|
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma ( cephalothorax). It is a distinctive feature of the subphylum Chelicerata (arachnids, horseshoe crabs and others). Although it is similar in most respects to an abdomen (and is often referred to as such), the opisthosoma is differentiated by its inclusion of the respiratory organs ( book lungs or book gills) and the heart. Segments The number of segments and appendages on the opisthosoma vary. Scorpions have 13, but the first is only seen during its embryological development. Other arachnids have fewer; harvestmen, for instance, have only ten. In general, appendages are absent or reduced, although in horseshoe crabs they persist as large plate-like limbs, called opercula or branchiophores, bearing the book gills, and that function in locomotion and gas exchange. In most chelicerates the opisthosomal limbs are greatly reduced and persist only as specialized structures, such as the silk- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horseshoe Crab
Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpions. The body of a horseshoe crab is divided into three main parts: the cephalothorax, abdomen, and telson. The largest of these, the cephalothorax, houses most of the animal's eyes, limbs, and internal organs. It is also where the animal gets its name, as its shape somewhat resembles that of a horseshoe. Horseshoe crabs have been described as "living fossils", having changed little since they first appeared in the Triassic. Only four species of horseshoe crab are extant today. Most are marine, though the mangrove horseshoe crab is often found in brackish water, and the Atlantic horseshoe crab is resident in brackish estuarine ecosystems such as the Delaware and Chesapeake bays. Additionally, certain extinct species transitioned t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opiliones
The Opiliones (formerly Phalangida) are an Order (biology), order of arachnids, Common name, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered worldwide, although the total number of extant taxon, extant species may exceed 10,000. The order Opiliones includes five suborders: Cyphophthalmi, Eupnoi, Dyspnoi, Laniatores, and Tetrophthalmi, which were named in 2014. Representatives of each extant suborder can be found on all continents except Antarctica. Well-preserved fossils have been found in the 400-million-year-old Rhynie cherts of Scotland, and 305-million-year-old rocks in France. These fossils look surprisingly modern, indicating that their basic body shape developed very early on, and, at least in some taxa, has changed little since that time. Their Phylogenetics, phylogenetic position within the Arachnida is disputed; their closest relatives may be camel spiders (Solifugae ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Book Lung
A book lung is a type of respiration organ used for atmospheric gas-exchange that is present in many arachnids, such as scorpions and spiders. Each of these organs is located inside an open, ventral-abdominal, air-filled cavity (atrium) and connects with its surroundings through a small opening for the purpose of respiration. Structure and function Book lungs are not related to the lungs of modern land-dwelling vertebrates. Their name instead describes their structure and purpose as a case of convergent evolution. Stacks of alternating air pockets and tissue filled with hemolymph give them an appearance similar to a "folded" book. Their number varies from just one pair in most spiders to four pairs in scorpions. The unfolded "pages" (plates) of the book lung are filled with hemolymph. The folds maximize the surface exposed to air, and thereby maximize the amount of gas exchanged with the environment. In most species, no motion of the plates is needed to facilitate this ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whip Spider
Amblypygi is an order of arachnids also known as whip-spiders or tailless whip-scorpions, not to be confused with whip-scorpions or vinegaroons that belong to the related order Thelyphonida. The name "amblypygid" means "blunt tail", a reference to a lack of the flagellum that is otherwise seen in whip-scorpions. Amblypygids possess no silk glands or venom. They rarely bite if threatened but can grab fingers with their pedipalps, resulting in thorn-like puncture-injuries. As of 2023, five families, 17 genera, and around 260 species had been discovered and described. They are found in tropical and subtropical regions worldwide, mainly in warm and humid environments. They like to stay protected and hidden within leaf litter, caves, or underneath bark. Some species are subterranean; all are nocturnal. Fossilized amblypygids have been found dating back to the Carboniferous period, such as ''Weygoldtina''. Description Body-plan Being arachnids, Amblypygi possess two body-segments; ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whip Scorpion
Uropygi is an arachnid order comprising invertebrates commonly known as whip scorpions or vinegaroons (also spelled vinegarroons and vinegarones). They are often called uropygids. The name "whip scorpion" refers to their resemblance to true scorpions and possession of a whiplike tail, and "vinegaroon" refers to their ability when attacked to discharge an offensive, vinegar-smelling liquid, which contains acetic acid. The order may also be called Thelyphonida. Both names, Uropygi and Thelyphonida, may be used either in a narrow sense for the order of whip scorpions, or in a broad sense which includes the order Schizomida. Taxonomy Carl Linnaeus first described a whip scorpion in 1758, although he did not distinguish it from what are now regarded as different kinds of arachnid, calling it ''Phalangium caudatum''. '' Phalangium'' is now used as a name for a genus of harvestmen (Opiliones). In 1802, Pierre André Latreille was the first to use a genus name solely for whip scorpions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pecten (biology)
