Key to Families of Polychaetes

Phylum Annelida
 Class Polychaeta

Taken primarily from  Kozloff, 1987, 1996 p. 110 (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a  Body short, grublike, with a horny plate and a tuft of filamentous gills at the posterior end Sternaspidae:
Sternaspis scutata
1b Body generally not grublike, and with neither a horny plate nor a tuft of filamentous gills at the posterior end 2
2a Eyes large, bulbous, occupying about half of the dorsal surface of the prostomium (prostomium with 4 or 5 antennae; slender worms that taper gradually to the posterior end; strictly planktonic Alciopidae
2b Eyes, if present, not bulbous, and not occupying as much as half of the dorsal surface of the prostomium 3
3a Body transparent, strictly planktonic 4
3b Body not transparent; mostly benthic, but includes some species whose sexual individuals swim 5
4a
4b
5a Prostomium conical, ringed, tapering to a point and tipped with 4 small antennae (pharynx eversible, its distal end either with 4 hooklike jaws or with 2 large jaws and 2 arcs of smaller jaws) 6
5b Prostomium, if distinct, not as described in choice 5a 7
6a
6b
7a Most of the segments, even when contracted, longer than wide 8
7b Few if any of the segments, when contracted, longer than wide 9
8a
8b
9a All or much of the dorsal surface covered by paleae (these are flattened notosetae, arranged in transverse rows), by scalelike elytra (photo), or by a felt that consists of hairlike, interwoven notosetae (photo) 10
9b Dorsal surface not covered by paleae, elytra, or felt 14
10a Much of the dorsal surface covered by brassy or golden paleae (length generally less than 1 cm) Chrysopetalidae
10b All or much of the dorsal surface covered by scalelike elytra or by long, hairlike notosetae that are interwoven to form a tough felt (in Aphroditidae, the felt obscures the elytra underneath it) 11
11a Elytra obvious, not covered by felt 12
11b Elytra hidden by felt that consists of long, interwoven notosetae (photo) Aphroditidae
12a At least some of the neurosetae compound (divided into 2 units) (look at the neurosetae with a compound microscope!) 13
12b All setae simple Polynoidae
13a Elytra and dorsal cirri alternating regularly from setiger 5 to the posterior end Polyodontidae: 
Peisidice aspera
13b Elytra and dorsal cirri alternating only in the anterior part of the body (in the posterior part, elytra occur on all segments, and there are no dorsal cirri) Sigalionidae
14a Slender capillary setae distinctly cross-barred, so that they appear to consist of many units (prostomium with a pair of grooved palps; body surface usually papillated) 15
14b Capillary setae, if present, not cross-barred 16
15a
15b
16a Head region (the region consisting of the prostomium and peristomium) with at least some of the following structures:
  1 or more prostomial antennae (in the Euphrosinidae, which are rare, the antennae are small and visible only from the ventral side);
  a pair of anteroventral palps on the prostomium;
  a pair of dorsal palps on the peristomium;
  1 or more pairs of peristomial tentacular cirri;
  several to many featherlike radioles or unbranched filaments that are closely associated with the mouth and that are used in feeding
    (in certain families, there are also specialized large setae that are used in digging or that form part of a device for closing the tube when the animal withdraws)
17
16b Head region without any of the structures listed in choice 15a 44
17a With a single median prostomial antenna (no other head appendages) Paraonidae (in part)
17b Head appendages not limited to a single median prostomial antenna 18
18a Anterior end with a crown of several to many featherlike peristomial radioles, the complex formed by these resembling a feather-duster (in Manayunkia, found in fresh and brackish water, there are only a few radioles, each divided into 2 branches) 19
18b Anterior end without a crown of featherlike radioles (there may, however, be simple filaments or other head appendages) 21
19a Secreting a calcareous tube closed by a funnel-shaped or globular operculum (this is a modified radiole) 20
19b Secreting a leathery, parchmentlike, or mucous tube, this not closed by an operculum Sabellidae
20a Tube generally sprawling, although its oldest portion may be coiled; with more than 4 setigers comprising the thoracic region Serpulidae
20b Tube neatly coiled; with only 4 setigers comprising the thoracic region Spirorbidae
21a Notosetae forming transverse rows that extend nearly to the midline of the dorsal surface; gills (up to several pairs on both sides of some segments) situated behind the rows of notosetae; prostomial antennae visible only in ventral view (subtidal; rare) Euphrosinidae
