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see chromospherechromosphere
[Gr.,=color sphere], layer of rarefied, transparent gases in the solar atmosphere; it measures 6,000 mi (9,700 km) in thickness and lies between the photosphere (the sun's visible surface) and the corona (its outer atmosphere).
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Spicules are spike-like prominences visible at the limb of the sun during solar eclipses or during observation of the sun in monochromatic light, for example, the light of the hydrogen line Hλ. They extend into the solar corona to heights of 6,000–10,000 km and have diameters of 200–2,000 km. The average lifetime of a spicule is 5–7 min. Spicules move upward at speeds of 20–30 km/sec; the speeds of internal movements are 5–10 km/sec. The temperature of a spicule is approximately 8000°K in the lower part and about 16,000°K in the upper part. The density of spicules varies with height from 2 × 1011 to 3 × 1010 atoms/cm3. Hundreds of thousands of spicules exist on the sun at one time. They arise primarily at the edges of the cells of the chromospheric network.



(1) In certain invertebrates a skeletal element consisting of calcium carbonate or, less commonly, silica (silicon dioxide). Spicules occur in sponges (in the form of one-, three-, four-, and many-rayed needles), octocorallians, aplacophorans, mollusks, holothurians and other echinoderms (in the form of small wheels, anchors, or lattices), and ascidians (in the form of thorny spheres).

(2) In nematodes, a part of the male copulatory organ. In some species the spicules are supplementary formations; they protrude from the cloacal opening of the male and serve to widen the female’s vagina. In other species sulcate spicules come together and conduct the spermatozoa into the vagina of the female.


One of an irregular distribution of jets shooting up from the sun's chromosphere. Also known as solar spicule.
An empty diatom shell.
(invertebrate zoology)
A calcareous or siliceous, usually spikelike supporting structure in many invertebrates, particularly in sponges and alcyonarians.
References in periodicals archive ?
Coronal rain and loops, along with spicular velocities and splashdown events, require the presence of condensed matter.
double dagger]) Some authors have attempted, although not very convincingly, to establish a relationship between spicular velocities and gravitational forces (e.
The spicular and cytological characters of both species strongly resemble those found in well-defined families of non-calcified demosponges.
In the case of Acanthochaetetes, we propose to classify the genus in the family Spirastrellidae Ridley and Dendy, 1886, in view of the spicular and cytological resemblances (periflagellar sleeve, central cell) and the low genetic distance between Acanthochaetetes and Spirastrella that is indicated by the present work.
ovifilamenta is characterized by the presence of a gubernaculum (a rare feature in the genus Rhabdochona), a pre-equatorial vulva, 9 pairs of preanal papillae, and by spicular ratio (1:9.
moraveci also differ from the new species in that both have less numerous pairs (6) of preanal papillae and shorter spicular ratio (1:4.
can be distinguished from these reported Pakistani species and those described from other parts of the world by the metrical arrangement, number of caudal papillae and spicular ratios.
02 mm in size; a thick, muscular, backwardly directed vagina; 10 teeth in the prostome; two very unequal and dissimilar spicules with spicular ratio 1:2.