A pecten (: pectens or pectines) is a comb-like structure, widely found in the biological world. Although pectens in various animals look similar, they have a varied range of uses, from grooming and filtering to sensory adaptations. Etymology The adjective, pectinate, means supplied with a comb-like structure. This form, cognate to pecten with both derived from the Latin for comb, ''pectin'' (genitive ''pectinis''), is reflected in numerous scientific names in forms such as pectinata, pectinatus or pectinatum, or in specific epithets such as '' Murex pecten''. Some toothcombs are referred to as pectinations. Oral use In ducks, they exist on the sides of the bill and serve both as a strainer for food and a comb for preening. Whales have a similar oral comb-like structure called baleen. Retinal use The avian eye also contains a structure called a pecten oculi, which is a comb-like projection of the retina. It is thought to enhance nutrition for the cells of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spider
Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and rank seventh in total species diversity among all Order (biology), orders of organisms. Spiders are found worldwide on every continent except Antarctica, and have become established in nearly every land habitat. , 53,034 spider species in 136 Family (biology), families have been recorded by Taxonomy (biology), taxonomists. However, there has been debate among scientists about how families should be classified, with over 20 different classifications proposed since 1900. Anatomy, Anatomically, spiders (as with all arachnids) differ from other arthropods in that the usual body segmentation (biology), segments are fused into two Tagma (biology), tagmata, the cephalothorax or prosoma, and the opisthosoma, or abdomen, and joined by a small, cylindr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinneret (spider)
A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are typically segmented. While most spiders have six spinnerets, some have two, four, or eight. They can move both independently and in concert. Most spinnerets are not simple structures with a single orifice producing a single thread, but complex structures of many microscopic spigots, each producing one filament. This produces the necessary orientation of the protein molecules, without which the silk would be weak and useless. Spigots can be singular or found in groups, which also permits spiders to combine multiple filaments in different ways to produce many kinds of silk for various purposes. Spinneret morphology can help arachnologists identify the taxon of a specimen and the specific morphology of a spigot can determine its use as well. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Book Gill
A book is a structured presentation of recorded information, primarily verbal and graphical, through a medium. Originally physical, electronic books and audiobooks are now existent. Physical books are objects that contain printed material, mostly of writing and images. Modern books are typically composed of many pages bound together and protected by a cover, what is known as the ''codex'' format; older formats include the scroll and the tablet. As a conceptual object, a ''book'' often refers to a written work of substantial length by one or more authors, which may also be distributed digitally as an electronic book (ebook). These kinds of works can be broadly classified into fiction (containing invented content, often narratives) and non-fiction (containing content intended as factual truth). But a physical book may not contain a written work: for example, it may contain ''only'' drawings, engravings, photographs, sheet music, puzzles, or removable content like paper dolls ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harvard University Press
Harvard University Press (HUP) is an academic publishing house established on January 13, 1913, as a division of Harvard University. It is a member of the Association of University Presses. Its director since 2017 is George Andreou. The press maintains offices in Cambridge, Massachusetts, near Harvard Square, and in London, England. The press co-founded the distributor TriLiteral LLC with MIT Press and Yale University Press. TriLiteral was sold to LSC Communications in 2018. Notable authors published by HUP include Eudora Welty, Walter Benjamin, E. O. Wilson, John Rawls, Emily Dickinson, Stephen Jay Gould, Helen Vendler, Carol Gilligan, Amartya Sen, David Blight, Martha Nussbaum, and Thomas Piketty. The Display Room in Harvard Square, dedicated to selling HUP publications, closed on June 17, 2009. Related publishers, imprints, and series HUP owns the Belknap Press imprint (trade name), imprint, which it inaugurated in May 1954 with the publication of the ''Harvard Guide to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heart
The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrients to the tissue, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the thorax, chest, called the mediastinum. In humans, the heart is divided into four chambers: upper left and right Atrium (heart), atria and lower left and right Ventricle (heart), ventricles. Commonly, the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. In a healthy heart, blood flows one way through the heart due to heart valves, which prevent cardiac regurgitation, backflow. The heart is enclosed in a protective sac, the pericardium, which also contains a sma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
