- Animalia: Multicellular holotrophic organisms with a diplontic lifecycle)
- Eumetazoa (Metazoans with organs, mouth, and permanent digestive cavity)
- Tribloblastica (animals with true mesoderm)
- Bilateria (animals with primary bilateral symmetry and – may be modified later in development
- Protostomia (Animals with primary bilateral symmetry. Spiral determinant cleavage with the mouth arising at or near the blastopore)
- Lophotrochozoans (animals with either a lophophore of trochophors Biochemically defined clade.
- Spirallia (Animals with a spiral determinant cleavage)
- Trochozoa (Amimals with trochphore larvae
- Phylum Annelida: Segmented schizocoelous worms with a complete digestive tract usually with regional specialization, a closed circulatory system, a well developed nervous system with a ventral nerve cord and segmental ganglia as well as a dorsal cerebrial ganglia, metanephridia, paired segmentally arranged epidermal setae bundles, a head composed of a presegmental prostomium and a peristomium, and usually with a trochophore larva.
- Class Polychaeta: sand worms, tube worms, clam worms, and others (Figure 2). With numerous setae (chaetae) on the trunk segments; most with well developed parapodia; prostomium and peristomium usually bear sensory organs (palps, tentacles, cirri) or extensive feeding and gas exchange tentacular structures; foregut often modified as eversible stomodeal pharynx (proboscis), sometimes armed with chitinous jaws; reproductive structures simple, often transient; without a clitellum; most are gonochoristic; development often indirect, with a free-swimming trochophore larva; mostly marine; burrowers, errant, tube- dwelling, interstitial, or planktonic; some live in brackish water, a few inhabit fresh water or are parasitic. The class is divided into 25 orders and 87 families, some of which are listed below to illustrate the diversity within the class. The annotations are not diagnostic, merely descriptive synopses (see Fauchald 1977 and Pettibone 1982 for complete listings and diagnoses of all orders and families).
- Scolecida: Prostmial appendages absent most burrowers or tube dwellers with a bulbous protrusable pharynx.
- Family Arenicolidae: The so-called lugworms have a rather thick, fleshy, heteronomous body divided into two or three distinguishable regions; pharynx unarmed but eversible and aids burrowing and feeding; arenicolids live in intertidal and subtidal sands and muds in J-shaped burrows; direct deposit feeders. (e.g., Arbarenicola, Arenicola*)
- Family Cirratulidae: Elongate, relatively homonomous polychaetes with up to 350 segments, each with a pair of threadlike branchial filaments; pharynx unarmed and noneversible; cirratulids are mostly shallow-water burrowers lying just beneath the surface of the sediment, from where they extend their branchiae into the overlying water; most are selective deposit feeders, extracting organic detritus from the surface sediments. (e.g., Cirratulus, Cirriformia, Dodecaceria)
- Family Opheliidae: Homonomous polychaetes with up to 60 segments; general body shape varies among genera from rather short and thick to elongate and somewhat tapered; most opheliids burrow in soft substrata, but many swim in undulatory body movements; pharynx unarmed; most are direct deposit feeders. (e.g., Armandia, Euzonus, Ophelia, Polyophthalmus)
- Family Maldanidae: Body elongate and homonomous except that some mid-trunk segments are elongate, hence the common name of "bamboo worms"; burrow head downward and secrete a mucous sheath to which sand particles adhere, thereby forming a tube; proboscis unarmed by eversible and used in burrowing and selective deposit feeding. (e.g., Clymenella*, Maldane, Praxillella)
- Palpata: Sister taxa to the Scolecida – with a pair of sensory palps on the prostomium.
- Acciculata All have well developed biramous parapodia with at least one acciculum.
- Order Phylodocidae: Aciculates with a tubular muscular eversible pharynx
- Family Phyllodocidae: With thin, elongate bodies of up to 700 homonomous segments; most common as active epibenthic predators on solid substrata, a few burrow in mud. (e.g., Eteone, Eulalia, Notophyllum, Phyllodoce)
- Family Alciopidae: Body homonomous, but form varies from short and broad to long and slender; body transparent except for pigment spots in some genera; with pair of huge complex eyes on prostomium; planktonic, predaceous. (e.g., Alciopa, Alciopina, Torrea, Vanadis)
- Family Tomopteridae: Body flattened,, with finlike parapodia; transparent; planktonic, swimming predators. Monogeneric: Tomopteris.
