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Pholoidae
Description
The prostomium is truncated and the peristomium reduced
lips. A pair of lateral antennae and a median antenna
usually present. The ventral palps are fused
the ventral side of the first segment; they taper and have
articulations. Nuchal organs have not been observed. The
arrangement of the longitudinal muscles has not been
recorded. Segmentation of the body is distinct. The first
segment curves around the prostomium and bears welldeveloped
parapodia, the neuropodia of which are fused to
lower side of the head; chaetae are present in some taxa and
two pairs of tentacular cirri may be present. In other
segments, the neuropodia are better developed than
notopodia, but both have a well-developed ramus. The dorsal cirri alternate with elytra in
segments in Pholoides; Pholoe, however, lacks cirriform
dorsal cirri and elytra are present on every second segment
anteriorly and on all posterior segments. Ventral cirri and
pair of pygidial cirri are present. Branchiae and epidermal
papillae are lacking and lateral organs and dorsal cirrus organs
have not been observed. The buccal organ is an axial,
muscular, eversible pharynx, bearing terminal papillae
anteriorly and two pairs of dorso-ventrally arranged jaws.
gular membrane is lacking; the gut is a straight tube. In juvenile Pholoe minuta, nephridia
reported to be metanephridia without any mesodermal
involvement; the condition of
mature individuals is unknown. Aciculae are present.
Compound falcigerous chaetae are present and
have single ligaments (soft tissue connects the shaft to
blade in compound chaetae); they resemble those present
certain sigalionids (for example, Sthenelanella). Other
chaetae are variously ornamented capillaries.
Epidermal papillae similar to those present in the aphroditids
may be 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
Pholoids are small scale worms in which the dorsal surface may be covered with scattered tubercles and the ventral surface may bear papillae. Members of the genus Pholoides have concentric rings on each elytron, such rings are absent on other members of the family.
Pholoids are most likely to be confused with one of the other families that also have dorsal rows of scales. The quick guide to scale worms should help separate these 6 families.
Distinguishing species
Genera definitions in this family are currently being debated, and it has been suggested that the only valid genus in the family is Pholoides and the correct family name is Pholoididae and the genus Pholoe should be placed within the Sigalionidae.
Description | Identification
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