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Polychaetes
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the sandworm or clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe ''Nereus'' at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species (less than 2% of all polychaetes) are known from fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annelid
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 various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments. The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eunice Aphroditois
''Eunice aphroditois'' is a Benthic zone, benthic polychaete, bristle worm of warm marine waters. It lives mainly in the Atlantic Ocean, but can also be found in the Indo-Pacific. It ranges in length from less than to nearly . Its exoskeleton displays a wide range of colors, from black to purple and more. This species is an ambush predator; it hunts by burrowing its whole body in soft sediment on the ocean floor and waiting until its antennae detect prey. It then strikes with its sharp mandibles. It may also be found among coral reefs. ''Eunice aphroditois'' is also known as the bobbit worm or bobbitt worm. The name is believed to be taken from the John and Lorena Bobbitt case. It is sometimes called the sand striker or trap-jaw worm. Traces of their burrows have been found among fossils near Taiwan dating back twenty million years. Description These ambush predators have five antennae on their head that are used to sense prey. The body is covered by a hard exoskeleton. The ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Errantia
Errantia is a diverse group of marine life, marine polychaete worms in the phylum Annelida. Traditionally a subclass (biology), subclass of the paraphyletic class Polychaeta, it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Errantia and Sedentaria. These worms are found worldwide in marine environments and brackish water. Phylogeny The phylogeny of polychaetes is slowly being resolved. Errantia and Sedentaria are the two biggest clades of polychaetes, and together they compose clade Pleistoannelida. Two groups are nested within Errantia: Aciculata (Eunicida + Phyllodocida) and Protodriliformia (progenesis, small meiofaunal worms such as the Protodrilida). Historically, the order Amphinomida was part of this subclass. However, phylogenetic analyses place Amphinomida inside a basal clade with Sipunculida and ''Lobatocerebrum'', and this clade is the sister group to Pleistoannelida. Some taxon, taxa, such as Spintheridae and Myzostomida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parapodia
In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; : parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed lateral outgrowths that bear the chaetae. In several groups of sea snails and sea slugs, 'parapodium' refers to lateral fleshy protrusions. __TOC__ Annelid parapodia Most species of polychaete annelids have paired, fleshy parapodia which are segmentally arranged along the body axis. Parapodia vary greatly in size and form, reflecting a variety of functions, such as, anchorage, protection and locomotion. General description Parapodia in polychaetes can be uniramous (consisting of one lobe or ramus) but are usually biramous (two lobes or rami). In the latter case, the dorsal lobes are called notopodia and the ventral lobes neuropodia. Both neuropodia and notopodia may possess a bundle of chaetae (neurochaetae and notochaetae respectively ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sipuncula
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162 species of marine annelid worms, that have secondarily lost their segmentation. Sipuncula was once considered a phylum of unsegmented worms, but was demoted to a class of Annelida, based on recent molecular work. Sipunculans vary in size but most species are under in length. The body is divided into an unsegmented, bulbous trunk and a narrower, anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ... section, called the "introvert", which can be retracted into the trunk. The mouth is at the tip of the introvert and is surrounded in most groups by a ring of short tentacles. With no hard parts, the body is flexible and mobile. Although found in a range of habitats thro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 arthropods. Polychaete annelids (''polychaeta'' literally meaning "many bristles") are named for their chaetae. In Polychaeta, chaetae are found as bundles on the parapodia, paired appendages on the side of the body. The chaetae are epidermal, extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ... structures, and clearly visible in most polychaetes. They are probably the best-studied structures in these animals. Segments bearing chaetae are called chaetigers. Use in taxonomy and identification The ultrastructure of chaetae is fundamentally similar for all taxa but there is vast diversity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abyssal Plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins, the other elements being an elevated mid-ocean ridge and flanking abyssal hills. The creation of the abyssal plain is the result of the spreading of the seafloor (plate tectonics) and the melting of the lower oceanic crust. Magma rises from above the asthenosphere (a layer of the upper mantle), and as this basaltic material reaches the surface at mid-ocean ridges, it forms new oceanic crust, which is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alitta Virens
