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Lithopera bacca
Ehrenberg, 1872
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Description - Add description
Benson, 1966, p. 489-491; pl. 33, figs. 10-11:
Lithopera bacca Ehrenberg
Lithopera bacca Ehrenberg, 1873a, Akad. Berlin, Monatsb. (1872), pp. 314-315; 1873b, Akad. Berlin, Abhandl. (1872), Pl. 8, fig. 1; Popofsky, 1913, Deutsche Südpolar-Exped., vol. 14, pp. 355-356, text figs. 61-63.
Lithopera bursella Ehrenberg, 1873a, Akad. Berlin, Monatsb. (1872), p. 315; 1873b, Akad. Berlin, Abhandl. (1872), Pl. 10, fig. 4.
Lithopera ananassa Haeckel, 1887, Challenger Rept., Zoo!, vol. 18, p. 1234, Pl. 57, fig. 3.
Test consisting of a spherical, generally rough cephalis which is half depressed within a broad, cylindrical to ovate thorax with a rounded closed mouth. Pores of cephalis small, equal, polygonal to subcircular, hexagonally arranged, surrounded by polygonal frames, in a few tests infilled with silica. A long, straight, vertical, generally conical, eccentric apical horn extends from the apical bar which is a dorsal cephalic rib occupying a slight dorsal sagittal furrow in the cephalis. Vertical spine short, inconspicuous. Collar ring heavy, with four small circular collar pores. Dorsal and primary lateral bars extend from the collar ring as bars which are free within the thoracic cavity proximally, but distally they extend for a short distance as thoracic ribs coincident with slight furrows in the surface of the thorax; ribs terminate in short, inconspicuous spines at the level of maximum proximal curvature of the thorax. In several specimens the distal portion of the thorax is marked by a transverse ridge separating its cylindrical portion from the lower, rounded or dome-shaped, closed portion (Pl. 33, fig. 10); this feature absent in a few tests. Surface of thorax rough but without long spines in the few specimens observed. Pores of thorax, including its dome-shaped distal portion, small, equal, hexagonal, hexagonally arranged in longitudinal rows, surrounded by hexagonal frames.
Measurements; based on 3 specimens from stations 27 and 46: maximum length of test 132-135 µm, maximum breadth 92-117 µm; length of cephalis 27-28 µm, of thorax 117-123 µm, of apical horn 14-30 µm.
Remarks. The species listed in the synonymy differ from one another only slightly in the shape of the thorax. Lithopera ananassa Haeckel differs only in the presence of thicker intervening bars and in longer spines originating from the nodes of the intervening bars of the thorax, both of which are subject to intraspecific variation. Haeckel (1887, p. 1234) states that he observed the thoracic ribs in the specimen of Lithopera bursella Ehrenberg that he studied, but Ehrenberg did not. None of the species have a transverse raised ridge on the distal portion of the thorax; this feature, however, is not present in all specimens from the Gulf.
Distribution. This species is very rare and occurs only at stations 27, 34, 46, 56, and 60 in the southern half of the Gulf. It is, therefore, an oceanic species with little affinity for Gulf waters.
This species is widespread in Recent tropical seas. L. bacca occurs in the tropical Pacific at the surface ("Challenger" stations 200, 224, 266, 271), in the Philippine Sea, and in the western tropical Indian Ocean. L. bursella was reported from the tropical Indian Ocean near Zanzibar. L. ananassa was reported from the surface of the tropical Atlantic at "Challenger" stations 347-352.
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