Ekin Tilic

Senckenberg Research Institute · Department of Marine Zoology

Sabellida is a well-known clade containing tube-dwelling annelid worms with a radiolar crown. Iterative phylogenetic analyses over three decades have resulted in three main clades being recognized; Fabriciidae, Serpulidae and Sabellidae, with Fabriciidae proposed as the sister group to Serpulidae. However, relationships within Sabellidae have remai...

Three major clades of tube-dwelling annelids are grouped within Sabellida: Fabriciidae, Serpulidae and Sabellidae. The most characteristic feature of these animals is the often spectacularly colorful and flower-like radiolar crown. Holding up such delicate, feathery appendages in water currents requires some sort of internal stabilization. Each of...

Sthenelanella is an unusual genus of tube‐dwelling scale worms, with fine fibrous threads that appear on either side of the body. These fibers emerge dorsally in long silvery bundles that are then tightly interwoven to construct the felt‐like material of the tube. In the literature, these fibers are described as the products of so‐called “spinning...

Aciculata (Eunicida + Phyllodocida) is among the largest clades of annelids, comprising almost half of the known diversity of all marine annelids. Despite the group’s large size and biological importance, most phylogenomic studies on Annelida to date have had a limited sampling of this clade. The phylogenetic placement of many clades within Phyllod...

Annelid chaetae are extracellular chitinous structures that are formed in an extracellular epidermal invagination, the chaetal follicle. The basalmost cell of this follicle, the chaetoblast, serves like a 3D-printer as it dynamically shapes the chaeta. During chaetogenesis apical microvilli of the chaetoblast form the template for the chaeta, any s...

Sea cucumbers (Holothuroidea) are a diverse clade of echinoderms found from intertidal waters to the bottom of the deepest trenches. Their reduced skeletons and limited number of phylogenetically-informative traits have long obfuscated morphological classifications. Sanger-sequenced molecular datasets have also failed to constrain the position of m...

The taxonomy of ribbon worms (Nemertea) is particularly challenging due to the sparsity of distinct morphological characters, causing a significant underestimation of the group's true diversity. The number of named deep-sea species is very limited and there is a vast number of undescribed deep-sea nemerteans still to be discovered. In this paper we...

Phylotranscriptomic studies of the past decade have repeatedly placed Oweniidae together with Magelonidae, as the sister group to remaining annelids. This newly established placement clearly makes them a key-lineage for understanding annelid evolution and morphology. One of the most prominent morphological features of all annelids are their chaetae...

Oenonidae are an unusual group of annelids in that many of them are parasitic or have a parasitic phase in their life, often in other polychaetes. Most Oenonidae adults are medium- to large-sized annelids, ranging from 1 to 90 cm long with over 1000 segments (Paxton, 2000a) but usually thin. Externally many of them resemble Lumbrineridae , from whi...

Lumbrineridae adults are medium sized to large annelids, ranging from a few centimetres to over half a metre in length and several hundred segments (Pl. 6a).

Pilargidae is part of Phyllodocida , with adult sizes of the animals usually one to a few centimetres long but having up to several hundred segments. Many live Pilargidae lack specific pigmentation patterns and are of a whitish colour, although the posterior half of some (e.g. Pilargis ) is reddish with darker spots.

Acoetidae are large annelids with many segments and are unusual among scale-worms in being tubiculous (Fig. 8.1a).

Nephtyidae have a well-deserved difficult reputation among workers involved in benthic monitoring who try to identify them. They can be very abundant in shallow water sediments and there are often several different nephtyids in the same sample.

Named for their strange anatomy, Aberranta is a small, rare, and morphologically homogenous and characteristic group of free-living annelids, with adult length up to near 7 mm for about 40 chaetigers.

Fauveliopsidae is a small group of only around 30 species, best known for some Fauveliopsis taxa living in the empty shells of gastropods or scaphopods.

The first members of Annelida were named by Linnaeus (1758) and in the intervening period there have been thousands of others added. We estimate that the current number of accepted species level taxa is just under 21,000, though several thousand more have been named and are considered invalid. This is based on a count of the estimates presented in...

Hesionidae is named after the mythical Hesione, princess of Troy, who was rescued from a sea monster by Hercules. This group of beautiful worms are not uncommon in the sublittoral, especially on rocky and mixed bottoms, and they also seem to thrive in deep-sea environments with many species described from hydrothermal vents (Fig. 15.2c), whalefalls...

