Glossary of Polychaeta terminology

Polikey glossary. Adapted from Glasby, C.J., Fauchald, K. & Hutchings, P.A. (2000). Glossary. Pp. 401–412 in Beesley, P.L., Ross, G.J.B. & Glasby, C.J. (eds). Polychaetes & Allies: the Southern Synthesis. Fauna of Australia. Vol. 4A Polychaeta, Myzostomida, Pogonophora, Echiura, Sipuncula. CSIRO Publishing : Melbourne xii + 465 pp.
See also POLiKEY ABRS site.

A | B | C | D | E | F | G | H | I-J | K | L | M | N | O | P | Q | R | S | T | U-V | W-Z



abdomen: body region posterior to the thorax, sometimes followed by a tail.

abyssal: oceanic waters between depths of 4000 m and 6000 m.

achaetigerous: see achaetous.

achaetous: without chaetae.

acicula, aciculae: a stout supportive chaeta found internally in projecting parapodial rami.

acicular chaeta: stout, projecting chaeta.

acicular muscle: see oblique muscle.

acoelomate: pertaining to animals lacking a coelom.

aileron: accessory jaw plate in Glyceridae.

anal cirrus, anal cirri: see pygidial cirrus

anal plaque: depressed (or sunken) plate-like pygidium of some maldanids and other polychaetes.

annulated: ringed or marked with grooves delineating segments.

antenna, antennae: sensory projection arising from the dorsal, lateral or frontal surface of the prostomium.

antennular auricle: = auricule.

antennular membrane: see cephalic veil.

anterior gut: see foregut.

apical tooth: see primary tooth.

apodous: segments without parapodia.

apomorphy: an advanced or derived feature; compare plesiomorphy.

arborescent: branching like a tree.

arenicoliform: body forms that are swollen anteriorly and tapered posteriorly.

arista, aristae: fine hair-like or bristle-like structure.

aristate chaeta: simple chaeta with smooth shaft and a tuft of hairs or a single spine distally.

article: demarcated sections of chaetae or cirri separated by joints.

articulate: jointed, as in antennae, tentacular cirri, palps and dorsal cirri.

asetigerous: see achaetigerous.

atoke: non-sexual, unmodified state of an individual in some polychaete groups; pertaining to species which undergo epitoky.

auricule: paired ear-shaped processes at the base of an antenna (ceratophore) characteristic of some sigalionids.

autapomorphy: a derived character unique to a particular taxon.

avicular: beaked; shaped like a bird’s head.

axial: pertaining to, or situated on the axis.



basal lappet: = auricule.

benthic: pertaining to the sea floor.

benthonic: pertaining to the benthon or community of organisms that inhabit the sea floor.

biarticulate: with two joints; pertaining to antennae, tentacular cirri, palps and dorsal cirri.

bidentate chaeta: chaeta with two teeth distally.

bifid: distally split in two; usually pertaining to chaetae.

bifurcate chaeta: simple chaeta with two prongs.

bilabiate: with two lips, usually about parapodial lobes.

bilimbate chaeta: simple chaeta with two wings; see limbate.

bipectinate: branching like a feather from a central axis; similar to pinnate, but branches coarser.

bipinnate: a structure that is pinnate for both its primary and secondary divisions; see pinnate.

biramous parapodium: parapodium with two branches, a notopodium and a neuropodium.

blade: a distal, flattened portion of a compound or simple chaeta.

boss: small projection or knob-like process in compound and simple chaetae.

brain: ganglionic mass situated at least in part in the prostomium.

branchia, branchiae: extension of the body wall with a loop of the vascular system; usually well equipped with capillary blood-vessels.

branchial crown: see radiolar crown.

branchiole: see radiole.

bristle: see chaeta.

brush-tipped chaeta: see penicillate chaeta.

buccal cavity: mouth cavity.

buccal cirri: cirri in or around the mouth; sensory function rather than feeding (cf. buccal tentacles).

buccal organ: anterior part of alimentary canal derived from larval stomodaeum, comprising a complex set of folds, musculature and glands; see pharynx, proboscis; see also ventral buccal organ.

buccal tentacles: elongate, grooved, usually ciliated appendages in or around the mouth; palpal derivatives.

bulbus: knob-like structure swollen in appearance.



caecum, caeca: blind sac arising from the alimentary canal; applied also to other organ systems, such as nephridia.

calicinate: like the calyx of a flower.

camerate: divided into chambers.

canaliculate: with a (fine) canal or groove.

capillary chaeta: slender, often long, chaeta tapering to a fine point.

capillary, capillaries: see capillary chaeta.

caruncle: projection from the posterior end of the prostomium carrying nuchal organs.

cauda: see pygidium.

caudad: towards the tail.

caudal plaque: flattened pygidium.

cephalad: towards the head.

cephalic cage: structure formed from long, forwardly directed chaetae more or less enclosing the head.

cephalic keel: median ridge on the prostomium or head, as in some Maldanidae.

cephalic peaks: see prostomial peaks.

