PORT PHILLIP BAY


Hydroid 

Amphisbetia minima (Thomson, 1879)

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 branched or unbranched with two close-set rows of tubular hydrothecae, apertural margin of hydrotheca with two opposite, sharply pointed cusps. Several species of Amphisbetia are common southern Australia, some are small, simple stems and others are taller, pinnately branched stems.

Species identification.
Colonies comprising many simple, unbranched stems growing from a wandering tubular hydrorhiza. Stem with paired of opposite hydrothecae, bases of hydrothecae touching across stem, body bent outwards, apertural margin with two long, opposite cusps. Gonothecae large, ovoid, flattened, borne on hydrorhiza or lower stem region, aperture terminal, circular, surrounded by a short collar and flanked by a pair of blunt spines. Colour: buff to yellow, gonophores cream to yellow. Up to 1 cm high.

Taxonomy

Phylum:
Cnidaria
Class:
Hydrozoa
Subclass:
Leptothecatae
Order:
Conica
Family:
Sertulariidae
Genus:
Amphisbetia
Species:
minima

General Description

Colony of individual polyps (hydranths) joined by root-like network of tubular stolons at the base. Colony shape is simple stems. Colour: buff to yellow, gonophores cream to yellow. Up to 1 cm high.

Biology

This species is a very common epiphyte, often growing on red and brown algae. Colonies grow from spring through summer.

Habitat

On red or brown seaweeds.

Reefs

Distribution guide

Southern Australia.

Species Group

Hydroids

Depth

Shallow (1-30 m)

Water Column

On or near sea floor

Max Size

1 cm

Diet

Plankton or Particles

Harmful

Generally not harmful but still able to sting bare skin.

Commercial Species

No

Species Code

MoV 3473

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, Amphisbetia minima, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 25 Feb 2025, http://136.154.202.208:8098/species/7096

Text: creative commons cc by licence