Glyceriformia

Glycera alba, copyright Hans Hillewaert.

Belongs within: Phyllodocida.

The glyceriforms: stabby worms and grabby worms
Published 20 February 2021

Historically, the annelid worms have been considered a difficult group to classify. Whereas most of the recognised families have been fairly well established, higher taxa uniting these families have tended to be a bit on the vague side. Nevertheless, there are some supra-familial groups that can be considered well established, one such group being the Glyceriformia.

Specimen of Goniadidae (head to the right), from NOAA Fisheries.

The glyceriforms are two families of marine worms, the Glyceridae and Goniadidae. More than a hundred species are known in this clade (over forty glycerids and over sixty goniadids), found in habitats ranging from the intertidal to the abyssal. They range in size from about a centimetre in length to well over half a metre. The front end of the body tapers to a narrow, elongate conical point in front of the mouth, bearing two terminal pairs of small, slender appendages that may correspond to the antennae and palps of other worms. Eyes may be present or absent. The pharynx forms a remarkably elongate, eversible proboscis. In Glyceridae, the proboscis ends in a ring of four hook-shaped jaws, all similar to each other. In Goniadidae, the arrangement of jaws is more complex with the usual arrangement being small micrognaths on one side of the ring and larger macrognaths on the other. Glycerids usually have a transparent skin and an overall red or white colour reflecting the coloration of the internal fluids (red-coloured individuals are sometimes known as ‘bloodworms’, as are many other similarly coloured worm-like invertebrates). Goniadids have a more opaque cuticle and often have an iridescent sheen (Rouse & Pleijel 2001).

Glycera dibranchiata with everted proboscis, from the Yale Peabody Museum.

Glyceriforms most commonly live as burrowers in muddy or sandy substrates though some live on the surface of rocks. Most are carnivores of active invertebrates such as crustaceans or other worms; some may be detritivores. They may be vagile or they may construct permanent galleries of burrows with multiple entrance and exit openings in which they wait to lunge at anything foolish enough to pass nearby. In glycerids, the stabby jaws are associated with venom glands leading to ducts opening through pores on the jaw’s underside. In some species, this venom is strong enough to cause a painful reaction in humans (though I haven’t come across any references to long-term consequences). Goniadids lack venom glands and seem to rely on the physical use of their jaws to capture prey. As with many other marine worms, reproduction happens via pelagic epitokes. As a suitable time approaches (Prentiss, 2020, records goniadid epitokes emerging only during a full moon), the glyceriform worm undergoes a metamorphosis involving the break-down of the digestive system and enlargement of the parapodia. The transformed epitokes swim towards the surface where they release gametes through ruptures of the body wall, ending their life in a suicidal orgasm.

Close-up on proboscis of Glycera alba, copyright Hans Hillewaert.

Because of their hardened jaws, which are mostly constructed of protein but partially mineralised, glyceriforms have quite a good fossil record compared to many other worms (Böggemann 2006). Fossilised glyceriform jaws have been found as far back as the Triassic and are little different from those of modern glyceriforms. Body fossils are, unsurprisingly, much rarer but a worm from the Carboniferous Mazon Creek fauna, Pieckonia helenae, has been identified as a stem-group goniadid. The glyceriform body plan seems to have been a very successful one, remaining essentially unchanged over hundreds of millions of years.