Ampharetidae are tubicolous, as are most members of Terebelliformia , and share with Alvinellidae and Melinnidae the feature that their multiple grooved palps, usually called tentacles, can be retracted into the mouth. Typically, Ampharetidae are 10 to 60 mm long, though some adults are only a few millimetres long.

The name Chrysopetalidae , from the Latin for ‘golden petals’, refers to the shape and the colour of the shiny, flattened notochaetae which cover the dorsum in one of the three major clades in the group, Chrysopetalinae (Pl. 3c).

Alvinellidae (‘Pompeii worms’ or ‘palm worms’), are a relatively recently discovered group known only from sites associated with deep-sea hydrothermal vents in the Pacific and Indian Oceans.

Aeolosomatidae is a group of minute worms living almost exclusively in freshwater habitats.

Melinnidae (Pl. 12c, d) is a small taxon of tubicolous Terebelliformia , containing only around 50 accepted species that are generally found in deeper waters. The group’s name is seemingly derived from an ancient Greek women’s name, Melinna, and this was the first genus name for the group (Read and Fauchald, 2021).

Trichobranchidae have multiple grooved palps (‘tentacles’), often of two kinds, and resemble their close relatives Terebellidae in several ways, though Melinnidae is actually closer to Terebellidae. Historically, they have often been included within the latter taxon.

Sphaerodoridae is a relatively small annelid group, with around 138 nominal species. The animals can be easily recognized by the conspicuous spherical macro- and microtubercles that give sphaerodorids their name (Figs. 19.1b, c).

Polynoidae is the largest group of Aphroditiformia , and one of the more species-rich of annelid clades covered in a chapter here. The body is dorso-ventrally flattened and often has an oval shape, but some can be long and slender (e.g. Polynoe scolopendrina ; Pl. 2e).

Members of Sabellidae (feather-duster worms) are among the most easily recognizable of annelid groups due to their possession of an often spectacularly colourful radiolar crown and by the mucus/ parchment/ sediment tubes that they generally inhabit (Pl. 8a–d).

Eunicidae is a well-known group of annelids, mainly for being one of the few groups that are regularly eaten by humans. Their exposed complex and intimidating jaws can often be observed in some giant Eunicidae waiting for their prey in Indonesia. This has resulted in the common name ‘sand striker worms’ for these majestic, avid predators.

The multiple grooved palps (‘tentacles’) of Terebellidae gives rise to their common name, spaghetti worms. These tentacles are a common sight extending out over the substrate in shallow marine waters worldwide. When disturbed the tentacles, often brightly coloured, can be seen coiling and looping as they are retracted back towards the worm.

Amphinomida includes two major groups: Amphinomidae and Euphrosinidae . Amphinomidae occur mainly in littoral warm waters. Some are called fireworms and are known for their brittle chaetae that easily break when touched and produce a burning sensation.

Capitellidae are commonly found, and it is a bit surprising there is no common name for the group. They are easily recognized, for the most part, by the division of the body into an anterior region with capillary chaetae only and a posterior region with long-handled hooks.

Members of Sternaspidae (from the Greek words for breast and shield) are instantly recognizable in their remarkable yellow, reddish, violet, or even black shield that lies ventro-posteriorly, and the posterior veil of branchiae.

Acrocirridae is a small taxonomic group comprising around 40 accepted species that are generally found in intertidal or shallow coarse sediments and muds. They often will also be found attached to the undersurface of stones or rubble. Some extraordinary holopelagic members of Acrocirridae ( Swima and Teuthidodrilus ) have also been described in rec...

Heterospio is a small group with only nine named species and no common name. Usually placed under the redundant names Longosomatidae or Heterospionidae , the systematic position of Heterospio is uncertain, though a relationship with Cirratulida is now apparent.

Chaetopteridae is a clade with small membership of around 75 valid species and nearly all are tubicolous. The taxon name is derived from the Greek for ‘chaetae’ and ‘wing’ and refers to the long aliform notopodia with aciculae in some taxa.

Paraonidae (no common name, but jesting students often call them ‘paranoids’) is a relatively small group in taxonomic terms and, because they tend to be found in deeper waters, there is little known about them.

Flabelligeridae, with a common name of bristle-cage worms, are generally recognizable by their papillose body, often coated with thick covering of sediment and the fact that the head is retractable between anterior segments which may project forward a ‘cage’ of chaetae (Pl. 14b–d).

Apistobranchus has small membership and has had a long period of uncertain affinity, though it is now apparent it is part of Chaetopteriformia .

