Metacylis
Metacylis Jorgensen, 1924
[ref. ID; 3597]
Lorica generally small, ovate or elongate capsular, consisting of a short annulated collar and a bowl; oral margin usually entire; aboral region rounded or conical to a blunt or pointed end; wall usually single-layered and hyaline, occasionally separated and with a fine prismatic structure. (ref. ID; 3597)
Type species; Metacylis mediterranea (Mereschkowsky) Jorgensen (ref. ID; 3597)
- Metacylis angulata (ref. ID; 2343 original paper) or Lackey & Balech (ref. ID; 3772) reported author and year? (ref. ID; 4471)
- Metacylis annulifera Ostenfeld & Schmidt (ref. ID; 3772) reported author and year? (ref. ID; 4464)
- Metacylis corbula Kofoid & Campbell, 1929 (ref. ID; 3544) reported year? (ref. ID; 3597)
- Metacylis corbula var. perspicax Hada, 1938 (ref. ID; 3597 original paper)
- Metacylis jorgenseni Cleve (ref. ID; 3597) reported year? (ref. ID; 1924)
- Metacylis jorgensenii Cleve (ref. ID; 4669) reported author and year? (ref. ID; 4464)
- Metacylis mediterranea (Cleve) (Mereschkowsky) Jorgensen (ref. ID; 3597)
- Metacylis mereschkowskii Kofoid & Campbell (ref. ID; 3597) reported author and year? (ref. ID; 2343)
- Metacylis pontica (Mereschkowsky) (ref. ID; 3597)
Metacylis angulata (ref. ID; 2343 original paper) or Lackey & Balech (ref. ID; 3772) reported author and year? (ref. ID; 4471)
Descriptions
The lorica is always cordate in optical section, with straight or slightly wavy sides and rounded shoulders giving rise to a short collar with a wide opening. Some of the loricae develop a short aboral and somewhat eccentric posterior spine, more or less acute but more frequently this tip is lacking. The walls extend upward and outward at an angle of 70-90 degrees, and at about three-fourths its height they turn inward forming a rounded shoulder. This shoulder is, in general, 10-12 um wide. The collar rises ventrically from the shoulder, in some loricae somewhat flaring, 4-6, generally 6 um high; its opening is three-fourths to five-sixths of maximum width of bowl. The collar is made up of a spiral lamina of two to three turns slightly deflected from the horizontal; its edge is slightly irregular or wavy, but never denticulated. Wall colorless, bi- or trilaminate, with lamellae fused in some places. Prismatic structure minute but evident, especially at shoulder, where there are in addition many small, irregular and very faint fenestrae; prisms 1-0.5 um in diameter. The collar also has a prismatic structure; the distal turn has stronger prisms arranged in more or less regular longitudinal rows, sometimes simulating elongate fenestrae. Wall of the bowl almost uniform in thickness, sometimes a very little increase at shoulders. Wall of the collar somewhat thinner. On the shoulders and extending up to the base of the collar there are some 15-30 small rounded elevations or plicae. The organism does not fill the lorica, but may withdraw completely into it. It attaches to the shell by a thin peduncle or filament from its base to the aboral region of the lorica. The mouth is in the center of a peristomial disc surrounded by a ring of approximately 17 membranelles. The membranelles approximate one-third body length. Ingested Prorocentrum triangulatum and naviculoid diatoms were observed. The macronucleus is a long oval. (ref. ID; 2343)
Notes
The closest relative is Metacylis mereschkowskii. This specimens is larger (significantly larger as to loricae than the Mediterranena species), has a conical lorica with almost straight sides, which slant evenly to a pointed antapex often provided with a minute and eccentric tip or spine. In Jorgensen's species the body is hemi-elliptical with convex sides and a more or less rounded aboral region, never really acute, and always lacking the aboral tip. In our species the shoulders are more prominent (1.50-1.55) of the oral diameter as compared to 1.30-1.35 in M. mereschkowskii). The thickness of the wall is almost the same throughout in our species except it sometimes increases very slightly at the shoulders, but is distinctly thicker in M. mereschkowskii. This last has a more evident spiral structure in the collar, but its wall structure is, on the contrary, very faint. It also lacks the ridges and fenestrae of our species. In short, the cordate shape, wall structure and wall thickness at the shoulders, the size and width of the shoulders, separate the two species. (ref. ID; 2343)
