PORT PHILLIP BAY


Scaleworm 

Thormora argus (Quatrefages, 1865)

View scientific description and taxonomy

Scientific Details

Family level description.
Polynoidae are predators in which the dorsal cirri of an alternating series of segments are modified to form scales which lie flat covering the top of the worm and make two rows like overlapping tiles on a roof. The scales (elytrae) are typically pigmented and/or pigmented in distinctive, species-specific patterns. The commonly-observed shallow water species are mostly short-bodied, often with a fixed number of segments and elytrae. Anteriorly the prostomium and appendages are varied but generally a a pair of large conical palps and pairs of antennae and tentacular cirri can be seen (although the anterior-most scales usually have to be removed to reveal these structures). The muscular eversible pharynx, if dissected, can be seen to have two pairs of jaws that close in a vertical plane. Chaetae are generally numerous and conspicuous, always simple (compound chaetae are absent) and ornamented with a diverse array of spines, teeth and other gothic ornaments.

Species level technical description.
Elytrae number 12 pairs. Elytra present on chaetigers 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23. Last pair on the expected chaetiger; present to posterior end ( 3 or fewer segments without elytrae); Elytrae covering body completely, or large but leaving middle of dorsum uncovered (anterior dorsum not completely covered by elytrae in large specimens only). Elytral coloration: All elytrae mottled with brown, green or grey pigment, often with a darker central spot. Elytral surface ornamentation present as microtubercles, or present as macrotubercles. Elytral ornamentation similar in all elytrae. Distal end of microtubercles simple; soft-walled. Cylindrical, distally slightly club-shaped. Basic shapes sessile mounds, pustules, cushions, or ovate papillae. Sessile macrotubercles ovate or rounded, sessile (chitinized) papillae. Ovate or rounded chitinized sessile macrotubercles egg-shaped, chitinized tubercles, or sphaerical chitinized papillae covered with spines. Elytral pockets absent. Free margin without papillae (fimbriae). Elytrae flat or undulating.

Taxonomy

Phylum:
Annelida
Class:
Polychaeta
Order:
Phyllodocida
Family:
Polynoidae
Genus:
Thormora
Species:
argus

General Description

In members of this genus there are 12 pairs of elytrae and 26 segments. In Thormora argus the elytrae are covered with large macrotubercles giving a rough appearance, and the elytrae do not quite cover the dorsum which allows glimpses of transverse pigmented bands to be seen down the midline. Body up to about 5 cm long.

Biology

This is probably the most common scale worm in southern Australia in shallow reef habitats such as holdfasts and mussel clumps.

Habitat

Port Phillip Bay and other similar coastal habitat, inshore and continental shelf.

Reefs

Soft substrates

Distribution guide

Southern Australia.

Species Group

Worms Scaleworms

Depth

Shore (0-1 m)
Shallow (1-30 m)

Water Column

On or near sea floor

Max Size

5 cm

Diet

Carnivore

Commercial Species

No

Global Dispersal

Native to Australia

Species Code

MoV 4156

Identify

Conservation Status

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

Author

article author Wilson, R.

Robin Wilson is a Senior Curator of marine invertebrates at Museum Victoria.

citation

Cite this page as:
Wilson, R., 2011, Scaleworm, Thormora argus, in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 19 Sep 2017, http://portphillipmarinelife.net.au:8098/species/11157

Text: creative commons cc by licence