- Family Glyceridae: Long, cylindrical, tapered, homonomous body; enormous pharynx armed with four hooked jaws used in prey capture; large pharyngeal proboscis also used in burrowing; most are infaunal burrowers in soft substrata. (e.g., Glycera*, Glycerella, Hemipodus)
- Family Syllidae: Mostly small, homonomous worms found on various substrata; active predators on small invertebrates, some eat diatoms; pharynx armed with a single tooth or a ring of small teeth for grasping prey; a few are interstitial. (e.g., Autolytus, Brania, Odontosyllis, Syllis, Trypanosyllis)
- Family Nereidae: Moderate to large polychaetes tending to homonomy; mostly errant predators with well developed parapodia; one pair of large curved pharyngeal jaws; some burrow, but most are epibenthic in protected habitats: among mussel communities, in holdfasts of algae, crevices, under rocks, et. (e.g., Cheilonereis, Dendronereis, Neanthes, Nereis*,Platynereis)
- Family Nephtyidae Often large, with well developed parapodia; burrowers in marine sands and muds; eversible, jawed pharynx used in prey capture and burrowing. (e.g., Algaophamus, Micronephytes, Nephtys)
- Family Aphroditidae: Body broad, oval or oblong, with less than 60 segments; with flattened, solelike ventral surface, and rounded dorsum covered with scales (elytra) overlaid by a thick felt- or hairlike layer, giving some the common name of "sea mouse"; slow moving, epibenthic or burrowers; most are omnivorous. (e.g., Aphrodita*, Pontogeneia)
- Family Polynoidae: Most relatively short and somewhat flattened dorsoventrally; one Antarctic species, Eulagisca gigantea, reaches a length of nearly 20 cm and a width of about 10 cm; polynoids tend to have relatively few segments of a more- or-less fixed number; the dorsum is covered by scales (elytra), hence the common name: scale worms:; pharynx with one pair of jaws; well developed parapodia; errant but usually cryptic (under stones, etc.) predators; several forms are commensalistic. (e.g., Arctonoe, Halosydna, Harmothoe)
- Order Eunicida Acciculates with five antennae and well developed parapodial gills
- Family Eunicidae: Elongate, homonomous, generally large polychaetes, some exceeding 3 m in length; pharynx with complex set of jaw plates; some are sedentary in mucous or parchment-like tubes, many are gregarious in cracks and crevices in hard substrata; some leave their tube areas to feed, most are predatory carnivores, but many omnivorous species are known. (e.g., Eunice, Marphysa, Palola)
- Family Lumbrineridae: Thin, elongate polychaetes without head appendages and with reduced parapodia; pharynx with complex jaw apparatus of several elements; crawl in algal mats, holdfasts, hydroids, and small cracks in hard substrata; some burrow in sand or mud; lumbrinerids include a variety of feeding types including carnivores;, scavengers, detritivores, and deposit feeders. (e.g., Lumbrinerides, Ninoe)
- Canalipalpata: Sister taxa to the Aciculata Sedentary species in tubes or burrows, groved palps used for deposit feeding.