cephalic plaque: see cephalic plate.

cephalic plate: plate-like antero-dorsal surface of the head region in some Maldanidae and Pectinariidae.

cephalic rim: flange encircling the head in some polychaetes.

cephalic veil: Hood-like membrane between the paleae and the buccal tentacles in Pectinariidae. see also tentacular membrane.

cephalisation: incorporation of anterior, usually modified cephalised segments, with the head (prostomium/peristomium).

cephalon: see head.

ceratophore: basal part of an antenna.

ceratostyle: distal part of an antenna.

chaeta, chaetae: a chitinous bristle protruding from a pocket in the body wall.

chaetal gland: (= chaetal sac) a series of follicles in the parapodium that secrete the support rod, the hook in use, and a varying number of replacement hooks.

chaetal inversion: presence of uncini on the notopodia rather than the more usual position on the neuropodia.

chaetiger: segment bearing chaetae.

chaetigerous lobe: that projection or part of the notopodium or neuropodium which bears the chaetae.

chaetoblast: cell which forms, together with follicle cell, a chaeta.

chevron: V-shaped chitinised jaw piece at the base of the eversible pharynx in some Goniadidae.

chromaphil gland: see chromatophil gland.

chromatophil gland: densely staining gland in the ventral pinnule of Tomopteris; see also rosette gland.

chromatophore: special cell or group of cells carrying pigment.

ciliophore: distinct area or epidermal patch covered with cilia.

circular muscle: muscle layer encircling the body between the epidermis and longitudinal muscle layer.

circumoesophageal connective: tracts of nervous tissue passing down from the brain on either side of the foregut and connecting to the ventral nerve cord.

circumoral tentacles: see tentacles.

cirriform: slender and cylindrical.

cirrophore: basal projection on which a cirrus is mounted.

cirrostyle: distal part of a cirrus or tentacle.

cirrus, cirri: sensory appendage; usually slender and cylindrical.

clade: a complete set of taxa with a common ancestor.

cladistics: classification of taxa based on lines of evolutionary descent, and, in principle, recognising only clades.

clavate: club-shaped.

coelom, coelomate: body cavity with peritoneal lining; formed in embryonic mesoderm; characteristic of almost all bilateral animals; lined with epithelium termed the peritoneum.

coelomocytes: amoebocytes present in the coelom.

coelomoduct: a tubule derived from coelomic tissue, connecting the coelom with the external environment; often combined with nephridium and termed nephromixia.

coelomostome: funnel at the inner end of a coelomoduct.

cold seep: emergence of fluid from sedimentary rocks under pressure, such as in regions of continental subduction; may comprise hydrocarbons, such as methane, or water, bearing salts such as sulphides.

collar: anterior encircling fold or flap, such as that covering the base of the radiolar crown in Sabellidae and Serpulidae.

comb chaeta: simple chaeta with a comb-like arrangement of teeth on the distal end; present in some Eunicida.

commensalism: an association between two species that live together, which benefits individuals of one species without harming those of the other.

commissure: a transverse band of neural tissue linking paired ventral nerves or longitudinal nerve tracks; one of four main tracts of nervous tissue passing through the brain.

companion chaetae: small, simple chaetae, accompanying, or alternating with larger chaetae, usually hooks of some kind.

compensatory vessel: see contractile vessel.

composite chaeta: see compound chaeta.

compound chaeta: chaeta having a terminal portion which articulates with the shaft.

compressed: flattened in one plane, usually laterally.

consecutive hermaphroditism: change from one sex to another in an individual; may be protandrous, protogynous, or bi-directional.

copragogue: see faecal groove.

cordate, cordiform: heart-shaped.

cristate: bearing a ridge or crest.

crotchet: see hook.

crown: a bilaterally symmetrical branched structure in some polychaetes formed by prostomial palps.

ctenidium, ctenidia: a finger-shaped or flattened structure presumed to have a respiratory function.

ctenognath: arrangement of complex jaw apparatus in which the jaws comprise relatively large basal maxillae and symmetrically arranged rows of numerous anterior denticles in longitudinal series without carriers.

cuticular shield: stiff, iron-impregnated shield on the posterior venter of Sternaspidae; see sternal shield.

cuticle: thin, non-cellular protective layer produced by and overlying the epidermis in many invertebrate groups; consists mainly of scleroprotein (not chitin).

cutis: see dermis.

cutting plate: distal part of eunicean mandible.



deciduous: pertaining to structures easily autotomised, or shed by the animal as a defensive reaction.

dendrites: branching cytoplasmic processes of sensory cells.

dental formula: notation showing the distribution of teeth on the crest of a hook or uncinus.

dentate: toothed.

denticle: a minute tooth.

denticulate: finely toothed.

depressed: flattened, usually dorso-ventrally.

dermis: layer of skin underlying the epidermis; comprises connective tissue and a range of other cell types, such as pigment and nerve cells.

detritus: particles of organic origin.

diagonal muscle: obliquely aligned dorso-ventral muscle in the body wall (cf. oblique muscle).

