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The Apicomplexa are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. The organelle is an adaptation that the apicomplexan applies in penetration of a host cell.
Bryozoa are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about 0.5 millimetres long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. 5,869 living species are known. One genus is solitary; all the rest are colonial.
Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelid, and cnidarians.
Uniramia is a group within the arthropods. In the past this group included the Onychophora, which are now considered a separate category. The group is currently used in a narrower sense.
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The coelom is the main body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups.
Entoprocta, or Kamptozoa, is a phylum of mostly sessile aquatic animals, ranging from 0.1 to 7 millimetres long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly.
Kinorhyncha is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos. They are also called mud dragons. Modern species are 1 mm or less, but Cambrian forms could reach 4 cm.
Cephalization is an evolutionary trend in which, over many generations, the mouth, sense organs, and nerve ganglia become concentrated at the front end of an animal, producing a head region. This is associated with movement and bilateral symmetry, such that the animal has a definite head end. This led to the formation of a highly sophisticated brain in three groups of animals, namely the arthropods, cephalopod molluscs, and vertebrates.
Xiphosura is an order of arthropods related to arachnids. They are sometimes called horseshoe crabs. They first appeared in the Hirnantian. Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera.
A polydnavirus (PDV) is a member of the family Polydnaviridae of insect viruses. There are two genera in the family: Bracovirus and Ichnovirus. Polydnaviruses form a symbiotic relationship with parasitoid wasps, but these wasps are themselves parasitic on Lepidoptera. Little or no sequence homology exists between BV and IV, suggesting that the two genera have been evolving independently for a long time.
Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill, Amphionides and Angustidontida. They are characterised by having the carapace fused to all thoracic segments, and by the possession of stalked eyes.
In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. Its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox.
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa, trochanter, femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus, patella.
The Phrynophiurida are an order of brittle stars containing the basket stars.
The Orussidae or the parasitic wood wasps represent a small family of sawflies ("Symphyta"). Currently, about 85 extant and four fossil species are known. They take a key position in phylogenetic analyses of Hymenoptera, because they form the sister taxon of the megadiverse apocritan wasps, and the common ancestor of Orussidae + Apocrita invented parasitism for the first time in course of the evolution of the Hymenoptera. They are also the only sawflies with carnivorous larvae.
Mesenchyme is a type of loosely organised animal embryonic connective tissue of undifferentiated cells that gives rise to blood and lymph vessels, bone, and muscle.
The Calyx of Held is a particularly large synapse in the mammalian auditory central nervous system, so named after Hans Held who first described it in his 1893 article Die centrale Gehörleitung because of its resemblance to the calyx of a flower. Globular bushy cells in the anteroventral cochlear nucleus (AVCN) send axons to the contralateral medial nucleus of the trapezoid body (MNTB), where they synapse via these calyces on MNTB principal cells. These principal cells then project to the ipsilateral lateral superior olive (LSO), where they inhibit postsynaptic neurons and provide a basis for interaural level detection (ILD), required for high frequency sound localization. This synapse has been described as the largest in the brain.
An accessory bone or supernumerary bone is a bone that is not normally present in the body, but can be found as a variant in a significant number of people. It poses a risk of being misdiagnosed as bone fractures on radiography.
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insects from other arthropods: they have a body divided into three regions, have three pairs of legs, and mouthparts located outside of the head capsule. It is this position of the mouthparts which divides them from their closest relatives, the non-insect hexapods, which includes Protura, Diplura, and Collembola.
References
- ↑ R.C.Brusca, G.J.Brusca. Invertebrates. Sinauer Associates, 2 ed.(2003)
- ↑ A.R.Maggenti et al., Online Dictionary of Invertebrate Zoology, digitalcommons.unl.edu, 2005
- ↑ Held, H."Die centrale Gehörleitung" Arch. Anat. Physiol. Anat. Abt, 1893
- ↑ Satzler, K., L. F. Sohl, et al. (2002). "Three-dimensional reconstruction of a calyx of Held and its postsynaptic principal neuron in the medial nucleus of the trapezoid body." J Neurosci 22(24): 10567-79.
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