The World of Protozoa, Rotifera, Nematoda and Oligochaeta
Colurella
Colurella Bory de St. Vincent, 1824
Class Monogonontaet: Order Ploimida: Family Colurellidae (ref. ID; 6806)
Synonym Colurus Ehrenberg, 1830 (ref. ID; 2978, 3514, 3688) reported year? (ref. ID; 1345)
See Paracolurella.
ref. ID; 1663
Lorica composed of two lateral plates, strongly compressed laterally. Frontal head hood present. Lorica open along anterior, ventral and posterior margins. Terminal foot segment short. Toes long and tapering. Small species. (ref. ID; 1663)
ref. ID; 1923
No joint of foot longer than toes. The head carried a semicircular shield dorsal to corona which is retractable within lorica. Littoral, browsing over plants, scraping up small organisms with head shield. Very common. (ref. ID; 1923)
ref. ID; 3334
In this genus the lorica is flattened laterally so that it appears mussel-shaped in side view. The head carries a small, retractable, semi-circular shield dorsal to the corona. The foot consists of three or four segments and two slender toes, which are normally longer than the foot. There are usually two lateral eyes. The mastax has malleate trophi. (ref. ID; 3334)
Body length 110 µm. (ref. ID; 2860)
Body length 85-93, body height 42-51, length of toes 30-40 µm. (ref. ID; 3275)
Length of body 100-110, length of toes 25-35 µm. (ref. ID; 3521)
Marine and estuarine species. (ref. ID; 1924)
Body oval, laterally compressed, with a rigid shell-shaped lorica and a head plate which, though slightly stiffened, can be retracted together with the anterior apart of the body. Foot in 3 segments, about one-fourth of the length of the body. Toes long and of equal length, sharply pointed, sometimes fused. (ref. ID; 3180)
Marine and brackish water. (ref. ID; 3573)
Comments
von Hofsten (1912, p.213 ff) and Hauer (1925, p.174 ff) distinguish C. colurus from C. adriatica by the shape of the lorica, which is posteriorly rounded in the former and pointed in the latter. This characteristic exceedingly variable, however, and two figures in Hauer would seem to represent intermediate forms. Pejler found an even more obvious transitional form in the river Abiskojakk. Rutter-Kolisko (1953, p.153) reports both C. colurus and "C. lepta (Gosse)" from Lake Tornetrask's psammon. The latter ought, however, to be considered synonymous with "C. adriatica" (see von Hofsten 1912, p.218, Harring 1913, p.29, Hauer 1924, p.183 and 1925, p.175 and Voigt 1956-57, p.208), i.e. with C. colurus. Both "C. colurus s. str." and "C. adriatica s. str." are stated by Voigt (1956-1957) as specially characteristic of flowing waters. Both are also reported to exist in brackish water and salt water. (ref. ID; 1450)
Measurements
Total length 90; dorsal lorica length 60; anterior extremity 20 high, highest part 31; foot+toes 40 µm. (ref. ID; 3083)
Body length 70-85; body height 38-43; length of toes 28-35 µm. (ref. ID; 3275)
Length of body 90; length of toe 30 µm. (ref. ID; 3521)
Egg: The eggs are brown and oval (70 µm by 45 µm). (ref. ID; 3334)
Male: The male, which lacks both trophi and a digestive system, is half the size of the female. (ref. ID; 3334)
Comments
Some confusion exists in the literature as regards the status of compressa. Bjorklund (1972) regards it as a separate species, Kutikova (1970) as a variety, while Koste (1978) regards it merely as a form of Colurella colurus. We are inclined to support Koste's view; however, our identification of the Signy specimens with the form compressa must remain tentative because we were unable to examine the ventral aspects of the lorica in sufficient detail. (ref. ID; 3334)
Measurements
Overall length of specimens 154 µm. (ref. ID; 2282)
Length of body 112; foot 12; toes 30 µm. (ref. ID; 3128)
It is a small rotifer, with a lorica length of 108 µm and a depth of 54 µm. The foot has three segments and two slightly curved toes, which are the same length as the foot (36 µm). (ref. ID; 3334)
Hauer, in 1924, described this species under the term 'Sinnesgrube', and referred to the very well-developed foot. To the belly fold-keel he attached little importance. Later (1935), the same author wrote: 'Vielleicht sind C. hindenburgi und C. gastracantha nur Formen der folgenden Art. Colurella obtusa (Gosse)'. Yet Carlin (1939), examining rotifers in the lakes of Aneboda district, remarked that it is difficult distinguish C. hindenburgi from C. gastracantha, but that these species can be easily distinguished from C. obtusa. Therefore he continued to refer to C. obtusa, but C. hindenburgi and C. gastracantha he jointed together as C. hindenburgi. But Carlin has examined in the Aneboda district only the lake rotifers, and according to my observations there is reason to think that he has not seen C. gastracantha under the microscope. Since I have found this rotifer only in places which have not been examined by Carlin. By examining the rotifer of Aneboda district I found specimens of the genus Colurella in moss covering the granite rocks. These corresponded perfectly with Hauer's figure (1924, fig.2) showing the specimens from Lunz. I observed this rotifer living, when the belly-keel could be seen very distinctly. To test the form stability of this keel, I fixed these animals in formalin of different concentrations, thus acquiring a series of specimens showing different degrees of contraction, but in all these the peculiar belly fold-keel showed but slight change in its form, and remained clearly visible. It is closely connected with C. hindenburgi and C. obtusa, but has to be distinguished. (ref. ID; 3036)
Measurements
Length of lorica 56-59; height of lorica 32-26; depth of lorica 22-26; length of toes 24-27; length of foot 11-13; length of proximal foot joint 4; length of middle foot joint 3; length of distal foot joint 5 µm. (ref. ID; 3036)
