann et al, 2008;Pimenov et al, 30 2000). Thus we expected sediment sulfide concentrations at GHP5 to be lower than those at the other pingos, and too low to sustain the frenulate worms and their symbionts.…”