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Litharachnium tentorium Haeckel, 1862

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Litharachnium tentorium:
The upper part of the lattice shell is slenderly conical, widened out below to a broad brim which is at the outside edge bent again upwards, giving the appearance of the brim of a hat. At the top of the conical part, there is a tiny semispherical cephalis.

The pores in the upper part of the shell are small, round and scattered; farther down they are lattice windows (as in the genus Plectopyramis HCK.) and are more regularly arranged in horizontal rows. The shape gradually lengthens out horizontally, so that from being round they become rectangular with rounded corners. Only still farther down do the straight ribs in the wall of the lattice shell appear, and the pores now become regularly rectangular, and are arranged in distinct rows, both radially and tangentially. When the radial pores have attained a certain size, new straight longitudinal ribs appear in the wall of the lattice shell, pushed in between the old ones.

The number of principal ribs in the well developed specimen which is illustrated in fig. 90, was 32. Very numerous secondary ribs, their number increasing in proportion to the distance from the cephalis, were present between these 32. The diameter of the brim 340 µm, of the cephalis only 8-9 µ. The largest meshes (high up) 9 µ, in the brim about 6 µ.

Notwithstanding, that there are really great differences in Haeckel’s and my descriptions, it seems - on account of the remarkable correspondence in so many details with Haeckel’s illustration - that my species and Haeckel’s are after all identical.

This species answers perhaps best in structure to the many-jointed genera (division Stichocyrtida), and might be considered as such a many-jointed form, where the strictures and annular septa between the different joints have disappeared.

Very rare, only singly: Skroven, 4/4 1899, 0-150 m.; the Folden Fiord, 6/4 1900, 300-200 m.

Distribution: In the sea between Norway and the Faeroe Isles (also mentioned from here by Cleve, L. 40 [1901]. Found by Haeckel at Messina.

Seems to be southern, temperate, oceanic form.
Jørgensen 1905
Benson, 1966, p. 427-430; pl. 29, figs. 5-6:

Litharachnium tentorium Haeckel

Litharachnium tentorium Haeckel, 1861b, Akad. Berlin, Monatsb. (1860), p. 836; 1862, Die Radiolarien, pp. 281-282, Pl. 4, figs. 7-10; 1887, Challenger Rept., Zool., vol. 18, p. 1163; Jørgensen, 1905, Bergens Mus. Skrifter, pp. 138-139, Pl. 16, figs. 90-91; Popofsky, 1913, Deutsche Südpolar-Exped., vol. 14, pp. 331-332, text fig. 40.
Litharachnium araneosum Haeckel, 1887, Challenger Rept., Zool., vol.18, p.1163, Pl. 55, figs. 8, 10.

Most tests incompletely developed, consisting of a very small, smooth, hyaline cephalis, with three collar pores at its base. Cephalis not separated by a stricture from thorax. In complete specimens thorax slenderly conical proximally, becoming very broadly conical distally where, at its base, it flares outward with its margin turned up in a gentle curve; thorax with 20-39 or more distinct, subequally spaced, longitudina1 ribs. Proximal portion of thorax consisting of 6-10 longitudinal primary ribs which originate from the collar ring; three of these ribs extend from the dorsal and primary lateral bars. The primary ribs connected by 3-4 parallel transverse bars that are continuous around the circumference. Arising from the third or fourth transverse bars are secondary longitudinal ribs that are located halfway between the primary ribs. In a similar manner third, fourth, fifth order ribs, etc., arise at varying intervals distally. The first through third order ribs represent the 20-30, distinct, longitudinal ribs of complete tests. Distally from the slender conical portion of the thorax the ribs have between them a reticulate network of thin bars dividing rectangular pores. In the upper, slender, conical portion of the thorax where the first through third order ribs originate, the pores are rectangular, separated by heavy intervening bars representing the distinct transverse bars and longitudinal ribs; in some tests a delicate, reticulate, secondary meshwork covers the pores.

Measurements; based on 2 complete specimens from station 130: length of test 120-150 µm; maximum breadth 597-643 µm.

Remarks. Although most specimens of this species are incomplete, this species can be identified by its distinct, reticulate network and by the presence of longitudinal ribs of various orders.

There is no doubt that this species is Litharachnium tentorium Haeckel. It is tent-shaped with concave outward lateral outline and with at least 20 longitudinal ribs. L. araneosum Haeckel differs from this species only in its relatively straight lateral outline, although Haeckel's illustration (Haeckel, 1887, Pl. 55, fig. 10) shows a slightly concave outward outline of apparently an incomplete specimen.

Distribution. This species is rare at all stations and occurs as far north as station 208 in the Gulf, but it is absent at several stations which include 27, 46, 64, 90, 99, 130, 191, 192, 194, 203, 206, and 214. Its general absence at marginal localities (except station 208) indicates its preference for offshore or more nearly oceanic waters. Its frequency and distribution are similar in both the northern and southern halves of the Gulf. It does not respond significantly to upwelling in either region.

Haeckel (1861b) first reported this species from the Mediterranean Sea near Messina. Jørgensen (1905, pp. 138-139) reported that it is very rare in Norwegian fjords and is found in the sea between Norway and the Faeroe Islands. He concludes that it seems to be a southern temperate oceanic form. Popofsky (1913, p. 333) states that this species is abundant in the tropical part of the western Indian and South Atlantic Oceans. Haeckel (1887, p. 1163) reported L. araneosum Haeckel from the surface of the central Pacific at “Chal1enger" station 271. L. tentorium Haeckel, therefore, is a cosmopolitan species, present in all oceans and at low as well as high latitudes, but it may have a more general distribution in tropical to temperate seas.
Benson 1966











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