Microtriches (singular microtrix) are the highly specialized

microvilli Microvilli (: microvillus) are microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellula ...

covering the entire surface of the tegument of

cestodes Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, commonly known as tapeworms. Their bodies con ...

. They are fine hair-like filaments distributed throughout the surface of the body, both unique to and ubiquitous among cestodes, giving the body surface a smooth and silky appearance. They are different from typical microvilli in that they contain conspicuous electron dense materials at the tip. Due to their morphological variation they make up unique defining structures in cestodes. Since cestodes are devoid of any digestive and

excretory system The excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to help maintain internal chemical homeostasis and prevent damage to the body. The dual function of excret ...

s, the tegument with its microtriches is the principal site of absorption and secretion. In fact the tegument highly resembles the gut of

animals Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ...

turned inside out.

Structure

The microtriches are fine cylindrical tubular filaments, with smooth rounded ends, and arranged in rows corresponding to the regular ridges of the tegument. Microtriches are documented to exhibit wide range of

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

in different

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

tapeworms Cestoda is a class of parasitic worms in the flatworm phylum (Platyhelminthes). Most of the species—and the best-known—are those in the subclass Eucestoda; they are ribbon-like worms as adults, commonly known as tapeworms. Their bodies con ...

, and serve as an identifying character among the members of

Eucestoda Eucestoda, commonly referred to as tapeworms, is the larger of the two subclasses of flatworms in the class Cestoda (the other subclass being Cestodaria). Larvae have six posterior hooks on the scolex (head), in contrast to the ten-hooked Ce ...

. They are also of special interest in pharmacology as they are the basic interface of the tapeworm with its surrounding, thus serve as the primary site of absorption of nutrients and the target site of anthelmintics.Mansour TE, mansour JM (2002).
Chemotherapeutic Targets in Parasites
'. Cambridge University Press, UK, pp. 192-297. Though microtriches have been described for several decades, the consensus terminology for the structure was made only at the turn of the 21st century. Standardised terms were resolved based on discussions that occurred at the International Workshops on Cestode Systematics in

Storrs, Connecticut Storrs ( ) is a village and census-designated place (CDP) in the New England town, town of Mansfield, Connecticut, Mansfield in eastern Tolland County, Connecticut, United States. The village is part of the Capitol Planning Region, Connecticut, ...

, United States in 2002, in

České Budějovice České Budějovice (; ) is a city in the South Bohemian Region of the Czech Republic. It has about 97,000 inhabitants. The city is located in the valley of the Vltava River, at its confluence with the Malše. České Budějovice is the largest ...

, Czech Republic in 2005 and in Smolenice, Slovakia in 2008. The following terms were endorsed for the components of each microtrix: the distal, electron-dense portion is the "cap", the proximal more electron-lucent region is the "base", and these two parts are separated from one another by the "baseplate". The base is composed of, among other elements,

microfilaments Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other p ...

, while the cap is composed of cap tubules. The electron-lucent central portion of the base is referred to as the "core". The core may be surrounded by an electron-dense tunic. The entire microthrix is enveloped by a

plasma membrane The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extr ...

, the external layer of which is referred to as the

glycocalyx The glycocalyx (: glycocalyces or glycocalyxes), also known as the pericellular matrix and cell coat, is a layer of glycoproteins and glycolipids which surround the cell membranes of bacteria, epithelial cells, and other cells. Animal epithe ...

. Two distinct sizes of microtriches are recognised: those < or = 200 nm in basal width, termed "filitriches", and those >200 nm in basal width, termed "spinitriches". Filitriches are considered to occur in three lengths: papilliform (< or = 2 times as long as wide), acicular (2-6 times as long as wide), and capilliform (>6 times as long as wide). Spinitriches are much more variable in form.

Functions

All cestodes lack digestive and

s, therefore, the tegument with its microtriches constitute the principal site of absorption of nutrients and elimination of waste materials. Moreover, the microtriches are the primary structures for

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

interface, and are metabolically active performing all the vital activities such as sensory, absorptive and secretory functions. Thus, their structure constitutes an effective amplification of the total surface area of the tegument. The surface

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

complex called

is responsible for inhibition of the host

digestive enzymes Digestive enzymes take part in the chemical process of digestion, which follows the mechanical process of digestion. Food consists of macromolecules of proteins, carbohydrates, and fats that need to be broken down chemically by digestive enzymes ...

, absorption of

cations An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

and

bile Bile (from Latin ''bilis''), also known as gall, is a yellow-green/misty green fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is primarily composed of water, is pro ...

salts, and enhancement of the host

amylase An amylase () is an enzyme that catalysis, catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large ...

activity.Cheng TC (1986). ''General Parasitology, 2nd edn''. Academic Press, Division of Hardcourt Brace & Company, USA, pp. 253-2546. The acidic glycosaminoglycans of the

are specific for inhibiting a number of

of the host.Bogitsh BJ, Carter CE, Oeltman TN (2005).
Human Parasitology, 3rd Edition
'. Academic Press, pp. 177-179. The microtriches in cestodes, and pits and spines in

trematodes Trematoda is a class of flatworms known as trematodes, and commonly as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is a moll ...

increase the surface area of the teguments for enhanced absorption of

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s. In addition, they act as

sensory organs A sense is a biological system used by an organism for sensation, the process of gathering information about the surroundings through the detection of stimuli. Although, in some cultures, five human senses were traditionally identified as s ...

for detecting the surrounding environmental cues and primary target site of anthelmintic drugs. The capacity of the tegument to absorb exogenous materials is proportional to the number and extent of pits or microtriches and the number of

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

in the distal cytoplasm.Smyth JD, Halton DW (1983).
The Physiology of Trematodes
'. Cambridge University Press, UK, pp.

References

{{Reflist

External links

Schistosomiasis Research Group at University of Cambridge

Cestoda Platyhelminth anatomy

Structure

Functions

See also

References

External links