Key to Common Families of Sedentary Polychaetes in Hong Kong

        The key is for identification of common families of sedentary polychaetes in Hong Kong.   Before using the key, please make sure that the polychaete to be identified is Sedentary Polychaete.   For more information to define whether it is Errants or Sedentaries, please visit the pages of 'What are Sedentary Polychaetes?', 'The difference between Errants and Sedentaries' and 'Marine Errant Polychaetes in Hong Kong'.

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1.

(a)    Most of Errant Polychaetes have the following characters:
          -  Prostomium with sensory appendages.
          -  Pharynx armed with jaws or teeth.
          -  Parapodia well developed and often bear compound setae.

Errantia

(b)    Most of Sedentary Polychaetes have the following characters:
          -  Prostomium seldom with sensory appendages and often fused to the peristome which may bear grooved palps, buccal cirri or a branchial crown.
          -  No jaws or teeth.
          -  Parapodia often reduced and compound setae very rare.

Sedentaria

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2.  (1b)

(a)    Body short and stout.   Posterior end covered ventrally by a chitinized shield.

Sternaspidae
(b)    Body elongate.   Posterior end not covered by a shield.

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3.  (2b)

(a)    Anterior end with specialized setae or protective spines (paleae).

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(b)    Anterior end without specialized setae or protective spines (paleae).

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4.  (3a)

(a)     Specialized setae long and chambered, forming a protective cage around the retractable anterior end; body with numerous epithelial papillae.

Flabelligeridae
(b)     Specialized anterior setae do not form a protective cage; anterior end not retractable; skin-papillae few and small, or absent.

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5.  (4b)

(a)     Specialized anterior setae form 2 fascicles of golden paleae in a transverse row.   Tube conical, usually formed of closely fitted sand grains.

Pectinariidae
(b)     Specialized anterior setae form a fan-shaped group of paleae on either side of the anterior end.  Anterior end with two to four pairs of branchiae.   Buccal tentacles retractable.

Ampharetidae

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6.  (3b)

(a)     Anterior region with tentacles.

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(b)     Anterior region without tentacles.

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7.  (6a)

(a)    Head with a crown of bipimmate radioles for suspension feeding.    Body symmetrical; more than four thoracic setigers.   Tube calcareous and irregular twisted or straight, sometimes coiled near base.

Serpulidae
(b)     Head with soft tentacles for deposit feeding.   Tentacles grooved and not retractile into the mouth.   Both thoracic and abdominal uncini short-handled.

Terebellidae

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8.  (6b)

(a)     Prostomium conical.

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(b)     Prostomium not conical.

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9.  (8a)

(a)    Palp(s) present.

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(b)     Palp(s) absent.

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10.  (9a)

(a)     With a single mid-dorsal palp on one of the first setigers (usually setiger 3 - 6).

Cossuridae
(b)     With series of long, slender branchial filaments and tentacular and dorsal cirri along the body (often lost, scars remain).

Cirratulidae

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11.  (9b)

(a)     Body separated into two regions with different kinds of setae in a thoracic and abdominal region.

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(b)     Body not separated into regions; setal distribution and parapodial shapes grade along the body.

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12.  (11a)

(a)    Thorax with lateral parapodia; abdomen with both noto- and neuropodia in dorsal positions.

Orbiniidae
(b)    Thorax (and sometimes in the first few abdominal segments) with slender capillary setae; abdomen with retractable filaments if branchiae present.

Capitellidae

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13.  (11b)

(a)    Branchiae present on maximally 15-20 segments, starting from one of setigers 4 - 10.

Paraonidae
(b)    Branchiae cirriform, pectinate or absent.   All setae simple capillaries.   Body fusiform, often grooved ventrally.

Opheliidae

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14.  (8b)

(a)    Body divided into two or three distinct parts.

Chaetopteridae
(b)    Body not divided into distinct parts.

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15.  (14b)

(a)    Palps present.

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(b)    Palps absent.   Segments usually elongated and jointed in appearance like a bamboo.

Maldanidae

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16.  (15a)

(a)    Prostomium flattened and spade-shaped.   A pair of palps papillose.    Gills absent.

Magelonidae
(b)    Prostomium not flattened.   A pair of palps grooved.   Gills often present.

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17.  (16b)

(a)    Notopodial cirri flask-shaped in some setigers, plumose setae present.

Poecilochaetidae
(b)    Notopodial cirri cirriform or foliose, plumose setae absent.

Spionidae

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