digitiform: finger-shaped.

dioecious: (= gonochorism, gonochoric) pertaining species, in which individuals are either male or female throughout life.

direct developers: embryos that develop completely into juveniles without intermediate larval stages.

distal: that part of a structure towards the end.

diverticulum, diverticula: blind tube(s) or sac-like extension(s) of the lumen of an organ.

dorsal blood vessel: longitudinal vessel which carries blood forward through the body; situated above the gut.

dorsal cirrus: cirrus normally situated on the upper edge of the notopodium.

dorsal cirrus organ: sensory organ, with numerous long cilia at the ventral base of the dorsal cirrus in Eunicida.

dorsum: dorsal surface of body.

dorso-ventral muscle: see diagonal muscle.



echinulate: prickly.

elytrigerous segment: polychaete segment bearing a scale.

elytron, elytra: dorsal scales found in the scale-worms; homologous with the dorsal cirrostyles.

elytrophore: cirrophore carrying an elytron, as in scale-worms.

endoderm: the innermost layer of germ cells developed during gastrulation.

endothelium: epithelial cells lining the inner wall of the circulatory system.

entire margin: smooth edged; lacking papillae, teeth or other projections.

enteronephridia: blind ciliated canals opening into the stomach.

epidermis: outer layer of the skin, usually one cell thick in invertebrates; derived from ectoderm.

epigamy: structural modification of an entire adult individual polychaete into a reproductive state or epitoke (cf. schizogamy).

epitoke: an individual polychaete morphologically modified to leave the bottom to reproduce (epitoky); epigamous epitokes result from the transformation of an atoke to the epitoke; schizogamous epitokes arise by modification and separation from the posterior end of the worm. Often swarms of epitokes appear.

eversible pharynx: part of pharynx being capable of being extended by turning the inner part outwards.

eversible proboscis: see eversible pharynx.

eye: light receptive organ which usually occurs on the prostomium but may occur elsewhere on the body or appendages.

eyespot: light sensitive structure in several polychaete groups. See ocellus.



facial tubercle: projecting ridge or lobe on the upper lip of certain polychaetes, especially scale-worms.

faecal groove: groove, on the posterior region of a tubicolous polychaete, along which the faecal pellets pass before being voided from the tube.

falcate chaeta: distally curved, usually blunt chaeta.

falciform: hook-shaped.

falciger: compound chaeta with a stout, hooked appendage or blade.

fang: a major tooth-like projection of an uncinus, hook or maxillary plate.

fascicle: a small bundle, of tissue, such as muscle or nerve fibres, or structures, such as chaetae.

felt: matted thin chaetae produced by the notopodia in some species of scale-worms.

fenestrated: with one or more window-like openings; used to refer to the ladder-like arrangement of transparent compartments in the shaft of some polychaete chaetae.

fibrocyte: connecting tissue cell, synonymous with, or derived from a fibroblast.

filamentous: shaped like a fine thread.

filiform: slender and thread-like.

fimbricated: having flattened, leaf-like processes.

flail chaeta: abruptly tapering and distally bent capillary chaeta of some orbiniids.

flanged chaeta: see limbate or bilimbate chaetae.

foliaceous: thin and leaf-like.

foot: see parapodium.

foregut: anterior, cuticle-lined part of the alimentary canal including the pharynx and oesophagus; derived from the ectoderm; see also stomodaeum.

forked chaeta: see furcate chaeta.

formalin: a solution of formaldehyde in water, used for fixing tissues.

frontal palps: anterior, sensory appendages of prostomium in Onuphidae.

frontal peaks: see prostomial peaks.

furcate chaeta: short (usually), bifurcated simple chaeta.

fusiform: cigar- or spindle-shaped.



geniculate chaeta: simple chaeta formed like a bent knee.

genital hook: modified notopodial chaeta used in mating in some Capitellidae.

genital papilla: projection on which a reproductive duct opens.

genital pore: modified nephridial opening.

genital pouch: a pocket-like skin fold between neuropodia in some Spionidae.

giant fibre: enlarged fibre in the nerve cord capable of very rapid conduction of nerve impulses.

gill: see branchia.

gizzard: muscular, barrel-shaped part of the foregut behind the pharynx in some Spionidae.

glabrous: smooth, glistening.

gonads: paired segmented peritoneal organs producing eggs or sperm.

gonochorism, gonochoric: (= dioecious) individuals are either male or female throughout life.

gonoduct: see coelomoduct; see also nephridia in echiurans and sipunculans.

guard: paired delicate chitinous sheaths protecting the tip of some chaetae.

gular membrane: a muscularised septum between two successive anterior segments; divides the coelom into anterior and posterior parts.

gut sinus: thin-walled open chamber of circulatory system around the gut.

gynandry: development of female reproductive system before male system in consecutive hermaphrodites.



hadal: oceanic depths exceeding 6000 m.

haemerythrin: respiratory pigment in sipunculans; in different taxa may comprise two, three or eight units of polypeptide attached to two Fe ions.

