Family ORBINIIDAE

Orbiniidae

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Family ORBINIIDAE

Compiler and date details

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

25 July 2003

Introduction

Orbiniids are burrowing deposit feeders that do not make permanent tubes. They are common on tidal flats and sometimes attain dense populations in sediments of mixed sands and muds. Their bodies are distinctive with a well-developed, smooth, firm, flattened thoracic region and a long, tapering and fragile abdominal region bearing branchiae and parapodial lobes that give a ragged appearance. The prostomium is smooth without any sensory appendages or palps.

The most important modern review of orbiniid systematics is by Hartman (1957), who redefined all the genera. She was also the first to create the 2 subfamilies: Orbiniinae and Protoariciinae. None of the later works (Day, Mackie and Solis-Weiss & Fauchald) substantially alter the system established by Hartman.

Figures of 6 genera and ~25 species were given by Beesley et al. (2000: App. 1) for representation of the family in Australian waters, and 17 genera and ~150 species worldwide. This database includes 27 species from 9 genera.

See Glasby (2000) for detailed treatment of the family.

Database Notes

proof read against Day & Hutchings 1979 by RW;
Day, 1977 and Mackie, 1987 updates by RJ
checked against DELTA CD 2003 by RTJ

Diagnosis

General features. Body shape vermiform; segments numerous (more than about 15); regionation absent (rarely), or present, comprising distinct thorax and abdomen; regions demarcated by laterally-directed thoracic parapodia and dorsally-directed abdominal parapodia. Ventral groove absent. Pygidium simple ring or cone. Pygidial appendages present; one pair of cirri, or four cirri.
Head & head structures. Head discrete and compact, dorsal to mouth. Prostomium conical, tapering to slender tip. Eyes absent, or present; one pair; situated on prostomium; without lenses. Palps absent. Nuchal organs indistinct paired dorsolateral patches. Peristomial ring double, or single.
Pharynx & pharyngeal apparatus. Foregut a non-muscular axial proboscis, or a ventral pharyngeal organ (eversible part is either lobate or branching); dorsolateral ciliated folds absent, or present.
Body segments & parapodia. First segment chaetigerous. First chaetiger with both notochaetae and neurochaetae. Parapodia biramous with parapodial lobes absent or low (lobes may be more prominent posteriorly); notopodial lobes represented by at least one chaetal lobe; neuropodial lobes represented by at least one chaetal lobe. Interramal fleshy process absent, or present, cirrus-like (probably a non-retractile lateral organ). Lateral organs present. Dorsal cirri absent. Ventral cirri absent. Branchiae present (rarely absent); arise from dorsum; occur on at least some chaetigerous segments; digitiform (may be flattened).
Chaetae. Notochaetae present. Aciculae present; in dorsal position (=notoaciculae) (posterior parapodia only). Capillary chaetae hair-like, or sharply bent; hirsute-serrate, or crenulate. Forked chaetae absent, or present; lyrate type; tines more or less equal in length. Spines present in most or all chaetigers; in both notopodia and neuropodia; slightly curved and more-or-less smooth, or harpoon or arrow-shaped with reverse barbs, or sharply bent (=geniculate) or curved (may be smooth or ribbed). Hooks absent, or present (rarely); unprotected; occur in many chaetigers but only one ramus (abdomen only).
Tube & burrow. Tube absent or unconsolidated. Burrow traces absent.

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)