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Bell Pettigrew Museum
of Natural History
Interpretative Panels
Text: Dr Iain Matthews
Design: Steve Smart & Cavan Convery
A University of St Andrews Development Fund Project
School of Biology
http://biology.st-andrews.ac.uk
10:4 Pogonophora
P hy l u m
Pogonophora
Body Plan:
• Bilaterally symmetrical
• Triploblastic
• Coelomate
• Partly segmented
• Protostome
S u b p hy l u m
Super class
Class
The entirely marine phylum Pogonophora was first
discovered in 1900 from deep-water trawls off the
coast of Indonesia. Early, incomplete specimens
suggested that they were related to lophophorate
and deuterostome groups. However analysis of the
first complete specimens, collected in 1964, revealed
a segmented, chaetae-bearing holdfast region, which
in conjunction with evidence of larval forms, suggests
that they are closely related to the annelids.
The body is usually extremely elongated relative to
its thickness and is contained in a close-fitting
chitonous tube, secreted by a glandular region of
the trunk. The body is made up of an anterior
tentaculate section (bearing from 1 to 1000
branchiae), then a glandular collar region, a long
trunk and finally a short segmented tail or holdfast.
The nature of the body cavity, which can be single
or paired, is uncertain.
Adult pogonophorans lack both a mouth and a gut.
Some nutrients are absorbed through the microvilli
of the tentacles, however, in the species so far
investigated intracellular chemoautotrophic bacteria
have been found in the trophosome. The
haemoglobin of some pogonophorans is able to
carry hydrogen sulphide and distribute it to the
bacteria. The bacteria metabolize this, in the presence
Gut
Endoderm
Body Cavity
Mesoderm
Ectoderm
of carbon dioxide, into larger organic compounds
on which the worms feed.
There are around 140 species in 2 classes. The
relatively small (< 85cm in length) perviatan worms
live in soft sediments in shallower waters, while the
deepwater vestimentiferans can reach lengths in
excess of 2m.
Recent molecular data suggests that pogonophorans
are highly modified polychaete annelids. However,
in recognition of their distinctive anatomy and life
style, they are given the status of phylum.
It has also been proposed that the order
Vestimentifera should be reclassified as a separate
phylum containing two classes and three orders.
However at present they are most often retained as
a class within Pogonophora.
Classification
within
Pogonophora
Class: Perviata
Order: Athecanephria
Order: Thecanephria
Class: Obturata
Order: Vestimentifera
See specimen.
Beard Worms
Beard worms are remarkable in having no mouth or
digestive system. They absorb some nutrition through
their tentacles, while the rest is provided by bacteria
that live inside the worm and metabolize sulphur.
Most pogonophoran worms are found in deep water in
the Atlantic and Pacific oceans.
Some species
live in large colonies around
hydrothermal vents and new species are being found
at almost each new vent that is explored.