Terminology Description
Terminology Description
Abdomen body region posterior to the thorax, sometimes followed by a tail.
Abyssal oceanic waters between depths of 4000 m and 6000 m.
Achaetigerous seeachaetous.
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 seeachaetigerous.
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.
Biramousparapodium 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 seeradiolar crown.
Branchiole seeradiole.
Bristle see chaeta.
Brush-tipped chaeta seepenicillate 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 seepygidium.
Caudad towards the tail.
Caudal plaque flattenedpygidium.
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 seeprostomial peaks.
Cephalic plaque see cephalic plate.
Cephalic plate plate-likeantero-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 achitinous 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-shapedchitinised jaw piece at the base of the eversible pharynx in some goniadidae.
Chromaphil gland seechromatophil gland.
Chromatophil gland densely staining gland in the ventral pinnule oftomopteris; 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 prostomialpalps.
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); epigamousepitokes result from the transformation of an atoke to the epitoke; schizogamousepitokes 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 tubicolouspolychaete, 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 seelimbate or bilimbate chaetae.
Foliaceous thin and leaf-like.
Foot seeparapodium.
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 seeprostomial peaks.
Furcate chaeta short (usually), bifurcated simple chaeta.
Fusiform cigar- or spindle-shaped.
Geniculate chaeta simple chaeta formed like a bent knee.
Genital hook modifiednotopodial chaeta used in mating in some capitellidae.
Genital papilla projection on which a reproductive duct opens.
Genital pore modifiednephridial 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 seebranchia.
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 seecoelomoduct; see also nephridia in echiurans and sipunculans.
Guard paired delicate chitinous sheaths protecting the tip of some chaetae.
Gular membrane amuscularised 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 oftomopteris; 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 acirriform 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 inpolycirrus;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 42mm 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 oweniidpolychaete; 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 metanephridiumthough 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 fineproteinaceous longitudinal fibres forming a network within the nerve cell body, axons and dendrites.
Neuropodium, neuropodia ventral branch or ramus of a parapodium.
Neuroseta seeneurochaeta.
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 seenotochaeta.
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 seeommatophore.
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 seestatocysts.
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 spioniformpolychaetes.
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 sclerotiniseddenticle 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 seeschizotomy.
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 seeperistomium.
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 seebuccal 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 seepyriform.
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 seepostchaetal.
Prechaetal anterior to the chaetae, used in relation to parapodial lobes or ligules.
Presetal seeprechaetal.
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 seeproventricle.
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 seepseudocompound.
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 aradiolar 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 oftomopteris; 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.
Schizogamousepitoke seeepitoke.
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 seehemigomph (articulation).
Sesquiramousparapodium see sub-biramousparapodium.
Sessile pertaining to organisms attached to or situated directly on the substratum; without a stalk.
Seta, setae see chaeta, chaetae.
Setal seechaetal.
Setiger seechaetiger.
Setigerous pertaining to setae.
Setigerous lobe seechaetigerous 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 withstriae.
Stylet a small pointed tooth-like structure.
Stylode finger-like projection associated with a parapodium, usually small and distinctly longer than wide.
Sub-biramousparapodium 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-likeprotruberance; often referring to a large (macrotubercle) or small (microtubercle) projection on the elytron of some polynoidae.
Unciniger segment carrying uncini.
Uncinigerous bearinguncini.
Uncinus, uncini deeply embedded short beak-like chaeta with a heavily dentate crest and weklydevleloped (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 seelimbate or bilimbate chaetae.
Zygote product of fused haploid spermatozoa and ovum, forming a diploid cell.