Crucibulum | |
---|---|
Crucibulum laeve | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Basidiomycota |
Class: | Agaricomycetes |
Order: | Agaricales |
Family: | Nidulariaceae |
Genus: | Crucibulum Tul. & C.Tul. (1844) |
Type species | |
Crucibulum laeve | |
Species | |
Crucibulum cyathiforme Contents |
Crucibulum | |
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Glebal hymenium | |
Cap is infundibuliform | |
Hymenium attachment is not applicable | |
Lacks a stipe | |
Ecology is saprotrophic | |
Edibility is inedible |
Crucibulum is a genus in the Nidulariaceae, a family of fungi whose fruiting bodies resemble tiny egg-filled bird's nests. Often called "splash cups", the fruiting bodies are adapted for spore dispersal by using the kinetic energy of falling drops of rain. [2] The "eggs" inside the bird's nests (technically known as peridioles) are hard waxy shells containing spores, and tend to stick to whatever nearby herbage they land on, thus increasing the odds of being consumed and dispersed by herbivorous animals. [3] Members of this genus are saprobic, obtaining nutrients from dead organic matter, and are typically found growing on decayed wood and wood debris. The three known Crucibulum species (C. laeve, C. parvulum, and C. cyathiforme) are distinguished from other genera of the Nidulariaceae by their relatively simple funiculus – a cord of hyphae that connects the peridiole (the "eggs") to the exterior of the bird's nest.
Bird's nest fungi were first mentioned by Flemish botanist Carolus Clusius in Rariorum plantarum historia (1601). Over the next couple of centuries, these fungi were the subject of some controversy regarding whether the peridioles were seeds, and the mechanism by which they were dispersed in nature. For example, the French botanist Jean-Jacques Paulet, in his work Traité des champignons (1790–3), erroneously suggested that peridioles were ejected from the fruiting bodies by some sort of spring mechanism. [4]
The structure and biology of the genus Crucibulum was better known by the mid-19th century, when the brothers Louis René and Charles Tulasne published a monograph on the bird's nest fungi. [5] Subsequently, monographs were written in 1902 by Violet S. White (American species), [6] Curtis Gates Lloyd in 1906, [7] Gordon Herriot Cunningham in 1924 (New Zealand species), [8] and Harold J. Brodie in 1975. [9]
The type species for the genus Crucibulum described by the Tulasne brothers was Crucibulum vulgare, an older synonym of the species known today as C. laeve. However, this naming choice was later deemed invalid by rules of fungal nomenclature; the first name validly applied to the species was C. laeve, use by De Candolle, who had based his species upon Nidularia laevis as it appeared in Bulliard's Histoire des Champignons de la France (Paris, 1791). [10] Kambly and Lee published the first taxonomically valid description of the genus in 1936. [1] In their 1844 monograph on the Nidulariaceae, [5] the brothers Louis René and Charles Tulasne used the name Crucibulum vulgare, and the species was known by this name until the International Commission on the Taxonomy of Fungi (ICTF) changed the starting-point date for the naming of fungi, and C. vulgare was deemed invalid. [10] The etymology of the specific epithet is derived from the Latin laeve, meaning "smooth". [10]
Crucibulum species have light tan to cinnamon-colored fruiting bodies, known as a peridium, that are cup- or crucible-shaped. Depending on the species, the size of the peridium may range from 2–4 mm tall by 1.5–3 mm wide at the mouth (for C. parvulum) [11] to 5–10 mm tall by 5–8 mm wide (for C. laeve). [12] Viewed microscopically, the wall of the peridium is made of a single layer of tissue, in contrast to the three-layered peridium wall in Cyathus species. The outer surface of the peridium has hyphae that agglutinate so as to form a texture with visible filaments, a condition known as fibrillose; this outer layers of hairs typically wears off with age to leave a relatively smooth surface. [13]
Young specimens have a thin layer of tissue called an epiphragm that covers the top of the peridium; it wears off at maturity to expose the peridioles within. There are usually four to six peridioles (up to 15 have been noted for C. laeve) [12] that are disc-shaped, whitish in color, and attached to the endoperidium by a strand called a funicular cord. Made of mycelia, the funicular cord tends to wither away and disappear as the fruiting body ages. [14] Spores from Crucibulum species typically have an elliptical or roughly spherical shape, and are thick-walled, translucent (hyaline) or light yellow-brown in color, with dimensions of 5–15 μm by 5–8 μm. [15] The spores of C. cyathiforme are notably slightly or strongly curved. [11]
Because the basic fruiting body structure in all genera of the family Nidulariaceae is essentially similar, Crucibulum may be readily confused with species of Nidula or Cyathus , especially older, weathered specimens of Cyathus that may have the hairy ectoperidium worn off. [13] It distinguished from Nidula by the presence of a funiculus, a cord of hyphae attaching the peridiole to the endoperidium. Cyathus differs from genus Crucibulum by having a distinct three-layered wall and a more intricate funiculus. [16]
Derived from the Greek word peridion, meaning "small leather pouch", [17] the peridiole is the "egg" of the bird's nest. It is a mass of basidiospores and glebal tissue enclosed by a hard and waxy outer shell. In Crucibulum, the disc-shaped peridioles are light buff or white; the white colouring is due to a persistent layer of tissue surrounding the peridioles, called a tunica. Inside the peridiole is a spore-bearing tissue (the hymenium) that is made of spore-bearing cells (basidia), sterile (non-reproductive) structures, and spores.
