Cestode glossary

acaudate

condition of a metacestode characterized by the absence of tail-like cercomer Antonym: caudate

acetabulate scolex

scolex with four lateral muscular membrane-bound attachment organs (i.e., bothridia or acetabula) Synonym: tetrafossate scolex as in Wardle & McLeod, 1952; Hoberg et al., 2001 Remarks: for the purposes of the present database, we have adopted the interpretations of Caira et al. (1999) who considered bothridia having principally the same organization as acetabula

acetabulum

muscular membrane-bound attachment organ, usually cup-shaped, sunk within the surface of the scolex and consisting of muscular fibres perpendicular to the tegument and extending between the tegument and the bounding membrane (modified from Wardle & McLeod, 1952; Caira et al., 1999)

acraspedote

configuration of the strobila (or proglottides), in which the posterior portion of the proglottis does not overlap the anterior portion of the next proglottis Synonym: amphidote Antonym: craspedote

adult

sexually mature stage in the life cycle characterized by the presence of functional reproductive organs containing fully developed gametes

amphidote

See preferred term: acraspedote

anapolysis

mode of strobilar development characterized by the non-detachment of gravid proglottides Antonym: apolysis

apical organ

organ at the anterior extremity of the body of the adult and/or metacestode, consisting of muscular and/or glandular tissue, and typically specialized in an attachment function

apolysis

mode of strobilar development characterized by the detachment of terminal gravid proglottides Antonym: anapolysis

armatetrathyridium

See preferred term: fimbriocercus

asexual reproduction

mode of reproduction in which new individuals are produced without participation of gametes

autotomicrocercus

See preferred term: urocysticercoid

bladder

fluid-filled cavity in metacestodes of some Trypanorhyncha, Tetraphyllidea and Cyclophyllidea

bothriate scolex

scolex with two, rarely four or six, lateral muscular attachment organs called bothria Synonym: difossate scolex as in Wardle & McLeod, 1952 and in Hoberg et al., 2001

bothridium (pl. bothridia)

muscular membrane-bound attachment organ on the scolex consisting of muscular fibres perpendicular to the tegument and extending between the tegument and the bounding membrane (modified from Caira et al., 1999)

bothrium (pl. bothria)

muscular attachment organ, not membrane-bound, not consisting of radial muscular fibres and situated on the ventral and dorsal surface of the scolex (modified from Caira et al., 1999)

budding

mode of asexual reproduction in which somatic part of a parental organism detaches and forms new individual(s)

calcareous corpuscles

corpuscles found in many cestodes, especially in larval stages, and made up mostly of calcium carbonate, magnesium carbonate and a hydrated form of calcium phosphate embedded in an organic matrix (modified from Slais, 1966)

caudate

condition of a metacestode characterized by the presence of tail-like cercomer Antonym: acaudate

caudate diplocysticercoid

cysticercoids in which the scolex is enveloped by two layers of larval tissue, the internal one is the ‘real’ cyst and the external one is formed by part of the cercomer while the remaining part of the cercomer is tail-like Synonym: ramicercus sensu Chervy, 2002 Remarks: we consider ‘floricercus’ (see Bondarenko & Kontrimavichus, 1976) as a modification of caudate diplocysticercoid in which the most external envelope is not totally closed

cercocysticercoid

caudate cysticercoid (from Chervy, 2002)

cercomer

most posterior part of the body in metacestodes, separated from the anterior body part by constriction formed by circular muscle delimiting small cavity containing the orifice(s) of the osmoregulatory system. The cercomer can be tail-like or form additional protective envelopes surrounding the remaining part of the body of the metacestode

cercoscolex

See preferred term: merocercoid

cladothyridium

See preferred term: merocercoid

coenurus (pl. coenuri)

metacestode of some species of Taenia (Cyclophyllidea), which consists of a large fluid-filled cyst containing many scoleces formed asexually from the internal germinative membrane (i.e., endogenous scolex development)

coracidium (pl. coracidia)

developmental stage of some cestodes, representing an oncosphere and surrounding embryonic envelope (i.e., embryophore), which is ciliated and is thus adapted for swimming after emergence from the egg

craspedote

configuration of the strobila (or proglottides), in which the posterior portion of the proglottis (i.e., velum) overlaps the anterior portion of the next proglottis Antonym: acraspedote, amphidote

cross-fertilisation

mode of sexual reproduction in which new individuals are produced as a result of syngamy of gametes from different parents Synonym: out-crossing Antonym: self-fertilisation, selfing