harpoon chaeta: stout pointed chaeta with recurved barbs near the tip.

hastate: shaped like the blade of a spear.

head: collective term used for a structure formed by the fusion of peristomium, prostomium and, in many instances, one or more cephalised segments.

hemigomph: compound chaeta with articulation which re-aligns the tip at close to a right angle to its long axis.

hermaphroditism: presence of functional male and female reproductive systems in an individual, at the same time (simultaneous hermaphroditism) or sequentially (consecutive hermaphroditism).

heterogomph: compound chaeta with articulation which clearly re-aligns the tip obliquely to the long axis of the shaft.

hindgut: posterior-most region of the alimentary canal, usually short; ectodermally derived.

hirsute: hairy, often with reference to chaetae.

hispid: minutely hairy; furry, often with reference to chaetae.

homogomph: compound chaeta with articulation which re-aligns the tip at a right angle to its long axis.

homologues: structures of common evolutionary origins, irrespective of functionality, derived from the same structure in the common ancestor.

homology: fundamental similarity in different organisms as a result of their common ancestry.

homoplasy: correspondence in morphology of different organisms as a result of evolutionary convergence or parallel evolution.

hood: a delicate chitinous envelope with a single opening, covering the apex of hooks or other chaetae (see also guards).

hook: stout-shafted, unjointed, distally-curved chaeta with or without teeth near the apex.

hyaline: transparent, glassy.

hyaline gland: gland in the pinnules of certain species of Tomopteris; usually translucent, sometimes with a yellow spot in the centre.

hydrostatic skeleton: controlled support provided by muscular pressure on body fluids, especially the major venous sinuses; used to modify body or organ shape.

hydrothermal vent: site of emerging, often highly sulphidic hot water, after it has circulated through new crustal rocks at spreading ridges in the deep-sea floor.



imbricated: overlapping like tiles.

intermediate cirrus: cirriform structure attached to the body wall between the notopodium and neuropodium.

inter-ramal cirrus: a cirriform structure attached to the notopodium, projecting into the space between the notopodium and the neuropodium.

intersegmental: between segments.

intestine: absorptive part of the midgut, usually a straight tube.

iteroparity: breeding in more than one season, often at regular intervals.



jaw formula: see maxillary formula.

jaws: hardened feeding or grasping apparatus with opposable units situated in the eversible pharynx.

jointed chaeta: see compound chaeta.



labial palps: ventral sensory appendages of prostomium in Eunicida.

labidognath: arrangement of complex jaw apparatus in which the larger jaw pieces are located in a pocket with the smaller pieces arranged in semi-circles at the anterior end.

lacuna(e): space(s) or cavity (cavities), usually with reference to those in tissues.

lamella, lamellae: fleshy, flattened or plate-like structure(s).

lamellate: plate-like, usually referring to a lobe.

lanceolate: pointed and shaped like a lance.

lappet: lobe or flap-like projection.

lateral caecum: blind sac arising laterally from the alimentary canal.

lateral lappet: lobe or flap-like projection on anterior segments in Terebellidae.

lateral organ: small, rounded inter-ramal elevations with stiff projecting hairs; see also dorsal cirrus organ, stereocilia.

lateral shield: glandular area on the lateral venter of thoracic segments in Polycirrus; cf. ventral pads.

lecithotrophy: form of development in which larvae generally do not feed, relying on yolk in egg.

ligule: compressed conical lobe of a parapodium; cf. lobe.

limbate chaeta: simple chaeta with a flattened wing projecting from one side along much of its distal half; see also bilimbate.

lobe: conical process of a parapodium; cf. ligule.

long-handled uncinus: uncinus with a long, rod-like basal extension.

longitudinal muscle: muscle layer running parallel to the long axis of the body, between the circular muscle and the peritoneum; usually arranged in two dorso-lateral and two ventro-lateral bands.

lyre chaeta, lyrate chaeta: delicate forked-type chaeta. See furcate chaeta.



macrobenthos: benthic invertebrate fraction retained in a 1 mm sieve.

macrognaths: paired lateral jaw pieces of Goniadidae.

macrotubercle: see tubercle.

main fang: see fang, see also primary tooth.

mammillate: pertaining to nipple-like process.

mammiliform: breast-shaped.

mandible: ventral jaw plate in Eunicida.

maxilla: dorsal jaw plate in Eunicida.

maxillary carrier: posterior support for the maxillae.

maxillary formula: summary of the number and arrangement of maxillary plates and teeth in Eunicida.

maxillary ring: distal part of the everted pharynx in Nereididae.

medial: the mid-line regions of the body.

median: in the mid-line.

meiobenthos: benthic invertebrate fraction that passes through a 1 mm sieve but is retained on a 42 m m sieve.

metamerism, metameres: segmentation of the body into a series of similar units, termed metameres.

metanephridia: type of nephridia in which the coelomic end has an open funnel

metastomium: rarely used term covering the segmented body between the prostomium/peristomium and the pygidium, but including neither.