Peridioles are attached to the fruiting body by a funiculus, a structure of hyphae that may be differentiated into three regions: the basal piece, which attaches it to the inner wall of the peridium, the middle piece, and an upper sheath, called the purse, connected to the lower surface of the peridiole. In the purse and middle piece is a coiled thread of interwoven hyphae called the funicular cord, attached at one end to the peridiole and at the other end to an entangled mass of hyphae called the hapteron. In Crucibulum species the peridioles are covered by a whitish tunica. [18] The funiculus of Crucibulum species is markedly different from those of Cyathus species: in Crucibulum, the purse is a rounded knob 0.3–0.5 mm wide, attached to the underside of the peridiole. Attaching the purse directly to the wall of the peridium is a stout yellow-grey cord 0.1 mm wide and about 2.5 mm long. [19]
Spores are dispersed when a peridiole is dislodged by raindrops or water dripping off an over-hanging leaf. The smooth inner walls of the fruiting body consistently form an angle of 70–75° with the horizontal; it has been demonstrated experimentally that the combined effect of the crucible shape and internal wall angle produce a good splash action. [20] The force of the falling water splashes out the peridiole, uncoiling and snapping the funiculus, the cord that connects it to the fruiting body. As the peridiole continues its flight, the funiculus extends to its full length. The sticky end of the funiculus may adhere to a leaf or a twig some distance away, and the peridiole may end up being wrapped around or hanging down the object to which the funiculus is stuck. The spores can germinate when the thick outer wall of the peridiole wears away, or the peridiole may be eaten by a herbivorous animal, and ultimately passed through its digestive system. This method of spore dispersal, first suggested by John Ray in the late 17th century, was tested experimentally by Martin (1927), [14] and more thoroughly by Buller and Brodie in the 1940s. [21]
The life cycle of Crucibulum, which contains both haploid and diploid stages, is typical of the species of Basidiomycota that can reproduce both asexually (via vegetative spores), or sexually (with meiosis). Like other wood-decay fungi, this life cycle may be considered as two functionally different phases: the vegetative stage for the spread of mycelia, and the reproductive stage for the establishment of spore-producing structures, the fruiting bodies. [22]
The vegetative stage encompasses those phases of the life cycle involved with the germination, spread, and survival of the mycelium. Spores germinate under suitable conditions of moisture and temperature, and grow into branching filaments called hyphae, pushing out like roots into the rotting wood. These hyphae are homokaryotic, containing a single nucleus in each compartment; they increase in length by adding cell-wall material to a growing tip. As these tips expand and spread to produce new growing points, a network called the mycelium develops. Mycelial growth occurs by mitosis and the synthesis of hyphal biomass. When two homokaryotic hyphae of different mating compatibility groups fuse with one another, they form a dikaryotic mycelia in a process called plasmogamy. Prerequisites for mycelial survival and colonization a substrate (like rotting wood) include suitable humidity and nutrient availability. Crucibulum laeve is saprobic, so mycelial growth in rotting wood is made possible by the secretion of enzymes that break down complex polysaccharides (such as cellulose and lignin) into simple sugars that can be used as nutrients. [23]
After a period of time and under the appropriate environmental conditions, the dikaryotic mycelia may enter the reproductive stage of the life cycle. Fruiting body formation is influenced by external factors such as season (which affects temperature and air humidity), nutrients and light. As fruiting bodies develop they produce peridioles containing the basidia upon which new basidiospores are made. Young basidia contain a pair of haploid sexually compatible nuclei which fuse, and the resulting diploid fusion nucleus undergoes meiosis to produce basidiospores, each containing a single haploid nucleus. The dikaryotic mycelia from which the fruiting bodies are produced is long lasting, and will continue to produce successive generations of fruiting bodies as long as the environmental conditions are favorable. [24]
The initial studies on the development of the fruiting bodies in Crucibulum were performed by the brothers Tulasne (1844), [5] Sachs (1855), [25] DeBary (1866), [26] Eidam (1877), [27] and Walker (1920). [28] Collectively, these early researchers determined that basidiospores are produced on club-shaped basidia which line the internal cavity of the peridiole. Basidia typically have 4 spores, attached by a short projection (a sterigma ); after being detached from the basidia the spores migrate towards the center of the peridiole concurrently with the collapse and gelatinization of the underlying tissues.
