Suborder Filifera Kühn, 1913

diagnosis

Hydroid colonial, always with filiform tentacles except rarely in some dactylozooids. Medusa gonads on the walls of the manubrium, sometimes also on basal extensions of the manubrium, manubrium usually with tetra-radial symmetry, either trough cruciform lips or manubrial tentacles. The cnidome never includes stenoteles.

higher classification

Metazoa, Cnidaria, Medusozoa, Hydrozoa, Anthoathecata

References

Bouillon, J. 1985. Essai de classification des hydropolypes-hydroméduses (Hydrozoa-Cnidaria). Indo Malayan Zoology 2: 29-243.

Bouillon, J., & Boero, F. 2000b. Synopsis of the families and genera of the Hydromedusae of the world, with a list of the worldwide species. Thalassia Salentina 24: 47-296.

Harris, V. A. 1990. Sessile animals of the sea shore. Chapman & Hall, London, New York etc 1-379. (polyp of Australomedusa)

Schuchert, P. 1996. The marine fauna of New Zealand: athecate hydroids and their medusae (Cnidaria: Hydrozoa). New Zealand Oceanographic Institute Memoir 106: 1-159.

Classification

Family Australomedusidae

Hydroids stolonal, hydranth naked, with a single row of filiform oral tentacles near the middle of the body, hypostome extensible. Medusa with simple mouth lips; four or exceptionally eight simple radial canals; perradial tentacles grouped into four clusters, with or without four groups of interradial tentacles or four interradial rudimentary bulbs; gonads on manubrium or on manubrium and partially on proximal part of radial canals; with or without ocelli.

Family Balellidae 

Hydroid colonies erect, branched, polysiphonic. Hydranths polymorphic. Gastrozooids with club-shaped body and with two well separated whorls of tentacles. Gonozooids with either one tentacle or none, with one whorl of gonophores. Dactylozooids small, tentacle- like. Gonophores released as immature medusae. Young medusa with four filiform tentacles, manubrium simple.

Family Bougainvilliidae

Hydroids solitary or colonial; hydranths stolonal, branched, or rarely sessile, arising from creeping hydrorhiza; erect colonies monopodial with terminal hydranths, stems monosiphonic or polysiphonic; perisarc terminating either at base of hydranths or forming a pseudohydrotheca; hydranths with one or more whorls of filiform distal tentacles, tentacles confined to narrow zone below hypostome; gonophores free medusae or fixed sporosacs developing either on hydrocauli, stolons, or blastostyles.
Medusae bell-shaped; mouth circular, with simple or dichotomously branched oral tentacles inserted distinctly above mouth rim, ending in nematocyst clusters; four radial canals and circular canal; marginal tentacles solid, contractile, either solitary or in clusters, borne on 4, 8, or 16 tentacular bulbs; gonads on manubrium, either forming a continuous ring or in adradial, interradial, or perradial position; adaxial ocelli absent or present. . 

Family Bythotiaridae

Hydroids living in the prebranchial cavities of ascidians, unbranched, naked, arising from fleshy, plate-like hydrorhiza; hydranths with indistinct, naked pedicel, up to five irregular whorls of filiform tentacles; medusae buds arising from polyps at junction to pedicel. Medusa with four lips, simple or crenulated; with or without centripetal canals; gonads on manubrial wall, adradial or interradial, simple or folded; four or eight radial canals, simple or branching; four, eight, or more hollow marginal tentacles, each a large terminal swelling, basal portion of tentacles often adnate to exumbrella; marginal bulbs highly reduced or absent; with or without rudimentary or dwarf solid tentacles; rarely with abaxial ocelli. 

Family Cytaeididae

Hydroids sessile, usually not polymorphic, hydrorhiza reticulate, covered by perisarc, without spines; hydranth with one whorl of filiform tentacles below conical hypostome, naked, at base of hydranth perisarc forming a cup-shaped collar, sometimes hydranths of two sizes, smaller ones acting as dactylozooids; gonophores on hydrorhiza, developing into free medusae, or medusoids with four radial canals, or to fixed sporosacs. Medusa umbrella bell-shaped; manubrium bulbous; mouth simple, circular, with four or more unbranched oral arms, either on or above mouth rim; four radial canals and circular canal; four or eight solid marginal tentacles; gonads interradial or encircling manubrium; no ocelli. 

