The prostomium (From Ancient Greek, meaning "before the mouth"; PL: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth. The prostomium together with the peristomium, which includes the mouth and pharynx, make up the annelid head.
The prostomium is part of the head and holds at least part of the brain and often bears sensory structures such as the eyes, antennae and palps. [1] It may function like a kind of overlip when the animal is feeding. The prostomium bears many important taxonomic characters and its shape and composition are important for annelid systematics.
In addition to the eyes, antennae and palps, the prostomium can possess appendages such as tentacles or cirri. Moreover, some polychaete prostomia have a posterior extension or ridge with sensory function, called a caruncle. Another sensory organ, the nuchal organ (or a variation, the nuchal epaulette), is a chemosensory, ciliated pit or groove at the posterior end of the prostomium. [2]
There may be three antennae present: a pair of lateral antennae and one median antennae. These are most commonly simple, tapering structures, but they may also be articulated or ornamented. [1] There are different arrangements of insertion of the lateral and median antennae, with the lateral antenna sometimes inserted ventrally to the median antennae or vice versa, or they may be inserted on the same plane. In some taxa, the lateral antennae may be missing, leaving only a lone median antenna.
The palps are paired and innervated structures that tend to be located ventrally and laterally. They are often associated with the mouth and may have a feeding or sensory function. [2]
Tentacular cirri can be any sort of elongated, forward (anterior) facing cirri and can occasionally be found on the prostomium.
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 an eversible pharynx is present, it is contained in this segment as well, and can fill up to 20 segments when inverted, depending on the species.
Prosphaerosyllis battiri is a species belonging to the phylum Annelida, a group known as the segmented worms. The species name comes from an Aboriginal word, battiri, meaning "rough". Prosphaerosyllis battiri is a species characterized by having only partially fused palps, an unretracted prostomium on its peristomium or showing only slight retraction, the shape of its dorsal cirri and its arrangement of papillae, being numerous anteriorly while less numerous posteriorly. It resembles Prosphaerosyllis semiverrucosa, but its arrangement of dorsal papillae is reversed.
Salvatoria pilkena is a species belonging to the phylum Annelida, a group known as the segmented worms. The species name comes from an Aboriginal word, pilkena, meaning "different", due to its characteristic features. Salvatoria pilkena belongs to a reduced group of species that possess rugose dorsal cirri, contrary to the typical spindle-shaped cirri found in its genus. It also lacks dorsal cirri on chaetiger 2. It resembles Salvatoria swedmarki and S. celiae, differing from pilkena in that the latter has significantly longer proventricles, while its compound chaetae are short and unidentate. At the same time, S. opisthodentata has a similar body and compound chaetae but appears to possess dorsal cirri on its chaetiger 2.
Salvatoria koorineclavata is a species belonging to the phylum Annelida, a group known as the segmented worms. A related species in Australia has been described as Brania clavata and subsequently as Salvatoria clavata. While similar, the Australian species has a longer pharynx and proventricle; at the same time, blades of chaetae are present in the Australian species, with longer and upwards curved spines, which are straight in S. clavata; its pharyngeal tooth is located more anteriorly than in S. clavata. Other global species, like those in the genus Brania, are also similar to S. koorineclavata. Salvatoria californiensis has similar chaetae, with shorter spines and less developed teeth. Its acicula lacks a defined acute tip, and the proventricle is quite shorter, running through 5 segments in S. koorineclavata, with fewer rows of muscle cells. The species name comes from an Aboriginal word, Koorine, meaning "daughter", due to the similarity of the Australian species to the European species of S. clavata.
Sphaerosyllis levantina is a species belonging to the phylum Annelida, a group known as the segmented worms. It was first described from Haifa Bay in the eastern Mediterranean. It is similar to Sphaerosyllis hystrix, and is thought to show a cosmopolitan distribution. Its name derives from its type locality, levantina being the feminine form of a Neo-Latin adjective meaning "pertaining to the region where the sun raises"; the adjective is feminine to agree with the feminine genus name, Syllis being a river nymph in Greek mythology.
Erinaceusyllis cirripapillata is a species belonging to the phylum Annelida, a group known as the segmented worms. E. cirripapillata is characterized by its papillae on its dorsal cirri, one of them being distinctively mushroom-shaped. No species of this genus or Sphaerosyllisis is known to possess this particular kind of papillae. The name of the species refers to these same papillae.
