Euchitonia elegans/furcata group
Description - Add description
|Euchitonia elegans (p. 535):|
Distance between the paired arms half as large as their distance from the odd arm. This latter is straight, while both the former are concavely curved towards the middle line. Arms five times as long as broad, at the distal end pointed and armed with a short conical terminal spine. Patagium nearly complete, enveloping four-fifths of the arms, with four to five concave chamber-rows.
Dimensions: Radius of the arms 0.2, breadth of the 0.03.
Habitat: Tropical Pacific, Philippine Sea, depth 3300 fathoms (Ehrenberg).
|Benson, 1966, p. 230-232, 233; pl. 14, figs. 1-2; text-fig. 17:|
Euchitonia elegans (Ehrenberg)
Pteractis elegans Ehrenberg, l872a, Akad. Berlin Monatsb. (1872), p. 319; l872b, Akad. Berlin Abhandl. (1872), P1. 8, fig. 3.
Euchitonia elegans Haeckel, 1887, Challenger Rept., Zool., vol. 18, p.535; Popofsky, l9l2, Deutsche Südpolar-Exped., vol. 13, pp. 138-139, P1. 7, fig. 2, text figs. 55-57.
Test bilateral, with a distinct odd arm that is broader than the other two and whose axis bisects the smallest of the three angles between the arms. Central region of test distinct, circular, with a hyaline or nearly hyaline center on each surface; consisting of a constant number of three latticed, concentric rings surrounding an internal spherical to subspherical shell; in side view the rings appear as concentric discoidal shells in the plane of the disc, but they merge with the latticed plates covering both surfaces of the central part of the test, thus they are actually rings (text-fig. 17). Arms with 10-35 generally distinguishable but irregular internal concentric rings; arms broader and thicker distally with rounded terminations; in most specimens arms appear spongy, but a distinct latticed sheath envelops them. Odd arm straight, the other two arms narrower proximally and in most specimens curve or bend toward one another. A spongy layered patagium generally incomplete or rudimentary, absent in a few specimens, thinner and delicate with layering more distinct, proximally. Many specimens were observed with one or two but as many as five conical to three-bladed terminal spines arising from one, two, or all three arms, 4-34 µm in length.
Measurements; based on 30 specimens from stations 27, 34, 46, 56, 60, 64, 71, and 81: angle A 126°-l52°, mean 137°; angle B 67°-106°, mean 87°; angle C 128°-148°, mean 136°; ratio of angle A to B 1.19-2.27, mean 1.57, of angle C to B 1.21-2.10, mean 1.57; diameter of outer concentric ring of central region 66-81 µm; length of odd arm 97-271 µm, of each of the two similar arms 98-320 µm and 95-301 µm; minimum breadth of odd arm 28-50 µm, of each of the two similar arms 26-39 µm and 25-43 µm; maximum breadth of odd arm 37-92 µm, of each of the two similar arms 28-68 µm and 30-68 µm; length of base of triangular test 187-463 µm, of altitude 208-588 µm; maximum breadth of complete patagium 207-271 µm.
Remarks. This species differs from Euchitonia mülleri [=Euchitonia sp. herein] in the presence of three concentric rings in the central region instead of concentric discoidal shells and in the distinct bending toward one another of the two arms opposite the odd arm.
Distribution. This species is rare at all stations in the Gulf but occurs as far north as station 208. It is absent at stations 115, 130, 151, 191, 192, 203, 206, and 214. It has a greater average frequency in the southern Gulf and a spotty distribution in the northern half of the Gulf; therefore, although cosmopolitan in the Gulf, it has a greater affinity for oceanic water masses.
Ehrenberg reported Pteractis elegans from the Philippine Sea. Haeckel reported Euchitonia elegans from the same region as well as from the tropical Pacific. Popofsky reported this species from the western part of the tropical Indian Ocean and off the Cape of Good Hope. It has not been reported from high latitudes, and, therefore, is confined to tropical seas.
|Euchitonia elegans (Ehrenberg) |
"Similar to Euchitonia furcata, but differing in the shape of its arms. Arms slender, tapering distally, and sometimes terminating in 1 or 2 short, fairly stout spines. Angle between paired arms of E. elegans generally small than that of E. furcata.
"A patagium may or may not be present. When well developed it forms a delicate meshwork around the central structure and between each of the 3 arms (generally less well developed between paired arms). Meshwork forms rows of chambers, convex outwards in larger angles, concave between paired arms, and thickens towards its outer edge. Sometimes patagium shows partial development or, often, only a few initial branches are present. In other specimens there is no indication of a pagatium forming...
"It is usually difficult, if not impossible, to distinguish between E. elegans and E. furcata. These species are differentiated by the shape of the arms of faily complete and well-developed specimens. However, the majority of specimens found are either broken or not completely developed, making it impossible to identify them to species. One is tempted to make E. elegans and E. furcata and the indeterminant forms conspecific, but the difference between end members of such a series is sufficiently great to indicate that two species are, in fact, involved. Thus, a few specimens definitely belonging to each species and a large number of unidentifiable fragments were present in the samples examined." (from Nigrini, 1967).
DIMENSIONS "Average length of arms (measured from center of innermost sphere) 147-289 microns (usually 200-289 microns). Maximum breadth of arms 35-63 microns. Angle between paired arms 54 degree - 75 degrees." (from Nigrini, 1967).
|Nigrini and Moore 1979|
|Euchitonia furcata Ehrenberg |
Euchitonia furcata Ehrenberg 1872a, p. 308; 1872b, pl. 289, pl. IV (iii), fig. 6; Ling and Anikouchine, 1967, p. 1484, pl. 189, 190, figs. 1-2, 5-7.
Euchitonia mulleri Haeckel, Nigrini, 1967, p. 37, pl. 4, figs. 1a, b
"Shell bilaterally symmetrical with 3 arms of approximately equal length, elliptical in cross section. Arms arise from a central structure composed of 2 inner spherical shells and an outer oblate spheroidal shell, all quite smooth and connected by numerous, discontinuous, radial beams. In addition, there is an outer ring of mesh in the plane of the shell which is normally oriented perpendicular to the microscope axis. This central structure is the same as that of Amphirhopalum ypsilon.
"Arms fairly heavy, increasing in breadth distally and having a blunt or irregularly rounded termination; sometimes with 1-3 slender terminal spines. Proximally arms appear chambered, but a rather dense mesh of subcircular pores generally obscures distal chambers, and gives arms a spongy appearance. Paired arms form the smaller angle opposite odd arm and often curve slightly towards each other.
"A patagium may or may not be present. Specimens having a well-developed patagium are rare, and examination of it has not been sufficiently extensive to warrant any general conclusions. Usually, patagium shows partial development or, often, only a few initial branches are present. In other specimens there is no indication of a patagium forming." (from Nigrini, 1967).
DIMENSIONS "Average length of arms (measured from center of innermost sphere) 164-289 microns. Maximum breadth of arms 54-90 microns. Angle between paired arms 59 degrees - 94 degrees." (from Nigrini, 1967).
|Nigrini and Moore 1979|
|Euchitonia elegans/furcata (Ehrenberg) group? |
(Figure 15.70) [=?Euchitonia furcata, Euchitonia elegans]. Differs from D. profunda in that the three arms are more slender, longer, and their orientation defines two larger angles and one smaller one. E. elegans intergrades smoothly with Euchitonia furcata; end members differ in that distal tips of arms taper in E. elegans (Figure 15.70c), while in E. furcata their terminations are club-shaped and more blunt (Figure 15.70a, b). Length of arms (from center of shell): 150-300 µm. Ref: Nigrini and Moore (1979).