In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the creature's body, each of which is in turn composed of multiple segments. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the prothorax, the mesothorax, and the metathorax. In extant insects, the prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments.
In arthropods
Thorax
Thorax | In arthropods
It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites. The thorax is one of the three main divisions of the arthropod's body, each of which is in turn composed of multiple segments. In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae, and the ribs. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites.
what is ypresiomyrma?
user
It is an extinct genus of ants in the subfamily Myrmeciinae.
assistant
how are they classified?
user
As "incertae sedis"
assistant
who described them for thr first time?
user
Bruce Archibald, Stefan Cover and Corrie Moreau
assistant
who is the first person?
user
Sorry. I cannot find the answer based on the context.
assistant
how do they look like?
user
The waist connecting the thorax and the abdomen is composed of a single segment, the head is in various shapes, and mandibles are a distinct triangular shape and shorter than the head.
assistant
what is thorax?
user
It is the part of the anatomy of humans, mammals, other tetrapod animals located between the neck and the abdomen.
assistant
from where did it get its name?
user
The word comes from the Greek θώραξ "thorax" "breastplate, cuirass, corslet.
assistant
how does one experience pain in this part of the body?
user
Cardiac arrest - feelings of sudden pressure in the chest or a crushing pain in the back, neck, and arms; noncardiac issues - burning feeling along the digestive tract or pain when deep breaths are attempted.
assistant
how is its structure?
user
Humans and hominids - the chest region of the body between the neck and the abdomen, along with its internal organs and other contents; protected and supported by the rib cage, spine, and shoulder girdle.
assistant
what are the injuries one can have in this part of the body?
user
Major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, or both in combination.
assistant
how is this part of the body in arthropods?
user
The thorax is the midsection (tagma) of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma or cephalothorax in other arthropods. It is formed by the prothorax, mesothorax and metathorax and comprises the scutellum; the cervix, a membrane that separates the head from the thorax; and the pleuron, a lateral sclerite of the thorax. In dragonflies and damselflies the mesothorax and metathorax are fused together to form the synthorax.
Thorax (arthropod anatomy) | Introduction
The thorax or chest is a part of the anatomy of humans, mammals, other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the creature's body, each of which is in turn composed of multiple segments. The human thorax includes the thoracic cavity and the thoracic wall. It contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain.
Thorax | Introduction
In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae, and the ribs. It extends from the neck to the diaphragm, and does not include the upper limbs. The heart and the lungs reside in the thoracic cavity, as well as many blood vessels. The inner organs are protected by the rib cage and the sternum. Thoracic vertebrae are also distinguished in birds, but not in reptiles.
Thorax | In tetrapods
Arthropods comprise the largest phylum in the animal kingdom with over a million known invertebrate species. Insects possess segmented bodies supported by a hard-jointed outer covering, the exoskeleton, made mostly of chitin. The segments of the body are organized into three distinct parts, a head, a thorax and an abdomen. The head typically bears a pair of sensory antennae, a pair of compound eyes, one to three simple eyes (ocelli) and three sets of modified appendages that form the mouthparts. The thorax has three pairs of segmented legs, one pair each for the three segments that compose the thorax and one or two pairs of wings.
Anatomy | Arthropod anatomy
In humans and other hominids, the thorax is the chest region of the body between the neck and the abdomen, along with its internal organs and other contents. It is mostly protected and supported by the rib cage, spine, and shoulder girdle.
Thorax | Structure
In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the creature's body, each of which is in turn composed of multiple segments. It is the area where the wings and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the prothorax, the mesothorax, and the metathorax. In extant insects, the prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments.
Thorax | In arthropods
The articulate midlength part of the body (or thorax) consists of 8 segments. Furrows in the parts outside the axis (or pleural furrows) are diagonal. The pygidium is rounded, and has a long axis with concave, posteriorly parallel sides. Some rings may be faintly defined anteriorly and the axis dissolves in the postaxial field. The areas outside the axis (or pleural fields) are smooth or very faintly ribbed.
Asaphus | Description
The articulated middle part of the body (or thorax) has 7-11 segments (9 in "A. wheeleri"), with rounded tips. The tailshield (or pygidium) is about 30% of the body length, is semi-circular in shape, with a wide flat border, and an entire margin.
Asaphiscus | Description
Some zoologists consider the thorax to consist of the two regions with appendages, and the abdomen the region without appendages. Others believe the region of fused segments to be part of the abdomen. For clarity, this article uses "thorax" to mean the two body regions with limbs.
Triops longicaudatus | Structure
The thorax is composed of three segments, each of which bears a single pair of legs. As is typical of arthropods adapted to life on land, each leg has only a single walking branch composed of five segments, without the gill branches found in some other arthropods and with gill on the abdominal segments of some immature aquatic insects. In most insects the second and third thoracic segments also support wings. It has been suggested that these may be homologous to the gill branches of crustaceans, or they may have developed from extensions of the segments themselves.
