PORT PHILLIP BAY


Hydroid 

Sertularia tenuis Bale, 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.
Colony branched or unbranched, monosiphonic or polysiphonic, hydrothecae borne on stem and branches in two longitudinal rows, margin of hydrotheca with two lateral cusps, gonotheca usually barrel-shaped containing gonophores with eggs and sperm. Sertularia is a common southern Australian genus, species of which often form large conspicuous colonies.

Species identification.
Hydrorhiza creeping over substrate, stems monosiphonic, unbranched, a distinct hinge joint at base. Hydrocladia alternate, hydrothecae in opposite pairs on stem and hydrocladia, tubular, sides in contact, narrowing to margin. Margin with a pair of lateral cusps, operculum tent-shaped. Gonothecae attached to stem, pear-shaped, surface smooth, terminal aperture circular, surrounded by a low collar with an internal row of denticles. Colour: dark grey to black. Up to 2 cm long.

Taxonomy

Phylum:
Cnidaria
Class:
Hydrozoa
Subclass:
Leptothecatae
Order:
Conica
Family:
Sertulariidae
Genus:
Sertularia
Species:
tenuis

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: dark grey to black. Up to 2 cm long.

Biology

Colonies of this species appear in early spring to autumn.

Habitat

On algae and invertebrates, especially brown seaweeds in shallow, sheltered water.

Reefs

Distribution guide

New Zealand and southern Australia.

Species Group

Hydroids

Depth

Shallow (1-30 m)

Water Column

On or near sea floor

Max Size

2 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

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, Sertularia tenuis, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 13 Jan 2025, http://136.154.202.208:8098/species/7137

Text: creative commons cc by licence