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Margarites Helicinus
''Margarites helicinus'', common name the helicina margarite or spiral margarite, is a species of sea snail, a marine gastropod mollusk in the family Margaritidae. ''Margarites helicinus'' has been established by Phipps in 1774 and not by Fabricus in 1780 as Winchworth (1932), Sneli (1970) (and others) mention. Dall established in 1919 two varieties, but both have become synonyms of ''Margarites helicinus''. * ''Margarites helicinus'' var. ''elevatus'' Dall, 1919 * ''Margarites helicinus'' var. ''excavatus'' Dall, 1919 Description The size of the shell varies between 3. mm and 11 mm. The umbilicate, thin shell has a depressed-conoidal shape. It is flesh-colored, with paler at periphery and below the suture, fading into corneous around the umbilicus. The surface is very bright, shining, polished, and smooth except for fine subobsolete concentric lines around the umbilicus. The spire is conoidal. The apex is minute but obtuse. The suture is impressed. The shell contains abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Name
In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrasted with the scientific name for the same organism, which is often based in Latin. A common name is sometimes frequently used, but that is not always the case. In chemistry, IUPAC defines a common name as one that, although it unambiguously defines a chemical, does not follow the current systematic naming convention, such as acetone, systematically 2-propanone, while a vernacular name describes one used in a lab, trade or industry that does not unambiguously describe a single chemical, such as copper sulfate, which may refer to either copper(I) sulfate or copper(II) sulfate. Sometimes common names are created by authorities on one particular subject, in an attempt to make it possible for members of the general public (including s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an international border with the Mexico, Mexican state of Baja California to the south. With almost 40million residents across an area of , it is the List of states and territories of the United States by population, largest state by population and List of U.S. states and territories by area, third-largest by area. Prior to European colonization of the Americas, European colonization, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. European exploration in the 16th and 17th centuries led to the colonization by the Spanish Empire. The area became a part of Mexico in 1821, following Mexican War of Independence, its successful war for independence, but Mexican Cession, was ceded to the U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Margarites
''Margarites'' is a genus of sea snails, marine gastropod mollusks in the family Margaritidae. This genus belonged previously to the subfamily Margaritinae in the family Turbinidae Turbinidae, the turban snails, are a family of small to large marine gastropod molluscs in the superfamily Trochoidea.Bouchet, P. (2014). Turbinidae Rafinesque, 1815. Accessed through: World Register of Marine Species at http://www.marinespecie .... Description This genus consists of small species of variable size between 3 mm and 15 mm. The Alaskan specimens of '' Margarites costalis'' reach almost 25 mm in diameter. Their flat shell has a turbiniform shape with convex whorls and a typical iridescent lustre. Species Species within the genus ''Margarites'' include: * '' Margarites albolineatus'' (E. A. Smith, 1899) * '' Margarites angulatus'' Galkin, 1955 * '' Margarites argentatus'' (Gould, 1841) * '' Margarites atlantoides'' (Quinn, 1992) * '' Margarites avachensis'' Galkin, 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, jellyfish, 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"). Generally organisms with a larval stage undergo metamorphosis, and during metamorphosis the organism loses larval characteristics. Etymology The word ''metamorphosis'' derives from Ancient Greek , "transformation, transforming", from ('), "after" and ('), "form". Hormonal control In insects, growth and metamorphosis are controlled by hormones synthesized by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torsion (gastropod)
Torsion is a gastropod synapomorphy which occurs in all gastropods during larval development. Torsion is the rotation of the visceral mass, mantle, and shell 180˚ with respect to the head and foot of the gastropod. This rotation brings the mantle cavity and the anus to an anterior position above the head. In some groups of gastropods ( Opisthobranchia) there is a degree of secondary detorsion or rotation towards the original position; this may be only partial detorsion or full detorsion. The torsion or twisting of the visceral mass of larval gastropods is not the same thing as the spiral coiling of the shell, which is also present in many shelled gastropods. Development There are two different developmental stages which cause torsion. The first stage is caused by the development of the asymmetrical velar/foot muscle which has one end attached to the left side of the shell and the other end has fibres attached to the left side of the foot and head. At a certain point in lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Veliger
A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxonomic classes. It is produced following either the embryonic or trochophore larval stage of development. In bivalves the veliger is sometimes referred to as a D-stage (early in its development) or pediveliger (late in its development) larva. This stage in the life history of these groups is a free-living planktonic organism; this mode of life potentially enhances dispersal to new regions far removed from the adult mollusks that produced the larvae. The general structure of the veliger includes a shell that surrounds the visceral organs of the larva (e.g., digestive tract, much of the nervous system, excretory organs) and a ciliated wikt:velum#English, velum that extends beyond the shell as a single or multi-lobed structure used for swimming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trochophore
