| Home> Cenozoic> Holocene (Recent)> North Atlantic>
 

List species

Actinomma boreale Cleve, 1899

Description - Add description

Actinomma boreale:
Primoridal shell. Thick walled, 0.06mm in diameter, with rounded, regular pores (0.003 to 0.005mm in diameter), two to three times broader than the bars, four on the radius. Spines in variable number, with triangular and forked apophyses half way to the apex.

Secundary (Haliomma-) shell. Thick walled , 0.08mm in diameter, with rounded pores of unequal size (0.01 to 0.02mm in diameter), three to four on the radius. Bars 0.001 to 0.002mm thick. Spines variable number, stout shorter than the radius, scattered at intervals.

Tertiary (Actinomma) shell. Thin walled. 0.1 to 0.12mm in diameter, with numerous, small (0.002 to 0.007mm in diameter), irregular rounded pores. Bars as broad as the pores. Spines numerous, scattered, half as long as the radius.
Cleve 1899
Chromyechinus borealis:
This remarkably species is easily recognized by its four shells, of which the outside one is exceedingly delicate and very differently developed. This outside shell is very often wanting, but there are usually indications of it in the transverse processus on the radial spines.

On the outside shell there are – but only rarely in the material which I have examined – narrow byspines, few in number, which most often form more or less obliquely (not straightly radially) protruding extensions of the walls between the pores. They may also sometimes be seen as bristle-shape branches extending obliquely out from the main spines. They are thus not radial byspines, although they have undoubtedly the same biological value as these.

On account of these spines, it will, I think, be most correct to enter the species as a Chromyechinus, especially as, on the shell next to the outside one, there are both main spines and byspines (both having the same appearance) in the same sense as in Echinomma trinacrium.

It is quite remarkably to what variations this species is subjected, even in the matter of dimensions. I have found the following dimensions the three outer shells, for 6 specimens.

Outside shell: 96, 114, 100, 118, 121, 116µm
Next to the outside one: 77, 83, 83, 83, 89, 86µm
Next to the inside one: 34, 35, 37, 36, 40, 36µm

It will be seen that the dimensions of the shell next to the inmost one differ only a little from the corresponding ones in Hexacontium enthacanthum, Hexacontium pachydermum and Echinomma leptodermum (as well as in Echinomma trinacrium and Drymyomma elegans). The third shell too correspond, on the whole, well to the third one in the species mentioned.

This is a very interesting phenomenon, seeming to indicate a development of all these forms from a common, comparatively young, principal form, the balls being probably formed centrifugally, at any rater, after the second. It may, on the other hand, perhaps be the case that the less developed inmost shell is formed later, centripetally. I mean that I have seen traces which lead me to conclude that its connection with the second ball is not merely a prolongation of the radial spines.

In this species, it seem to be possible to distinguish between two series of forms, which in their extreme forms are so different that one would not hesitate to class them as distinct species, if there where not so many variations within each series that as yet it does not seem able to fix any certain limits. It is not unlikely that really here exist several closely allied forms.

The one series of forms (cfr. Jřrgensen 1905, pl. 8, fig. 35) has shorter broader spines, not very different in development, on the whole very similar to those of Echinomma leptodermum. The outer shell is very delicate, closed.

The outer series has longer, more slender spines, varying considerably in size. The outer shell is of firmer construction, and always seems to be open on one side (not complete). Here the radial spines and the byspines are particularly long, and this circumstance together with the large hole in the outer shell causes a foreign appearance, sometimes like in certain species belonging to the Nassellaria and Phaeodaria groups.

On strongly developed forms of this second series, there are also sometimes seen "false" byspines, as described above, at any rate in the form of side branches on the largest radial spine on open side on the outer shell.

On those forms too where the outer ball is closed, there often seems, however, to be comparatively strong development of the spines on one side of the shell.

The pores on the outside shell vary considerably in size and shape, both on one and the same individual and on different ones. They range from quite tiny, circular shaped, to large longish holes. Also the width of the intermediate walls between the pores is very variable; on the other hand, their thickness is never great. The shell next to the outside one is always strong, thick-walled, with very uneven pores, roundish and oblong, most of them being 10-16µm, although sometimes considerably smaller or larger. The ball next to the inside one answers in all important respects to the corresponding one in Echinomma leptodermum. The innermost shell is difficult to see. Its diameter is about 16µm. I have not succeeded in getting it out unijoured when breaking the outer balls, so that I cannot give a good drawing of it.

Cleve's Actinomma boreale is undoubtedly the same as this species. He seems, however, to go too far in his opinion of the variation in the radiolaria, as will be seen on references to his illustrations pl. 1, figs. 5a and 5b. He looks upon the as young forms of the same species which he illustrates in fig. 5c. I think that fig. 5b = Echinomma leptodermum, fig. 5a is probably the same species (too few main spines depicted on the illustration?) without a developed outer shell.

