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Saccocirridae
Description
Saccocirrids are slender, distinctly segmented, and reach
about 20 mm in length for up to 200 segments.
The prostomium bears two palps (previously referred to as
‘tentacles’) with internal canals that connect behind the brain
by basal ampullae, two nuchal organs and usually two
pigmented eyes. A ventral pharynx with a
muscular tongue-like organ and ventral ciliation may be
present. Gonads are present on one or both sides of the body.
The uniramous parapodia are retractile and bear different
kinds of simple chaetae. The pygidium is
bilobed and bears adhesive papillae.
The above description is taken from Paxton (2000).
Identification tips
Recognising the family
Saccocirridae are one of a number of interstitial polychaete families with reduced structures and uncertain relationships. These taxa, previously catered for by the poorly-defined category Archiannelida, are difficult to study and identification should rely on the interactive key to families. Saccocirridae are unique in having a ventral groove and uniramous parapodia throughout all segments.
Distinguishing species
Species of Saccocirrus can be distinguished using the following characters: whether the gonads are arranged bilaterally or unilaterally, the structure of the chaetae and the ornamentation of the tips, presence or absence of a pharyngeal organ and whether or not the ventral surface is ciliated or smooth. A key to species can be found in Jouin, 1971.
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Identification tips |
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Identification guide
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