Hexapoda | Morphology
Fuxianhuiids possess specialized post-antennal appendages with serrated edges used for food processing. In most fuxianhuiids, the thorax tergites narrow posteriorly, terminating in either a swimming paddle or paired flukes with a tailspine. In members of Fuxianhuiidae the thorax is divided into two sections, the anterior wide opisthothorax and the posterior narrow limbless tail-like abdomen. Many specimens are known with exceptional soft tissue preservation, including preserved guts and neural tissue, which given their basal phylogenetic position makes them important in understanding the evolution of arthropoda as a whole.
Fuxianhuiida | Introduction
The body of an amphipod is divided into 13 segments, which can be grouped into a head, a thorax and an abdomen. The head is fused to the thorax, and bears two pairs of antennae and one pair of sessile compound eyes. It also carries the mouthparts, but these are mostly concealed. The thorax and abdomen are usually quite distinct and bear different kinds of legs; they are typically laterally compressed, and there is no carapace. The thorax bears eight pairs of uniramous appendages, the first of which are used as accessory mouthparts; the next four pairs are directed forwards, and the last three pairs are directed backwards.
Amphipoda | Anatomy
The articulate middle part of the body (or thorax) has three segments. The tailshield (or pygidium has a wide, subconical axis of more than eight rings. The pleural areas to the right and left of the axis lack furrows or are extremely weakly furrowed (on the internal mold only). The border becomes narrower further backwards and usually carries about 8 ventral spines at each side.
Serrodiscus | Description
The thorax is the human chest, or division of an animal's body that lies between the head and the abdomen. Thorax may also refer to:
Thorax (disambiguation) | Introduction
Hardened plates in the exoskeleton are called sclerites. Sclerites may be simple protective armour, but also may form mechanical components of the exoskeleton, such as in the legs, joints, fins or wings. In the typical body segment of an insect or many other Arthropoda, there are four principal regions. The dorsal region is the tergum; if the tergum bears any sclerites, those are called "tergites". The ventral region is called the sternum, which commonly bears sternites. The two lateral regions are called the pleura (singular pleurum) and any sclerites they bear are called pleurites.
Arthropod cuticle | Morphology
In the human body, the region of the thorax between the neck and diaphragm in the front of the body is called the chest. The corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to that part of the thoracic skeleton that encloses the heart and lungs. All the breadth of the shoulders is due to the shoulder girdle, and contains the axillae and the heads of the humeri. In the middle line the suprasternal notch is seen above, while about three fingers' breadth below it a transverse ridge can be felt, which is known as the sternal angle and this marks the junction between the manubrium and body of the sternum.
Thorax | The chest
Ventrally, a large plate has been interpreted as a hypostome. The head shield overlaps a tapering series of 12–17 trunk tergites, which lead into a set of limb-bearing segments comprising the thorax. The limbs are simple in form, consisting of a smooth oval exopod and a stout, annulated endopod. There is no one-to-one correspondence between the thoracic tergites and the limbs, but, rather, there appear to be two or three limbs per tergite. Behind the thorax is a narrower abdominal region, consisting of 14 tergites, that bears no appendages. The abdomen is terminated by a telson-like spine.
Fuxianhuia | Description
Some key events in the evolution of the arthropod body resulted from changes in certain Hox genes' DNA sequences. The trunks of arthropods comprise repeated segments, which are typically associated with various structures such as a pair of appendages, apodemes for muscle attachment, ganglia and (at least embryologically) coelomic cavities. While many arthropod segments are modified to a greater or lesser extent (for example, only three of the insect thorax and abdominal segments typically bear appendages), arthropodists widely assume that all of the segments were nearly identical in the ancestral state. However, while one can usually readily see the segmental organisation of the trunks of adult arthropods, that of the head is much less obvious.
Arthropod head problem | Background
In the Apocritan Hymenoptera, the first abdominal segment is fused to the metathorax, where it forms a structure known as the propodeum. Accordingly, in these insects, the functional thorax is composed of four segments, and is therefore typically called the mesosoma to distinguish it from the "thorax" of other insects. Each thoracic segment in an insect is further subdivided into various parts, the most significant of which are the dorsal portion (the notum), the lateral portion (the pleuron; one on each side), and the ventral portion (the sternum). In some insects, each of these parts is composed of one to several independent exoskeletal plates with membrane between them (called sclerites), though in many cases the sclerites are fused to various degrees.
Thorax | In arthropods
As an arthropod, "D. personata" is bilaterally symmetrical. The body is composed of a head, which contains the cephalon, and an elongated trunk, which consists of a thorax and abdomen. From the cephalon, there are two pairs of antennae and a mandible placed anteriorly, in addition to two pairs of maxillae positioned laterally. The trunk sprouts five pairs of walking legs, which are segmented medially to laterally: coxa, basis, ischium, merus, carpus, manus, and dactyl. The coxa, basis, ischium are smaller aspects that serve to attach the jointed limb to the crab's body. The exoskeleton is composed of a chitin cuticle.
Dromia personata | Morphology
The part of the skeleton that is ‘tucked under’ (the doublure) has no sutures crossing it to form a rostral plate.The thorax has 11 (rarely 10) segments, the side lobes (or pleurae) are furrowed, and the articulating facets distinct.
Phacopina | Description
The thorax reaches its greatest width at the 6th segment. The frontal part or prothorax consists of 6 segments, with number 5 and 6 fused, and the 6th carrying very large trailing spines. The rear part or opistothorax consists of a variable but extremely large number of segments (up to 97).
