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Aplacophora
Aplacophora is a presumably paraphyletic taxon. This is a class of small, deep-water, exclusively benthic, marine molluscs found in all oceans of the world. MolluscaBase eds. (2021). MolluscaBase. Aplacophora. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=411 on 2021-04-13 All known modern forms are shell-less: only some extinct primitive forms possessed valves. The group comprises the two clades Solenogastres (Neomeniomorpha) and Caudofoveata (Chaetodermomorpha), which between them contain 28 families and about 320 species. The aplacophorans are traditionally considered ancestral to the other mollusc classes. However, the relationship between the two aplacophoran groups and to the other molluscan classes and to each other is as yet unclear. Aplacophorans are cylindrical and worm-like in form, and most very small, being no longer than ; some species, however, can reach a length of . Habitat Caudofoveates generall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solenogastres
The Solenogastres (less often referred to as Neomeniomorpha), common name the solenogasters, are one class of small, worm-like, shell-less molluscs (Aplacophora), the other class being the Caudofoveata (Chaetodermomorpha). MolluscaBase eds. (2021). MolluscaBase. Solenogastres. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=2094 on 2021-04-14 Some recent literature, and recent molecular evidence, indicates that the Aplacophora may be polyphyletic, and therefore these taxonomists divide Solenogastres and Caudofoveata into separate classes. Morphology In contrast to all other molluscan classes, the Aplacophora have no shell, and are instead covered by aragonite, aragonitic sclerites (calcareous wikt:spicule, spicules), which can be solid or hollow. These spicules can be arranged perpendicular to one another within the cuticle to form a skeleton, or can stick up to form a palisade, or can lie flat against the cuticle. 80 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusca
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radula
The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus. The radula is unique to the molluscs, and is found in every class of mollusc except the bivalves, which instead use cilia, waving filaments that bring minute organisms to the mouth. Within the gastropods, the radula is used in feeding by both herbivorous and carnivorous snails and slugs. The arrangement of teeth ( denticles) on the radular ribbon varies considerably from one group to another. In most of the more ancient lineages of gastropods, the radula is used to graze, by scraping diatoms and other microscopic algae off rock surfaces and other substrates. Predatory marine snails such as the Naticidae use the radula plus an acidic secretion to bore through the shell of other molluscs. Other predatory marine sn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caudofoveata
Caudofoveata is a small class within the phylum Mollusca, also known as Chaetodermomorpha. The class is often combined with Solenogastres and termed Aplacophora, but some studies have cast doubt on the monophyly of this group. Anatomy Caudofoveata are small (1–30 mm), mainly deep sea molluscs. They are worm-like, lacking shells or distinct muscular feet; they instead have scales and calcareous spines called sclerites, for movement. Ecology Caudofoveates live by burrowing through soft sediment, and feed by lying vertically in the sediment with just the mouthparts exposed and taking in passing organic detritus. During sexual reproduction, the female produces eggs which are fertilized and brooded, and then the larvae swim freely. Diet Caudofoveates feed on foraminifera. Taxonomy Caudofoveata comprises the following families and genera: * Chaetodermatidae ** ''Caudofoveatus'' ** '' Chaetoderma'' * Falcidentidae ** '' Chaetoderma'' ** ''Falcidens'' ** '' Furcillidens'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Falcidens
''Falcidens'' is one of three genera within the family Chaetodermatida; its radula consists of a single row of teeth which are mineralized in crystalline hydroxyapatite (a most unusual mineral in organisms), and its teeth are not periodically shed and replaced like in other molluscs. '' For details of the radula, see Radula#In caudofoveates.'' It contains the following species: * ''Falcidens acutargatus'' Salvini-Plawen, 1992 * ''Falcidens aequabilis'' Salvini-Plawen, 1972 * ''Falcidens caudatus'' Heath, 1918) * ''Falcidens chiastos'' Scheltema, 1989 * ''Falcidens crossotus'' Salvini-Plawen, 1968 * ''Falcidens gutturosus'' Kowalewsky, 1901) * ''Falcidens halanychi'' Schander, Scheltema & Ivanov, 2006 * ''Falcidens hartmanae'' Schwabl, 1961) * ''Falcidens hoffmanni'' Stork, 1939) * ''Falcidens indicus'' Stork, 1941) * ''Falcidens ingolfensis'' Salvini-Plawen, 1971 * ''Falcidens limifossorides'' Salvini-Plawen, 1986 * ''Falcidens liosqueameus'' Salvini-Plawen, 1969 * ''Falcide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusc Shell
The mollusc (or molluskOften spelled mollusk shell in the USA; the spelling "mollusc" are preferred by ) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater. The ancestral mollusc is thought to have had a shell, but this has subsequently been lost or reduced on some families, such as the squid, octopus, and some smaller groups such as the caudofoveata and neomeniomorpha, solenogastres. Today, over 100,000 living species bear a shell; there is some dispute as to whether these shell-bearing molluscs form a monophyletic group (conchifera) or whether shell-less molluscs are interleaved into their family tree. Malacology, the scientific study of molluscs as living organisms, has a branch devoted to the study of shells, and this is called conchology—al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aculifera
Aculifera is a proposed clade of molluscs incorporating those groups that have no conch or shell, that is, the Polyplacophora, Caudofoveata (=Chaetodermomorpha) and Solenogastres (=Neomeniomorpha). For a summary, see It is sister to the Conchifera. The oldest known aculiferan is ''Qaleruaqia'', which was found in the Aftenstjernesø Formation in Greenland, which dates back to the Cambrian Stage 4 Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commissio .... References Mollusc taxonomy {{mollusc-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valve (mollusc)
A valve is each articulating part of the shell of a mollusc or another multi-shelled animal such as brachiopods and some crustaceans. Each part is known as a valve or in the case of chitons, a "plate". Members of two classes of molluscs, the Bivalvia (clams) and the Polyplacophora (chitons), have valves. Species within one family of very unusual small sea snails, marine opisthobranch gastropods in the family Juliidae, also have two articulating shells or valves, which resemble those of a bivalve. This exceptional family is commonly known as the bivalved gastropods. Gastropods in general are sometimes called "univalves", because in those that have a shell, the shell is usually in one part. Chitons The valves of chitons are eight dorsal, articulated shell plates, which are frequently coloured and sculpted. After death the girdle that holds the plates together disintegrates and the plates separate. Thus individual plates can be found washed up in beach drift, as shown i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cloaca
In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, and a few mammals ( monotremes, tenrecs, golden moles, and marsupial moles), have this orifice, from which they excrete both urine and feces; this is in contrast to most placental mammals, which have two or three separate orifices for evacuation. Excretory openings with analogous purpose in some invertebrates are also sometimes referred to as cloacae. Mating through the cloaca is known as cloacal copulation, commonly referred to as cloacal kiss. The cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent-marking behavior of some reptiles, marsupials, amphibians, and monotremes. Etymology The word is from the Latin verb ''cluo'', "(I) cleanse", thus the noun ''c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, the equivalent Latin term ''cladus'' (plural ''cladi'') is often used in taxonomical literature. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between org ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoderm
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. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holothuroidea
Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothurian () species worldwide is about 1,717, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as '' trepang'', ''namako'', ''bêche-de-mer'', or ''balate''. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process. Like all echinoderms, sea cucumbers have an endoskeleton just below the skin, calcified structures that are usually reduced to isolated microscopic ossicles (or sclerietes) joined by connective tissue. In some species these can sometimes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