A trochophore () is a type of free-swimming planktonic marine larva with several bands of cilia. By moving their cilia rapidly, they make a water eddy to control their movement, and to bring their food closer in order to capture it more easily. Occurrence Trochophores exist as a larval form within the trochozoan clade, which include the entoprocta, entoprocts, molluscs, annelids (including echiurans and sipunculans) and nemerteans. Together, these phyla make up part of the Lophotrochozoa; it is possible that trochophore larvae were present in the life cycle of the group's common ancestor. Etymology The term ''trochophore'' derives from the ancient Greek (), meaning "wheel", and () — or () —, meaning 'to bear, to carry', because the larva is bearing a wheel-shaped band of cilia. Feeding habits Trochophore larvae are often planktotrophic; that is, they feed on other plankton species. Life cycle The example of the development of the annelid ''Pomatoceros lamarckii ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastrula
Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of Cell (biology), cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as the gastrula. Before gastrulation, the embryo is a continuous Epithelium, epithelial sheet of cells; by the end of gastrulation, the embryo has begun Cellular differentiation, differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. Anatomical terms of location#Dorsal and ventral, dorsal–ventral, Anatomical terms of location#Anterior and posterior, anterior–posterior), and internalized one or more cell types, including the prospective Gastrointestinal tract, gut. Gastrula layers In Triploblasty, triploblastic organisms, the gastrula is trilaminar (three-layered). These three germ layers are the ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).Mundlos 2009p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spiral Cleavage
In embryology, cleavage is the division of cells in the early development of the embryo, following fertilization. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula, or of the blastocyst in mammals. Depending mostly on the concentration of yolk in the egg, the cleavage can be holoblastic (total or complete cleavage) or meroblastic (partial or incomplete cleavage). The pole of the egg with the highest concentration of yolk is referred to as the vegetal pole while the opposite is referred to as the animal pole. Cleavage differs from other forms of cell division in that it increases the number of cells and nuclear mass without increasing the cytoplasmic mass. This means that with each successive subdivision, there is rough ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
San Juan Islands
The San Juan Islands is an archipelago in the Pacific Northwest of the United States between the U.S. state of Washington and Vancouver Island, British Columbia, Canada. The San Juan Islands are part of Washington state, and form the core of San Juan County, Washington, San Juan County. In the archipelago, four islands are accessible to vehicular and foot traffic via the Washington State Ferries system. History The Gulf of Georgia Culture Area encompasses the San Juan and Gulf Islands, which share many archaeological similarities. These islands were home to various Coast Salish languages, Coast Salish peoples, including the Nooksack (tribe), Nooksack and Northern Straits Salish, Northern Straits groups (consisting of the Lummi people, Lummi, Klallam, Saanich dialect, Saanich, Samish people, Samish, and Songhees dialects). European exploration in the area introduced smallpox in the 1770s. The Spanish explorer Francisco de Eliza named the San Juan Islands ''Isla y Archipié ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spawning
Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is known as spawning. The vast majority of aquatic and amphibious animals reproduce through spawning. These include the following groups: *Bony fishes *Crustaceans (such as crabs, shrimps, etc.) *Mollusks (such as oysters, octopus, squid) *Echinoderms (such as sea urchins, sea stars, sea cucumbers, etc.) *Amphibians (such as frogs, toads, salamanders, newts) *Aquatic insects (such as dragonflies, mayflies, mosquitoes) *Coral, which are living colonies of tiny, aquatic organisms—not plants, as they are sometimes perceived to be. Corals, while appearing sedentary or botanical by nature, actually spawn by releasing clouds of sperm and egg cells into the water column, where the two mix. As a general rule, aquatic or semiaquatic reptiles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Of Okhotsk
The Sea of Okhotsk; Historically also known as , or as ; ) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands on the southeast, Japan's island of Hokkaido on the south, the island of Sakhalin along the west, and a stretch of eastern Siberian coast along the west and north. Its northeast corner is the Shelikhov Gulf. The sea is named for the port of Okhotsk, itself named for the Okhota River. Geography The Sea of Okhotsk covers an area of , with a mean depth of and a maximum depth of . It is connected to the Sea of Japan on either side of Sakhalin: on the west through the Sakhalin Gulf and the Gulf of Tartary; on the south through the La Pérouse Strait. In winter, navigation on the Sea of Okhotsk is impeded by ice floes. Ice floes form due to the large amount of freshwater from the Amur River, lowering the salinity of upper levels, often raising the freezing point of the sea surface. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