Emuellidae | Introduction
Below is the procuticle, which is designed as the main structural element to the body. The procuticle is made of two sections, the exocuticle on the outer part, and the endocuticle on the inner part. The exocuticle is denser than the endocuticle; the endocuticle makes up about 90 volume % of the exoskeleton. Both the exocuticle and endocuticle are made with a Bouligand structure.
Bouligand structure | Arthropods
As in all arthropods, the chelicerate body has a very small coelom restricted to small areas round the reproductive and excretory systems. The main body cavity is a hemocoel that runs most of the length of the body and through which blood flows, driven by a tubular heart that collects blood from the rear and pumps it forward. Although arteries direct the blood to specific parts of the body, they have open ends rather than joining directly to veins, and chelicerates therefore have open circulatory systems as is typical for arthropods.
Chelicerata | Body cavities and circulatory systems
Arthropod exoskeletons are made of cuticle, a non-cellular material secreted by the epidermis. Their cuticles vary in the details of their structure, but generally consist of three main layers: the epicuticle, a thin outer waxy coat that moisture-proofs the other layers and gives them some protection; the exocuticle, which consists of chitin and chemically hardened proteins; and the endocuticle, which consists of chitin and unhardened proteins. The exocuticle and endocuticle together are known as the procuticle. Each body segment and limb section is encased in hardened cuticle. The joints between body segments and between limb sections are covered by flexible cuticle.
Arthropod | Exoskeleton
The abdomen is composed of eleven segments, some of which may be fused and houses the digestive, respiratory, excretory and reproductive systems. There is considerable variation between species and many adaptations to the body parts, especially wings, legs, antennae and mouthparts. Spiders a class of arachnids have four pairs of legs; a body of two segments—a cephalothorax and an abdomen. Spiders have no wings and no antennae. They have mouthparts called chelicerae which are often connected to venom glands as most spiders are venomous. They have a second pair of appendages called pedipalps attached to the cephalothorax. These have similar segmentation to the legs and function as taste and smell organs.
Anatomy | Arthropod anatomy
Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax.
Spider | Circulation and respiration
Arthropod bodies are also segmented internally, and the nervous, muscular, circulatory, and excretory systems have repeated components. Arthropods come from a lineage of animals that have a coelom, a membrane-lined cavity between the gut and the body wall that accommodates the internal organs. The strong, segmented limbs of arthropods eliminate the need for one of the coelom's main ancestral functions, as a hydrostatic skeleton, which muscles compress in order to change the animal's shape and thus enable it to move. Hence the coelom of the arthropod is reduced to small areas around the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows.
Arthropod | Internal organs
The articulating middle part of the body (or thorax) has 7 segments, the outer tips bending backwards, pointed and darker. The tailshield (or pygidium) is semicircular, straight or almost indented and has a long, low, tapering axis with 5 or 6 rings, and 4 or 5 pleural furrows. The border in the pygidium is as wide as in the cephalon and is also often darker, but the border furrow is very shallow or absent.
Cedaria | Description
General outline of the body is rounded the front third, parallel sided the middle third, and progressively tapering backwards in the back third, ending at an angle of approximately 45° with the midline. Headshield (or cephalon is approximately ⅝× as long as wide. The (in this case only slightly) vaulted central axis in the head or glabella tapers gently forward and does not reach the anterior margin. The outer backside of the cephalon (or genal angle) has short genal spines. The thorax has 17 or 18 articulating segments, maintaining width or widening slightly backward to 8th segment, then tapering posteriorly.
Buenellus | Description
Anatomically, spiders (as with all arachnids) differ from other arthropods in that the usual body segments are fused into two tagmata, the prosoma, or cephalothorax, and opisthosoma, or abdomen, and joined by a small, cylindrical pedicel (however, as there is currently neither paleontological nor embryological evidence that spiders ever had a separate thorax-like division, there exists an argument against the validity of the term cephalothorax, which means fused cephalon (head) and the thorax. Similarly, arguments can be formed against use of the term abdomen, as the opisthosoma of all spiders contains a heart and respiratory organs, organs atypical of an abdomen).
Spider | Introduction
Insects, like all arthropods, have no interior skeleton; instead, they have an exoskeleton, a hard outer layer made mostly of chitin which protects and supports the body. The insect body is divided into three parts: the head, thorax, and abdomen. The head is specialized for sensory input and food intake; the thorax, which is the anchor point for the legs and wings (if present), is specialized for locomotion; and the abdomen for digestion, respiration, excretion, and reproduction. Although the general function of the three body regions is the same across all insect species, there are major differences in basic structure, with wings, legs, antennae, and mouthparts being highly variable from group to group.
Insect morphology | Anatomy summary
The thorax is a series of articulated segments that lie between the cephalon and pygidium. The number of segments varies between 2 and 103 with most species in the 2 to 16 range. Each segment consists of the central axial ring and the outer pleurae, which protected the limbs and gills. The pleurae are sometimes abbreviated or extended to form long spines. Apodemes are bulbous projections on the ventral surface of the exoskeleton to which most leg muscles attached, although some leg muscles attached directly to the exoskeleton. Determining a junction between thorax and pygidium can be difficult and many segment counts suffer from this problem.
