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Ampharetidae
Description
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The prostomium is relatively small, and is elongated,
rounded, or pointed. It is situated on top of a larger unit
consisting of the fused first and second segments. The
peristomium is reduced to lips and the roof of the mouth.
Antennae are absent. Palps are short, slender peristomial
buccal tentacles attached to a dorsally located curtain within
the buccal cavity; occasionally one or two very much larger
grooved palps are present. Nuchal organs are
comma-shaped, and are situated laterally on the prostomium.
Longitudinal muscles are in four bands; segmentation is welldefined.
Parapodia first occur on segments III to V. Short
cylindrical notopodia are present on the thorax and
neuropodia are tori throughout. Dorsal and ventral cirri are
absent. Up to four pairs of branchiae are present on the
anterior segments; branchiae may all be similar or structurally
different along the body or between species. Epidermal
papillae are absent. The pygidium may be unadorned or may
have many cirri. Lateral
organs are present, but dorsal cirrus organs
have not been observed; presumably they are absent. The
buccal organ is non-eversible (this structure has also been called a foodsorter). A gular membrane is present between
two anterior segments. The gut is
straight in some taxa, but is mostly looped.
Segmental organs are mixonephridia; the
first pair is excretory, the others act as gonoducts (only a few
anterior pairs are present). The circulatory system is closed
and a heart body is present. Aciculae are absent. Chaetae are
present as notopodial thoracic capillaries and neuropodial
uncini; in some taxa, slender, peg-like chaetae are present in
anterior neuropodia. Anterior notopodial paleae are present in
some taxa; other taxa have paired large hooks
dorsally in paleal positions, but many taxa are
without either paleae or hooks.
The above description is based on Hutchings (2000), which in turn is based on Fauchald & Rouse (1997).
Identification tips
Recognising the family
Ampharetids are often confused with terebellids, however only ampharetids are able to "swallow" their buccal tentacles. The neuropodial uncini differ between the two families. Ampharetids tend to have a compact muscular body with a well defined thorax and abdomen, whereas terebellids have less compact muscular bodies. Branchial structure also differs, no ampharetids have branching branchiae and the branchiae are far more obviously segmentally arranged in terebellids in comparison to ampharetids. Ampharetids have a single type of buccal tentacle present, whereas in some terebellids (namely the polycirrines) two kinds are present.
Ampharetids may also be confused with trichobranchids. Trichobranchids also have two types of buccal tentacles which cannot be withdrawn into the mouth, they have a relatively small number of notopodia and the neurochaetae on the first few neuropodia are different in structure to those of remaining thoracic neurochaetae. Abdominal neurochaetae are avicular in structure and differ from the long handled thoracic ones. They also have an extended tentacular membrane in comparison to either terebellids or ampharetids. Branchiae may be single simple filaments arranged segmentally or forming a four-lobed structure.
Distinguishing species
Ampharetid species are somewhat difficult to identify because almost all diagnostic characters are soft-body features; with a few exceptions, the only hard structures (the chaetae) do not differ much even among genera. Specimens with detached branchiae are impossible to identify as are anterior fragments, all thoracic segments and at least some abdominal segments must be present to identify them to even genus.
Description | Identification
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