- Order Spionida
- Family Spionidae: Body thin, elongate, homonomous; peristomial palps long and coiled; pharynx unarmed; most burrow, or form delicate sand or mud tubes; a few bore into calcareous substrata, including mollusc shells; most use the grooved peristomial palps to selectively extract food from sediment surface. (e.g., Polydora, Scolelepis, Spio, Spiophanes)
- Family Chaetopteridae: Body fleshy, relatively large and distinctly heteronomous, divided into two or three functional regions with modified parapodia; chaetopterids live in more-or- less permanent U-shaped burrows lined with secretions from the worm, most are mucous-net filter feeders, eating plankton and detritus passed through the tube by water currents. (e.g., Chaetopterus*, Mesochaetopterus, Phyllochaetopterus)
- Order Terebellida
- Family Terebellidae: Moderate-sized tube-dwelling polychaetes with fragile, fleshy bodies; heteronomous; body of two distinct regions; most lack eversible pharynx; most live in various types of permanent tubes (e.g., mud, sand, shell fragments); head bears numerous elongate feeding tentacles; most with 1-3 pairs of well developed branchiae on anterior trunk segments; feed on surface detritus. (e.g., Amphitrite*, Pista, Polycirrus, Terebella)
- Family Pectinariidae: Body short and conical, with only about 20 segments; live in conical sandy tubes open at both ends (the "ice-cream-cone worms:) feed on detritus extracted from sediment. (e.g., Amphictene, Pectinaria*, Petta)
- Family Sabellariidae: Heteronomous tube dwellers; anterior setae modified as operculum; tubes of some may form extensive shelves or "reefs". (e.g., Phragmatopoma, Sabellaria)
- Order Sabellida
- Family Sabellidae: Tube-dwelling polychaetes commonly called "fan worms" or "feather-duster worms"; body heteronomous, divided into two regions similar to those of terebellids; pharynx unarmed and noneversible; peristomium bears a classy crown of branched, feathery tentacles that projects from the tube and functions in gas exchange and ciliary suspension feeding. (e.g., Eudistylia, Myxicola, Sabella*, Schizobranchia)
- Family Serpulidae: Heteronomous body divided into two regions; tube dwellers; anterior end bears a tentacular crown as in sabellids, plus a funnel-shaped operculum that can be pulled into the end of the calcareous tube when the worm withdraws; ciliary suspension feeders. (e.g., Hydroides, Serpula, Spirobranchus)
- Family Spirorbidae: Small heteronomous polychaetes living in coiled calcareous tubes attached to hard substrata; tubes coil to the right or left, usually depending on species; anterior end with tentacular crown and operculum similar to those of serpulids. (e.g., Circeis, Paralaeospira, Spirorbis)
- Order Pogonophora: (Beard worms) Deep water polycheats associated with the continental shelf and hydothermal vents. Slender sedentary heteronomous worms in chitin protein tubes. No mouth anus or digestive tract in the adults
- Clitellata Annelids with a clitellum associated with reproduction. No parapodia.
- Class Oligochaeta: Earthworms and many freshwater worms (Figure 3). With few setae and no parapodia; cephalic sensory structures reduced; body externally homonomous except for clitellum; often with complex reproductive systems; hermaphroditic; often placed as a subclass of the class Clitellata; fresh water, terrestrial, some marine. This class comprises three orders based in part on details of the male reproductive system, the first two contain a single family each. There is some controversy about the taxonomic arrangement of oligochaetes.
- Order Lumbriculida (family Lumbriculidae): Moderate- size, freshwater oligochaetes, many of which are known only from Lake Baikal in the Soviet Union. (e.g., Lamprodilus, Stylodrilus, Styloscolex, Trichodrilus)
- Order Moniligastrida (family Moniligastridae): Presumed primitive terrestrial oligochaetes (some workers consider these as a suborder of the order Haplotaxida; see Jamieson 1978); most known from damp soil, Asia; a few quite large, exceeding 1 m in length. (e.g., Desmogaster, Moniligaster)
- Order Haplotaxida: With over 25 families, includes the vast majority of oligochaete species; all habitats; diverse body forms; a few families are listed here as examples.