Systematics of Glyceriformia
<==GlyceriformiaRP07
|--GoniadidaeSS07
| |--GlycindeSS07
| | |--G. armigera Moore 1911SS07
| | |--G. bonhourei Gravier 1904HG14
| | `--G. nipponica Imajima 1967HG14
| |--Carbosesostris megaliphagon Schram 1979W93
| |--Progoniadides Hartmann-Schröder 1974H-S86
| | `--P. laevis Hartmann-Schröder 1974H-S86
| |--Goniadides Hartmann-Schröder 1960H-S86
| | |--G. aciculata Hartmann-Schröder 1960H-S86
| | `--G. falcigera Hartmann-Schröder 1962H-S86
| `--GoniadaSS07
| |--G. brunnea Treadwell 1906SS07
| |--G. emerita Audouin & Milne Edwards 1834HG14
| |--G. maculata Öersted 1843RP07
| |--G. maoricaPG98
| |--G. norvegicaM62
| |--G. oculata Treadwell 1901H56
| |--G. paucidens Grube 1878HG14
| |--G. quinquelabiata Augener 1906 [incl. G. magna Treadwell 1945]H56
| `--G. teres Treadwell 1931H56
`--GlyceridaeSS07
|--Glycerites Hinde 1879H62
| `--*G. sulcatus Hinde 1879H62
|--Ildraites Eller 1936H62
| `--*I. bipennis (Eller 1934) [=Arabellites bipennis]H62
|--Paraglycerites Eisenack 1939H62
| `--*P. necans Eisenack 1939H62
|--Hemipodia simplex (Grube 1857)HG14
`--Glycera Savigny 1818PE16, H62
|--*G. unicornis Savigny 1818H62
|--G. alba (Müller 1776)RP07
|--G. americanaZHT01
|--G. capitata Oersted 1843 [incl. Hemipodia canadensis Treadwell 1937]H56
|--G. convolutaM62
|--G. derbeyensis Hartmann-Schröder 1979HG14
|--G. dibranchiata Ehlers 1868SS07
|--G. lamelliformisPG98
|--G. lamellipodiaHS01
|--G. lancadivae Schmarda 1861HG14
|--G. lapidumM62
|--G. macintoshi Grube 1877HG14
|--G. tesselata Grube 1863 [incl. G. abranchiata Treadwell 1901, G. spadix Treadwell 1943]H56
`--G. tridactyla Schmarda 1861HG14

*Type species of generic name indicated

References

Böggemann, M. 2006. Worms that might be 300 million years old. Marine Biology Research 2: 130–135.

[H56] Hartman, O. 1956. Polychaetous annelids erected by Treadwell, 1891 to 1948, together with a brief chronology. Bulletin of the American Museum of Natural History 109 (2): 239–310.

[H-S86] Hartmann-Schröder, G. 1986. Polychaeta (incl. Archiannelida). In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 210–233. E. J. Brill/Dr W. Backhuys: Leiden.

[HS01] Hayward, B. W., A. B. Stephenson, M. S. Morley, W. M. Blom, H. R. Grenfell, F. J. Brook, J. L. Riley, F. Thompson & J. J. Hayward. 2001. Marine biota of Parengarenga Harbour, Northland, New Zealand. Records of the Auckland Museum 37: 45–80.

[H62] Howell, B. F. 1962. Worms. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt W. Miscellanea: Conodonts, Conoidal Shells of Uncertain Affinities, Worms, Trace Fossils and Problematica pp. W144–W177. Geological Society of America, and University of Kansas Press.

[HG14] Hutchings, P., C. Glasby, M. Capa & A. Sampey. 2014. Kimberley marine biota. Historical data: polychaetes (Annelida). Records of the Western Australian Museum Supplement 84: 133–159.

[M62] Monniot, F. 1962. Recherches sur les graviers a Amphioxus de la région de Banyuls-sur-Mer. Vie et Milieu 13: 231–322.

[PE16] Parry, L. A., G. D. Edgecombe, D. Eibye-Jacobsen & J. Vinther. 2016. The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. Proceedings of the Royal Society of London Series B—Biological Sciences 283: 20161378.

Prentiss, N. K. 2020. Nocturnally swarming Caribbean polychaetes of St. John, U.S. Virgin Islands, USA. Zoosymposia 19: 91–102.

[PG98] Probert, P. K., & S. L. Grove. 1998. Macrobenthic assemblages of the continental shelf and upper slope off the west coast of South Island, New Zealand. Journal of the Royal Society of New Zealand 28: 259–280.

Rouse, G. W., & F. Pleijel. 2001. Polychaetes. Oxford University Press.

[RP07] Rousset, V., F. Pleijel, G. W. Rouse, C. Erséus & M. E. Siddall. 2007. A molecular phylogeny of annelids. Cladistics 23: 41–63.

[SS07] Struck, T. H., N. Schutt, T. Kusen, E. Hickman, C. Bleidorn, D. McHugh & K. M. Halanych. 2007. Annelid phylogeny and the status of Sipuncula and Echiura. BMC Evolutionary Biology 7: 57.

[W93] Wills, M. A. 1993. Annelida. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 271–278. Chapman & Hall: London.

[ZHT01] Zrzavý, J., V. Hypša & D. F. Tietz. 2001. Myzostomida are not annelids: molecular and morphological support for a clade of animals with anterior sperm flagella. Cladistics 17: 170–198.

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