PORT PHILLIP BAY


Hydroid 

Synthecium patulum (Busk, 1852)

View scientific description and taxonomy

Scientific Details

Genus level detail.
Hydroids with tubular hydrothecae into which the hydranth can be fully withdrawn. Hydrothecae attached to stem or branch for part of length. Margin of hydrotheca circular without an operculum. Gonophores with eggs and sperm, protected by a gonotheca that grows from inside the hydrotheca. Although Synthecium is not a common genus several species notable for their colour are widely distributed in moderately deep water around Australia.

Species identification.
Colonies comprising tufts of stiffly erect pinnate stems. Stems monosiphonic Hydrocladia alternate, standing out almost perpendicular to stem. Hydrothecae opposite on stem and hydrocladia, two on each internode, tubular, adnate (attached) for two-thirds of length then bent outwards, margin circular. Gonothecae ovoid, borne on lower stem and branches, growing out of aperture of a hydrotheca, slightly flattened and deeply ridged with a tubular terminal neck. Colour: purple. Up to 5 cm high.

Taxonomy

Phylum:
Cnidaria
Class:
Hydrozoa
Subclass:
Leptothecatae
Order:
Conica
Family:
Syntheciidae
Genus:
Synthecium
Species:
patulum

General Description

Colony of individual polyps (hydranths) joined by root-like network of tubular stolons at the base. Colony shape is feather-like (pinnate). Colour: purple. Up to 5 cm high.

Biology

Colonies may grow over several years and are fertile in summer. They are common in tidal channels in Port Phillip and Western Port Bays.

Habitat

On pebbles and old shell in good current flow.

Reefs

Distribution guide

Southern Australia.

Species Group

Hydroids

Depth

Shallow (1-30 m)

Water Column

On or near sea floor

Max Size

5 cm

Diet

Plankton or Particles

Harmful

Generally not harmful but still able to sting bare skin.

Commercial Species

No

Identify

Conservation Status

  • DSE Advisory List : Not listed
  • EPBC Act 1999 : Not listed
  • IUCN Red List : Not listed

Author

article author Watson, J.

Jan Watson is a consultant with expertise in hydroid taxonomy.

citation

Cite this page as:
Watson, J., 2011, Hydroid, Synthecium patulum, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 25 Feb 2025, http://136.154.202.208:8098/species/7109

Text: creative commons cc by licence