Opheliidae are commonly found in sandy or muddy substrates from intertidal regions down to more than 7000 m. They are often noticed when disturbed by rapidly swimming in an energetic way and some

Lobatocerebrum is a small, exclusively meiofaunal clade with only three known species. The placement of these enigmatic animals has long been problematic, but recent molecular work establishes their placement within Annelida . The animals have an unsegmented, slender, and elongate body with a length of 1–3 mm.

Sabellariidae (known as honeycomb worms or sandcastle worms) build distinctive hard tubes from glued sand or other coarse particles and are commonly seen forming colonies on rocky surfaces in intertidal marine environments (Pl. 9a).

Dinophilus was erected by Schmidt (1848) and the name refers to the whirling motion these worms can show owing to their ciliary movement. Dinophilidae are all small, at less than 3 mm long as adults, and lack chaetae and obvious segmentation.

Syllidae constitutes a large and variable, but nevertheless highly characteristic group of polychaetes. The name comes from Syllis , a nymph in Greek mythology, who was the lover of the god Apollo and the mother of king Zeuxippos of Sikyon.

Serpulidae (fanworms), like Sabellidae , are very well-known owing to their colourful radiolar crown (Pl. 8e–g). Serpulidae are usually easily distinguished from Fabriciidae and Sabellidae in that they live in a calcareous tube, though this is sometimes embedded in coral.

The annelid body consists of three fundamental regions. There is always a presegmental region derived from the larval episphere, anterior to the prototroch region around the mouth.

Clitellata is clade of hermaphroditic, direct-developing Annelida found worldwide in most aquatic and terrestrial habitats. They comprise nearly half of the total known species diversity of Annelida , with an estimated 8800 accepted species.

Sipuncula is a group of animals that for a long time was considered a distinct clade outside Annelida and the issue of their phylogenetic affinity has been a controversial and much disputed subject (Saiz-Salinas, 2018, for references).

Orthonectida , from the Greek for ‘straight’ and ‘swimming’, is a small group of marine Annelida that are parasites of Acoela , other Annelida , Echinodermata , Mollusca , Nemertea , Platyhelminthes , and Xenoturbella (Kozloff, 1992; Nakano and Miyazawa, 2019).

Lacydonia is a small and morphologically very homogenous group in Phyllodocida about which we know very little. The adults have a relatively small number of segments, and the reported length is up to 8 mm; the body shape in dorsal view is cylindrical with tapering anterior and posterior ends (Pl. 5c).

Compared with most annelid groups, Cirratulidae has been well studied in terms of biology, physiology, and population structure, but the overall systematics and taxonomy of the group remains quite problematic.

Named after Spio, one of the Nereids from Greek mythology, Spionidae represents one of the larger taxonomic groupings and currently is poorly understood in a phylogenetic sense and hence needs substantial revision.

For many years this group was referred to as Echiura , with the rank of phylum following Newby’s (1940) embryological study. The group is now consistently recognized as the sister group to

Oweniidae is a taxon with small membership that, until recently, was more famous for its larval form, the unusual and beautiful ‘mitraria’ (Fig. 77.1g), than for the adults.

Protodrilida (‘first’ or ‘original’ ‘worms’) is a clade that currently comprises around 65 accepted species that are known historically for being members of the now defunct taxon Archiannelida .

Hrabeiella is an enigmatic terrestrial member of Annelida that appears to be the sister group to Aeolosomatidae .

Annelids (the segmented worms) exist in a remarkably diverse range of mostly marine but also freshwater and terrestrial habitats, varying greatly in size and form. Annelida provides a fully updated and expanded taxonomic reference work which broadens the scope of the classic Polychaetes (OUP, 2001) to encompass wider groups including Clitellata (co...

Microphthalmidae is a small group within Phyllodocida. Herein, we follow the delineation of the group by Salazar-Vallejo (2019a) and include Hesionides as well as Struwela . Both Microphthalmus and Hesionides are interstitial animals.

Despite its minute size, the first member of Nerillidae ( Nerilla antennata ) was described in 1848 by Schmidt. In his original description he admits initially mistaking Nerilla for the juvenile of a known worm and becoming aware of his discovery only after finding mature specimens.

Tomopteridae with the charming common name ‘gossamer worms’, is an easily recognized group of transparent holoplanktonic annelids that lack external chaetae (Pl. 5b).

Myzostomida (from the Latin myzo to suck and stomum for mouth) is an unusual and in some ways diverse group of worms(Figs. 35.1, 35.2, 35.3, 35.5), comprised of more than 180 nominal species (Read and Fauchald, 2021. Lacking a common name, they are generally referred to as ‘myzostomes’.