Erinaceusyllis hartmannschroederae is a species belonging to the phylum Annelida, a group known as the segmented worms. This species was previously described in Australia as Sphaerosyllis erinaceus and S. erinaceus erinaceus, a species distributed throughout the globe. These species appear to be a species complex. Previous descriptions stated that the two aforementioned species possess compound chaetae blades which are long and slender. Several subspecies of S. erinaceus were described on the basis of differences in shapes and sizes of their compound chaetae; such differences are enough to consider them as distinct species. The species is named in honour of Gesa Hartmann-Schröder, an expert on syllid species.
Erinaceusyllis kathrynae is a species belonging to the phylum Annelida, a group known as the segmented worms. E. kathrynaen is similar to E. cirripapillata, but lacks characteristic papillae on its cirri. At the same time, Sphaerosyllis perspicax - which according to San Martín (2005) could belong to the genus Erinaceusyllis - is also similar, but its anterior dorsal cirri are inflated at their bases; the eyes and antennae are arranged linearly, and the palps are fused along their length. This species is named in honour of Kathryn Attwood of the Australian Museum.
Sphaerosyllis georgeharrisoni is a species belonging to the phylum Annelida, a group known as the segmented worms. Sphaerosyllis georgeharrisoni is distinct by its large parapodial glands with hyaline material; by its small size; short proventricle; a median antenna that is inserted posteriorly to the lateral antennae; as well as long pygidial papillae. Juveniles of S. hirsuta are very similar to this species. Sphaerosyllis pygipapillata has all of its antennae aligned, a smooth dorsum, while its pygidial papillae are longer and slender. The species' name honours George Harrison, musician who died prior to the species' describing article's publication.
Parapionosyllis winnunga is a species belonging to the phylum Annelida, a group known as the segmented worms. Parapionosyllis winnunga is characterized by the shape of the blades of its compound chaetae, which have a long subdistal spine, in turn much longer than in other cogenerate species. Its species name is derived from the Aboriginal word winnunga, meaning "small".
Ophryotrocha craigsmithi is a species of polychaete worm. O. craigsmithi is named after Craig R. Smith. This species is similar to Palpiphitime lipovskyae and O. Platykephale, among others, in having branchial structures dorsally and ventrally. It differs from O. platykephale in the shape of its prostomium and parapodia. Palpiphitime lipovskyae has jaws of both P- and K-type, while no specimens of O. craigsmithi have been found with K-type jaws thus far. Ophryotrocha craigsmithi differs from P. lipovskyae genetically, but also by the presence of a prominent ventral chaetal lobe with a bulging simple chaeta in the former.
Ophryotrocha eutrophila, is a species of polychaete worm. Ophryotrocha eutrophila is named after its habitat, liking organically enriched environments. This species resembles O. puerilis in jaw morphology. O. eutrophila is dimorphic, with males being than females, while possessing K-type maxillae. Ophryotrocha eutrophila, however, differs from O. puerilis in the absence of eyes and the presence of a developed median pygidial stylus. O. eutrophila is also similar to O. Fabriae, differing from the latter from its mandibles morphology.
Leucia is a genus of marine polychaete worms belonging to the family Polynoidae, the scaleworms. Leucia contains 2 species, both found in the northern Atlantic Ocean. This genus is distinguished from the closely related genus Harmothoe by having sixteen pairs of elytra, as opposed to fifteen.
Leucia nivea is a species of polychaete worm, commonly known as a "scale worm", in the family Polynoidae. This species occurs in the northeastern Atlantic Ocean, the North Sea and the Mediterranean Sea.
Sternaspidae, commonly known as mud owls, are a family of marine polychaete worms with short swollen bodies. They have a global distribution and live buried in soft sediment at depths varying from the intertidal zone to 4,400 m (14,400 ft).
Eunoe barbata is a scale worm, described from Puget Sound and Monterey Bay in the North-east Pacific Ocean.
Australonoe willani is a species of marine annelids in the family Polynoidae, and the sole member of the genus Australonoe, known only from the south-east Indian Ocean at Rottnest Island, Western Australia.
Bathynoe is a genus of marine annelids in the family Polynoidae. The genus includes 6 species, 5 of which occur in the Pacific Ocean while one occurs in the Atlantic Ocean. Bathynoe species have been recorded from depths of about 500 – 3000 m.
Bylgides is a genus of marine annelids in the family Polynoidae. The genus contains 9 species, all found in the Northern Hemisphere and from shallow inshore waters to depths of about 5000 m.
Eucranta is a genus of marine annelids in the family Polynoidae. The genus includes 5 species which are globally distributed from depths of about 40 to 600 m, mostly from high latitudes in the northern and southern hemispheres.