PORT PHILLIP BAY


Hydroid 

Symplectoscyphus subdichotomus (Kirchenpauer, 1884)

View scientific description and taxonomy

Scientific Details

Family level detail.
Colonies may be unbranched or branched and always with two rows of hydrothecae on opposite sides of stem, attached to stem and branches by part of their length. Hydrothecae bilaterally symmetrical, usually with a cuspate aperture with a segmented operculum. Gonophores are sporosacs female producing eggs and the male producing sperm, and protected by a gonotheca. The family Sertulariidae includes many genera and species and is known is a world-wide ranging from the tropics to arctic seas. They occur in all habitats from the intertidal zone to the deepest ocean and are very abundant in cool temperate seas southern Australia. Species range from small simple stems with a few hydrothecae to large, complexly branched pinnate colonies with hundreds of hydrothecae.

Genus level detail.
Stems simple or branched, hydrothecae alternate, tubular, with three marginal cusps, operculum of hydrotheca pyramidal, gonotheca barrel-shaped, deeply ridged with distal neck. Species of Symplectoscyphus are widespread in southern Australian seas although some are small and cryptic and therefore not easily seen. The three marginal cusps of the hydrotheca are distinctive.

Species identification.
Colonies comprise tufts of loosely branched, often entangled stems from a hydrorhiza winding over the substrate. Stems monosiphonic, hydrothecae alternate, adnate most of length, facing upwards at an acute angle to branch, body cylindrical, margin with three cusps separated by deep embayments, operculum pyramidal. Gonothecae borne thickly on lower branches, barrel-shaped, deeply ridged, terminal aperture funnel-shaped and slightly displaced to one side. Perisarc of colony thick. Colour: buff to dark greyish-brown, sometimes covered by pink coralline alga. Up to 5 cm high.

Taxonomy

Phylum:
Cnidaria
Class:
Hydrozoa
Subclass:
Leptothecatae
Order:
Conica
Family:
Sertulariidae
Genus:
Symplectoscyphus
Species:
subdichotomus

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: buff to dark greyish-brown, sometimes covered by pink coralline alga. Up to 5 cm high.

Biology

These hydroids are widespread in southern Australian seas although some are small and cryptic and therefore not easily seen. Their colonies grow throughout the year, and are fertile in winter.

Habitat

Tidal channels and reef in areas of strong 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, Symplectoscyphus subdichotomus, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 29 Jun 2017, http://portphillipmarinelife.net.au:8098/species/7110

Text: creative commons cc by licence