Description - Add description
|Benson, 1966, p. 215-217; pl. 11, figs. 2-3; text-fig.15 |
Spongopyle osculosa Dreyer
Spongopyle osculosa Dreyer, 1889, Jenaische Zeitschr. Naturwiss., vol. 23, pp. 118-119, P1. 11, figs. 99, 100; Riedel, 1958, B.A.N.Z.A.R.E. Repts., ser. B, vol. 6, pt. 10, pp. 226-227, Pl. 1, fig. 12.
Test circular in outline, spongy appearing, with a latticed tubular pylome, generally circular in section, arising from within the test but not from its central darker area and in most specimens extending beyond the margin as a distinct tube whose rim is surmounted by a few short triangular teeth. In side view tests either flat or with broad, convex outward curvature, with margin rounded to trapezoidal in outline; internal structure of test not spongy but consisting of numerous (8-10 or more), closely and equally spaced, concentric, discoidal shells (text-fig. 15), with outer shell somewhat thickened in a few tests giving the appearance of a sieve-plate covering the spongy-
appearing, internal part of the test. Structure of tubular pylome consisting of a small-pored lattice developed between 5-6 parallel beams or spines that are arranged around a circle.
Measurements; based on 30 specimens from stations 27, 34, 46, and 81: diameter of disc 121-289 µm; length of tubular pylome including its visible portion within the test 18-68 µm; breadth of pylome 10-25 µm.
Remarks. There is no doubt that this species is the same as Spongopyle osculosa described by Dreyer (1889) and Riedel (1958). Those authors did not describe the internal concentric shell structure of the test, but in surface view the specimens appear spongy. The only differences between S. osculosa Dreyer and S. setosa Dreyer (1889, p. 119, P1. 11, figs. 97, 98) is that the latter has weakly developed peripheral spines and has a smaller disc diameter; whether or not it is an incompletely developed form of S. osculosa cannot be determined without reference to Dreyer's type material.
Distribution. This species is rare but cosmopolitan in the Gulf, occurring as far north as station 208. It is absent at stations 91, 130, 184, 191, 194, 203, 206, and 214. Its frequency undergoes no significant changes from station to station; therefore, the control of its distribution by upwelling cannot be assessed. It has a slightly greater average frequency in the southern half of the Gulf, indicating its preference for oceanic waters.
Riedel (1958, p. 227) states that this species may be cosmopolitan because it was reported from Antarctic sediments as well as from the southern Indian Ocean and the tropical and northern Pacific Ocean.
|Spongy shell in form of biconvex lens. Its shape varies: approximates to a more or less regular circle. Spongy tissue fine; central thickened part of shell constructed of denser spongy mass than marginal. Entire surface of shell in adult specimens covered by mantle similar to that of Spongurus pylomaticus. Because of mantle shell has clear contours. Radial pieces pass among cross-pieces of spongy tissue in form of indistinct radial striation. Do not emerge to the outside, and shells devoid of radial needles. Distinct pylome characteristic. This is not a simple funnel in spongy tissue...but specialized formation in form of porous tubule with notches at end.|
Growth changes are expressed by a continual increase in size of disk. Young specimens smaller that adults; more slender and transparent, their radial pieces more marked; their surface not covered by mantle. Pylome tubule present even in comparatively young specimens.
Dimensions: diameter of disk of adult specimens 190-270 micrometer.
|Well preserved specimens with mantle and pylome are easily distinguished from other species. When badly preserved or not well developed (?) and the mantle and pylome are not well preserved, it is difficult to differentiate from some variants of Spongotrochus glacialis. As described by Dreyer, Riedel and Petrushevskaya the shell has the shape of a biconvex lens. The central thickened part is made of a denser spongy mass. The entire surface of the shell in adult specimens is covered with a mantle so the shell has a well defined contour. It is also characterized by the presence of a tubular pylome...However, under subantarctic and subtropical waters a variant is found which has flat sides in lateral view acquiring a subhexagonal outline...and some specimens are difficult to differentiate from a variant of Spongotrochus glacialis.|
|...it is difficult to differentiate Spongopyle osculosa from Spongotrochus glacialis without its characteristic mantle and pylome...|