micrognaths: numerous small jaw pieces arranged in a ring in the pharynx of Goniadidae.

microtubercle: see tubercle.

microvilli: minute, very slender (>0.01 mm diameter) extensions of surface of epithelial cells.

midgut: central part of the alimentary canal comprising the stomach, when present, and the intestine; endodermal origin.

mitraria larva: larva of oweniid polychaete; swim by ciliary action of an umbrella-like structure.

moniliform: beaded or beadlike.

monophyly, monophyletic: pertaining to a group of taxa comprising a common ancestor and all its descendants.

mouth: anterior opening of the alimentary canal; usually anterior opening of fully everted pharynx.

mucro: a sharp point or tip on an abruptly tapering structure.

mucronate: sharply pointed.

multiarticulate: with three or more joints.

multidigitate: with many finger-like lobes or projections.

mutualism: symbiotic association between two members of different species which benefits both organisms.

myo-epithelium: epidermal layer which includes contractile epithelial cells.



natatory: swimming.

nectochaete: developmental stage of an annelid following metatrochophore (up to 20 or so chaetigers); ciliation is reduced and parapodia function in locomotion.

nematoform: worm-like.

nephridial papilla: projection on which the excretory organ opens.

nephridiopore: the external opening of a metanephridium; see also nephridium.

nephridium, nephridia: excretory organ(s) opening to the exterior via a duct and a nephridiopore; fluid enters the internal end of the more primitive protonephridium through selenocytes; fluid enters the internal end of metanephridium though an open, ciliated funnel termed a nephrostome.

nephromixia: combinations of coelomoduct and nephridium termed protonephromixium, metanephromixium and mixonephridium; in protonephromixium, mesodermal components are fused with a protonephridial canal; in a metanephromixium, the mesodermal funnel has become joined with an open nephrostome; in a mixonephridium the coelomic end of the nephridium is completely fused with the funnel of a coelomoduct.

nephrostome: ciliated funnel of the coelomic opening of a metanephridium; see also nephridium.

nerve cord: ventral, segmentally ganglionated nerve trunk passing along the length of the body.

neuroacicula: acicula of the neuropodium.

neurochaeta: chaeta of a neuropodium.

neurocirrus: see ventral cirrus.

neurofibrils: fine proteinaceous longitudinal fibres forming a network within the nerve cell body, axons and dendrites.

neuropodium, neuropodia: ventral branch or ramus of a parapodium.

neuroseta: see neurochaeta.

neurotroch: longitudinal ventral band of cilia in trochophore.

notoacicula: acicula of the notopodium.

notochaeta, notochaetae: chaeta of a notopodium.

notocirrus: see dorsal cirrus.

notopodium, notopodia: dorsal branch or ramus of a parapodium.

notoseta: see notochaeta.

nototroch: regularly scattered dorsal ciliary bands on body of trochophore larva.

nuchal: pertaining to the neck.

nuchal cirrus: see nuchal papilla.

nuchal epaulettes: see nuchal organs.

nuchal organs: paired chemosensory structures situated postero-laterally on the prostomium, developed variously as pits, grooves, epaulettes, or elongated ridges.

nuchal papilla: papilla found on the posterior margin of the prostomium of some Phyllodocidae and Spionidae.



oblique muscle: muscle attached to the aciculae and chaetae; cf. diagonal muscle.

occipital: pertaining to the postero-dorsal part of the prostomium.

occipital collar: a prominent fold immediately overlapping the posterior part of the prostomium.

occipital fold: see occipital collar.

occipital lappet: see occipital collar.

occipital papilla: see nuchal papilla.

ocellus, ocelli: small eye spot(s).

ocular: pertaining to the eye.

ocular peduncle: see ommatophore.

oesophageal caecum: blind sac arising from the oesophagus.

oesophagus: posterior part of the foregut connecting the pharynx to the intestine; includes the gizzard or proventricle, and caeca when present.

ommatidium: functional optic unit of the compound eyes on the tentacular crown of some sabellidans.

ommatophore: projecting structure supporting the eyes, especially in scale-worms.

oocyte: female reproductive cell; diploid primary oocyte forms, through meiosis during oogenesis, a haploid secondary oocyte which divides to form an ovum.

oogenesis: formation and development of female gametes from diploid oogonia to mature, haploid ova.

oogonia: diploid precursor of primary oocytes, derived by mitosis during oogenesis.

operculum, opercula: plug at the anterior end of some tube-dwellers which blocks the tube opening when the worm retracts.

oral cavity: mouth cavity.

oral filaments: see tentacles.

oral ring: proximal part of the everted pharynx in Nereididae.

otocysts: see statocysts.

oviduct: tube conducting eggs or oocytes to exterior.

oviparous: pertaining to deposition of eggs which develop completely and hatch externally.

ovoid: shaped like a bird’s egg.



palea, paleae: broad, usually flattened chaetae, often with a metallic sheen.

palmate: resembling the fronds of a palm.

