Description - Add description
Shell triquetrous, head rounded, bearing a terminal spine. Body or second articulation having large unequal cells, and three acute ridges prolonged into long acute basal spines. Length including spines 4 ¼ "m" (= 0,00425 inch = 0,108mm). Cells 3 to 4 in 1 "m" (=0,001 inch = 0,025mm).
|Dictyophimus gracilipes: |
Cephalis hemispherical, with a single stout horn of variable length. Pores rounded. Thorax a three-sided smooth pyramide, with three decurrent ribs, prolonged in long, smooth three-sided feet. Pores rounded irregular decreasing in size towards the cephalis. Cephalis 0,02mm long; horn 0,04-0,05mm. Thorax 0,05mm long and 0,07mm broad.
This genus is by Haeckel made to include rather highly differentiated forms, which probably ought to be kept distinct from the species which I have here referred to it. There does not, however, appear to be any great disadvantage in placing them here preliminarily.
From these two species, the genus should be defined as follows:
The four primary spines are present, as well as the ventral, sagittal one. The three basal ones (Lr, Ll and A) extend from the central rod to the upper part of the thorax, a little below the neck, hence running for a little way in the thoracic wall, and then protruding either as thoracic feet (D. histricosus), or leaving the thorax above its free brim. The thorax is broadly campanulate or conical.
The protruding part of all five spines of uniform breadth, much broader than the inside part, with three distinct edges. In young specimens, the three basal spines extend from the lower part of the thorax. They are partly running in the thorax, but on older individuals always appear to protrude above the free brim.
The irregular, small spines on the free brim of the thorax are here, as in the preceding species, only temporary formations, which later on become intermediate walls between new meshes.
In the passage from the cephalis to the thorax, there are three distinct swellings, two lateral, outside the primary, lateral arches (Br and Bl), as well as a ventral one between the primary, lateral spines. The thorax is wide, flatly campanulate.
Dictyophimus gracilipes Bail. (1856) does not appear from the description to be this species (triquetrous; three acute ridges prolonged into long acute basal spines).
Rare in deep water samples.
Distribution: Rare on the west coast of Norway. Cleve mentions D. gracilipes from a few places in the northern part of the Atlantic up to the north west point of Spitzbergen, at the most northern places only in deep water. Baily's species was found in the Northern Pacific and Kamtschatka.
Probably boreal oceanic.
|Benson, 1966, p. 382-384; pl. 25, figs. 4-6:|
Dictyophimus gracilipes Bailey
Dictyophimus gracilipes Bailey, 1856, Amer. Jour. Sci., vol. 22, p.4, Pl. 1, fig. 8; Cleve, 1899, Kongl. Svensk. Vetenskap-Akad., Handl., vol. 32 (3), p. 29, Pl. 2, fig 2 ; Bernstein, 1932, Archiv für Protistenkunde, vol. 76, Pl. 3, figs. 4, 5; ? Riedel, 1958, B.A.N.Z.A.R.E. Repts., ser. B, vol. 6, pt. 10, pp. 233-234, Pl. 3, fig. 5; text-fig. 5.
Dictyophimus clevei Jųrgensen, 1900, Bergens Mus. Aarbog (1899), p. 80, Pl. 5, fig. 26; Mielck, 1913, Conseil Permanent Internat pour 1 'Exploration de la Mer, Bull. Trimestriel, 3, pp. 370- 371; Petrushevskaya, 1962, Zool. Zhurnal, vol. 41, pp. 337-338, fig. 7.
Cephalis subglobular to sub-hemispherical with a straight dorsal face; generally smooth with circular pores about as broad as the intervening bars; not distinctly separated from thorax except for a slight ventral stricture and a change in contour. Thorax conical, becoming subcylindrical to pyramidal toward its base, generally smooth, with subequal to unequal, subcircular to elliptical pores without definite arrangement; just below cephalis, thorax is slightly lobate--the lobes developed between the dorsal and primary lateral thoracic ribs; basal margin of thorax commonly with long, tooth-like spines. Four collar pores present; cardinal pores of type B, defined by the apical-lateral arches which occupy a slight constriction between the two dorso-lateral lobes of the thorax and the dorso-lateral surfaces of the cephalis; no specimens were observed with secondary lateral spines or bars. A long vertical three-bladed apical spine or horn extends from and is collinear with the straight apical bar which is present as a rib in the dorsal cephalic face; prominent, three-bladed to conical vertical spine arises from ventral stricture and ascends ventrally, but in several tests has a slight downward curvature. The three thoracic ribs corresponding to the dorsal and primary lateral bars extend as prominent, sharply-pointed, three-bladed feet which arise from the thorax above its base; proximally, the feet have a strong, convex outward curvature where they originate from the wall of the thorax, but for the remainder of their length they are either straight but divergent or with slight outward convexity.
Measurements; based on 12 specimens from stations 106, 115, 133, 136, and 151: length of cephalis 16-32 µm, of thorax 25-62 µm; breadth of cephalis 23-34 µm, of thorax 55-69 µm; length of apical spine or horn 12-74 µm, of vertical spine 4-31 µm, of feet 33-92 µm.
Remarks. This species is closely related to Dictyophimus platycephalus Haeckel from the Gulf but differs from it in the presence of subterminal rather than terminal feet, in the generally larger and less regular thoracic pores, the less broadly conical and more nearly cylindrical thorax, and in the straighter or less broadly convex outward feet. Riedel (1958, p. 233) states that D. platycephalus may be identical with D. gracilipes, but although these species are rare in the Gulf, I observed enough specimens to be confident in their separation as distinct species. Popofsky's (1909, pp. 274-275, Pl. 30, figs. 12, 13; Pl. 31, fig. 15; Pl. 34, fig. 6) illustrations of D. gracilipes resemble D. platycephalus, but they were not placed in synonymy with this species.
Distribution. This species is rare but occurs generally throughout the Gulf except at stations 90, 99, 130, 191, 194, 203, and 214. Its greatest abundance, though rare, occurs at stations located within the diatomite facies, particularly stations 115, 133, 136, 151, 184, and 192; therefore, its distribution may be influenced by upwelling in this region.
Riedel (1958, pp. 233-234) states that this species is an apparently cosmopolitan species with reported occurrences from the western Bering Sea, northeastern Pacific, northern Atlantic, the Barents and Kara Seas, the Indian:and American Ocean sectors of the Antarctic, and is widespread in the northern Pacific and tropical parts of the Pacific and Indian Oceans. Petrushevskaya (1962, p. 331) reported its occurrence in bottom sediments of the Pacific Ocean off the California coast.
|Dictyophimus gracilipes: |
Skeleton consists of two segments: secondary segment, and a small "cephalis" indistinctly demarcated from it. At their boundary outgrowths are formed similar to those in representatives of genus Lithomelissa. Walls of shell fairly thick. Second segment often closed below. Width of first segment half of or equal to width of second. Inside shell are elements of basic internal skeleton; their structure was elaborated by Riedel (1958). Sharp needles A and Vert extending outside on cephalis not long. Needles D, Lr and Ll fused to walls of second segment in their upper portions and then passing through walls to form strong triagonal "legs" diverging laterally downwards at more acute angle. "Legs" slightly twisted, bent outwardly. Pores on shell round, quite large; on second segment usually disposed in five in a lower row between rays formed from needles D and L, or Lr and Ll.
Appearance of shell very variable. Size of pores, nature of wall (smooth or spiny), form a second segment, all vary. Most constant feature is ratio of first to second segment and presence of facets or ray on legs.
Dimensions: length of first segment 15-20µm, width 25-32µm, length of second segment 40-50µm, width 55-65µm.