Family Clathrozoellidae

Hydroids colonial, polymorphic, forming erect and branched or unbranched stems resulting from the addition of successive tubular pseudohydrothecae. Pseudohydrotheca formed by fused, stolon-like perisarc tubules with a core of coenosarc. Each pseudohydrotheca sitting on lower one, floor consisting of external wall of lower pseudohydrotheca; without direct communication between successive pseudohydrothecae. External surface of tubules provided with nematothecae. One hydranth per pseudohydrotheca, without distinct pedicel (sessile), hypostome conical, surrounded by a whorl of filiform tentacles. Gonophores sessile sporosacs arising directly from floor of pseudohydrotheca; thus without gonozooids. Cnidome comprises microbasic mastigophores, microbasic euryteles, desmonemes and haplonemes.

Family Eucodoniidae

Hydroid: unknown. Medusae without pointed apical projection, exumbrella without nematocyst tracks or clusters, with gastric peduncle; manubrium tubular; mouth quadrangular, with four inconspicuous nematocyst-clusters, with medusa budding on manubrium wall; gonads encircle manubrium without radial interruptions; four radial canals and circular canal present; four small perradial marginal bulbs and four tentacles; tentacles with a single terminal swelling; no ocelli; cnidome comprises microbasic euryteles and desmonemes.

Family Eudendriidae

Hydroid colony sometimes stolonal, but mostly with erect branched stem, arising from a creeping hydrorhiza; stem, branches and hydranth pedicels covered by perisarc, sometimes enveloping also lower half of hydranth in a cup-like process; hydranth large, urn-shaped with undercut hypostome, one or more whorls of solid filiform tentacles immediately below it, hydranth body sometimes with basal, tentacle-like protrusion; near base of hydranth epidermal groove from which periderm is secreted, sometimes with a nettle ring immediately above groove; reproduction by fixed sporosacs borne on the hydranth body below the tentacles; reproductive hydranth often reduced to blastostyle, male gonophores usually with several chambers in linear series, female gonophores initially with curved spadix, each spadix holding a single egg.

Family Hydractiniidae

Hydroids sessile, hydranths often polymorphic, usually epizootic; hydrorhiza either perisarc-covered stolonal tubes, or as an encrusting mat resulting from the coalescence of the stolonal system, either covered by a common layer of perisarc or with naked coenosarc; in some genera the hydrorhizal mat is reinforced by a calcareous skeleton; frequently with chitinous or calcareous spines forming sometimes pillars and branches, sometimes with protective tubes overarching the hydranths; gastrozooids either with one or several whorls of filiform tentacles beneath hypostome, or with scattered tentacles on the upper half of the body, exceptionally with one or two tentacles only; dactylozooids, when present, with no tentacles. Gonophores typically borne on gonozooids, these with one or more whorls of filiform tentacles or without tentacles and mouth (= blastostyles), giving rise to fixed sporosacs, eumedusoids, or free medusae.
Medusa umbrella more or less bell-shaped, with or without slight apical process; manubrium tubular to sac-shaped, not extending beyond bell margin; with or without gastric peduncle; mouth with four simple or branched oral lips drawn out to form arms with terminal nematocyst clusters; four, eight, or more, solid, marginal tentacles, tentacles not in groups; four radial canals and circular canal; gonads on manubrium, interradial, sometimes extending along basal, perradial protrusions of the manubrium; with or without ocelli.  