''Alitta virens'' (common names include sandworm, sea worm, and king ragworm; older scientific names, including ''Nereis virens'', are still frequently used) is an annelid worm that burrows in wet sand and mud. They construct burrows of different shapes (I,U,J and Y) They range from being very complex to very simple. Long term burrows are held together by mucus. Their burrows are not connected to each other; they are generally solitary creatures. The spacing between the burrows depends on how readily they can propagate water signals. It was first described by biologist Michael Sars in 1835. It is classified as a polychaete in the family Nereididae. Sandworms make up a large part of the live sea- bait industry. To fulfill the needs of this industry, some sandworms are commercially grown. Sandworming, the harvesting of sandworms from mudflats, employs over 1,000 people in Maine, US. , the population of sandworms had diminished greatly over the preceding few years due in large p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaetopteridae
The Chaetopteridae are a Family (biology), family of marine filter feeding, filter-feeding Polychaete, polychaete worms that live in vertical or U-shaped tubes in tunnels buried in the sedimentary or hard substrate of marine environments. The worms are highly adapted to the hard tube they secrete. Inside the tube the animal is segmented and regionally specialized, with highly modified appendages on different segments for cutting the tunnel, feeding, or creating suction for the flow of water through the tube home. The modified segments for feeding are on the 12th segment from the head for members of this family.Ruppert, E., Fox, R., & Barnes, R. (2007). ''Invertebrate Zoology: A functional Evolutionary Approach''. 7th Edition. Belmont:Thomson Learning. Larvae Chaetopteridae larvae are the largest among the polychaete worms. The larvae will range in size from 0.4 mm to 2.5 mm (largest polychaete larvae reported having a maximum length of 12 mm; the late stage of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lugworm
''Arenicola'', also known as sandworms, is a genus of capitellid annelid worms comprising the lugworms and black lugs. ''A.cristata'' is the dominant warm-water lugworm on the shores of North America and Humboldt Bay, California. ''A. caroledna'' dominates in China and Japan while ''Arenicola marina'' is mostly found in Europe, up to Norway. ''Arenicola loveni'' is restricted to Southern Africa. Species The following species are recognised in the genus ''Arenicola'': *'' Arenicola bombayensis'' Kewalramani et al * '' Arenicola brasiliensis'' Nonato, 1958 *'' Arenicola caroledna'' Wells * '' Arenicola cristata'' Stimpson, 1856 * '' Arenicola defodiens'' Cadman & Nelson-Smith, 1993 * '' Arenicola glasselli'' Berkeley & Berkeley, 1939 * '' Arenicola loveni'' Kinberg, 1866 * '' Arenicola marina'' (Linnaeus, 1758) Life in a burrow A lugworm lives in a U-shaped burrow in sand. The U is made of an L-shaped gallery lined with mucus, from the toe of which a vertical unlined shaft run ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedentaria
Sedentaria is a diverse clade of annelid worms. It is traditionally treated as a subclass of the paraphyletic class Polychaeta, but it is also a monophyletic group uniting several polychaetes and the monophyletic class Clitellata. It is the sister group of Errantia. Sedentaria are mainly found within marine environments that have low oxygen levels and are specially adapted to these low oxygen environments by increasing gill surface area and having high-affinity respiratory proteins. Furthermore, they go through a process of metabolic depression which lowers their energy use so that they can inhibit these low oxygen zones . Phylogeny The phylogeny of polychaetes is slowly being resolved. Sedentaria and Errantia are the two biggest clades of polychaetes, and together they compose clade Pleistoannelida. Sedentaria's most basal clade is Orbiniida. Other groups that are nested within Sedentaria are: Clitellata, the Sabellida/ Spionida clade, Opheliida, Echiura, Cirratulifor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myzostomida
The Myzostomida or Myzostomatida are an order of small marine (ocean), marine worms, which are Parasitism, parasitic on echinoderms, mostly crinoids. These highly unusual and diverse annelids were first discovered by Friedrich Sigismund Leuckart in 1827. Morphology A typical myzostomid has a flattened, rounded shape, with a thin edge drawn out into delicate radiating hairs called Cilium, cirri. The dorsal surface is smooth, with five pairs of Parapodium, parapodia on the bottom surface. These parapodia are armed with supporting and hooked setae, by means of which the worm adheres to its host. Beyond the parapodia are four pairs of organs, often called suckers. These organs are probably of sensory nature, and are comparable to the lateral sense organs of capitellids. The mouth and cloacal opening are generally at opposite ends of the bottom surface. The former leads to a protrusible pharynx, from which the esophagus opens into a wide intestinal chamber with branching lateral Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
