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Acrocirridae
Description
The prostomium is either rounded and distinct, as in
Macrochaeta, or forms a narrow keel between
the compressed anterior segments, as in Acrocirrus; eyespots
are present. Antennae are absent. Rouse & Fauchald (1997)
considered the peristomium to be limited to the buccal region.
Although typically the peristomium is referred to as the first
segment which forms a narrow ring dorsally and then projects
forward under the prostomium, it is in fact the peristomium.
The issue was confused by Banse (1969), who was unable to
decide whether or not the palps were prostomial or
peristomial. According to Rouse & Pleijel (in press) the
peristomium is limited to the pair of palps. The palps are
readily lost and have not been described in numerous early
publications. Nuchal organs are present.
The above definition is taken from Hutchings (2000), which in turn is based on that of Fauchald & Rouse (1997).
Identification tips
Recognising the family
Acrocirridae have epidermis with irregularly arranged papillae, with the first segment a smooth ring. Branchiae present.
Distinguishing species
These small thread like worms are fragile and the palps and branchiae often become detached. Chaetal structure is important for species identifications and these need to mounted and examined under high power.
Description | Identification
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