cysticercoid

metacestode with primary lacuna (sometimes not distinct), scolex retracted within solid cyst, with cercomer or reduced cercomer (modified from Chervy, 2002)

cysticercus (pl. cysticerci)

metacestode with primary lacuna (sometimes not distinct) and a single invaginated scolex (from Chervy, 2002)

decacanth

See preferred term: lycophore

definitive host

host harbouring the adult stage Synonym: final host

dioecy

See preferred term: gonochorism

diplocyst

See preferred term: diplocysticercoid

diplocysticercoid

cysticercoid in which the scolex is enveloped by two layers of larval tissue, the internal one is the ‘real’ cyst and the external one is formed by the cercomer (modified from Chervy, 2002) Synonym: diplocyst

echinococcus

See preferred term: hydatid

egg

embryo and the surrounding protective and nutritive tissues (whether in uterus of gravid cestode or in the environment)

egg capsule

common envelope embedding an aggregation of eggs or an additional envelope around a single egg situated externally to the outer shell

embryophore

layer of cellular origin covering the oncosphere and derived from the inner envelope of the egg

endogenous scolex development

mode of asexual reproduction in some types of metacestodes (hydatids, coenuri and, probably, some cysticercoids), characterized by the formation of new scoleces (i.e., protoscoleces) developing toward the interior of the parental organism

endopolygeny

mode of asexual reproduction in which a mother metacestode (in Mesocestoides) produces internally daughter metacestode(s) Synonym: internal budding

enteral

site of parasite (location) in the alimentary tract of the host Antonym: parenteral

euparatenic host

paratenic (and, therefore, facultative) host, in which metacestodes do not undergo any development but remain infective for the definitive host (modified from Bozkov, 1982)

euryxeny

condition of host specificity for a parasite species that can develop in a wide range of host species, which are ecologically similar but phylogenetically distant (modified from Euzet & Combes, 1980) Synonym: polyxeny sensu Odening, 1976

evagination

process by which metacestodes with invaginated scolex adopt a functional configuration when reaching the definitive host

excystment

process by which metacestodes with retracted scolex adopt a functional configuration when reaching the definitive host

exogenous scolex development

mode of asexual reproduction in metacestodes, characterized by the formation of new scoleces developing toward the exterior, as continuation of the external wall of the parental organism

fecundity

reproductive potential of the whole organism in term of egg production (roughly assessed by the number of eggs produced per proglottis, multiplied by the number of proglottides)

fimbriocercus

cysticercus characterized by an elongated unsegmented body Synonym: armatetrathyridium (after Chervy, 2002)

fissioning

mode of asexual reproduction in which an organism splits itself in two, almost identical, parts

flame cell

ciliated cell specialized for excretion and osmoregulation, being a part of the protonephridium

gamete

haploid and mature reproductive cell; spermatozoon in male, ovum in female

genital pore

external openings of the male and female reproductive systems or a common opening of the two genital systems

gonochorism

state of strobilar development characterized by the possession of gonads of only one sex (male or female) Synonym: dioecy Antonym: hermaphroditism, monoecy

gravid

for cestode worm or individual proglottis, containing developed eggs, ready to be released into environment

hermaphroditism

state of strobilar development characterized by the presence of both male and female reproductive organs in the same organism (not necessarily at the same time) Synonym: monoecy Antonym: gonochorism, dioecy

heteroxeny

condition of host alternation for a parasite species that uses more than one host species to complete its entire life cycle (from Odening, 1976) Antonym: homoxeny

hexacanth

See preferred term: oncosphere

homoxeny

condition of host alternation for a parasite species that only uses one host species to complete the entire life cycle (from Odening, 1976) Antonym: heteroxeny

hydatid

metacestode of some species of the genus Echinococcus (Cyclophyllidea) which is a large fluid-filled cyst containing multiple invaginated scoleces and daughter cysts that also contain multiple invaginated scoleces Synonym: echinococcus

hyperapolysis

early detachment of proglottides that leads to an independent existence while maturing and/or developing ripe eggs

inner egg envelope

envelope surrounding the oncosphere, situated internally to the outer egg envelope, formed as result of the fusion of three mesomeres (i.e., having three nuclei in a syncytial organization) and giving rise to the embryophore

intermediate host

obligatory host in the life cycle, in which metacestodes undergo development and become infective for the definitive host or for another intermediate host (modified from Odening, 1976)