Rather frequent, both on the north and west coast, though rarely at all somewhat numerous. As is the case with other Spumellaria with us only found in deep water.

Distribution: The same as that of Echinomma leptodermum. Frequent also on the west coast of Norway and in the Norwegian Sea. Found by Cleve in deep water samples form the sea west and south of Spitsbergen. Also known from a few places in the North oceans as well as a couple on the American side of the Atlantic, near the surface.
Jřrgensen 1905
Benson, 1966, p. 166-169; pl. 5, figs. 7-9:

Sphaeropyle langii Dreyer

Sphaeropyle langii Dreyer, 1889, Jenaische Zeitschr. Naturwiss, vol. 23, p. 89, Pl. 9, fig. 54.
?Prunopyle antarctica Dreyer, 1889, op. cit., p. 100-101, P1. 10, fig. 75; Riedel, 1958, B.A.N.Z.A.R.E. Repts., ser. B, vol. 6, pt. 10, p. 225, P1. 1, figs. 7,8.

Test consisting of three inner spherical shells and an outer, generally ellipsoidal or ovoid shell with a distinct opening or pylome at one pole of its major axis. Outer shell thin-walled, relatively smooth except for numerous subregularly arranged, three-bladed main spines (10-70) or thorns and, in a few specimens, scattered, thin, conical by-spines; pores of outer shell small, subequal, but of irregular shape and arrangement, 18-40 on half the minor circumference; pylome an opening at one pole of the shell but without a distinct peristome, with 1-8 radial beams surrounding it or within it, a few of which are prolonged into three-bladed spines that are generally longer than the other main spines of the test. Third shell without pylome, like the cortical shell of the small diameter members of Actinomma sp. except for the presence of three-bladed beams arising from its surface but not extending inward to the second shell; pores relatively large, unequal to subequal, subcircular to subpolygonal, with subregular arrangement, 7-10 on the half circumference; third shell joined to outer shell by 10-70 (generally 30-40) three-bladed radial beams, approximately one-third to one-half of which arise from the surface of the third shell. Second shell spherical to globular, with relatively smooth surface, with relatively small, subequal, polygonal to subcircular, subregularly arranged pores, 6-9 on the half circumference. First shell subspherical to globular to subpolyhedral, with subequal, polygonal to subpolygonal pores slightly larger than those of the second shell, 2-3 on the half circumference. Twelve to thirty radial beams joining all four shells arise from the surface of the first shell, subregularly arranged, three-bladed beyond the second shell; these beams plus the secondary beams arising from the third shell extend beyond the fourth shell as main spines or thorns that are subequal in length except for the longer spines associated with the pylome.

Measurements; based on 30 specimens from stations 27, 34, 46, 56, 60, 71, and 151: major diameter of fourth shell 116-148 µm, minor diameter 98-148 µm; diameter of third shell 71-101 µm, of second shell 32-46 µm, of first shell 12-18 µm; length of spines associated with pylome 6-43 µm (generally 15-25 µm); of remaining spines 5-43 µm (generally 10-18 µm).

Remarks. Sphaeropyle langii Dreyer differs from most of the Gulf specimens of this species in the presence of fewer radial beams and spines and a smoother, more nearly spherical, fourth shell with generally equal circular pores. Dreyer’s illustration (1889, P1. 9, fig. 54), however, is somewhat diagrammatic, and, for this reason, appears different from the Gulf specimens. A few specimens from the Gulf were observed with only 10 radial beams, thus not unlike Dreyer’s species. Prunopyle antarctica Dreyer differs from Sphaeropyle langii Dreyer in an ellipsoidal fourth shell and in the presence of more numerous radial beams. Riedel’s description and illustration of the former (Riedel, 1958, p. 225, P1. 1, figs. 7, 8) does not differ appreciably from the Gulf specimens except for the presence of a thicker wall of the fourth shell. It is placed in tentative synonymy with S. langii only because Riedel (loc. cit.) states that no form
resembling it has been found in the tropical parts of the Pacific or Indian Oceans, whereas S. langii was described from “Challenger” stations 241 and 265 in the northwestern and tropical central Pacific, respectively (Dreyer, op.cit., p. 89). Until type material of both species can be examined, the synonymy must remain tentative.

Distribution. This species is rare at all stations where it is present and is absent at stations 64, 81, 130, 191, 192, 203, 206, 208, and 214. There are no significant changes in its frequency throughout the Gulf. Since it occurs as far north as station 194, it is nearly cosmopolitan, at least in most of the axial portion of the Gulf, being absent at a few of the marginal stations.
If Sphaeropyle langii and. Prunopyle antarctica are the same as this species, it has a cosmopolitan distribution in all latitudes. Otherwise, it is apparently confined to the tropical to temperate parts of the Pacific and possibly the other oceans as well.
Benson 1966


Description

 

Images

 

Synonyms

 

References

 

Distribution

 

Discussion / Comments

 

Web links