palp, palpi: one of a set of paired, elongate or cushion-like structures arising from the sides of the head; anteroventral and sensory in many ‘errant’ polychaetes; placed postero-dorsally and used in feeding in spioniform polychaetes.

palpode: tapering anterior projection of the prostomium.

palpophore: basal part of a jointed palp.

palpostyle: distal part of a jointed palp.

papilla, papillae: a small, nipple-like projection.

papillose: bearing numerous small, rounded to conical projections.

paragnath formula: summary of number and arrangement of denticles on the pharynx in Nereididae.

paragnath: sclerotinised denticle on the pharynx in Nereididae.

paraphyly, paraphyletic: pertaining to a group of taxa comprising a common ancestor but not all of its descendants; see polyphyly and monophyly.

parapodial trunk: proximal, undivided part of an elongate parapodium.

parapodium, parapodia: one of the two fleshy lateral projections from a body segment, usually bearing chaetae and sometimes greatly reduced.

paratomy: see schizotomy.

parenchyma: mesodermal tissue surrounding, and filling spaces between organs, muscles and other tissues.

pectinate: comb-like; with series of projections arranged like the teeth of a comb.

pectinate chaeta: see comb chaeta.

pedicel: a short stalk.

penicillate chaeta: simple chaeta with a brush-like tip.

peristalsis: rhythmic, directional wave of muscular contraction in a vessel or tube.

peristome: see peristomium.

peristomial cirri: paired, elongated cirri on the peristomium.

peristomial ring: annulus associated with the peristomium.

peristomium: presegmental region of the body that lies between the prostomium and the first segment; in many polychaetes the peristomium only forms an area around the mouth.

peritoneum: serous membrane lining the coelomic cavity.

pharyngeal organ: see buccal organ.

pharynx, pharynges: anterior muscular part of the foregut, including the eversible proboscis.

pilose: covered with very short hairs giving a velvety appearance.

pinnate: feather-like; two rows of pinnules branching from a central axis (cf. bipinnate; bipectinate).

pinnules: small side branches, in a feather-shaped process, such as the radiole in Sabellidae and Serpulidae.

piriform: see pyriform.

planktotrophic: larval development in which eggs with little yolk hatch as small, free-swimming trochophores which feed on algae in the water column.

platelet: syncytial mass of spermatozoa.

plesiomorphy: primitive retained character; compare apomorphy.

plumose: resembling down; hairy.

polyphyly: pertaining to a group comprising two or more taxa derived from distinct lineages.

polytelic: pertaining to individuals or species in which adults survive to spawn during two or more breeding seasons.

polytomy, polytomous: incompletely resolved node on tree of relationships, where several branches originate together.

polytypic: pertaining to a genus with more than one species, a family with more than one genus, etc.

postchaetal: posterior to the chaetae; used in relation to parapodial lobes or ligules.

postsetal: see postchaetal.

prechaetal: anterior to the chaetae, used in relation to parapodial lobes or ligules.

presetal: see prechaetal.

primary tooth: larger distal tooth of an unequally bidentate chaeta.

prionognath: arrangement of complex jaw apparatus in which the generally similar jaw-pieces are located in two rows on longitudinal ridges.

proboscis, proboscides: eversible, non-muscular part of the buccal organ (strictly); often used interchangeably with pharynx.

prostomial keel: see cephalic keel.

prostomial peaks: antero-lateral projections, often chitinised, of the prostomium in some scale-worms.

prostomium, prostomia: anteriormost, presegmental and pretrochal region of the body, sometimes bearing eyes and antennae; may not be externally recognisable.

protandry, protandrous: sequence of sexual stages, from a functional male stage to a hermaphroditic and/or a functional female stage in consecutive hermaphrodites.

protogyny, protogynous: sequence from a functional female stage to a hermaphroditic and/or a functional male stage in consecutive hermaphrodites.

protonephridia: type of nephridia in which the coelomic end is closed

Protostomia, protostomes: primary grouping in bilateral animals characterised by determinate cleavage, in which the fate of cells is pre-determined; found in platyhelminthes, annelids, molluscs and arthropods.

prototroch: primary, anterior-most transverse ring of locomotory cilia on the body of the trochophore larva, lying anterior to the mouth.

proventricle: muscularised region of the anterior digestive tract occurring posterior to the pharynx; with muscle fibres arranged radially; characteristic of the Syllidae.

proventriculus: see proventricle.

proximal: part of a structure nearer to the base or main body.

psammophilic: pertaining to sand-dwelling organisms.

pseudocompound: pertaining to compound chaeta in which the articulation is incomplete.

pseudocopulation: a form of sperm transfer in some polychaete groups involving spermatophores, spermatozeugmata, or free spermatozoa.

pseudofaeces: sediment particles transported upwards from feeding depths by a polychaete worm and ejected from the tube; texturally indistinguishable from faeces.

pseudojointed: see pseudocompound.

pygidial: pertaining to the anal region or pygidium.

pygidial cirrus: cirrus projecting from the pygidium.

pygidium: post-segmental terminal part of the body surrounding the anus.

