Polikey glossary. Adapted from Glasby, C.J., Fauchald, K. & Hutchings, P.A. (2000). Glossary. Pp. 401412 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.
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abdomen:body region posterior to the thorax, sometimes followed by a tail.
abyssal:oceanic waters between depths of 4000 m and 6000 m.
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.
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 birds head.
axial:pertaining to, or situated on the axis.
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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.
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.
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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.
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).
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.
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.
cristate:bearing a ridge or crest.
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).
cutting plate:distal part of eunicean mandible.
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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.
denticle:a minute tooth.
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).
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.
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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.
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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.
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.
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.
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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.
gizzard:muscular, barrel-shaped part of the foregut behind the pharynx in some Spionidae.
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.
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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 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.
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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.
intestine:absorptive part of the midgut, usually a straight tube.
iteroparity:breeding in more than one season, often at regular intervals.
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jaw formula:see maxillary formula.
jaws:hardened feeding or grasping apparatus with opposable units situated in the eversible pharynx.
jointed chaeta:see compound chaeta.
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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.
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macrobenthos:benthic invertebrate fraction retained in a 1 mm sieve.
macrognaths:paired lateral jaw pieces of Goniadidae.
main fang:see fang, see also primary tooth.
mammillate:pertaining to nipple-like process.
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.
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.
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.
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nectochaete:developmental stage of an annelid following metatrochophore (up to 20 or so chaetigers); ciliation is reduced and parapodia function in locomotion.
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.
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.
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.
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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.
oviduct:tube conducting eggs or oocytes to exterior.
oviparous:pertaining to deposition of eggs which develop completely and hatch externally.
ovoid:shaped like a birds egg.
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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.
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.
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.
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.
prechaetal:anterior to the chaetae, used in relation to parapodial lobes or ligules.
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.
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.
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.
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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.
ramus, rami:branch, in relation to the dorsal or ventral branch of a parapodium.
raptorial:feeding mode involving snatching, seizing or tearing apart.
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.
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sabre chaetae, sabre-like chaetae:chaeta with a broad curved blade.
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.
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.
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.
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.
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.
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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.
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unciniger:segment carrying 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.
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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.
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winged capillary chaeta:see limbate or bilimbate chaetae.
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zygote:product of fused haploid spermatozoa and ovum, forming a diploid cell.