- Family Tubificidae: So-called sludge worms or tubifex worms; up to 2 cm long; fresh water and marine; some are very common in areas of high pollution. (e.g., Clitellio, Limnodrilus, Tubifex)
- Family Naididae: Many freshwater species; some live in marine or brackish water; some parasitic forms; some build tubes; several species bear an elongate prostomial proboscis; a few possess gills; almost all reproduce asexually; but most possess gonads at some stage of development; these fully aquatic oligochaetes are known worldwide. (e.g., Branchiodrilus, Dero, Ripistes, Slavina, Stylaria)
- Family Lumbricidae: Includes the various terrestrial earthworms, often relatively large; with well developed and complex reproductive systems; most are direct deposit feeders. (e.g., Allolobophora, Diporodrilus, Eisenia, Lumbricus*)
- Class Hirudiniomorpha: Leeches (Figure 4). Body with fixed number of segments, each with superficial annuli; heteronomous, with clitellum and a posterior and usually anterior sucker; often placed as a subclass of the class Clitellata; complex reproductive systems, hermaphroditic; most are fresh water or marine, a few are semiterrestrial; ectoparasitic, predaceous or scavenging. The class is presently recognized as comprising three subclasses described briefly below.
- Subclass Acanthobdellida: With a single family and species (Acanthobdellidae, Acanthobdella peledina). To 3 cm long; found in cold, freshwater lakes; part of the animal's life is spent as an ectoparasite on freshwater fishes (notably trout, char, and grayling), and presumably the rest of the time is spent in vegetation; body with 30 segments, posterior sucker only; with paired setae on anterior segments; coelom partially reduced, but obvious and with intersegmental septa; considered to represent something of a pre-leech condition.
- Subclass Branchiobdellida: With a single family (Branchiobdellidae). Usually less than 1 cm long; ectocommensal or ectoparasitic on freshwater crayfishes; body with 15 segments; with anterior and posterior suckers; setae absent; coelom partially reduced, but spacious throughout most of the body; ultrastructure studies suggest these animals may be intermediate between oligochaetes and "true" leeches (hirudineans); sometimes placed with oligochaetes. (e.g., Cambarincola, Stephanodrilus)
- Subclass Hirudinea: The "true" leeches; with two orders and about 12 families. Most are marine or fresh water, a few are semiterrestrial or amphibious; many are ectoparasitic bloodsuckers, others are free-living predators or scavengers; some parasitic forms serve as vectors for pathogenic protozoa, nematodes, and cestodes; body of 34 segments; with anterior and posterior suckers; no setae; coelom reduced to a complex series of channels (lacunae); two principal orders are the Rhynchobdellae and the Arhynchobdellae. (e.g., Glossiphonia, Hirudo*, Ozobranchus, Pontobdella)
- Phylogenetic outline of the annelids
Taxonomic Overview of the Annelids
▼ ▼Opistokonts Opistokonts (1)
• Hirodinomorpha (C)
▼ Metazoa (2)
▼ Eumetazoa (3)
▼ Triploblastica (4)
▼ Bilateria (5)
▼ Protostomia (6)
▼ Lophotrochozoa (7)
▼ Spirallia (8)
▼ Trochozoa (9)
• Annelida (P)
▼ Polychaet (C)
▼ Scolecida:
• Arenicholidae (F)
• Maldanidae (F)
• Capitellidae (F)
• Orbiniidae (F)
• Opheliidae (F)
▼ Palpata:
▼ Aciculata
• Phyllodocidae (F)
• Tomopteridae (F)
• Alciopidae (F)
• Neritae (F)
• Glyceridae (F)
• Nephtyidae (F)
• Aphroditidae (F)
• Hesionidae (F)
▼ Myzostomidae (O)
• Myzostomidae (F)
▼ Eunicida (O)
• Eunicidae (F)
• Amphinomidae (F)
▼ Onuphidae (F)
• Syllidae (F)
• Oenonidae (F)
• Lumbrineridae (F)
• Ichthyotomidae (F)
▼ Canalipalpata
▼ Spionida (O)
• Spionidae (F)
• Megelonidae (F)
• Chaetopteridae (F)
▼ Terebellida (O)
• Terebellidae (F)
• Ampharetidae (F)
• Cirratulidae (F)
• Pectinariidae (F)
• Flabelligeridae (F)
▼ Sabellida (O)
• Sabellariidae (F)
• Sabellidae (F)
• Serpulidae (F)
• Spirobidae (F)
• Oweniidae (F)
• Pogonophora (O)
▼ Clitellata
• Oligocheata (C)