Described by Linnaeus (1758), Aphrodita is among the oldest introduced generic annelid names. One characteristic feature of Aphrodita is the presence of fine capillary notochaetae that form a felt over the dorsum.

Annelids (the segmented worms) exist in a remarkably diverse range of mostly marine but also freshwater and terrestrial habitats, varying greatly in size and form. This text provides. This text begins with an introduction to the phylum and an outline of annelid taxonomy. The book describes their collection and the methods to ensure their optimal pr...

The first described Eulepethidae was Eulepis hamifera by Grube (1875). However, since the generic name was preoccupied

Typhloscolecidae are all holoplanktonic and have a cylindrical body. Adult animals range from 0.5 to 4 cm in length with up to 50 segments, although many taxa have a segment number not exceeding 20–25. This suggests a fixed adult number of segments in some taxa.

Dorvilleidae is a morphologically heterogeneous group, including some of the smallest described annelids with adult length of only a few hundred µm and only a few segments ( Neotenotrocha ). Others may attain a size up to 10 cm and have many segments (e.g. Dorvillea ). The colour of live animals is variable, transparent to whitish being common (Pl....

Pontodora is a small and poorly known holopelagic group including only the two described taxa Pontodora pelagica Greeff, 1879 and Epitoka pelagica Treadwell, 1943.

Spinther is a small group of easily recognized annelids, all living as ectoparasites or commensals on sponges. The name means spark/sparkling in Greek and most-likely refers to the shimmering appearance of the worm.

Paralacydonia is a small and morphologically homogenous group of Phyllodocida . As may be guessed from the name they were thought by Fauvel to be close to Lacydonia , yet their position within Phyllodocida still remains unresolved today.

Magelona (‘shovelhead worms’), contains over 70 described nominal species that are relatively uniform in appearance. They have a somewhat unusual morphology and have historically been difficult to relate with other annelids. They are now regarded as sister group to Oweniidae , and as Oweniida , are the sister group to all other living Annelida (see...

Arenicolidae (lugworms and their smaller relatives) is a taxonomically small group that in the previous edition of this work was reported on as being relatively well studied, possibly because it represents one of the few groups of annelids of any direct economic importance. In recent decades, however, they have received little attention from anneli...

Lopadorrhynchidae is a small group of holopelagic annelids. A common misspelling of the name is Lopadorhynchidae with a single ‘r’ (Read and Fauchald, 2021).

Quillworms ( Hyalinoecia ) and the Australian beachworms ( Australonuphis ) are among the better known Onuphidae ; the former with highly characteristic tubes (Pl. 6f) and the latter for their size (up to several metres) and occurrence on sandy beaches and their importance as bait in fisheries. Overall, Onuphidae vary in size from a few millimetres...

Parergodrilidae is a group of terrestrial or semi-terrestrial Annelida that are now known to be closely related to Orbiniidae . Parergodrilus heideri and the Stygocapitella species complex, comprise the clade, with the former living in damp terrestrial soils across Europe and the latter group of species found worldwide in coarse marine sands around...

Fabriciidae were for many years considered to be part of Sabellidae and share similarities such as the radiolar crown and dwelling in a mucus/sediment tube (Figs. 40.2a, b)

Siboglinidae is among the most famous and well-studied clades of Annelida , though until recently they were treated as one or two phyla, Pogonophora and Vestimentifera , separated from Annelida .

Maldanidae (bamboo-worms) are easily recognizable in that the body is comprised of a set number of long cylindrical segments which, combined with low rows of hooked chaetae, results in a bamboo-like appearance. Depending on the group, adult Maldanidae range in size from 3 mm to more than 200 mm in length and usually have a fixed maximum number of s...

Scalibregmatidae (sometimes called maggot worms and one group, Travisia are not too fondly, but appropriately, called stink worms) are not routinely encountered, though they can occur in huge numbers in shallow waters in Northern Europe. More often, they occur in muddy sediments at more than 1000 m depth.

Psammodrilus , meaning ‘sand worm’, is a group of tiny Annelida containing eight named species and several yet to be described. All live among sand grains and can be loosely regarded as interstitial taxa. To date Psammodrilus have all been described from the Northern Hemisphere, with only two records from south of the equator.

Pectinariidae , the aptly named ‘ice-cream cone’ worm, are an anatomically complex, if relatively uniform group that is known worldwide. They mainly occur in shallow marine sediments and are immediately recognizable from their elegant cone or tusk-shaped tubes, constructed from a single layer of sand grains, forams, shell fragments, spicules, or ot...

