PORT PHILLIP BAY

Hydroid

Enlarge image of Hydroid

Hydroid

Diphasia subcarinata (Busk, 1852)

Taxonomy

Cnidaria : Hydrozoa : Conica : Sertulariidae

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.
Colony erect, simple or pinnately branched, hydrothecae opposite or alternate, tubular, base attached to stem, expanding from base to spout-shaped margin, operculum of one flap, gonotheca often covered in spines. Diphasia is a genus with about 30 known species worldwide. Only one species, Diphasia subcarinata is common in southern Australia.

Species identification.
Stems simple, monosiphonic, unbranched, arising at a creeping hydrorhiza. Hydrothecae opposite on stem, long, tubular, upper half bent outwards, expanding in diameter towards margin, a distinct angular ridge running down the front of the hydrotheca from aperture to base; aperture with three large lobate cusps. Gonothecae borne in a row along stem, balloon-shaped, covered in short spines. Colour: purplish-brown. Up to 5 cm high.

Taxonomy

Phylum:: Cnidaria
Class:: Hydrozoa
Subclass:: Leptothecatae
Order:: Conica
Family:: Sertulariidae
Genus:: Diphasia
Species:: subcarinata

General Description

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

Biology

Colonies of this species grow throughout the year, and are fertile in spring to late summer.

Habitat

Among holdfasts of seaweed and on sponge in sheltered oceanic waters.

Reefs

Distribution guide

New Zealand and southern Australia.

Species Group

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

Global Dispersal

Recorded in Australia

Identify

Hydroids

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.

Cite this page as:
Watson, J., 2011, Hydroid, Diphasia subcarinata, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 09 Jun 2025, http://136.154.202.208:8098/species/7101

Text:

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