Grown in liquid culture, Crucibulum laeve produces bioactive chemicals called salfredins that are structurally related to benzofuran and chromene, molecules that contain cyclic amide or lactone five-membered ring structures; these compounds are unique to this species. [30] Salfredin B11 was first identified in 1995, [31] while later research confirmed the presence of additional salfredin-type metabolites. These compounds are inhibitors of aldose reductase, an enzyme that has been implicated in the formation of cataracts in advanced stages of diabetes mellitus. [32] [33] The salfredin compounds may have therapeutic use in the treatment of this disorder. [30]
Like other bird's nest fungi, Crucibulum species are saprobic and derive their nutrients from decomposing organic matter. They are typically found growing on wood and woody debris such as stems, twigs, wood chips, old nut shells, and old matting; [34] they are sometimes found on "dried manure cakes". [7] Brodie notes (of C. laeve) they are "never" found on soil or large logs. [11] C. parvulum has been found on the roots and stems of old or dead dry land plants such as Juniperus horizontalis and Artemisia species.
C. laeve, the most well-known species of Crucibulum, is a temperate-zone species with a circumpolar distribution. It has been collected in most European countries and the Canary Islands; in North America it has been found from Alaska to Mexico, while South American locations include Chile and Tierra del Fuego. It has also been found in Australia, [35] Iceland, [36] Japan, and New Zealand. [10] C. parvulum has a primarily North American distribution, having been found in Alaska, southern Alberta Badlands, the Canadian Rocky Mountains and in semi-deserts of Idaho; [37] in 2004 it was collected in China. [38] C. cyathiforme is only known from Colombia—where it was discovered growing at an elevation of nearly 7000 feet (2146 metres)— [39] and Armenia. [40]
Species in the family Nidulariaceae, including Crucibulum, are considered inedible, as they are "not sufficiently large, fleshy, or odorous to be of interest to humans as food". [41] However, there have not been reports of poisonous alkaloids or other substances considered toxic to humans.
Until the 1970s Crucibulum was thought to be monotypic, containing the single species C. laeve (formerly C. vulgaris). This was in part due to the stance that Curtis Gates Lloyd and other mycologists had taken in the early 20th century, believing that the designation of new species was not justifiable due to the existence of intermediate forms in similar habitats and close proximity. [13] In 1970–71, Brodie discovered and reported two variants that differed from C. laeve sufficiently to justify naming them as new species.