21b Notosetae not forming transverse rows that extend nearly to the midline of the dorsal surface; gills, if present, usually medial to the notosetae rather than behind them; prostomial antennae, if present, visible in dorsal view 22
22a Prostomium extending posteriorly on the dorsal surface as an elongated caruncle (this reaches backward for at least 2 or 3 segments and its texture is usually different from that of the segments it interrupts (with 3 antennae and a pair of palps; subtidal; rare) Amphinomidae
22b Prostomium not extending posteriorly on the dorsal surface as an elongated caruncle 23
23a With several to many more or less equal unbranched tentacles closely associated with the mouth (in the Apharetidae, the tentacles can be retracted into the mouth) 24
23b Without several to many more or less equal tentacles closely associated with the mouth (there may, however, be 1 or more prostomial antennae, a pair of prostomialpalps, a pair of long, grooved dorsal peristomial palps, or peristomial tentacular cirri) 28
24a Body with a distinct caudal (tail) region that lacks setae (this may be slender and nearly as long as the rest of the body or it may be oval and dorsally concave); opening of the tube stopped by an operculum that consists in part of large, golden setae 25
24b Body without a distinct caudal region that lacks setae; opening of the tube not stopped by a definite operculum 26
25a Caudal region slender and nearly as long as the rest of the body, without any traces of segmentaton (the caudal region is doubled back on the rest of the body, so the anus is directed toward the opening of the tube); tube sprawling, open only at one end (unless eroded), made of sand grains and bits of shell embedded in a hard, concretelike matrix, permanently affxed to rocks or shells Sabellariidae
25b Caudal region short, oval, dorsally concave, consisting of 5 or 6 segments; tube conical, open at both ends, made of sand grains (photo), not attached (the worms are mobile and live in sandy or muddy substrata, using their opercular setae to dig) Pectinariidae
26a Tentacles around the mouth rather short, smooth or somewhat warty, capable of being retracted into the mouth; with 2 clusters of simple gills behind the head region (these gills are stout and may resemble tentacular cirri of Nereidae and some other polychaetes; they are also likely to break off) Ampharetidae
26b Tentacles around the mouth long, threadlike, very extensile, not capable of being retracted into the mouth; with 1 or more pairs of simple or branched gills arising on successive segments behind the head region 27
27a All or most thoracic segments with soft, light-colored pads on the ventral surface; neuropodial uncini of the thoracic region, like those of the abdominal region, with short handles Terebellidae
27b Thoracic segments without soft pads on the ventral surface; neuropodial uncini of the thoracic region with long handles Trichobranchidae
28a Without prostomial antennae or peristomial tentacular cirri; with a pair of long palps (these are usually grooved) arising from the prostomium or dorsal side of the peristomium (photo) 29
28b With 1 or more (usually at least 2) prostomial antennae and sometimes with a pair of prostomialpalps (photo) and/or 1 or more pairs of peristomial tentacular cirri 34
29a Peristomial palps warty for all or most of their length, even when extended; head region flattened, resembling a spatula; gills absent Magelonidae
29b Peristomial palps not warty, at least when extended; head region not flattened; gills sometimes present 30
30a Body consisting of 2 or 3 regions, each with distinctive parapodia 31
30b Body not consisting of 2 or 3 regions (even if the anterior portion is slightly different from the posterior portion, the parapodia of both portions are similar) 32
31a
31b
32a Notopodia without setae other than aciculae Apistobranchidae
32b Notopodia with setae as well as aciculae 33
33a Several to many segments with long, filamentous gills Cirratulidae (in part)
(Photo)
33b Gills usually present (absent, however, in Spiophanes), arising from notopodia of most segments, but not filamentous (they are usually not more than several times as long as wide, and in some species they are pinnate) Spionidae
34a Prostomium with a pair of palps (these usually originate anteroventrally; and are often divided into 2 units; when they originate more or less anterolaterally [as in Protodorvillea, Dorvilleidae], they are reduced to small papillae; do not confuse any of the 4 prostomial antennae of Nephtyidae with palps 35
34b Prostomium without palps 43
35a Prostomial palps differentiated into 2 units (the distal unit may be small and nipplelike, however) 36
35b Prostomial palps not differentiated into 2 units 39
