Mosquito worm 

Pionosyllis sp. 2

View scientific description and taxonomy

Scientific Details

Family level description.
Syllidae are extremely common and diverse marine worms which have no common name but might easily be termed "mosquito worms" since their primary adaptation is to have mouthparts comprising a single piercing tooth (trepan) and a muscular gizzard (proventriculus) which are used to pierce and suck out the contents of hydroids, bryozoans and other encrusting prey organisms. The proventriculus has regular transverse bands and is often visible through the body wall and serves to immediately recognise members of the family. The prostomium has a pair of palps and a pair of antennae, sometimes with an additional median antenna. Chaetae often include short-bladed compound forms with a distinctly bidentate tip.

Species level technical description.
Adult size small, Usually less than 10mm in length, or large, usually greater than 10mm in length. Body shape cylindrical. Reproduction method epigamous reproduction. Palps free to base (separate) or palps fused at base, shorter than prostomium or subequal to prostomium. Ocular spots or ocelli present, or absent. Antennae present, slender and cirriform, smooth, or at most, wrinkled or articled, jointed or beaded, median antenna longer than lateral antennae. Tentacular cirri present, two pairs. Eversible pharynx straight or folded, with tooth/teeth, with single large mid-dorsal tooth, situated anteriorly on, or very near, pharynx rim; Anterior margin of smooth (sometimes with soft papillae). Nuchal organs as small projecting lobes. Segmental ciliary bands absent. Dorsal cirri present on all chaetigers, smooth and cirriform or digitiform or articled, jointed, or beaded, longer anteriorly or the length alternates on each successive chaetiger from long to short. Ventral cirri present, all short (shorter or subequal to parapodia length). Aciculae present, or absent. Chaetae simple and composite. Bayonet-shaped simple chaetae absent. Composite chaetae falcigerous. Superior falcigers; anteriorly unidentate, or bidentate; Inferior falcigers; anteriorly unidentate, or bidentate; posteriorly unidentate, or bidentate; Inferior falcigers; posteriorly unidentate, or bidentate; Falciger blades smooth margin, or serrated or spinulose. Smooth claw-like unidentate falcigers absent.



General Description

In members of this genus there are spherical, inflated ventral cirri on anterior segments. This species is easily recognised by the uniform bright red colouration, interrupted only by a conspicuous white patch immediately behind the prostomium and two rows of small white dorsal dots (one pair of dots per segment). Body up to about 6 cm long.


There are at least 100 species of Syllidae known from Australia and taxonomists are currently describing more species. Most species will require observation of chaetal structures at high magnifications before their identity can be confirmed. Myrianida sp. is one of a number of species now being described by taxonomists.


Often found under rocks and among holdfasts in Port Phillip Bay and other similar coastal habitat, inshore and continental shelf.


Distribution guide

Southern Australia.

Species Group

Worms Mosquito worms


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

Water Column

On or near sea floor

Max Size

6 cm



Commercial Species


Global Dispersal

Native to Australia

Species Code

sp. 2


Conservation Status

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


article author Wilson, R.

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


Cite this page as:
Wilson, R., 2011, Mosquito worm, Pionosyllis , in Taxonomic Toolkit for marine life of Port Phillip Bay, Museum Victoria, accessed 15 Jul 2020,

Text: creative commons cc by licence