pyriform: with a broad bulbous base and tapered tip; pear- or onion-shaped.

pyriform glands: multicellular epidermal glands which secrete chitin and mucopolysaccharides to form the pogonophoran (Siboglinidae) tube.



radiole, radii: primary branch in the tentacular crown in Sabellidae and Serpulidae.

radiolar crown: a radiolar crown is a feather-like feeding and respiratory structure comprising radioles which are basally attached to a lobe surrounding the mouth; in Serpulidae and Sabellidae only. See also branchial crown.

ramose: branched.

ramus, rami: branch, in relation to the dorsal or ventral branch of a parapodium.

raptorial: feeding mode involving snatching, seizing or tearing apart.

rectum: see hindgut.

reniform: kidney-shaped.

reticulate: pattern or structure forming a network or mesh.

retort organ: club-shaped gland opening into the buccal cavity in Typhloscolecidae.

rhabdomere: photoreceptive element of a compound eye.

ringent chaeta: simple, subdistally expanded chaeta with a narrow slit which is internally crenulated or serrated; in Euphrosinidae.

rosette gland: yellowish star-shaped glands in the pinnules of some species of Tomopteris; see also chromatophil gland.

rosette: syncytial mass of spermatozoa.

rostrum: enlarged first tooth or fang of a chaeta, usually a hook or uncinus.

rugose: roughened, lumpy.



sabre chaetae, sabre-like chaetae: chaeta with a broad curved blade.

scale: see elytron.

scaphe: flattened caudal end in Pectinariidae; see also pygidium.

schizogamous epitoke: see epitoke.

schizogamy: structural modification of the adult involving the budding off of sexual individuals; see also stolons, epigamy.

schizotomy: asexual reproduction involving two forms of subdivision of the body and regeneration of the missing parts; in paratomy, a recognisable complete individual forms and then separates from the 'parent' stock; in architomy, the body breaks or fragments without any prior cephalisation.

scleroprotein: one of a group of proteins incorporated into skeletal, connective or epidermal structure.

sclerotinised: pertaining to the hardening of the exoskeleton with the quinone-tanned protein sclerotin.

secondary tooth: smaller, proximal tooth of an unequally bidentate chaeta.

segment: one of the serially repeated units comprising the trunk; often separated internally by septa.

segmental organs: organs occurring in segmental arrangement; used specifically with reference to nephridia and nephridial ducts.

selenocyte: blind-ending region at the coelomic end of the metanephridium; see also nephridium.

semelparity: death following a single reproductive season.

sensory buds: epithelial sensory/secretory structures on antennae and cirri.

septum, septa: structural partition(s) or division(s) between two visceral regions, within a haemocoel, or separating two cavities or tissue masses.

sesquigomph: see hemigomph (articulation).

sesquiramous parapodium: see sub-biramous parapodium.

sessile: pertaining to organisms attached to or situated directly on the substratum; without a stalk.

seta, setae: see chaeta, chaetae.

setal: see chaetal.

setiger: see chaetiger.

setigerous: pertaining to setae.

setigerous lobe: see chaetigerous lobe.

shaft: proximal part of a compound or simple chaeta; or proximal part of a eunicean mandible.

sheath: hyaline envelope covering a capillary chaeta.

short-handled uncinus: uncinus without a long basal extension.

sickle chaeta: simple chaeta with a sickle-shaped blade in some Spirorbinae.

simple chaeta: unjointed chaeta, includes hair-like (capillary) and robust (spines) types.

simultaneous hermaphroditism: presence of functional male and female reproductive systems in an individual at the same time.

solenocytes: terminal cells at the internal end of a protonephridium; responsible for filtering waste products from the coelomic fluid.

spatulate, spathulate: simple chaeta with a broadly expanded distal margin; like a spatula; spoon-shaped.

spermathecae: seminal receptacles.

spermatid: haploid, immature precursor of spermatozoon; derived from secondary spermatocyte.

spermatogenesis: process of sperm formation from diploid primordial spermatogonia to haploid spermatozoa.

spermatogonia: the earliest germ cells in the spermatogenic sequence.

spermatophores: bundles of spermatozoa, all enclosed by a sheath or capsule isolating them from the surrounding environment; see also spermatozeugmata.

spermatozeugmata: bundles of spermatozoa which are not surrounded by an external covering; may resemble bundles of late spermatids; see also spermatophores.

spindle-shaped: shaped like a cigar with pointed ends.

spine: a thick acicular or spear-shaped chaeta; may be straight or slightly curved.

spiniger, spinigerous chaeta: compound chaeta tapering distally to a fine point.

spinning gland: gland secreting tube-forming material (threads) present in parapodia of certain scale-worms.

spinous pocket: enlarged, pocket-like serration along the margin of the chaetae of some scale-worms.

spinule: a small spine.

spinulose: bearing small spines.

squamous epithelium: epidermal layer of flattened, scale-like cells.

statocysts: paired epithelial organs at the base of the tentacular crown in sabellids that function in equilibrium and orientation.

