Family HESIONIDAE

Hesionidae

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Family HESIONIDAE

Compiler and date details

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

15 July 2003

Introduction

Hesionids range from large to very small interstitial worms. They occur widely in marine and estuarine environments, but are usually not abundant in benthic samples unless interstitial habitats are sampled. Most hesionids are thought to be carnivores and either actively search out prey, or scavenge dead food. Some hesionids are commensals with other invertebrates including other polychaete families. Like most predatory polychaetes, they do not make permanent burrow systems. Carefully preserved specimens have numerous long anterior and dorsal cirri, but these are very fragile and typically are missing on preserved specimens.

Figures of 6+ genera and 10+ species were given by Beesley et al. (2000: App. 1) for representation of the family in Australian waters, and 22 genera and ~150 species worldwide. This database includes 13 species from 9 genera. Hesionides and Microphthalmus (both interstitial forms), were removed from the Hesionidae by Pleijel & Dahlgren (1998); however, those authors made no new family assignment so, provisionally, they are listed here with Hesionidae.

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

Database Notes

Proof read against Day & Hutchings 1979 by RW; no subsequent records added.
Checked against DELTA CD 2003 by RTJ.

Diagnosis

Hesionides & Microphthalmus are recognised as forming one (or two) groups separate from Hesionidae. Descriptions of both groups are provided separately:

Hesionidae sensu stricto
General features. Body shape vermiform; segments numerous (more than about 15); regionation absent. Pygidium simple ring or cone. Pygidial appendages present; one pair of cirri, or one pair of cirri and single medial papilla.
Head & head structures. Head discrete and compact, dorsal to mouth. Prostomium rounded to oval (anteriorly truncate). Facial tubercle absent, or present. Eyes present (rarely absent); two pairs; situated on prostomium; compound with lenses. Prostomial antennae present; paired arising anterolaterally, or include paired anterolateral ones and single medial one; smooth. Palps paired, or absent (rarely); unarticulated, or bi-articulated; ventrolateral. Nuchal organs indistinct paired dorsolateral patches. Peristomial ring absent.
Pharynx & pharyngeal apparatus. Foregut a muscular axial pharynx; without jaws, or with one pair of lateral jaws; plate-like, or fang-like; with a single tooth, or without teeth; surface smooth; distal ring of papillae present (reduced in some taxa).
Body segments & parapodia. Enlarged dorsal cirri and cirrophores on segment 1-3, 1-4 or 1-5; enlarged ventral cirri and distinct cirrophores on segment 1-3 or 1-4; internal aciculae present in at least some enlarged anterior cirri. First chaetiger equals segment 4 or 5 (rarely 3), with neurochaetae only. Parapodia uniramous throughout, or biramous with prominent neuropodial lobes; notopodial lobes represented by at least one chaetal lobe, or absent; neuropodial lobes represented by at least one chaetal lobe. Dorsal cirri more-or-less cirriform. Ventral cirri present, distally or subdistally inserted on neuropodium. Branchiae absent.
Chaetae. Notochaetae absent, or present. Aciculae present; in both dorsal and ventral positions (=noto- and neuroaciculae). Capillary chaetae hair-like; hirsute-serrate. Forked notochaetae absent, or present; furcate type; tines distinctly unequal in length. Spines absent. Hooks absent (present in the notopodia of one genus). Compound chaetae present; appendage distally curved (=falcate); appendage not canaliculated; appendage without hoods or guards; joint distinctly asymmetrical (=heterogomph); joint effected by ligament; shaft tapering slightly or evenly thick from emergence to joint; shaft with camerated core. Compound falcigers present all chaetigers.
Tube & burrow. Tube absent or unconsolidated. Burrow traces absent.

Hesionides & Microphthalmus
General features. Body shape vermiform; segments numerous (more than about 15); regionation absent. Pygidium lamellate lobe(s) (single or bilobed). Pygidial appendages present; one pair of cirri.
Head & head structures. Head discrete and compact, dorsal to mouth. Prostomium rounded to oval (anteriorly truncate). Eyes absent, or present; one pair; situated on prostomium; without lenses. Prostomial antennae present; paired arising anterolaterally, or include paired anterolateral ones and single medial one; smooth. Palps paired (resemble antennae); unarticulated; ventrolateral. Nuchal organs indistinct paired dorsolateral patches. Peristomial ring absent.
Pharynx & pharyngeal apparatus. Foregut a muscular axial pharynx; distal ring of papillae present.
Body segments & parapodia. First segment with tentacular cirri. Enlarged ventral cirri on segment 1-2 or 1-3. First chaetiger equals segment 3 or 4, with both notochaetae and neurochaetae. Parapodia uniramous throughout; notopodial lobes absent; neuropodial lobes represented by at least one chaetal lobe. Dorsal cirri more-or-less cirriform. Ventral cirri present, cirriform or tapering. Branchiae absent.
Chaetae. Notochaetae present. Aciculae present; in both dorsal and ventral positions (=noto- and neuroaciculae). Capillary chaetae hair-like (often sickle-shaped); hirsute-serrate. Forked chaetae absent. Spines absent. Hooks absent. Compound chaetae present; appendage distally curved (=falcate); appendage not canaliculated; appendage without hoods or guards; joint distinctly asymmetrical (=heterogomph); joint effected by ligament(s); shaft tapering slightly or evenly thick from emergence to joint; shaft without distinct core. Compound falcigers present in most or all chaetigers.

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)