36a All setae simple (make sure by looking at them with a compound microscope); distal unit of palps usually small and nipplelike Pilargiidae
36b Compound setae present; distal unit of palps usually substantial, even if smaller than the proximal unit 37
37a With 2 prostomialantennae (antennae are absent, however, in Micronereis); pharynx, when everted, clearly consisting of 2 portions, with a pair of stout jaws on the distal portion and usually with conical teeth on one or more areas of both portions (to induce eversion of the pharynx, apply firm pressure just behind the head region) (proximal unit of the prostomial palps much larger than the distal unit) Nereidae
37b With 2 or 3 prostomialantennae; pharynx not divided into 2 portions, and not with the arrangement of jaws and teeth described in choice 37a (there may, however, be a pair of ventral mandibles and rows of toothed dorsal plates that form maxillae) 38
38a With 2 or 3 prostomial antennae; peristomium with 2-8 pairs of tentacular cirri; distal unit of prostomial palps usually longer than the proximal unit; pharynx (in our species) without jaws Hesionidae (in part)
38b With 2 prostomial antennae; peristomium without tentacular cirri; distal unit of prostomial palps much shorter than the proximal unit; pharynx with a pair of ventral mandibles and rows of toothed dorsal plates that form maxillae. Dorvilleidae (in part)
39a Peristomium without tentacular cirri; with 2 prostomial antennae (pharynx with a pair of ventral mandibles and rows of toothed dorsal plates that form maxillae; prostomial palps sometimes very small [Ophryotrocha, which has only a few setigers], sometimes prominent [Protodorvillea] Dorvilleidae (in part)
39b Peristomium with at least 1 pair of tentacular cirri (photo); with 2 or more prostomial antennae 40
40a Pharynx (in our species) without jaws or teeth (with 2 or 3 prostomial antennae; with 2-8 pairs of peristomial tentacular cirri) Hesionidae (in part)
40b Pharynx with jaws or teeth 41
41a Prostomium with 3 antennae; usually with 4 eyes (sometimes 2 or 6); pharynx with a single large tooth or a crown of small teeth, or both Syllidae
41b Prostomium with 2, 5, or 7 antennae; if eyes are present, there are usually 2; pharynx with a pair of ventral mandibles and 2 or more rows of toothed dorsal pieces that form maxillae 42
42a Prostomium with 7 antennae (the 5 arising near the posterior margin of the prostomium are usually much larger than the 2 arising near the anterior margin) Onuphidae
42b Prostomium with 5 antennae (photo) (prostomial palps stout, globular, often indistinctly demarcated from the prostomium) Eunicidae
43a Prostomium with 4 small antennae (prostomial palps stout, globular, often indistinctly demarcated from the prostomium; usually without eyes (but eyes present in some species) Nephtyidae
43b Prostomium with 4 or 5 antennae; these not arranged as described in choice 43a; usually with eyes; with 2-4 pairs of tentacular cirri on the peristomium Phyllodocidae
44a With not more than 15 segments when mature; most segments indistinct; length less than 1 cm 45
44b With more than 15 segments; most segments distinct; length generally greater than 1 cm 46
45a
45b
46a Prostomium indistinct; surface of body with prominent papillae, many of which are almost globular Sphaerodoridae
46b Prostomium distinct; even if small; if papillae are present on the body, they are not almost globular 47
47a Notopodial gills long and threadlike; with several long, grooved filaments arising from the dorsal surface of one of the first few setigers Cirratuladae (in part)
47b Notopodial gills, if present, not long and threadlike; without any grooved filaments arising from the dorsal surface of one of the first few setigers (there may, however, be a single filament growing out of setiger 2 or 3) 48
48a With a single threadlike filament growing out of the dorsal surface of setiger 2 or 3 Cossuridae
48b Without a single threadlike filament growing out of the dorsal surface of setiger 2 or 3 49
49a With several pairs of large, bushy gills in the middle third of the body Arenicolidae
49b Wthout several pairs of large, bushy gills in the middle third of the body (but small, usually simple gills may be present in that region, or there may be conspicuous bushy gills near the anterior end) 50
50a
50b
51a
51b
52a
52b
53a
53b
54a
54b
55a
55b
56a
56b



Taxonomic Levels Represented in This Key:

   Alvinellidae:
        Paralvinella palmiformis (Not in key but found at local hydrothermal vents)
        Paralvinella sulfincola (Not in key but found at local hydrothermal vents)

  Aphroditidae
  Arenicolidae
  Eunicidae
  Hesionidae
  Nephtyidae
  Nereidae
  Phyllodocidae
  Polynoidae
  Sabellidae
  Serpulidae
  Terebellidae
 



Page created by Dave Cowles, 2005
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