invaginated

for scolex, being withdrawn within the body of the metacestode by turning outside-in, in a way which renders its apex the bottom of a cavity while the external walls of the scolex become the internal walls of the same cavity. Reaching the definitive host, a metacestode with invaginated scolex evaginates

lacunate

condition of metacestodes characterized by the presence of a primary lacuna

larva

early stage of development that performs metamorphosis turning into a metacestode (Freeman, 1973). However, the term is also widely used for stages in intermediate and paratenic hosts (i.e., for metacestodes, as in Chervy, 2002) See preferred term: oncosphere, lycophore, metacestode

lycophore

early stage of development of some cestodes (Amphilinidea and Gyrocotylidea), provided with 10 embryonic hooks, which is ciliated and thus adapted for swimming after emergence from the egg, and undergoing metamorphosis after penetrating into the host

merocercoid

metacestode lacking a primary lacuna, in which scolex is invaginated (modified from Chervy, 2002) Synonym: tetrathyridium, cladothyridium, cercoscolex

merocercus

See preferred term: plerocercus

metacestode

all developmental stages between the oncosphere/lycophore and the adult (egg-producing stage), and therefore occurring in the intermediate or paratenic host(s). The etymology of the term is from ‘a changing cestode’ (Wardle & McLeod, 1952; Freeman, 1973)

metaparatenic host

kind of paratenic (and, therefore, facultative) host, in which metacestodes undergo development typical for the definitive host but do not reach maturation or egg production (modified from Bozkov, 1975)

microcysticercoid

cysticercoid with a vestigial cercomer (modified from Chervy, 2002)

monocysticercoid

cysticercoid in which the cercomer forms additional envelope around the cyst, which may disintegrate into globules or become granular in appearance (modified from Chervy, 2002) Synonym: monocercus

monoecy

See preferred term: hermaphroditism

monofossate scolex

scolex with ‘a single apical sucker only’. Term to be avoided because it is connected with the presence of an apical organ while the other two conditions (i.e., bothriate or difossate and acetabulate or tetrafossate) reflect the presence of lateral attachment organs

monoxeny

See preferred term: oioxeny

monozoic

with a single set of reproductive organs; used for the body organization of Gyrocotylidea, Amphilinidea and Caryophyllidea Antonym: polyzoic

neck

for polyzoic cestodes, undifferentiated portion of the worm between the scolex and the strobila, which contains stem cells that give rise to the proglottides Synonym: proliferation zone, germinative area, collum, pars proliferans scolecis

neoteny

process of development in which sexual maturation in the definitive site and host is associated with retention of some larval characters

oioxeny

condition of host specificity for a parasite species that can only develop in a single host species (from Euzet & Combes, 1980)

oligolecithal egg

egg formed with only one or two vitellocytes associated with each zygote (from Swiderski & Xylander, 2000)

oligoxeny

See preferred term: stenoxeny

oncosphere

early stage of development, common to all eucestodes, provided with six embryonic hooks and undergoing metamorphosis after penetrating into a parenteral site in the (first/only) intermediate host to become a metacestode

oocyte

See preferred term: ovocyte

ootype

organ of the female reproductive system that is typically surrounded by Mehlis’ gland, connected with two ingoing ducts (one coming from the vitellarium and another formed after the fusion of the ducts coming from seminal receptacle and from ovary) and with one outgoing duct leading to the uterus

operculum

lid or cap-like structure at the end of eggs in some cestodes

out-crossing

See preferred term: cross-fertilisation

outer egg envelope

envelope surrounding the inner egg envelope, formed as a result of fusion of two macromeres (i.e., having two nuclei in a syncytial organization)

oviduct

short duct that carries ova from the ovary to the ootype; often fusing with the seminal duct carrying spermatozoa from the seminal receptacle and forming a common duct leading to the ootype

oviparity

mode of embryonic development, in which the embryo does not develop in utero and hatches from protective envelopes outside the parental organism (modified from Tinsley, 1983)

ovocyte

in female gametogenesis, precursor of ovum Synonym: oocyte

ovoviviparity

mode of embryonic development, in which the embryo hatches from protective envelopes within the parental organism and develops in utero (modified from Tinsley, 1983)

ovum (pl. ova)

mature but non-fertilized gamete in female

paedogenesis

process of development resulting in sexual maturation by an organism in a (morphologically) larval state. It can be by means of neoteny or progenesis