Trilobite | Thorax
The articulating middle part of the body (or thorax) has 13 segments. The axis is convex, and less than ½× as wide as each of the so-called pleurae to its sides. Segments pointed sideways with a rounded front (a shape called falcate). The tailshield (or pygidium) is about ½× as wide as the cephalon, almost twice as wide as long, excluding the two flat, shark tooth shaped, widely spaced spines. The axis in the pygidium is 1¼× longer than wide, with almost parallel sides, almost reaching the rear margin, with 3 or 4 axial rings; 3 sets of interpleural grooves and pleural furrows ending at distance of the margin.
Meteoraspis | Description
The articulating middle part of the body (or thorax) has 12 segments. The axis is convex, and less than ½× as wide as each of the so-called pleurae to its sides. Segments pointed sideways with a rounded front (a shape called falcate). The tailshield (or pygidium) is about ½× as wide as the cephalon, almost twice as wide as long, excluding the two, widely spaced spines. These are at an angle of approximately 30° with the rest body. The axis in the pygidium is 1¼× longer than wide, with almost parallel sides, almost reaching the rear margin, with 3 or 4 axial rings; 3 sets of interpleural grooves and pleural furrows ending at distance of the margin.
Tricrepicephalus | Description
The thorax consists of 11-17 segments, with the 11th from the front bearing a backward directed spine on the midline.
Redlichia | Description
The contents of the thorax include the heart and lungs (and the thymus gland); the (major and minor pectoral muscles, trapezius muscles, and neck muscle); and internal structures such as the diaphragm, the esophagus, the trachea, and a part of the sternum known as the xiphoid process). Arteries and veins are also contained – (aorta, superior vena cava, inferior vena cava and the pulmonary artery); bones (the shoulder socket containing the upper part of the humerus, the scapula, sternum, thoracic portion of the spine, collarbone, and the rib cage and floating ribs). External structures are the skin and nipples.
Thorax | Contents
At the end of each male pedipalp is a spoon-shaped cymbium that acts to support the copulatory organ.
Anatomy | Arthropod anatomy
The thorax has 17 to 23 segments, gradually diminishing in size. The pleural spines are long and sickle-shaped. The tailshield (or pygidium) is very small and subquadrate in shape.
Nevadella | Description
The heart is typically a muscular tube that runs just under the back and for most of the length of the hemocoel. It contracts in ripples that run from rear to front, pushing blood forwards. Sections not being squeezed by the heart muscle are expanded either by elastic ligaments or by small muscles, in either case connecting the heart to the body wall. Along the heart run a series of paired ostia, non-return valves that allow blood to enter the heart but prevent it from leaving before it reaches the front. Arthropods have a wide variety of respiratory systems. Small species often do not have any, since their high ratio of surface area to volume enables simple diffusion through the body surface to supply enough oxygen.
Arthropod | Respiration and circulation
The body of "Nevadia" is very flat dorso-ventrally. The general outline of its thin, lightly calcified exoskeleton is inverted wide drop-shaped. The front is rounded, widest at the back of the headshield (or cephalon), and tapering from there to an eventually rounded termination. The central area of the cephalon (or glabella) is distinctly tapered forward, sides slightly concave, but not wedging out in the frontal half and with a narrow rounded front. The glabella and the frontal margin do not touch (in jargon: the preglabellar field is present). Cephalic margin clearly less wide as the most frontal thoracal segment. The thorax has 27 segments.
Nevadia | Description
(The cephalothorax (or prosoma) of chelicerates is a fusion of head and thorax.)
Mandible (arthropod mouthpart) | Introduction
The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms "prosoma" and "opisthosoma" are equivalent to "cephalothorax" and "abdomen" in some groups.) The word "cephalothorax" is derived from the Greek words for head (, ') and thorax (, '). This fusion of the head and thorax is seen in chelicerates and crustaceans; in other groups, such as the Hexapoda (including insects), the head remains free of the thorax. In horseshoe crabs and many crustaceans, a hard shell called the carapace covers the cephalothorax.
Cephalothorax | Introduction
Antennae, head, thorax and abdomen much as in the male.
Prosotas nora | Description
The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings. In hymenopterans of the suborder Apocrita (wasps, bees and ants), it consists of the three thoracic segments and the first abdominal segment (the propodeum). For historical reasons, in ants it is commonly referred to by the alternative name alitrunk. In scorpions, it is composed of six segments and forms the first part of the abdomen, containing all of the major organs.
Mesosoma | Introduction
The anterior thorax consists of eleven segments, each bearing a pair of appendages, called thoracopods or pereiopods. None of the thoracopods are modified into maxillipeds for feeding. The posterior thorax consists of 16–25 segments, incompletely separated to form "rings". Each ring may consist of as many as six fused segments and bear up to six pairs of appendages (there are 54–66 limbs altogether). Most of the thoracic appendages resemble each other, but the first eleven pairs are best developed. There is a slight tendency to regional specialization and the first pair of legs is unlike the rest. It is an elongated, cheliped-like structure with a sensory function, while all the other appendages aid in feeding, respiration, and locomotion.
