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The prostomium is fused to the peristomium and is largely indistinct, but forms, at least, a median keel. The peristomium is visible only as lips around the mouth. Antennae are absent. Paired palps are located lateral to the central ridge of the prostomium, and nuchal organs are present medial to the palpal base. The longitudinal muscles are grouped in bundles. Segmentation is distinctive. The first segment is completely fused to the head, with its notochaetae and those of the next segment forming the operculum, which consists of two lobes or peduncles the fusion of which varies between genera. The neuropodia are short cylinders, and the notopodia are reduced to tori. Dorsal and ventral cirri are absent. The branchiae lie dorsally and are flattened. Epidermal papillae and pygidial cirri are lacking. A ventral buccal organ and a gular membrane are lacking. The gut is a straight tube. The segmental organs are mixonephridia, comprising a single anterior pair of excretory organs, and posterior gonoducts. The circulatory system is closed and a heart body is present. Aciculae are absent. Chaetal inversion is present: the uncini are notopodial rather than neuropodial, and the chaetae comprise variously decorated capillaries, spines and uncini. The operculum has 1-3 rows of highly distinctive golden ornamented paleae.

The above definition is taken from Hutchings (2000), which in turn is based on that of Fauchald & Rouse (1997).

The Hermellidae is a junior synonym of the Sabellariidae, based on the synonymy of Hermella Savigny 1818 with Sabellaria Linnaeus 1767 (following Grube 1850). For details of the systematics of the family see Hartman 1944.

Identification tips

Prior to identification, worms need to be carefully removed from their tube.

Recognising the family
Sabellariids build distinctive thick-walled tubes of sand grains cemented to a rock, or sometimes to other individuals forming extensive reefs on sandy bottoms. Their anterior end has numerous golden paleae which surround the mouth and the buccal cirri and form an operculum at the entrance to the tube. The only other family with such wide golden paleae are the related Pectinariidae. If tubes are present the two families are readily distinguished. Pectinariidae have free-living smooth cone-shaped tubes with a slight bend made up of sand; the tube wall is only one grain thick. Sabellariid tubes are cemented to the substrate and are are usually several grains thick; they may form extensive reefs. Perhaps the most obvious difference between animals is the neuropodial position of uncini and absence of abdominal notopodia in Pectinariidae; in contrast Sabellariidae possess notopodia (though they are reduced) and the parapodial lobes are inverted, uncini being present in notopodial positions.

Distinguishing species
Characters used to distinguish sabellariid species are mostly chaetal, especially the shape and arrangement of the paleae (which may form 2 or 3 rows and the structure of each row may be different). In addition the degree of fusion of the opercular peduncles and the number of parathoracic segments are important generic characters..


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