|
Brachiolaria
A brachiolaria is the second stage of larval development in many starfishes. It follows the bipinnaria. Brachiolaria have bilateral symmetry, unlike the adult starfish, which have a pentaradial symmetry. Starfish of the order Paxillosida (''Astropecten'' and '' Asterina'') have no brachiolaria stage, with the bipinnaria developing directly into an adult. The brachiolaria develops from the bipinnaria larva when the latter grows three short arms at the underside of its anterior end. These arms each bear sticky cells at the tip, and they surround an adhesive sucker. The larva soon sinks to the bottom, attaching itself to the substrate, firstly with the tips of the arms, and then with the sucker. Once attached, it begins to metamorphose into the adult form. The adult starfish develops only from the hind-part of the larva, away from the sucker. It is from this part that the arms of the adult grow, with the larval arms eventually degenerating and disappearing. The digestive system of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Starfish
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at below the surface. Starfish are marine invertebrates. They typically have a central disc and usually five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipinnaria
A bipinnaria is the first stage in the larval development of most starfish, and is usually followed by a brachiolaria stage. Movement and feeding is accomplished by the bands of cilia. Starfish that brood their young generally lack a bipinnaria stage, with the eggs developing directly into miniature adults The bipinnaria is free-living, swimming as part of the zooplankton. When it initially forms, the entire body is covered by cilia, but as it grows, these become confined to a narrow band forming a number of loops over the body surface. A pair of short, stubby arms soon develop on the body, with the ciliated bands extending into them. In addition to propelling the larva through the water, the cilia also catch suspended food particles, and deliver them to the mouth (more correctly called a ''stomodeum''). Eventually, three additional arms develop at the front end of the larva; at this point it becomes a brachiolaria. In some species, including the common starfish ''Asterias'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paxillosida
The Paxillosida are a large order (biology), order of sea stars. Characteristics Paxillosida adults lack an anus and have no suckers on their tube feet. They do not develop the brachiolaria stage in their early development.Matsubara, M., Komatsu, M., Araki, T., Asakawa, S., Yokobori, S.-I., Watanabe, K. & Wada, H. (2005) The phylogenetic status of Paxillosida (Asteroidea) based on complete mitochondrial DNA sequences. Molecular Genetics and Evolution, 36, 598–605 They possess marginal plates, and have sessile pedicellariae. They mostly inhabit soft-bottomed environments of sand or mud. Systematics Recent analyses suggest Paxillosida may be a sister taxon of Asterina (starfish), Asterina. The order is divided into these families: * family Astropectinidae Gray, 1840 * family Ctenodiscidae Sladen, 1889 * family Goniopectinidae Verrill, 1889 * family Luidiidae Sladen, 1889 * family Porcellanasteridae Sladen, 1883 * family Pseudarchasteridae * family Radiasteridae Fisher, 1916 Fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoderm Biology
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian. The echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the biotic desert of the deep sea, as well as shallower oceans. Most echinoderms are able to reproduce asexually and regenerate tissue, organs, and limbs; in some cases, they can undergo complete regeneration from a single limb. Geologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asterias Sp Older Brachiolaria Larva From Below
''Asterias'' is a genus of the Asteriidae family of sea stars. It includes several of the best-known species of sea stars, including the (Atlantic) common starfish, ''Asterias rubens'', and the northern Pacific seastar, '' Asterias amurensis''. The genus contains a total of eight species in all. All species have five arms and are native to shallow oceanic areas (the littoral zone) of cold to temperate parts of the Holarctic. These starfish have planktonic larvae. ''Asterias amurensis'' is an invasive species in Australia and can in some years become a pest in the Japanese mariculture industry. History The genus ''Asterias'' was first described by Carl Linnaeus in the 10th edition of Systema Naturae in 1758 when he published ''A. rubens''. It was for a time the only species, but by the early 1800s a few dozen taxa had been described in this genus. In 1825 Thomas Say listed six species native to the coasts of the United States (which at the time consisted of the east coast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The larva's appearance is generally very different from the adult form (''e.g.'' caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. Larvae are frequently adapted to different environments than adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments, but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form. In some organisms like polychaetes and barnacles, adults are immobil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Symmetry (biology)
Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a plane of symmetry down its centre, or a pine cone with a clear symmetrical spiral pattern. Internal features can also show symmetry, for example the tubes in the human body (responsible for transporting gases, nutrients, and waste products) which are cylindrical and have several planes of symmetry. Biological symmetry can be thought of as a balanced distribution of duplicate body parts or shapes within the body of an organism. Importantly, unlike in mathematics, symmetry in biology is always approximate. For example, plant leaves – while considered symmetrical – rarely match up exactly when folded in half. Symmetry is one class of patterns in nature whereby there is near-repetition of the pattern element, either by reflection or rotation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astropecten
''Astropecten'' is a genus of sea stars of the family Astropectinidae. Identification These sea stars are similar one to each other and it can be difficult to determine with certainty the species only from a photograph. To have a certain determination, in some cases, animals should be analyzed in the laboratory or using genetic testing, but often it isn’t possible. In order to determine the species, with a reasonable margin of error, it’s necessary to observe the appearance of the animal, in particular, based on some typical features described by principal authors that have analyzed over the years a large number of specimens in the laboratory. The main elements, to determine the various species from photo, are: the appearance of the dorsal marginal plates and spines, the size, the shape of disc and arms. For a good identification by sea photo it is important to take a complete picture of all the subject, a picture of the detail of the marginal plates and to measure as pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asterina (starfish)
''Asterina'' is a genus of asteroideans in the family Asterinidae. The species occurring in Australian waters are considered to not be congeneric with the type species ''A. gibbosa'' ( Pennant, 1777) by Rowe and Gates (1995), and will possibly to assigned to another genus or a new genus. Rowe and Gates (1995) also suggested that ''Asterina'' should be restricted to Atlantic waters.Rowe, F. & Gates, J. (1995). Echinodermata. In Wells, A. (Ed.), ''Zoological Catalogue of Australia'', Volume 33. Melbourne: CSIRO Australia. Species *'' Asterina fimbriata'' Perrier, 1875Perrier, E. (1875). ''Revision de la Collection de Stellerides du Museum d'Histoire Naturelle de Paris''. Paris: C. Reinwald. *''Asterina gibbosa'' ( Pennant, 1777) Pennant, T. (1777). ''British Zoology. Vol. IV. Crustacea. Mollusca. Testacea''. London: Benj. White. *'' Asterina gracilispina'' Clark, 1923Clark, H. L. (1923). The echinoderm fauna of South Africa. ''Annals of the South African Museum'', 13, 221–435. * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals can be divided into species that undergo complete metamorphosis (" holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis (" ametaboly"). Scientific usage of the term is technically precise, and it is not applied to general aspects of cell growth, including rapid growth spurts. Generally organisms with a larva stage undergo metamorphosis, and during metamorphosis the organism loses larval characteristics. References to "metamorphosis" in mammals are imprecise and only colloquial, but historically idealist ideas of transformation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelom
The coelom (or celom) is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups. Etymology The term ''coelom'' derives from the Ancient Greek word (), meaning 'cavity'. Structure Development The coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron. In Protostomes, the coelom forms by a process known as schizocoely. The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Vascular System
The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet. Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract. The exact structure of the system varies somewhat between the five classes of echinoderm. The system is part of the coelomic cavities of echinoderms, together with the haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and perihaemal coelom. Other terms sometimes used to refer to the water vascular system are "ambulacral system" and "aquiferous system". In the past, "aquiferous system" was also used to refer to many unrelated invertebrate structures, but today, it is restricted to water channels in sponges and the hydrostatic skeleton of some mollusks ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