The specific epithet of this species refers to the vase-like or Cyathus -like (obconic) form of the peridia. It differs from Crucibulum laeve in the shape and pink-color of its peridia, as well as its slightly or strongly curved spores (typically 6.5–8 x 11–17 μm). It was found growing on rotten wood and soil in Colombia by mycologist Gastón Guzmán. [39]
Crucibulum laeve or the white-egg bird's nest [42] have peridia that are 3–7 mm in diameter x 3–8 mm tall, cup-shaped, short and cylindrical with roughly parallel side walls. The tomentose exterior surface is tan to yellow when young and whiter in age. Young specimens have a coarsely tomentose epiphragm (membranous cover) that soon disappears. The peridioles are 1–2 mm broad, tan to white in color, disc-shaped, and wrinkled when dry. This species grows on material like twigs, lignin-rich vegetable debris, wood chips, old matting, or manure. [43]
The immature fruiting body of Crucibulum laeve (technically, the peridium), is roughly spherical in shape, but in maturity the base is narrowed slightly relative to the top, so that it appears like a cup, or crucible. The fruiting bodies are usually 5–8 mm tall and almost as wide at the mouth. [10] When young, the mouth is enclosed by a thin membrane called an epiphragm, which is covered with surface hairs. As the fruiting body matures and the fruiting body expands, the epiphragm ruptures, exposing the internal contents. The wall of the fruiting body is made of a single uniform layer of closely interwoven hyphae (the threadlike filaments that form the mycelium) roughly 0.25–0.5 mm thick; this wall structure is in contrast to species from the bird's nest fungus genus Cyathus , which have a distinctly three-layered wall. Young species have a yellowish velvety cover of fine hairs, but this external surface becomes sloughed off and becomes smooth as the fruiting body matures; the color changes to brown, although some old weathered specimens may be bleached grey or dirty white. [7] The inner surface of the fruiting body is smooth and shiny. The cups contain tiny pale ochraceous or white "eggs," technically termed peridioles, usually 1–2 mm in diameter. In each peridiole is a spore-producing layer of tissue, the hymenium. This layer is largely composed of basidia (spore-producing cells) mixed with paraphyses (non-spore producing elements interspersed between basidia). Peridioles are covered by a thin membrane of loosely woven hyphae known as a tunica; separated from the light-colored tunica, the peridioles are black. The peridioles are attached to the inner wall of the peridium by a thin, elastic cord of mycelium, a funiculus, which can be extended at length when moist.
Crucibulum laeve has spores that are elliptical, hyaline (translucent), and smooth, with dimensions of 7–10 by 4–6 μm. [44]
This species, which is also known as the scanty bird's nest, [42] is characterized by its very small peridia (dimensions 1.5–3 mm wide at the mouth x 2–4 mm tall) with a color that may range from white to grey to pale buff, but never yellow – helping distinguish it from C. laeve. The peridia are obconic, thin-walled (150–180 μm at the lip, approximately 300 μm thick at the edge of the lip), tomentose on the outer side and smooth on the inner side, and taper to a narrow base. The peridioles range in width between 0.5 and 1.25 mm broad. Basidiospores have dimensions of 4–5 by 7–8 μm. [37]
A basidium is a microscopic spore-producing structure found on the hymenophore of reproductive bodies of basidiomycete fungi. The presence of basidia is one of the main characteristic features of the group. These bodies also called tertiary mycelia, which are highly coiled versions of secondary mycelia. A basidium usually bears four sexual spores called basidiospores. Occasionally the number may be two or even eight. Each reproductive spore is produced at the tip of a narrow prong or horn called a sterigma (pl. sterigmata), and is forcefully expelled at full growth.
Funiculus is any cord-like structure in anatomy or biology, and may refer to:
Cyathus striatus, commonly known as the fluted bird's nest, is a common saprobic bird's nest fungus with a widespread distribution throughout temperate regions of the world. This fungus resembles a miniature bird's nest with numerous tiny "eggs"; the eggs, or peridioles, are actually lens-shaped bodies that contain spores. C. striatus can be distinguished from most other bird's nest fungi by its hairy exterior and grooved inner walls. Although most frequently found growing on dead wood in open forests, it also grows on wood chip mulch in urban areas. The fruiting bodies are encountered from summer until early winter. The color and size of this species can vary somewhat, but they are typically less than a centimeter wide and tall, and grey or brown in color. Another common name given to C. striatus, splash cups, alludes to the method of spore dispersal: the sides of the cup are angled such that falling drops of water can dislodge the peridioles and eject them from the cup. The specific epithet is derived from the Latin stria, meaning "with fine ridges or grooves".
Nidularia is a genus of nine species of fungi in the family Agaricaceae. Their fruit bodies resemble tiny egg-filled bird nests. The name comes from the Latin nidus meaning nest. The related genus Mycocalia was segregated from Nidularia in 1961 based on differences in the microscopic structure of the peridium.