paraparatenic host

paratenic (and, therefore, facultative) host, in which metacestodes undergo development and are infective for the definitive host (modified from Bozkov, 1975)

paratenic host

facultative intermediate host, in which metacestodes infective to the definitive host may survive for indefinite period (modified from Odening, 1976) Synonym: reservoir host

parenchymatous capsule

envelope surrounding either a single egg and situated externally to outer shell or aggregation of eggs and having an origin from parenchyma

parenteral

site of parasite (location) outside the alimentary tract of the host Antonym: enteral

parthenogenesis

mode of sexual reproduction in which new individuals develop from a female gamete (i.e., ovum) without fertilisation from a male gamete (i.e., spermatozoon)

paruterine organ

organ appearing as fibrous or granular appendage to the uterus that usually receives the ripe eggs and retains them in a common capsule with protective and/or propagative function

plerocercoid

metacestode without primary lacuna, scolex not retracted, not withdrawn Synonym: merocercus, blastocyst, tentaculoplerocercoid

plerocercus

metacestode without primary lacuna, scolex retracted

polycysticercoid

See preferred term: monocysticercoid Remarks: term introduced by Chervy (2002) to mark ‘polycephalic diplocysticercoid (= polycyst)’ of Polycercus; however, the examination of the primary literature suggests that the ‘polycyst’ of Polycercus is in fact an aggregation of numerous monocysticercoids embedded in a common envelope consisting of host tissue (Genov, 1963)

polylecithal egg

egg formed with more than two vitellocytes associated with the zygote (from Swiderski & Xylander, 2000)

polyvalent host

host species acting as more than one host in the life cycle (e.g., intermediate and definitive host; intermediate and paratenic host)

polyxeny

See preferred term: euryxeny

polyzoic

with multiple sets of reproductive organs (i.e., having strobila consisting of two or more proglottides) Antonym: monozoic

primary lacuna (pl. primary lacunae)

sinus between cells that develops in the early stage of the morphogenesis of metacestodes of some Cyclophyllidea

procercoid

metacestode without primary lacuna and scolex

progenesis

process of development in which sexual maturation occurs precociously (i.e., in a larval site in an intermediate host)

proglottis (pl. proglottides)

part of strobila containing a set of reproductive organs. In most of the cases, there is coincidence between internal ‘proglottisation’ and external ‘segmentation’ of strobila and in these cases ‘proglottis’ and ‘segment’ are synonyms; however, in particular groups (e.g. Spathebothridea) one segment can contain a number of proglottides

proglottisation

process of formation of proglottides (i.e., repetition of reproductive organs), no matter if it is associated or not with external segmentation

protandry

condition in a sequential hermaphrodite in which male gonads mature before female gonads Antonym: protogyny, proterogyny

proterogyny

See preferred term: protogyny

protogyny

condition in a sequential hermaphrodite in which female gonads mature before male gonads Synonym: proterogyny Antonym: protandry

protonephridium

unit of the excretory (osmoregulatory) system consisting of flame cell(s) and outgoing duct(s)

protoscolex (pl. protoscoleces)

juvenile scolex formed asexually in Echinococcus spp. (Cyclophyllidea), and lacking fully developed hooks

protruded

for scolex, being outside the body, in a configuration similar to the adult

pseudoscolex

anterior end of the strobila modifies to function as an attachment organ

pyriform apparatus

modification of the embryophore in anoplocephalid cestodes assuming the shape of a pear, probably with protective and propagative functions

ramicercus

See preferred term: caudate diplocysticercoid

ramicysticercoid

cysticercoid with branching cercomer

retracted

for scolex, being withdrawn within the body of the metacestode (in a cyst) such that it keeps its definitive configuration (i.e., the scolex itself is not invaginated). Reaching the definitive host, a metacestode with retracted scolex is excysted

rostellum

a modification of the apical organ, usually associated with a crown of hooks

scolex (pl. scoleces)

anterior part (‘head’) of the cestodes specialized for attachment at the gut wall of the host

segment

externally distinct unit of the strobila defined by transverse grooves or partitions, which may contain one (typically) or more proglottides

segmentation

process of division of the strobila into externally distinct units

self-fertilisation

mode of sexual reproduction in which new individuals are produced by syngamy of gametes from the same parent (thus including cross inseminations between proglottides of the same strobila) Synonym: selfing Antonym: cross-fertilisation, out-crossing

selfing

See preferred term: self-fertilisation

sexual maturity

condition of an organism being able to reproduce sexually (i.e., having functioning reproductive organs containing fully developed gametes)