Triops longicaudatus | Thorax
The basic anatomy of the "N. tomentosus" is broken up into three separate functional body regions: the head, the thorax, and the abdomen. The entire body wall of "N. tomentosus" is called the exoskeleton. This tough outer layer provides strong protection and different areas where muscles can attach and provide movement. Their harder outer layer is made of cuticle yet the skin is broken up into many different hardened plates that are separated by sutures. This allows flexible movement and doesn’t cause it to move rigidly. The head houses the brain, eyes, antennae, and mouth parts. The eyes are compound eyes which are lens-like in appearance and have a pixel-like reception.
Nicrophorus tomentosus | Anatomy
The genal spine is short and stout. The articulate middle part of the body (or thorax) has 15 to 18 segments with long, sickle-shaped spines. The inner part of the ribs is about as wide as the axis. The tailshield (or pygidium) is longer than wide, slightly hexagonal, with a long, flat posterior area. The rear margin of the pygidium is truncate or indented. The pygidial axis is short, with 1 axial ring. The surface is smooth.
Anabaraspis | Description
Thoracic cavity The thoracic cavity is the chamber of the body of vertebrates that is protected by the thoracic wall. The central compartment of the thoracic cavity is the mediastinum.
Outline of human anatomy | Thoracic cavity
Adult cephalocaridans are between in length. The body is divided into a cephalon, a segmented thorax and a segmented abdomen, with a cephalic shield covering the cephalon. There are no eyes and the body is flexible and translucent. The thorax has a pair of limbs on each segment while the abdomen is limbless, apart from the telson with its slender caudal filaments. The body and limbs are ornamented with various setae and spines.
Hutchinsoniella | Description
This creates two very typical, isolated slits. The exoskeleton of "Mesonacis" is about 2⅓× as long as wide, measured between the genal angles. The outer ⅓ of the back (or posterior margin) of the headshield (or cephalon) angles forwards from the tip of the pleural spine to the genal angle. The central area of the cephalon (or glabella) and the frontal margin touch or the distance is as long as the margin at most (in jargon: the preglabellar field is short or absent). The thorax has approximately 25 segments, the pleura about 1½× as wide as the axis, excluding the genal spines.
Mesonacis | Description
"Daphnia pulex" is an arthropod whose body segments are difficult to distinguish. They can only be recognised by the appendages they bear (only ever one pair per segment), and by studying the internal anatomy. The head is distinct and is made up of six segments which are fused together even as an embryo. It bears the mouthparts, and two pairs of antennae, the second of which are enlarged into powerful organs used for swimming. There is no clear division between thorax and abdomen, which collectively bear five pairs of appendages. The shell surrounding the animal extends posteriorly into a long or short spine.
Daphnia pulex | Description
The free cheeks curve strongly downwards and have prominent borders, particularly to the side and the back, and these bear long tube- or blade-like genal spines. The articulating middle part of the body (or thorax) consists of 9 or 10 segments. The axis is extremely convex and the side-lobes (or pleurae) are narrow. The tailshield (or pygidium) is convex and its axis is prominent and has 2-4 rings. The most backward piece may bear a long spine. The seam of the exoskeleton (or doublure) is narrow.
Telephinidae | Description
They are made up of thousands of little receptors called ommatidia. The antennae are covered with many chemical receptors and act as sensory organs. "N. tomentosus" has a mandible for chewing its food. The thorax is the center of movement. It is separated into three different regions: the prothorax, the mesothorax, and the metathorax. It is heavily scleratized which provides extra support and acts as an anchor for moving parts. It is also divided into three different sections. The notum is the top most or dorsal area, the sternum is the lower or ventral side, and the pleuron is the sides where the legs are attached.
Nicrophorus tomentosus | Anatomy
In sea spiders, the chelicerae (also known as chelifores) are short and chelate and are positioned on either side of the base of the proboscis or sometimes vestigial or absent.
Arthropod mouthparts | Chelicerae
"Arthropleura" ranged in length from only about 0.3 metres long to "A. armata" which was 2.5 metres long. "Arthropleura" was able to grow larger than modern arthropods, partly because of the greater partial pressure of oxygen in Earth's atmosphere at that time and because of the lack of large terrestrial vertebrate predators. The flattened body of "Arthropleura" is composed of approximately 30 jointed segments, each of which was covered by two side plates and one center plate. The ratio of pairs of legs to body segments was approximately 8:6, similar to some present-day millipedes.
Arthropleura | Description
The body consists of a head and thorax, separated by a slight constriction. Unlike many other crustaceans, the body is not clearly divided into segments. The abdomen is regressed or absent, whereas the adult gonads are relatively large. The head is the largest part of the body, and bears most of the appendages. Two pairs of well-developed antennae are used to swim through the water. In addition, there is a pair of mandibles and two pairs of maxillae. The thorax typically has two pairs of appendages, but these are reduced to a single pair, or entirely absent, in many species.
Ostracod | Body parts
The cephalon of "Fallotaspis" is semi-circular in shape, with rounded cheeks that are continuous with long spines that go back to the first half of the thorax. Sutures absent. The thorax has up to 21 segments. The third segment terminating in a long spine that extends back to the fourteenth segment. The tail shield (or pygidium) is very small, about the same length as the two most backward thorax segments combined.
