''Sphaerosyllis voluntariorum'' is a species belonging to the phylum

Annelida The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to variou ...

, a group known as the segmented worms.San Martín, G. (2005). Exogoninae (Polychaeta: Syllidae) from Australia with the description of a new genus and twenty-two new species. Records of the Australian Museum. 57(1): 39-152., available online at https://dx.doi.org/10.3853/j.0067-1975.57.2005.1438, page(s): 55-57, figs. 11A-G, 12A-E. This species is closely related to '' Sphaerosyllis bifurcata'', '' Sphaerosyllis bifurcatoides'' and '' Sphaerosyllis rotundipapillata'', all

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

species to Australia, characterized by having large dorsal papillae, sometimes trilobed, and with shafts of compound chaetae distally bifid. ''S. voluntariorum'' is more densely papillated on its anterior segments and has a long subdistal spine on the ventral simple chaetae. This species' name alludes to the volunteers of the Marine Invertebrate section of The

Australian Museum The Australian Museum, originally known as the Colonial Museum or Sydney Museum. is a heritage-listed museum at 1 William Street, Sydney, William Street, Sydney central business district, Sydney CBD, New South Wales. It is the oldest natural ...

, who sorted specimens of syllids that led to the description of this animal.

Description

The species' body is small, with a total length of and width of , including 26 chaetigers. It possesses numerous papillae on its dorsum and a few on its parapodia, and none on its prostomium and palps; the papillae are long, with trilobed tips and dark inclusions. Its

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; : prostomia; sometimes also called the "acron") is the Cephalization, cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not in ...

is ovate, showing 4 large eyes in a trapezoidal arrangement. Its antennae are long, with bulbous bases and long tips, similar to the combined length of its prostomium and palps. The

palp Pedipalps (commonly shortened to palps or palpi) are the secondary pair of forward appendages among chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicera ...

s are similar in length than its prostomium, fused along their length, ventrally folded. Its

peristomium The peristomium is the first true body segment in an annelid worm's body in the anterior end. It is directly behind the prostomium and contains the mouth, tentacular cirri, and sometimes feeding palps, which may instead occur on the prostomium. If ...

measures the same as its succeeding segments, covering the posterior half of the prostomium. Its

tentacular In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work mainl ...

cirri are shorter than its antennae, the dorsal cirri being the same length as the tentacular cirri, with slender tips. Its parapodial lobes are conical, with 2 subdistal papillae. Its ventral cirri are long and slender, while its parapodial glands are very small. It shows anterior parapodia with 5 compound chaetae each, with unidentate blades. The blades of the dorsal compound chaetae possess marginal spines about 12

μm The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

long, while the blades of ventral compound chaetae are smooth, measuring about 9 μm long. ''Sphaerosyllis voluntariorum'' shows dorsal simple chaetae from chaetiger 1, unidentate with few spines. The ventral simple chaetae on posterior parapodia are smooth, sigmoid and distally hooked, provided with a long subdistal spine. Its parapodia count with a single

acicula Acicula (: aciculum) are strong, stout internal chaeta A chaeta or cheta (; ) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as art ...

each, bent to a right angle. The pharynx spans approximately 3 segments. Its pharyngeal tooth is probably located on its anterior rim. Its proventricle spans through 1 or 2 segments, with 12

muscle cell A muscle cell, also known as a myocyte, is a mature contractile Cell (biology), cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal muscle, skeletal, smooth muscle, smooth, and Cardiac muscle, cardiac ...

rows. Its

pygidium The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...

is small, with numerous rounded

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Papilla (worms), small bumps on the surface of certain worms * Basilar papilla, a sensory organ of lizards, amphibians and fish * ...

e and 2 anal cirri, which are similar to its dorsal cirri but quite longer.

Distribution

''Sphaerosyllis voluntariorum'' was found in Cape Range National Park,

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

, at a depth of in mixed

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

. Its distribution is thought to include the whole of WA.

References

External links

WORMS entry
{{Taxonbar, from=Q2004506 Syllidae Animals described in 2005

Description

Distribution

References

Further reading

External links