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Heliosphaera radiata Popofsky, 1912

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Benson, 1966, p. 160-162; pl. 5, figs. 1-2:

Heliosphaera radiata Popofsky

Heliosphaera radiata Popofsky, 1912, Deutsche Südpolar-Exped., vol. 13, p. 98, text fig. 10.

Single lattice-shell, spherical to subspherical, with 5-30 (generally 8-12) radial, three-bladed, in a few tests conical, equal to subequal main spines arising from its surface, without definite arrangement. Pores of shell generally polygonal (hexagonal), subequal in size, but ranging from subelliptical to irregular and unequal, generally with subregular to regular (hexagonal) arrangement, with or without polygonal frames, 10-24 (generally 12-15) on the half circumference. Thin, conical, equal by-spines arise from the nodes of the generally thin intervening bars as well as from along the bars, variable in number from very few to present at all nodes, with variable length (5-30 µm). In most specimens the main spines continue within the shell cavity as thin, conical, centripetal spines, generally short, in a few tests relatively long. No specimens were observed with an inner shell.

Measurement; based on 30 specimens from stations 27, 34, and 71: diameter of shell 101-212 µm (generally 110-154 µm); length of main spines 10-50 µm.

Remarks. This species does not differ from Popofsky's description and illustration of the single specimen he used in defining Heliosphaera radiata Popofsky (1912, p. 98). Study of numerous individuals from the Gulf revealed that the number and length of main spines is variable and that in numerous specimens the pores are not hexagonal but tend to be elliptical or irregular. Popofsky did not observe the presence of centripetal spines which are inward continuations of the three-bladed main spines, but this feature is not present in all specimens from the Gulf and when present is not easily observed.

Distribution. In the Gulf this species is rare at all stations except 184 and 194 where it is common. It is absent at stations 130, 203, and 214. Its increased frequency at stations 184 and 194 is parallel to that of Hexacontium entacanthum Jørgensen and Diploplegma banzare Riedel. Because these stations are in the northern Gulf whose waters are subject to greater ranges of salinity and temperature than in normal oceanic regions at comparable latitudes, Heliosphaera radiata Popofsky as well as the species mentioned above apparently have a greater tolerance for such changes. Elsewhere in the Gulf H. radiata does not undergo any significant increase in its frequency at marginal stations located in regions of upwelling.
Popofsky (1912, p. 98) reported H. radiata from the tropical part of the Indian Ocean east of Madagascar at a depth of 400 meters. It has not been reported from high latitudes; therefore, it is probably a tropical oceanic species.
Benson 1966











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