Fallotaspis | Description
Tardigrades lack several Hox genes and a large intermediate region of the body axis. In insects, this corresponds to the entire thorax and the abdomen. Practically the whole body, except for the last pair of legs, is made up of just the segments that are homologous to the head region in arthropods. All adult tardigrades of the same species have the same number of cells (see eutely). Some species have as many as 40,000 cells in each adult, while others have far fewer.
Tardigrade | Anatomy and morphology
Arthropods and most mollusks have an open circulatory system. In this system, deoxygenated blood collects around the heart in cavities (sinuses). This blood slowly permeates the heart through many small one-way channels. The heart then pumps the blood into the hemocoel, a cavity between the organs. The heart in arthropods is typically a muscular tube that runs the length of the body, under the back and from the base of the head. Instead of blood the circulatory fluid is haemolymph which carries the most commonly used respiratory pigment, copper-based haemocyanin as the oxygen transporter. Haemoglobin is only used by a few arthropods.
Heart | Invertebrates
The hypopharynx is a somewhat globular structure, arising from the base of the labium. It assists swallowing. It performs the role of the tongue found in large vertebrates.
Arthropod mouthparts | Hypopharynx
In most insects the femur is the largest region of the leg; it is especially conspicuous in many insects with saltatorial legs because the typical leaping mechanism is to straighten the joint between the femur and the tibia, and the femur contains the necessary massive bipennate musculature.
Arthropod leg | Femur
Spiders are chelicerates and therefore arthropods. As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel.
Spider | Body plan
The body plan is made up of a head, a thorax, and an abdomen.
Cymothoa elegans | Description
The size may reach to—Length, 73 mm. ; of the body-whorl, 36 mm. :breadth, 3 mm. The ribs in the longer form may be much narrower, and may be obsolete before reaching the body whorl.
Mitromorpha axicostata | Description
In chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace. In relation with the arthropod head problem, phylogeny studies show that members of the Malacostraca class of crustaceans have five segments in the cephalon, when not fused with the thorax to form a cephalothorax.
Cephalon (arthropod head) | Chelicerates and crustaceans
The telson is the posterior-most division of the body of an arthropod. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups.
Telson | Introduction
In some arthropods, especially trilobites (pictured at right), the cephalon, or cephalic region, is the region of the head which is a collective of "fused segments".
Head | Arthropods
The outline of the exoskeleton of "Beckwithia" is an inverted egg-shape with a stout sword-like tail spine or telson. The dorsal shield covering the cephalothorax (or prosoma) is semi-circular, with the margin curving smoothly from the front to an acute, but rather small genal spine at the outside and the back. The front and side margin is bordered by a flatted and undecorated zone of almost constant length/width. The area within that band is densely covered in pustules. Two distinctly raised eyes that are circular to oval are located at the outer rim of what could be compared to a trilobite glabella, with a strongly effaced outline and lobes.
Beckwithia (arthropod) | Description
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.
Opisthosoma | Introduction
The degree to which the area in front of the mouth is segmented remains one of the major controversies in the arthropod head problem. As already mentioned, earlier workers often considered the entire pre-oral region to be "acronal" and thus nonsegmental. Modern workers universally accept that at least the deuterocerebrum is segmental. However, the nature of the region in front of this is much less certain. Some molecular development studies have given limited support to the idea of an "ocular" segment corresponding to the protocerebrum; but these data are not unequivocal. The idea of the protocerebrum actually comprising two components has also received support from both molecular and embryological data.
Arthropod head problem | Nature of the preoral region
The arthropod body is divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). The appendages were attached to the prosoma, and although they are unknown in strabopids (except for one undescribed specimen of "Parapaleomerus"), it is most likely they owned several pairs of them. Although the chemical composition of the strabopid exoskeleton is unknown, it was probably mineralized (with inorganic substances), sturdy and calcareous (containing calcium). The head of the strabopids was very short, the back was rounded and lacked trilobation (being divided in three lobes), the abdomen was composed by eleven segments and succeeded by a thick tail spine, the telson.
Paleomerus | Description
The shed portions are called the exuviae. The animal then expands its body by swallowing liquid or gas and in the process it stretches the new integument to its proper size and shape. The new integument still is soft and usually is pale, and it is said to be teneral or callow. It then undergoes a hardening and pigmentation process that might take anything from several minutes to several days, depending on the nature of the animal and the circumstances.
Arthropod cuticle | Moulting
The thorax constitutes a large portion of the insect's body. As in all insects, it is composed of three segments: the prothorax, mesothorax, and metathorax. Each section "contains one pair of legs, however, the wings are found only on the mesothoracic and metathoracic segments."
Idolomantis diabolica | Thorax
Arthropods' primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph - analogue of blood - circulates; they have open circulatory systems. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong.
Marine invertebrates | Marine arthropods
The fat body has been best studied in insects nevertheless it has been identified in other arthropod phyla including Chelicerata, Crustaceans and all major classes of Myriapoda, although not all subtaxa.
Fat body | Other arthropods
The first eleven body rings compose the thorax and bear one pair of legs each, the last of which also bears the genital opening. In the female, it is modified to form a "brood pouch". The first one or two pairs of legs differ from the remainder, and probably function as sensory organs. The remaining segments form the abdomen. The number of body rings is variable both within and between species, and the number of pairs of legs per body ring can rise as high as six. The legs become progressively smaller along the abdomen, with the last segments being legless.