Nidula is a genus of fungi in the family Agaricaceae. Their fruit bodies resemble tiny egg-filled birds' nests, from which they derive their common name "bird's nest fungi". Originally described in 1902, the genus differs from the related genera Cyathus and Crucibulum by the absence of a cord that attaches the eggs to the inside of the fruit body. The life cycle of this genus allows it to reproduce both sexually, with meiosis, and asexually via spores. Species in this genus produce a number of bioactive compounds, including 4-(p-hydroxyphenyl)-2-butanone, a major component of raspberry flavor and insect attractor used in pesticides.
Mycocalia is a genus of fungi in the family Nidulariaceae. Basidiocarps are minute and irregularly spherical. Each produces one or more peridioles which contain the spores and are released from the disintegrating fruit bodies at maturity. Species are usually found growing on herbaceous stems and other plant debris. The genus was originally described in 1961 by British mycologist J.T. Palmer and has a north temperate distribution.
Cyathus is a genus of fungi in the Nidulariaceae, which is a family collectively known as the bird's nest fungi. They are given this name as they resemble tiny bird's nests filled with "eggs" – structures large enough to have been mistaken in the past for seeds. However, these are now known to be reproductive structures containing spores. The "eggs", or peridioles, are firmly attached to the inner surface of this fruit body by an elastic cord of mycelia known as a funiculus. The 45 species are widely distributed throughout the world and some are found in most countries, although a few exist in only one or two locales. Cyathus stercoreus is considered endangered in a number of European countries. Some species of Cyathus are also known as splash cups, which refers to the fact that falling raindrops can knock the peridioles out of the open-cup fruit body. The internal and external surfaces of this cup may be ridged longitudinally ; this is one example of a taxonomic characteristic that has traditionally served to distinguish between species.
Cyathus olla also known as the field bird's nest is a species of saprobic fungus in the genus Cyathus of the family Nidulariaceae. The fruit bodies resemble tiny bird's nests filled with "eggs" – spore-containing structures called peridioles. Like other bird's nest fungi, C. olla relies on the force of falling water to dislodge peridioles from fruiting bodies to eject and disperse their spores. The life cycle of this fungus allows it to reproduce both sexually, with meiosis, and asexually via spores. C. olla is a relatively common fungus, with a worldwide distribution. It is the subject of agricultural research to determine its potential as a means to accelerate the breakdown of crop residue, and reduce the population of plant pathogens. The specific epithet is derived from the Latin word olla, meaning "pot".
Cyathus stercoreus, commonly known as the dung-loving bird's nest or the dung bird's nest, is a species of fungus in the genus Cyathus, family Nidulariaceae. Like other species in the Nidulariaceae, the fruiting bodies of C. stercoreus resemble tiny bird's nests filled with eggs. The fruiting bodies are referred to as splash cups, because they are developed to use the force of falling drops of water to dislodge and disperse their spores. The species has a worldwide distribution, and prefers growing on dung, or soil containing dung; the specific epithet is derived from the Latin word stercorarius, meaning "of dung".
Cyathus helenae or Helena's bird's nest is a species of fungus in the genus Cyathus, family Nidulariaceae. Like other members of the Nidulariaceae, C. helenae resembles a tiny bird's nest filled with 'eggs'—spore-containing structures known as peridioles. It was initially described by mycologist Harold Brodie in 1965, who found it growing on mountain scree in Alberta, Canada. C. helenae's life cycle allows it to reproduce both sexually and asexually. One of the smaller species of Cyathus, C. helenae produces a number of chemically unique diterpenoid molecules known as cyathins. The specific epithet of this species was given by Brodie in tribute to his late wife Helen.
A coprophilous fungus is a type of saprobic fungus that grows on animal dung. The hardy spores of coprophilous species are unwittingly consumed by herbivores from vegetation, and are excreted along with the plant matter. The fungi then flourish in the faeces, before releasing their spores to the surrounding area.
Limnoperdon is a fungal genus in the monotypic family Limnoperdaceae. The genus is also monotypic, as it contains a single species, the aquatic fungus Limnoperdon incarnatum. The species, described as new to science in 1976, produces fruit bodies that lack specialized structures such as a stem, cap and gills common in mushrooms. Rather, the fruit bodies—described as aquatic or floating puffballs—are small balls of loosely interwoven hyphae. The balls float on the surface of the water above submerged twigs. Experimental observations on the development of the fruit body, based on the growth on the fungus in pure culture, suggest that a thin strand of mycelium tethers the ball above water while it matures. Fruit bodies start out as a tuft of hyphae, then become cup-shaped, and eventually enclose around a single chamber that contains reddish spores. Initially discovered in a marsh in the state of Washington, the fungus has since been collected in Japan, South Africa, and Canada.