stem cells: undifferentiated adult or embryonic cell capable of unlimited division and of giving rise to one or more cell types.

stereocilia: inter-ramal sensory cilia; see also dorsal cirrus organ, lateral organ.

sternal shield: modification of the last segments forming a ventral plate in Sternaspidae; see also cuticular shield.

stolon: secondary individual formed by budding, usually from the posterior end, or elsewhere on the body.

stolonisation: form of asexual reproduction involving the formation of stolons.

stomach: glandular and/or muscular region of the midgut of most ‘sedentary’ polychaetes.

stomodaeum, stomadeum: anterior part of the embryonic alimentary canal formed as an invagination of the ectoderm; see also foregut.

striae: fine parallel marks or lines.

striated: with striae.

stylet: a small pointed tooth-like structure.

stylode: finger-like projection associated with a parapodium, usually small and distinctly longer than wide.

sub-biramous parapodium: parapodium with a well-developed neuropodium and reduced notopodium.

suboesophageal ganglion: nerve centre at the junction of the circumoesophageal connectives and the ventral nerve cord.

subterminal: close to the apex of a structure.

subulate: awl-shaped.

subuluncinus, subuluncini: chaeta with a stout shaft tapering to a slender tip; intermediate between a capillary and an uncinus; see also aristate.

symbiont: participant in a mutualistic, commensal or parasitic relationship.

symplesiomorphy: primitive retained character shared by two or more taxa; compare synapomorphy.

synapomorphy: derived character shared by two or more taxa.

synapse: junction between two nerve cells or a nerve cell with another cell type such as muscle.



tentacles: general term for the long, paired or multiple food-gathering appendages; most are grooved and/or have a longitudinal row of cilia; see also buccal cirri, buccal tentacles, oral filaments.

tentacular cirri: dorsal and/or ventral cirri of parapodia of cephalised segments; often more elongate than those of more posterior parapodia; confused in the literature with peristomial cirri.

tentacular crown: array of elongated, longitudinally-grooved appendages on the head in Terebellida; used for feeding.

tentacular membrane: thin fold or hood extending from prostomium and bearing tentacles, often on its margin.

tentacular formula: notation indicating the arrangement of the tentacular cirri and chaetae; originally used for Phyllodocidae and Alciopidae, now also extended to other families.

tentaculophore: basal projection on which a tentacle is mounted.

terminal tooth: see primary tooth.

tessellated: pertaining to a surface with a network of grooves like a tiled wall.

thoracic membrane: thin fold extending from the dorsal part of the collar to the ventral side of the posterior thorax in most Serpulidae.

thorax: anterior region of the trunk in some polychaetes.

tine: prong of a forked-type chaeta; may be smooth or fringed with hairs

torus, tori: welt or ridge-like parapodial ramus, often with hooks or uncini.

trabeculae: struts of tissue forming a supportive or bracing framework within a space.

trepan: sclerotinised ring of teeth in the anterior pharynx of Syllidae.

trichogenic cells: cells which secrete fine hair-like threads.

tridentate: with three teeth.

trochophore: early, ciliated, free-swimming, planktonic larval stage before segment proliferation begins

truncate: pertaining to a structure that ends abruptly, without tapering.

trunk: the segmented region of the body between the peristomium and pygidium.

tubercle: knob-like protruberance; often referring to a large (macrotubercle) or small (microtubercle) projection on the elytron of some Polynoidae.



unciniger: segment carrying uncini.

uncinigerous: bearing uncini.

uncinus, uncini: deeply embedded short beak-like chaeta with a heavily dentate crest and wekly devleloped (or no) shaft; usually arranged in rows transverse to the long axis of the animal; see also long-handled uncinus.

unidentate: distally entire; often pertaining to chaetae.

uniramous parapodium: parapodium in which one ramus, most frequently the notopodium, is absent.

unjointed chaeta: see simple chaeta.

urite: projection from the pygidium.



venter, ventrum: the lower body surface.

ventral blood vessel: longitudinal vessel which carries blood posteriorly through the body; situated beneath the gut.

ventral buccal organ: variable, often complex set of folds, musculature and glands present on the ventral side of many polychaetes; see pharynx.

ventral cirrus: cirrus normally situated on the lower edge of the neuropodium.

ventral groove: longitudinal mid-ventral furrow.

ventral muscle bulb: see pharynx.

ventral pads: glandular areas on the lateral venter of thoracic segments in some Eunicida, where they replace ventral cirri; cf. lateral shields.

ventral shield: glandular, segmentally arranged pads on the mid-ventral thorax in many Terebellida.

vermiform: worm-like in form.

vestimentum: body region in vestimentiferans (Siboglinidae), on which lateral flaps enfold the anterior part of the body behind the plume.

villus, villi: series of small, digitate tubules arising from the contractile vessel of some sipunculans.

vitellogenesis: formation of egg yolk.



winged capillary chaeta: see limbate or bilimbate chaetae.



zygote: product of fused haploid spermatozoa and ovum, forming a diploid cell.