Notostraca | Description
Like all arthropods, the tarantula is an invertebrate that relies on an exoskeleton for muscular support. Like other Arachnida, a tarantula's body comprises two main parts, the prosoma (or cephalothorax) and the opisthosoma (or abdomen). The prosoma and opisthosoma are connected by the pedicel, or pregenital somite. This waist-like connecting piece is actually part of the prosoma and gives the opisthosoma a wide range of motion relative to the prosoma. Tarantula sizes can range from as small as the size of a BB pellet to as large as a dinner plate when the legs are fully extended. Depending on the species, the body length of tarantulas ranges from , with leg spans of .
Tarantula | Overview
The coxa is the proximal segment and functional base of the leg. It articulates with the pleuron and associated sclerites of its thoracic segment, and in some species it articulates with the edge of the sternite as well. The homologies of the various basal sclerites are open to debate. Some authorities suggest that they derive from an ancestral subcoxa. In many species the coxa has two lobes where it articulates with the pleuron. The posterior lobe is the meron which is usually the larger part of the coxa. A meron is well developed in Periplaneta, the Isoptera, Neuroptera and Lepidoptera.
Arthropod leg | Coxa
The body plan of hemichordates is characterized by a muscular organization. The anteroposterior axis is divided into three parts: the anterior prosome, the intermediate mesosome, and the posterior metasome. The body of acorn worms is worm-shaped and divided into an anterior proboscis, an intermediate collar, and a posterior trunk. The proboscis is a muscular and ciliated organ used in locomotion and in the collection and transport of food particles. The mouth is located between the proboscis and the collar. The trunk is the longest part of the animal. It contains the pharynx, which is perforated with gill slits (or pharyngeal slits), the esophagus, a long intestine, and a terminal anus.
Hemichordate | Anatomy
The parasitic pentastomida hatch with four head segments and three trunk segments, with two more body segments being added during postembryonic development. This number of segments then remains constant for the rest of their life. There are no antenna, and their mouth has no piercing, biting or sucking extremities. On each side of the mouth there is a pair of retractable hooks, and the mouth itself is sustained by a chitinous buccal ring. They feed through a pumping mechanism located in the pharynx, consisting of two rigid chitinous plates that is connected to several associated muscles.
Arthropod head problem | The head of pentastomids
The thorax has at least 20 segments. The tail shield (or pygidium) is small.
Nepeidae | Introduction
Chelicerate head structures differ considerably from those of mandibulates (i.e. insects, crustaceans and myriapods); they possess eyes and a single pair of grasping appendages innervated from the brain, plus a labrum-like structure. Behind the mouth lies another pair of mouthparts, the pedipalps, and behind them lie the series of walking limbs. In chelicerates, the leg-bearing segments are fused with the anterior segments to form a prosoma, so that in living arthropods a distinct head only exists in mandibulates.
Arthropod head problem | Head components
In arachnids, the sternum is the ventral (lower) portion of the cephalothorax. It consists of a single sclerite situated between the coxa, opposite the carapace.
Sternum | Arthropods
The articulate midsection of the body (or thorax) has 13 ("P. striata") or 14 ("P. dubinka") segments. Tail shield (or pygidium) is slightly over half as wide as the cephalon (a state called micropygous). The pygidial axis (or rachis) has 5 or 6 rings and a termination and 4 or 5 ribs in the outlying pleural regions. The pygidium in "Ptychoparia" lacks a border.
Ptychoparia | Description
As a rule, the arthropod exoskeleton is divided into different functional units, each comprising a series of grouped segments. Such a group is called a tagma, and the tagmata are adapted to different functions in a given arthropod body. For example, tagmata of insects include the head, which is a fused capsule, the thorax as nearly a fixed capsule, and the abdomen usually divided into a series of articulating segments. Each segment has sclerites according to its requirements for external rigidity; for example, in the larva of some flies, there are none at all and the exoskeleton is effectively all membranous; the abdomen of an adult fly is covered with light sclerites connected by joints of membranous cuticle.
Arthropod exoskeleton | Segmentation
An arthropod (, from Greek "arthron", "joint" and "pous", "foot" (gen. ποδός)) is an invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda, which includes insects, arachnids, myriapods, and crustaceans. The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora. Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Arthropods are bilaterally symmetrical and their body possesses an external skeleton.
Arthropod | Introduction
In almost all Cambrian arthropods, the post-oral limbs show very little differentiation compared to the trunk limbs; the heads posterior to the mouth shows a considerable degree of variability, however, in the number of segments incorporated into the head.
Arthropod head problem | Fossil evidence
This pattern is repeated with all thorax segments. Antennae are not known. Dorsal eyes are absent. The thorax segments are each about along the axis. The tail shield is dominated by a pair of large segmental marginal spines, reminiscent of large (or macropleural) spines in the thorax and of pygidial spines of certain trilobites. The one node it carries is larger and more sharply defined than the nodes on the segments. The frontal border of the tail shield is convex and curves laterally into the large spines which extend postero-laterally, constituting half the total body length. The back margin of the spines is concave and merges into a second pair of short, broad, triangular spines.