Family Magapiidae

Hydroid: unknown. Medusa: umbrella lobed, divided by peronial grooves or similar structures; four radial canals; ring canal obliterated; tentacles solid, inserted  above bell margin; alternating with tentacles there may be narrow exumbrellar cnidocysts bands or ciliated fields; manubrium simple, quadrangular, tubular or conical; mouth opening quadrangular to circular; gonads in four masses on the manubrium or as epidermal lining of interradial pockets of the manubrium; no sense organs; cnidome: macrobasic mastigophores or macrobasic euryteles. ( see note on classification)

Family Heterotentaculidae

Hydroid: unknown. Medusa umbrella with apical projection. Manubrium on gastric peduncle, four unbranched oral filiform tentacles attached above mouth margin, mouth simple, lips indistinct. Marginal tentacles in 8 groups, 4 perradial and 4 interradial, each group with one large tentacle flanked by two small tentacles; large tentacles hollow, without basal swellings, basal part adnate to umbrella and sunk into deep furrows of umbrella margin, adaxial ocellus at base of free portion of each tentacle. Gonads in 8 large adradial pads on manubrium wall. 

Family Niobiidae

Hydroid: unknown. Anthoathecata with two opposite simple and two opposite bifurcated radial canals, so that six canals reach the circular canal; gonads interradial on manubrium; marginal tentacular bulbs developing into medusae; no ocelli, no gastric peduncle, no mesenteries. 

Family Oceaniidae

Hydroids monomorphic or polymorphic, sessile, stolonal, or branched colonies. Gastrozooids bearing filiform tentacles scattered over at least distal third of hydranth body, not concentrated in a narrow band. Gonophores developing either below the hydranth body, or directly on stolons, or from stolonal blastostyles with perisarc-covered pedicels. Gonophores either free medusae or fixed sporosacs. Free medusa, where present, with four mouth lips, mouth margin fringed with numerous spherical nematocyst clusters; four simple radial canals, without centripetal canals, juveniles with four or more tentacles, adults with numerous tentacles, these not grouped, their nematocysts evenly distributed. Ocelli present on adaxial base of tentacles. Gonads on interradial walls of manubrium.

Family Pandeidae

Hydroids usually stolonal, rarely branching; hydranth tentacles filiform, normally in one whorl, exceptionally in two or more whorls, or scattered, or absent; perisarc developed to a variable degree, occasionally forming a pseudohydrotheca or missing completely; reproduction mainly by free medusae, except in some modified genera of questionable affinity. Medusa umbrella high bell-shaped, with or without apical projection; manubrium quadratic, usually large; with or without gastric peduncle; four oral lips, simple, crenulated, or complexly folded; four or exceptionally eight radial canals, often broad and ribbon-like; rarely centripetal canals; with or without mesenteries; gonads either with smooth surface or complexly folded, on manubrium walls in adradial or interradial position, sometimes extending along radial canals, or completely perradial; two or more hollow marginal tentacles; bulbs mostly tapering, elongated, conical; with or without rudimentary tentacles (tentaculae), or marginal warts; with or without abaxial ocelli; cnidome usually containing microbasic euryteles. 

Family Proboscidactylidae 

Hydroids sessile, hydrorhiza fromed by creeping naked stolons, epizooic on tubes sabellid polychaetes; hydranths polymorphic; gastrozooid with rounded hypostome separated from the body by a constriction and with large cluster of nematocysts that is somewhat shifted to one side, two filiform tentacles arising below hypostomial constriction, opposite to nematocyst cluster, thus giving bilateral symmetry; gonozooid and dactylozooid without tentacles, mouthless and smaller than gastrozooid; medusa buds very close to gonozooidal tip. Medusa mostly hemispherical; manubrium with four to six or more radial gastric lobes extending along proximal portions of radial canals; gonads surrounding manubrium and extending on gastric lobes; radial canals branched, obliterated canals sometimes present; usually no circular canal but a circular gastrodermal ring; numerous exumbrellar nematocyst clusters or bands alternating with tentacles; marginal tentacles hollow, with swollen hollow base connected to the lumen of radial canals. Cnidome with or without desmonemes.

