NIWA Guide to Polychaeta | Shore polychaetes | Shell polychaetes
Shell worm Polydora cornuta Spionidae (spionid)
Spionida (Annelida: Polychaeta)
Polydora  cornuta  Bosc, 1802.   Family Spionidae  
     Polydora cornuta from Crassostrea gigas
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 Identification tips:    Prostomium tip bifurcated or T-shaped. Occipital antenna present. Distinctive colour pattern(s) absent.
 Habitat: Estuarine. Known from mollusc shell. In bivalves. In shell crevices, or in sand. Recorded from living shells of New Zealand commercial shellfish: Crassostrea gigas. Occurrences in empty/dead shell also never reported. Tube lining constructed of sand grains. Tube chimney present as glued debri/sand-grains.
 Nomenclature: Genus Polydora in Family Spionidae. Polydora cornuta [NZ]. Described by Bosc, published in 1802, as Polydora cornuta. Type locality: USA Atlantic, South Carolina. Other synonyms: Polydora ligni, P. littorea, and P. amarincola
 Description:  Head region: Prostomium tip bifurcated into distinct frontal horns. Occipital antenna present. Caruncle extends to anterior chaetiger 4; separate mid-dorsal organ absent. Colouration: Eyes present, two pairs; coloured black. Dorsal pigmentation pattern present; dark anterior dorsal pigmentation absent; white (or yellow white) anterior dorsal pigmentation present (inconspicuous flecks of white pigment on: peristomium by palps; prostomium tip; and inconspicuous flecks of white also on anterior ( to at least s15) segments laterally around notopodial lobe base). Palp banding absent. White mid-body or posterior dorsal pigmentation absent. Branchiae, chaetae, and pygidium: Branchiae adjoining parapodia 7 and following; longest branchiae on chaetiger 8; near body end branchiae present. Anterior gut gizzard-like structure absent. Hooded hooks begin chaetiger 7; bifid, hook shaft constriction (manubrium) present, anterior hooded hook main fang more or less oriented at right angles to the shaft with narrow (acute) angle to apical tooth. Alternating capillaries adjacent hooded hooks absent; neurochaetal inferior chaetae below hooded hooks absent. Chaetiger one notochaetae absent; notopodial lobe present. Chaetiger 5 elongated relative to adjacent segments. Chaetae of chaetiger 5 'upper' (or 'posterior') row falcate with subterminal flange as a lateral tooth, 'lower' (or 'anterior') row are penicillate. Superior notochaetae of chaetiger 5 present. Inferior neurochaetae of chaetiger 5 absent. Posterior notochaetal spines absent. Pygidium flattened disc/saucer-rim with dorsal notch/gap. Pygidium large, distinctly wider than last chaetigers.
 Dimensions: Length 30 mm. Width 1 mm. Segment total 80.
 Reproduction: Larval nutrition mostly planktotrophic, with early larval release, or nurse egg lecithotrophic; poecilogony occurs. Paratomic budding absent or undetected. Architomic asexual division absent. Reproductive period unknown.
 Distribution:  World distribution includes New Zealand and elsewhere. Known to be anthropochoric/invasive. Global distribution includes New Zealand mainland, Australia, within south east coast and Tasmanian zone, South America, Atlantic coast, North America, Pacific coast (to Panamanian Isthmus), North America, Atlantic coast, Japan, and Sea of Japan coasts of Korea, Russia..
 Remarks:  Polydora cornuta is a very vigorous mover in life, with long chaetae. Further information may be found under the long-used name Polydora ligni
 Biology: Polydora cornuta is relatively new to New Zealand. It can occur as an epifaunal fouler on shell, and reportedly at densities elsewhere sufficient to cause 'mass oyster kills by accumulation of sediment' (fide citations in Light 1978 (as P. ligni). Feeding group: Surface deposit/filter-feeding.
 Best References:   Biology: Read and Gordon (1991) Adventive occurrence of the fouling serpulid Ficopomatus enigmaticus, Polychaeta, in New Zealand.. New Zealand Journal of Marine and Freshwater Research 25:269-274 Taxonomy: Read (1975) Systematics and biology of polydorid species (Polychaeta: Spionidae) from Wellington Harbour. Journal of the Royal Society of New Zealand 5:395-419.

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 Genus diagnosis More pictures Further references (biology, etc) Family Spionidae

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The information provided by this page and by the pages of the "more information" links is held in a structured form for rapid and frequent updating and improvement. Descriptive text is compiled from a number of database fields, some of which may occasionally be empty.
Data last edited 20/07/2004  (dd/mm/yy), and page last generated by G. Read, 25/07/2004  (dd/mm/yy)