Measurements
58-64 um; height of collar 4-6 um; height of shoulders around 9 um. Oral diameter 44.5-48.5 um; maximum diameter of the bowl 64-70.5 um (more often around 67 um). (ref. ID; 2343)
Metacylis corbula Kofoid & Campbell, 1929 (ref. ID; 3544) reported year? (ref. ID; 3597)
Descriptions
The lorica is urn-shaped and consists of a short cylindrical collar composed of several spiral turns and of an ovoidal bowl. (ref. ID; 3544)
Lorica subspherical, its length nearly equal to the oral diameter; collar forming a truncated convex cone with 3-5 annular rings situated at uniform intervals, slightly distinguished from the bowl by a faint constriction, 0.14-0.30 of the total length, its basal diameter 1.1-1.3 oral diameters; bowl hemispherical or ovate, broadest at the point of the anterior 0.4 of the lorica, 1.16-1.24 oral diameters in greatest transdiameter; aboral end rounded, more or less becoming conical; wall translucent. (ref. ID; 3597)
Comments
The species differs from all species of Metacylis by its globose contour. (ref. ID; 3597)
Measurements
Length 65; breadth 55; oral diameter 50 um. (ref. ID; 3544)
Length 35-41; oral diameter 33-40; greatest diameter 41-44 um. (ref. ID; 3597)
Metacylis corbula var. perspicax Hada, 1938 (ref. ID; 3597 original paper)
Descriptions
Lorica bowl-like, 0.95 oral diameter in length; oral aperture large; collar low, 0.22 of the total length in height, conical (60 degrees) upwards, ringed with three angular bands of which the diameter of the largest posterior one is 1.18 oral diameters; junction between collar and bowl barely visible as a slight constriction; bowl broadest just below the nuchal constriction, its greatest transdiameter almost equal to the diameter of the lowest band; aboral region broadly convex conical (130 degrees) to a subacute aboral end; wall hyaline. (ref. ID; 3597)
Comments
The variety differs from the typical form of M. corbula Kofoid & Campbell in the uneven collar and the conical aboral end. (ref. ID; 3597)
Measurements
Length 35; oral diameter 37; greatest diameter 42 um. (ref. ID; 3597)
Metacylis jorgensenii Cleve (ref. ID; 4669) reported author and year? (ref. ID; 4464)
Descriptions
- Variety A: The lorica is fairly short and the aboral end is slightly pointed. The collar is also short with 2 annuli. The lorica is about 1.4 oral diameters in length. (ref. ID; 4669)
- Variety B: It resembles Metacylis jorgensenii - variety A as far the collar region is concerned. It has shorter bowl. Furthermore, the oral diameter gives an unusual value (74.4 um) thus bringing down the ratio of length to oral diameter to approximately 1, against M. joregensenii var. (A), where, this ratio is 1.4. (ref. ID; 4669)
Comments
Variety A: The bowl portion of our species resembles the descriptions given by Silva (1954) and the species M. mediterranea described by Jorgensen (1927) though the numbers of annuli (in the collar) were 3 and 4 respectively in Silva's and Jorgensen's specimens. Marshall has given a range of 2.5 annuli for this species and, in our specimens the annuli were 2. The unusual size of our forms is worthy of mention. The length and oral diameters of this species reported by Silva (1954) and Marshall (1969) were only 46.0 um and 42.0 um and 61.0 um and 50.0 um respectively. (ref. ID; 4669)
Measurements
- Variety A: Length, 84.0 um (83.1-84.6 um); oral diameter, 60 um (60.0-60.4 um). (ref. ID; 4669)
- Variety B: Length, 74.4 um (74.2-74.8 um); oral diameter, 74.0-74.6 um. (ref. ID; 4669)
Metacylis mereschkowskii Kofoid & Campbell (ref. ID; 3597) reported author and year? (ref. ID; 2343)
Descriptions
Lorica vase-shaped, 1.06-1.21 oral diameters in length, consisting of a low collar and an ovoid bowl; oral margin entire, with a slight brim; collar very short, usually with a single annular ring at base, its length 0.06 of the total length; shoulder rounded, smoothly sloping outwards; bowl 1.13-1.27 oral diameters in greatest transdiameter, convex conical in the aboral region to a rounded end; wall hyaline. (ref. ID; 3597)
Comments
The species differs from M. pontica (Mereschkowsky) in the wide and low collar and from M. jorgenseni (Cleve) in the rounded aboral end. (ref. ID; 3597)
Measurements
Length 37-42; oral diameter 33-37; length of the collar 2.0-2.5 um; greatest diameter of the bowl 40-43 um. (ref. ID; 3597)