Cossura live in some shallow marine sediments but are more common in mixed sand and mud sediments in deeper seas. Around 30 accepted species have been described to date. They are recognizable by the thin mid-dorsal branchia that can be nearly as long as the body originating from an anterior segment.

Histriobdellidae (‘Charlie Chaplin worms’) are tiny members of Annelida that live as commensals on a variety of Crustacea . There are currently 13 nominal species placed into Histriobdella , Steineridrilus , and Stratiodrilus , with most of them known from rivers of South America. The name Histriobdella can be loosely translated as ‘clown animal’ a...

Sigalionidae was first erected by Kinberg (1856) (note that the name was incorrectly referred to Malmgren (1867) by Fauchald and Rouse (1997)).

Glyceroidea include two clades Glyceridae Grube, 1850 (often called‘bloodworms’) and Goniadidae Kinberg, 1866.

Phyllodocidae are sometimes known as paddle-worms owing to their (usually) large and flattened dorsal cirri. The holopelagic Alciopidae (see Pl. 5h) are previously treated as a separate taxon in the literature but is here included in Phyllodocidae as Alciopini .

Orbiniidae is a diverse group of over 200 named species that are mainly burrowers in shallow to deep marine sediments.

Depending on your viewpoint, Polygordius is a famous, or infamous, member of Annelida . These worms, nicknamed ‘knot worms’ (Tustison et al ., 2020), are generally found in coarse, well-sorted sediments.

Diurodrilus was erected by Remane (1925) and means ‘two-tailed worm’. Remane was referring to the unusual ‘toes’ at the posterior end of these minute worms

Nereididae (littoral ones often referred to as ‘ragworms’) are probably the most familiar of annelids, both from textbooks in zoology and marine biology and from their occurrence on seashores around the world. They are widely employed in teaching, in laboratory experiments, and as bait for fishing.

Hartmaniellidae is monotypic for Hartmaniella with the former being superfluous, we here just use the latter . Hartmaniella is known from a few records between depths of 45 and 210 m.

The annelid clade Amphinomidae, commonly known as “fireworms,” is notorious for causing skin inflammations after physical contact. These injuries are caused by the chaetae of the animals, which are calcified and particularly brittle. The incorporation of calcium carbonate particles and their disintegration cause the chitinous lamellae within a chae...

The bright iridescent chaetae of Aphrodita species have fascinated scientists for decades. The particular nanoscale substructure of these chitinous bristles resembles photonic crystals and manipulates the incident light in a way that results in spectacular structural coloration. Even though Aphrodita's chaetae have garnered great attention from the...

Amphinomida, some also known as fireworms, are not only notorious for their painful sting but also their painfully difficult phylogenetic placement. Current understanding of the annelid tree of life suggests a close affinity with Sipuncula, the unsegmented and sessile peanut worms. This sister-group relationship is hard to explain from a morphologi...

Background: Dietary high salt (HS) is a leading risk factor for mortality and morbidity. Serum sodium transiently increases postprandially, but can also accumulate at sites of inflammation affecting differentiation and function of innate and adaptive immune cells. Here, we focus on how changes in extracellular sodium, mimicking alterations in the c...

Background Numerous deep-sea invertebrates, at both hydrothermal vents and methane seeps, have formed symbiotic associations with internal chemosynthetic bacteria in order to harness inorganic energy sources typically unavailable to animals. Despite success in nearly all marine habitats and their well-known associations with photosynthetic symbiont...

In a recent paper published in Zoology, Righi et al. (2020) investigated the chaetae of the venomous fireworm Hermodice carunculata (Amphinomida, Annelida) and revived the hypothesis of venom injection by hollow chaetae. This conclusion reached by Rigihi et al. (2020) contradicts previously published results, and in our opinion, it is also not supp...

Here, we report the 15,103 bp mitochondrial genome of the freshwater fabriciid tubeworm Manayunkia occidentalis. We recovered 13 protein-coding genes, 2 rRNA, and 22 tRNA. The gene order is consistent with the conserved pattern observed in most annelids.

Background Numerous deep-sea invertebrates have formed symbiotic associations with internal chemosynthetic bacteria in order to harness inorganic energy sources typically unavailable to most animals. Despite success in nearly all marine habitats and their well-known associations with photosynthetic symbionts, Cnidaria remain one of the only phyla w...

We describe a long-unnamed Chaetopterus Cuvier, 1830 species from southern California, using a combination of DNA barcoding and detailed morphological investigation employing highresolution X-ray microtomography (micro-CT). Chaetopterus dewysee sp. nov. is not only one of the most dominant annelids in the benthic communities of the shallow end of t...