Barcheria is a fungal genus in the family Agaricaceae. This is a monotypic genus, containing the single sequestrate species Barcheria willisiana, found in western Australia.
Spongiforma thailandica is a species of fungus in the family Boletaceae, genus Spongiforma. The stemless sponge-like species, first described in 2009, was found in Khao Yai National Park in central Thailand, where it grows in soil in old-growth forests. The rubbery fruit body, which has a strong odor of coal-tar similar to Tricholoma sulphureum, consists of numerous internal cavities lined with spore-producing tissue. Phylogenetic analysis suggests the species is closely related to the Boletaceae genera Porphyrellus and Strobilomyces.
Geastrum quadrifidum, commonly known as the rayed earthstar or four-footed earthstar, is an inedible species of mushroom belonging to the genus Geastrum, or earthstar fungi. First described scientifically by Christian Hendrik Persoon in 1794, G. quadrifidum is a cosmopolitan—but not common—species of Europe, the Americas, Africa, Asia, and Australasia. The fungus is a saprobe, feeding off decomposing organic matter present in the soil and litter of coniferous forests.
Mycena nidificata is a species of fungus in the family Mycenaceae of the Agaricales. First collected in 2000 and reported as a new species in 2007, it is known only from Kanagawa, Japan, where it grows on the floor of oak forests. The dark brown irregularly wrinkled cap measures up to 25 mm (1.0 in) in diameter. The cap is supported by a thin stem up to 50 mm (2.0 in) long, which is covered at the base by a whitish hairlike growth, and attached to white, cord-like rhizomorphs—aggregations of mycelium that resemble plant roots. The underside of the cap features thin, distantly spaced grayish gills that have distinct veins running between them. At a microscopic level, distinguishing characteristics include the inamyloid spores, the club-shaped cheilocystidia with finger-like appendages, the diverticulate cells in the outer layer of cap and stem, and the presence of clamp connections.
The Nidulariaceae are a family of fungi in the order Agaricales. Commonly known as the bird's nest fungi, their fruiting bodies resemble tiny egg-filled birds' nests. As they are saprobic, feeding on decomposing organic matter, they are often seen growing on decaying wood and in soils enriched with wood chips or bark mulch; they have a widespread distribution in most ecological regions. The five genera within the family, namely, Crucibulum, Cyathus, Mycocalia, Nidula, and Nidularia, are distinguished from each other by differences in morphology and peridiole structure; more recently, phylogenetic analysis and comparison of DNA sequences is guiding new decisions in the taxonomic organization of this family.
Mycena chlorophos is a species of agaric fungus in the family Mycenaceae. First described in 1860, the fungus is found in subtropical Asia, including India, Japan, Taiwan, Polynesia, Indonesia, and Sri Lanka, in Australia, and Brazil. Fruit bodies (mushrooms) have pale brownish-grey sticky caps up to 30 mm (1.2 in) in diameter atop stems 6–30 mm (0.2–1.2 in) long and up to a millimeter thick. The mushrooms are bioluminescent and emit a pale green light. Fruiting occurs in forests on fallen woody debris such as dead twigs, branches, and logs. The fungus can be made to grow and fruit in laboratory conditions, and the growth conditions affecting bioluminescence have been investigated.
Calostoma fuhreri is a species of gasteroid fungus in the family Sclerodermataceae. Found in Australia, the original specimens were collected by mycologist Bruce Fuhrer, for whom the species is named. Fruit bodies grow to 28 mm (1.1 in) tall, and comprise a pseudostipe that is 15–20 mm (0.6–0.8 in) long by 5–8 mm (0.2–0.3 in) thick and supports a roughly spherical peridium. Atop the peridium is an irregular stoma (opening) that is red on the inside. Inside the peridium is a white gleba that consists of spores, basidia, and broken hyphae. The spores are oblong to elliptical, hyaline (translucent), and typically measure 20–26 by 9–11 μm.