Systematics of Systematics of HydrozoaHydrozoa

Phylogenetic relationships of classes within the Phylum Cnidaria

Classification of HydrozoaClassification of Hydrozoa

Order Limnomedusae Order Limnomedusae TrachymedusaeTrachymedusae Narcomedusae Narcomedusae ActinulidaeActinulidae AnthomedusaeAnthomedusae LeptomedusaeLeptomedusae SiphonophoraeSiphonophorae

Order LimnomedusaeOrder Limnomedusae

Craspedacusta sowerbyi

Olindias formosa: “Flower hat jelly”

Gonionemus

Limnomedusae

Gonionemus vertens

Adhesive pad

nematocysts

Gonads on radial canal

Order Trachymedusae Medusa bell hemispherical to higher than broad, margin not lobed, with ring of thickened tissue studded with nematocysts, mostly with 8 radial canals, 4, 6 or more than 8 also possible, gonads on radial canals; Common in open sea and deeper waters.

Geryoniidae- gastric peduncle, 4 radial canals

Rhopalonematidae- small manubrium, 8 radial canals, distinct lips

Order Narcomedusae

Aeginidae: Aeginopsis

Gastric pouches

Solmarisidae: Peganta- without gastric pouches

Order Narcomedusae

otoporpae

peronia

Cuninidae: Cunina peregrina- same no. of gastric pouches and tentacles

OtohydridaeUmbrella much reduced and

fused to manubrium; one ring of marginal tentacles of

two kinds: adhesive and armed ones; with or without a brood pouch (= subumbrellar

cavity); hermaphroditic, viviparous.

Order Actinulida

Order AnthomedusaeOrder Anthomedusae

Hydridae: Hydra

Hydra viridis

Chlorohydra viridissima

Order Anthomedusae: Hydractinia echinata

Order Anthomedusae: Order Anthomedusae: Tubularia indivisaTubularia indivisa

With outer and inner cluster of tentacles; unbranched stem

Bougainvillea ramosa

Order Anthomedusae

Order Anthomedusae: Order Anthomedusae: Stylaster venustus Stylaster venustus (Purple (Purple hydrocoral)hydrocoral)

Halocordylidae: Pennaria disticha

Eudendriidae: Eudendrium racemosum

Order Anthomedusae (Hydromedusae)

Order Anthomedusae

Stylaster californicus

Order LeptomedusaeAequoreidae: Aequorea victoria

Sertularia argentea

Order Leptomedusae

Order LeptomedusaeOrder Leptomedusae

Plumularia setacea 

Fine feather-like hydroid

Main stem is brown in colour

Gonothecae amphora-shaped

Order LeptomedusaeOrder Leptomedusae

Aglaophenia tubulifera 

corbulae

Aglaophenia pluma 

Obelia sp.

Order LeptomedusaeOrder Leptomedusae

Leptomedusae Obelia geniculata 

Zigzag, unbranched

stems arising from

a basal rhizome

Obelia longissima

Order SiphonophoraeOrder Siphonophorae

Siphonophorae: Siphonophorae: Suborder Suborder PhysonectaePhysonectae

Apical pneumatophore

Nectophore

Siphonophorae: Siphonophorae: Suborder Suborder CalycophoraeCalycophorae

Without pneumatophore, highly polymorphic, with a nectosome typically formed by one or two nectophores.

Siphonophorae: Siphonophorae: Suborder Suborder CystonectaeCystonectae

With a budding zone on only one side of the base of the aboral float; without bracts and without swimming bells; tentacles are generally simple

Order Siphonophora: Cystonectae/Physalia physalis