Family Protiaridae

Hydroids stolonal, arising from creeping stolons; hydranths on short hydrocaulus; hydrorhiza and hydrocaulus covered by perisarc, which forms a cup at hydranth base; hydranth with one whorl of filiform tentacles, large nematocysts alternating with tentacles; gonophores unknown. Medusa with four developed marginal tentacles arising from large, hollow tentacular bulbs; four simple radial canals and a circular canal, mouth with four simple lips; gonads interradial, with smooth surface; with or without mesenteries; without rudimentary bulbs; margin with or without cirri-like tentacles; exceptionally with ocelli.

Family Ptilocodiidae

Hydroids sessile, hydrorhiza stolonal, reticular or encrusting and covered by naked coenosarc; hydranths polymorphic; gastrozooid without tentacles; dactylozooids with four or more capitate tentacles, sometimes filiform; gonophores on gonozooids or gastro-gonozooids; reproduction by fixed sporosacs, eumedusoids or free medusae. Medusa umbrella more or less bell-shaped; with or without radial exumbrellar furrows; centripetal tracks or exumbrellar rows of refringent spots; with marginal nematocyst ring; marginal tentacles absent or present, solid and  nematocysts concentrated at tips; four radial canals and circular canal; manubrium tubular or bottle-shaped, with mouth arms with terminal nematocyst clusters, gonads adradial or interradial. 

Family Rathkeidae

Medusa bell-shaped, manubrium either with four elongated lips forming simple or branched oral arms with terminal knobs, or perradial unbranched oral tentacles inserted vertically or very oblique at level of mouth margin; immature animals with or without orthogonally arranged interradial medusa buds. With four or eight radial canals and a circular canal. Usually eight bulbs, interradial ones with more than one tentacle, rarely only four bulbs and four tentacles. Ocelli absent. Gonads encircle manubrium completely.
Hydroids (where known) colonial, arising from ramified stolons. Hydranths monomorphic, without pedicel, with one whorl of filiform tentacles. Medusa buds arise from stolons, or more rarely from base of hydranths.

Family Rhysiidae 

Hydroid stolonal or sessile, polymorphic; hydrorhiza tubular, covered with perisarc; gastrozooid naked, columnar, with either one whorl of filiform tentacles or with nematocyst clusters and a few thick filiform tentacles around hypostome; dactylozooids, when present, covered with perisarc up to capitate tip; gonads on hydranth resembling gastrozooid, on one side of the body, no gonophores; male hydranth with 3 or 4 filiform tentacles, female hydrants with or without tentacles and transforming into a sporosac-like structure with the endoderm forming a spadix, one egg, developing into a planula.

Family Stylasteridae

Hydroid colony erect, branched, usually flabellate, more rarely encrusting, with a thick calcareous exoskeleton (coenosteum); polyps polymorphic and retractile; gastrozooids with one whorl of filiform tentacles, exceptionally without tentacles; bottom of gastric cavity with or without an upright pointed or rounded toothed spine (gastrostyle); dactylozooids filiform, without tentacles, with or without dactylostyle; gastrozooids and dactylozooids retractable into special skeletal depressions: gastropores and dactylopores; gastro- and dactylozooids either irregularly distributed over colony, or limited to certain regions of colony, or often arranged in circles (cyclosystems) where one gastrozooid is surrounded by several dactylozooids; gonophores as reduced fixed sporosacs and developed inside vesicles (ampullae) covered by or buried in coenosteum.

Family Trichydridae

Hydroids sessile, stolons covered by thin perisarc; hydranth with a collar-like tube of perisarc at base, with one whorl of filiform tentacles; gonophores unknown. Nematocysts unknown. Medusa without gastric peduncle, mesogloea especially thick in upper part of umbrella; four large folded lips; four radial canals; numerous fine, lateral branched, anastomosing centripetal canals connecting non perradial marginal bulbs to radial canals; gonads interradial; marginal tentacles solid, with triangular marginal bulbs; no ocelli.

Family Tubiclavoididae

Anthoathecata Filifera hydroids, solitary or colonial, with elongate hydranths bearing filiform tentacles scattered over hydranth body, gonophores develop among the tentacles but independent of them. Stolons ramified. Hydrocauli and stolons covered by perisarc. Nematocysts include microbasic euryteles and desmonemes.