The prostomium is bilobed or entire, with a pair of reduced to
well-developed buccal lips. Species of Eunice have five
prostomial appendages comprising two palps and three
antennae; one to two antennae and/or palps may
be absent in other genera. Eyes are usually present. The
peristomium consists of two rings; a pair of peristomial cirri is
present or absent on the posterior ring. The parapodia are subbiramous; the notopodium is represented only by
a dorsal cirrus with or without embedded aciculae. Branchiae,
when present, consist of single or pectinate filaments. The
neuropodia have superior limbate and pectinate
chaetae, and inferior compound falcigers
or spinigers, and subacicular hooks,
and ventral cirri. Pygidial cirri number two or four. The jaws
comprise ventral, unfused mandibles, and dorsal
maxillae of the labidognath type. The maxillae
are mineralised with aragonite and comprise a pair of short
carriers and four to five toothed plates on the right and five to
six toothed plates on the left. The maxillary plates are
asymmetrical with the right maxilla III missing and the right
maxilla IV being larger than the corresponding left one.
The above description is based on Paxton (2000), which in turn is based on Fauchald (1992). However, the traditional terms for prostomial
appendages are replaced by those proposed by Orrhage (1995).
Identification tips
Recognising the family
Euncidae are typically large stout bodied worms; some are among the largest of polychaetes. Most eunicid genera (including the two most speciose genera, Eunice and Marphysa) have five prostomial appendages, although this number is reduced to three or one in some genera. The prostomial appendages are referred to as occupital antennae in much of the literature, however they are now known to comprise two palps and three antennae. They often have an irridescent epithelium with gills emerging dorsally from the base of the parapodia occurring along part of the body. In live specimens the gills are bright red. All species have well developed jaws, which are often partly visible at the front of the mouth.
Distinguishing species
Parapodia need to be mounted to reveal the presence or absence of chaetae such as comb chaetae and the segment on which sub acicular hooks first appear. Anterior fragments are difficult to identify as some diagnostic chaetae are only present from mid body and mature individuals are needed. The structure of the aciculae is also important and the degree to which they are emergent. Jaws may need to be dissected in order to determine the dentition of the various maxillae, dissection should be carried from the dorsal surface. Body shape and structure in this family is fairly conservative.
As is the case with many polychaete families, several species of eunicids have been widely reported but almost certainly represent complexes of sibling species ("Marphysa sanguinea" is such an example from the Eunicidae). Fauchald (1992) has published a revised description for all described species of Eunice based upon the type species which should help distinguish such species in this genus. Similar revisions are needed for the other genera in this family.
