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Cladoscenium sp. cf. C. tricolpium Benson, 1966

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Benson, 1966, p. 387-390; pl. 25, figs. 10-11:

Cladoscenium cf. tricolpum [sic.] (Haeckel) Jørgensen

?Euscenium tricolpium Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1147, Pl. 53, fig. 12.
?Cladoscenium tricolpium Haeckel, Jørgensen, 1900 Bergens Mus. Aarbog (1899), pp. 78-79; 1905, Bergens Mus. Skrifter, p. 134, Pl. 15, figs. 71-73.

Cephalis large, subcylindrical with a rounded or dome-shaped top, with unequal, irregular pores of all shapes, in most specimens with scattered short spines but with smooth surface in a few; in most specimens the basal margin of the cephalis is extended below the level of the centrally located median bar and has numerous long spines extending from it; in a few specimens a slight constriction in the cephalis at or near the level of the median bar separates an irregular lattice with terminal spines below from the cephalis above, but whether or not the former represents a thorax could not be determined. Three thin, nearly imperceptible ribs in the wall of the cephalis correspond to (1) two apical-lateral arches joining the distal end of the apical bar with the distal ends of the primary lateral bars, and (2) an arch joining the apical bar with the distal end of the dorsal bar. A large, nearly circular collar ring at the level of the median bar is generally visible in basal or apical views; the ventral arch ascends ventrally. The dorsal and primary lateral bars are long, cylindrical to three-bladed, and have a pair of divergent branches joining with the collar ring near their distal ends. The bars extend as equal, relatively heavy, three-bladed feet which are nearly horizontal proximally but have sharp outward convexity throughout most of their extent; the primary lateral feet are more strongly curved than the dorsal foot which descends proximally at a steeper angle than the former. A short, thorn-like, axial spine is generally present. The vertical bar is thinner than the other bars originating from the median bar, ascends ventrally, and extends as a relatively short, three-bladed to conical vertical spine which arises from the middle of the ventral face of the cephalis. The apical bar is a centrally located columella which extends as a three-bladed, straight to curved, vertical apical horn which originates from the center of the upper surface of the cephalis. The apical horn and basal feet are generally smooth, but a few specimens have one or two verticils of three conical branches, each branch arising from one of the three blades of the feet and horn.

Meaurements; based on 12 specimens from stations 60, 81, 115, and 151; length of cephalis (including its extension below level of median bar) 34-71 µm; maximum breadth of cephalis 48-96 µm; length of apical horn 20-68 µm, of vertical spine 12-31 µm, of feet (length of chord between origin and distal termination) 65-111 µm.

Remarks. This species differs from Jørgensen's illustration of Cladoscenium tricolpum in the general absence of serrations on each of the three-blades of the feet and apical horn. A few specimens from the gulf, however, have one or two verticils of three conical spines on the feet and apical horn (Pl. 25, fig. 11). This feature as well as the serrations on the blades may be an intraspecific variation. The shape and internal structure of the cephalis of the Gulf species and Jørgensen's species are identical. Jørgensen identified his species as Euscenium tricolpium Haeckel (1887, p. 1147, Pl. 53), but I am of the opinion that it is different from Haeckel’s species. Without study of Haeckel's type material, placement of E. tricolpium in synonymy with C. tricolpium is tentative.

Distribution. This species is cosmopolitan in the Gulf with a slightly greater frequency in the northern half of the Gulf, particularly at station 115 where it is nearly common. It is absent at stations 90, 99, 130, 194, 203, 208, and 214. It is rare at all the other Gulf stations sampled. It is an offshore or more nearly oceanic species whose slight increase in the northern Gulf may be a result of its response to upwelling.
Jørgensen (1905, p. 134) states that this species is found frequently in Norwegian fjords at water depths up to 100 meters. Off the west coast of Norway it is sparse but not rare when present in deep water samples. It was found in the warmer, more saline Atlantic waters in the sea beyond Söndmöre, off Lofoten, and off Finmarken. Jørgensen cites Cleve who found the species at a great depth west of Spitzbergen and at some places in the northern and northwestern parts of the Atlantic. Cleve considers this species as being probably derived from the northern polar basin or from the northern Pacific but remarks that it is often found together with temperate oceanic species. Haeckel (1887, p. 1147) reported Euscenium tricolpium from the central Pacific at "Challenger" station 266. The occurrence of specimens similar to, if not the same as, Cladoscenium tricolpium Jørgensen in the tropical eastern Pacific and Gulf of California and the presence of this species at high latitudes in the Atlantic and Arctic Oceans indicate that it may be cosmopolitan at all latitudes.
Benson 1966











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