sexual reproduction

mode of reproduction in which new individuals are produced by means of gametes (and, therefore, including parthenogenesis) Antonym: asexual reproduction

staphylocyst

See preferred term: staphylocysticercoid

staphylocysticercoid

polycephalic metacestode developing in the form of a bunch of grapes each representing a cysticercoid (from Chervy, 2002) Synonym: staphylocyst

stenoxeny

condition of host specificity for a parasite species that develops in phylogenetically related species of host, those from the same genus for example (modified from Euzet & Combes, 1980) Synonym: oligoxeny sensu Odening, 1976

strobila (pl. strobila)

body part of polyzoic cestodes consisting of proglottides

strobilation

process of formation of the strobila

strobilocercoid

cysticercoid containing within the cyst, in addition to scolex and neck, also a segmented body part (‘metacestode strobila’)

strobilocercus

cysticercus containing, in addition to scolex and neck, also a segmented body part (‘metacestode strobila’)

syncytium

cellular structure formed by fusion of cell bodies but with retention of separate nuclei

syngamy

process of fusion of ovum and spermatozoon cells into a zygote

tanned egg

egg with a hard inert shell, formed by sclerotin, a mixture of quinone and proteins

tentaculoplerocercoid

See preferred term: plerocercus

tetrafossate scolex

See preferred term: acetabulate scolex

tetrathyridium

metacestode of Mesocestoides developing in vertebrate host and characterized by invaginated scolex and lack of cercomer Synonym: merocercoid

urocyst

See preferred term: urocysticercoid

urocysticercoid

polycephalic metacestode exhibiting a mycelium-like development from which cysticercoids bud off (from Chervy, 2002) Synonym: urocyst, autotomicrocercus

uterine capsule

envelope surrounding single egg and situated externally to outer shell or aggregation of eggs and having an origin from uterine wall, either in gravid uterus or in environment

uterus

organ of the female reproductive system, connected with the ootype by the uterine duct, storing fertilized eggs and providing nutrients and protection during the development

vegetative reproduction

See preferred term: budding

velum

posterior part of a proglottis, overlapping subsequent proglottis

viviparity

mode of embryonic development, in which the embryo, without any protective envelope, develops in utero within the parental organism (modified from Tinsley, 1983)

zygote

diploid cell that results from the fusion of an ovum (female gamete) and a spermatozoon (male gamete)

References

• Bozkov D., 1982. [Helminths life-cycles and their evolution]. Jusautor, Sofia: 119 pp.
• Caira J. N., Jensen K. & Healy C. J., 1999. On the phylogenetic relationships among tetraphyllidean, lecanicephalidean and diphyllidean tapeworm genera. Systematic Parasitology 42: 77-151.
• Euzet L. & Combes C., 1980. Les problèmes de l’espèce chez les animaux parasites. In: Bocquet C., Genermont J., Lamotte M., editors. Les problèmes de l'espèce dans le règne animal. Société Zoologique de France, Paris: 239-285.
• Freeman R. S., 1973. Ontogeny of cestodes and its bearing on their phylogeny and systematics. Advances in Parasitology, 11: 481-557.
• Genov T., 1963. [The cysticercoids of Paricterotaenia paradoxa (Rudolphi, 1802) - Dilepididae Fuhrmann, 1907 found in Allolobophora caliginosa (Sav.) F. trapezoides (A. Dug) - Lumbricidae]. Zoologicheskii Zhurnal, 42: 1578-1579
• Hoberg E., Mariaux J. & Brooks D., 2001. Phylogeny among the orders of Eucestoda (Cercomeromorphae): Integrating morphology, molecules and total evidence. Systematics Association Special Volume Series 60: 112-126.
• Odening K., 1976. Conception and terminology of hosts in parasitology. Advances in Parasitology. 14: 1-93.
• Slais J., 1973. Functional morphology of cestode larvae. Advances in Parasitology, 11: 395-480.
• Swiderski Z. & Xylander W. E. R., 2000. Vitellocytes and vitellogenesis in cestodes in relation to embryonic development, egg production and life cycle. International Journal for Parasitology 30: 805-817.
• Tinsley R. C., 1983. Ovoviviparity in platyhelminth life-cycles. Parasitology 86: 161-196.
• Wardle R. A. & McLeod J. A., 1952. The zoology of tapeworms. University of Minnesota Press, Minneapolis: 780 p.