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Glyceridae
Description
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The prostomium is conical and annulated, and bears four
small terminal appendages. The conical
nuchal organs of Glycera convoluta are
apparently the only published observations of nuchal organs
in glycerids. A long muscular eversible
pharynx is present, and terminates with four jaws arranged in
a cross. Several types of pharyngeal papillae
cover the pharynx, usually with one or two types present on
any one species; species may be distinguished by the presence
of different types. The peristomium is reduced. Terminal
papillae are absent. The first segment with parapodia is
similar to subsequent segments. Parapodia are biramous in all
genera except Hemipodus, in which all are uniramous. In
biramous parapodia, the neuropodia are larger than the
notopodia, and prechaetal and postchaetal lobes and lappets
may be present. Dorsal and ventral cirri are present. True branchiae are absent, but the structures often termed branchiae are located dorsal to the parapodia and
contain no circulatory system;
these structures are referred to as coelomic loops. Coelomic loops are of taxonomic value, but are
retractile in some taxa and thus their apparent absence may be
difficult to verify. Aciculae are present. Notochaetae, if
present, are simple; neurochaetae are compound. One pair of pygidial cirri is present.
This description is taken from Wilson (2000), which in turn is based on that of Fauchald & Rouse (1997).
Identification tips
Recognising the family
Glycerids are strong, muscular polychaetes with long bodies almost circular in cross-section. The conical prostomium tapering to a fine tip with 4 small terminal appendages is distinctive and glycerids are only likely to be confused with the closely related Goniadidae. The two families are readily distinguished if the eversible pharynx is examined: in glycerids there are 4 similar-sized jaws arranged in a cross while goniadids possess only one pair of large jaws and numerous smaller jaw articles arranged in a circle. Parapodial morphology is also useful: notopodial lobes are present throughout the body in all glycerid genera except Hemipodus (which lacks notopodial lobes throughout), while goniadids lack
notopodial lobes on anterior chaetigers, but have well developed notopodial lobes on posterior chaetigers.
If the proboscis is not extended (and usually it is not), the jaws may still be visible through the body wall several segments behind the prostomium. If not, the proboscis will have to be dissected. In order to determine the structure of the proboscideal papillae a small piece of the pharyngeal wall must be mounted and examined under a compound microscope.
Distinguishing species
Characters which assist species recognition in the Glyceridae are the
form of the jaw supports (called ailerons), the structure of the
pharyngeal papillae and the number of prostomial and
segmental annulations. The number and shape of parapodial lobes
and coelomic loops (incorrectly referred to as "branchiae" in most of the published literature) is also useful although the retractile nature of the coelomic loops means that they can be difficult to observe.
Description | Identification
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