Family OWENIIDAE Rioja, 1917

Oweniidae

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Family OWENIIDAE Rioja, 1917

Sand Worm (in reference to their sand encrusted tubes)

Compiler and date details

Jan 2011 - P. Hutchings & M. Yerman, Australian Museum, Sydney, New South Wales, Australia

25 July 2003

Introduction

Oweniids are filter and deposit-feeding polychaetes that live in characteristic tubes of cemented sand grains and shell fragments that are considerably longer than the animal itself. They are frequently found still within their tubes in preserved benthic samples. Oweniids are often reported from moderate depths on the continental slope, but appear not to be common in abyssal depths. They may have a crown (feeding and respiratory in function) or this may be absent. The segments of oweniids are very elongate, especially near the anterior end which in the most commonly encountered genus, Owenia, carries a short crown of tentacles.

Figures of 5 genera and 5 species were given by Beesley et al. (2000: App. 1) for representation of the family in Australian waters, and 5 genera and 30 species worldwide. This database inlcudes the single described species (Owenia fusiformis) from Australia, however, the other 4 genera are present in Australia as well but do not have described species.

Until recently, one oweniid, Owenia fusiformisi, was regarded as having a cosmopolitan distribution, but examination of the neuropodial uncini using SEM has revealed a complex of sibling species and these are also being confirmed using molecular techniques (Michel Bhaud and his co-workers, personal communication). Description of new Australian species in this complex is imminent.

In a recent study of the phylogeny of Oweniidae, based on morphological data, Capa et al. (2012) confirmed monophyly of the family and revised the taxonomy of Australian representatives, describing four new species, adding 3 genera to the Australian faunal list and providing a key to species. Capa et al. (2012) also listed an unidentified species of the genus Myriowenia however this species remains undescribed and the genus is not included here.

Diagnosis

General features. Body shape vermiform; segments numerous (more than about 15); segments strongly elongate in midbody; elongate body segments with distinct (but truncate) notopodia and neuropodial tori (neuropodia with dense fields of very small hooks); regionation absent. Pygidium simple ring or cone, or with multiple digitate lobes. Pygidial appendages absent, or present; one pair of cirri.
Head & head structures. Head discrete and compact, dorsal to mouth, or comprising a radiolar crown around mouth (Owenia only; actually a ciliated lobe that resembles a radiolar crown). Prostomium rounded to oval (anteriorly truncate). Eyes absent, or present; one pair; situated on peristomium. Palps absent, or paired; longitudinally grooved; dorsolateral. Nuchal organs absent. Peristomial ring single.
Pharynx & pharyngeal apparatus. Foregut a ventral pharyngeal organ; dorsolateral ciliated folds present.
Body segments & parapodia. First segment chaetigerous. First chaetiger with notochaetae only. Parapodia biramous with parapodial lobes absent or low; notopodial lobes represented by at least one chaetal lobe; neuropodial lobes low ridges (tori) (throughout). Dorsal cirri absent. Ventral cirri absent. Branchiae absent.
Chaetae. Notochaetae present. Aciculae absent. Capillary chaetae hair-like; smooth, or spinose. Spines absent. Hooks present; unprotected; occur in many chaetigers but only one ramus (neuropodia only).
Tube & burrow. Tube translucent, chitin-like (covered with overlapping sediment grains).

The above description was generated from: 'C.J. Glasby & K. Fauchald (2002 onwards). POLiKEY. An information system for polychaete families and higher taxa: Version 1: September 2002.'
(See ABRS website: Online Resources: Polikey, for Version 2, released June 2003)