Aaveqaspis | Description
The basic copepod body consists of a head, a thorax with six segments, ancestrally each with a swimming leg, and an abdomen with five appendageless segments. Except in parasitic species, the body is divided functionally into two tagmata, that may be called a "prosome" and a "urosome", with an articulation between them allowing the body to flex. Different groups of copepods have the articulation at different places. In the Calanoida, the articulation is between the thoracic and abdominal segments, so that the boundary between the prosome and urosome corresponds to the boundary between thoracic and abdominal segments. However, in the Harpacticoida, the articulation is between the fifth and sixth thoracic segments, so that the sixth thoracic segment is in the urosome (see the diagram).
Tagma (biology) | Tagmosis
It is variable in form and may be fused dorsally with some of the thoracic segments or occasionally be in two parts, hinged dorsally. Typically, each of the thoracic appendages is biramous and the endopods are the better developed of the branches, being used for crawling or grasping. Each endopod consist of seven articulating segments; the coxa, basis, ischium, merus, carpus, propodus and dactylus. In decapods, the claw is formed by the articulation of the dactylus against an outgrowth of the propodus. In some taxa, the exopods are lost and the appendages are uniramous. There is a clear demarcation between the thorax and the six or seven-segmented abdomen.
Malacostraca | Tagmata
The typical thoracic leg of an adult insect is adapted for running, rather than for digging, leaping, swimming, predation or the like. The legs of most cockroaches are good examples. However, there are many specialized adaptations, including:
Arthropod leg | Variations in functional anatomy of insect legs
Spiders, like most arthropods, have an open circulatory system, i.e., they do not have true blood, or veins which transport it. Rather, their bodies are filled with haemolymph, which is pumped through arteries by a heart into spaces called sinuses surrounding their internal organs. The haemolymph contains hemocyanin, a respiratory protein similar in function to hemoglobin. Hemocyanin contains two copper atoms, tinting the haemolymph with a faint blue color. The heart is located in the abdomen a short distance within the middle line of the dorsal body-wall, and above the intestine. Unlike in insects, the heart is not divided into chambers, but consists of a simple tube.
Spider anatomy | Circulation
"Colobopsis anderseni" is light brown and glossy. Like any arthropod, its body contains three sections. The first part is called the prosoma while the middle part is called the mesosoma, and the posterior part is called the metasoma. The dorsum, or posterior side, of the mesosoma on "C. anderseni" is flattened. It also has distinct metanotum on the posterior of the thorax. It is lacking erect setae under its head, and its body is slightly raised on the tibiae, or fourth joint of each leg. Its eyes elongate looking outward, nearer to the mandibles than the vertex. It is dimorphic, meaning there are two separate forms based on class.
Colobopsis anderseni | Description
The body is oval shaped and is long and wide. The species is yellowish-brown in colour with tight top and bottom and golden hair. Its head is almost flat and is punctured. The distance between the body and the head is 5-1 long. The tips of the rear angle of the prothorax and its sensor are short. The prothorax itself is cushion-like, almost square shaped and is punctured just like the head. The margins are almost parallel and are located at the rear angle. The angles themselves are short and rounded closer to the eye. The species' prothorax is dense and punctured just like its pronotum, while its scutellum is almost oval-shaped and is long and wide.
Athous curtus | Description
The head is incapable of rotating laterally. Two pairs of antennae are set at the front of the head. The eyes are usually well developed and the mouthparts do not form a suctorial cone or proboscis. The thorax or pereon is smooth or slightly sculptured and sometimes spinose or rugose. A flexion occurs between it and the abdomen or pleon, so from a lateral view, the front part of the animal is arched up. The pereiopods are held close to the head, while the pleopods are attached to the pleon, making it appear no appendages on the pereon.
Arcturidae | Description
In arthropods, the open circulatory system is a system in which a fluid in a cavity called the hemocoel bathes the organs directly with oxygen and nutrients, with there being no distinction between blood and interstitial fluid; this combined fluid is called hemolymph or haemolymph. Muscular movements by the animal during locomotion can facilitate hemolymph movement, but diverting flow from one area to another is limited. When the heart relaxes, blood is drawn back toward the heart through open-ended pores (ostia). Hemolymph fills all of the interior hemocoel of the body and surrounds all cells. Hemolymph is composed of water, inorganic salts (mostly sodium, chloride, potassium, magnesium, and calcium), and organic compounds (mostly carbohydrates, proteins, and lipids).
Circulatory system | Open circulatory system
In general, however, they have three pairs of thoracic legs, each ending in two claws. The abdomen often has adhesive discs on the last two segments.
Neuroptera | Anatomy and biology
The thorax has fifteen segments, with number 9 (counted from the front) carrying a spine approximately as long as the entire main body.
Eoredlichia | Dorsal exoskeleton
"P. hammanni" is almost flat (dorso-ventrally). The upper (or dorsal) side of the body consists of a non-calcified headshield (cephalon) and tailshield (pygidium) of about equal length, without any body segments in between. The body is strongly narrowed at the articulation between cephalon and pygidium. Both shields have a narrow border, reminiscent of some effaced agnostid trilobites. The axis is not defined by furrows. There are no eyes. Appendages and internal organs are not yet known.
Pseudonaraoia | Description