The distinction between "C. obtusa s.str." and "C. hindenburgi" seems to Pejler to be extremity vague. Carlin (1939, p.9) mentions three distinguishing characteristics: the width of the lorica (viewed from the dorsal or ventral angle), the length of the toes and the position of the head opening. To first take the width of the lorica, this varies greatly in "C. obtusa s. str." as shown by the drawings in Hauer (1924, Fig.3, 1936 Pl.1:8a-c, 1952, Figs.1-4). As far as this characteristic is concerned the narrowest of Hauer's specimens could also be accepted as forms of "C. hindenburgi". In the river Abiskojakk Pejler found an even narrower specimen, which considering the length of the toes (15 µm) should be classed as "C. obtusa s. str.". According to Voigt (1956-57, pp.206-207) the length of the toes in "C. obtusa" 14-18 µm and in "C. hindenburgi" 21-23 µm. Hauer (1952, p.50) has, however, measured individuals with toes 19 µm long, which are classified as "C. obtusa". Like the whole shape of the lorica, the third of Carlin's distinguishing characteristics, the position of the head opening, is extremely variable in the array of forms in question. This clearly appears from the drawings in Hauer and Carlin mentioned above as well as from those in Klement (1957, Figs.17-18) and in the present essay. In Pejler material from Lapland it is quite impossible to distinguish between C. obtusa and C. hindenburgi as separate species. It is of course conceivable that they occur as such in other areas, but if this is to be established more conclusive proof must be present than has hitherto been the case. Hauer (1924, p.181), too, is doubtful whether it is justifiable to distinguish between the two "species" concerned, and Klement (1959) appears to have found transitional forms between them: "Die sichere Einordnung von Formen, die nach dem Rand der Kopfoffnung zwischen C. h. und C. obtusa stehen, wird durch verschieden starke Kkontraktion bei der Fixierung erschwert. Manchmal ist sie unmoglich." (Op. cit., p.208). In consequence of the elimination of C. tessellata and C. hindenburgi mentioned above one is led to conclude that C. paludosa Carlin (1939, pp.9-11) is probably a patterned form of C. obtusa. (ref. ID; 1450)
Measurements
Length of body 56; length of foot and toes 29 µm. (ref. ID; 2385)
Length 54-56; width 35; depth 30; foot 14-15; toes 13-14 µm. (ref. ID; 2597)
Total length 70; body 51-52 long; anterior extremity 0 wide; middle part 30 wide, 33-35 high; caudal extremity 14 wide; foot+toes 29 µm. (ref. ID; 3083)
Length of lorica 90; width 90; toes 20 µm. (ref. ID; 3181)
Body length 50-58; body height 35-37; length of toes 14-17 µm. We only encountered small individuals. (ref. ID; 3275)
Colurella paludosa Carlin, 1939 (ref. ID; 1345, 2993, 3263 original paper, 3275, 3688) reported author and year? (ref. ID; 3532)
Measurements
Body length 55-60; body height 32-40; head opening 25; length of toes 22-27 µm. (ref. ID; 3275)
Colurella salina Althaus, 1957 (ref. ID; 2284, 3271 original paper)
Measurements
Length of body 88; depth of body 58; length of toes 34 µm. (ref. ID; 2284)
Marine rotifer. A large Colurella species with posteriorly pointed lorica and only one acute toe. Colurella unicauda is the largest of all known Colurella species, and the only one with a single, undivided, acute toe. Seen laterally, the animal closely resembles C. adriatica Ehrenberg, but is considerably large. The posterior end of the lorica has long, acute tips which are thin and often divergent. There are two sets of ligaments along the lorica from the top of the posterior split to the base of the foot. Other Colurella species seem to have only one set of such ligaments but this is seldom mentioned or figured in the literature. The foot is three-jointed with a marked striped structure. There is a sensory pit near the base of the last joint. The toe shows no evidence of splitting at either end. The striped structure continues for about one fifth of the toe. A slightly different from of Colurella unicauda was found at Tvarminne Zoological Station, southern Finland, in the summer of 1965. The posterior end of the lorica was shorter and less acute, with more convex edges. (ref. ID; 3573)
Comments
Colurella unicauda has certainly been recorded in the literature earlier, but has been wrongly identified, especially as C. adriatica. C. adriatica seems to vary considerably in size and shape, but I have not found any evidence of overlapping between the two species, although they often occurred together. As far as I can see, C. unicauda was first recorded by Levander (1894). He figured a species identified as Monura dulcis Ehrenberg, and pointed out the single toe and large size. It was found in southern Finland in a rock-pool rich in algae and among sublittoral algae. It corresponds exactly to the form of C. unicauda which I have found at Tvarminne. Von Hofsten (1912) found specimens which probably belonged to C. unicauda on the Scandinavian west coast, but included them in C. adriatica. He gave no scale to his figures and measurements of only four specimens. The largest one agrees with C. unicauda. Idelson (1926) figured a specimen from a river mouth on Novaja Zemlja, and named it Colurella sp.?. It was unusually large (length of lorica 173 µm, height 82 µm, toe -only the distal part?- 44 µm, and foot -including the proximal part of the toe?- 42 µm). It closely resembles C. unicauda, with the posterior ends of the lorica longer and more pointed. C. unicauda has certainly also been found by De Ridder (1957) in brackish waters in Belgium, but identified as C. adriatica. Both the figure and measurements given agree with mine. She also recorded the species as C. adriatica from brackish waters in France (De Ridder 1958). Here, she described the specimens as resembling the form beta proposed by Hauer (1925), though of much greater size. (ref. ID; 3573)
Measurements
Length of lorica 90-110; height of lorica 50-60; length of toe 35-45 µm. (ref. ID; 3275)
Espegrend specimens: Length of lorica 135.4(124-149); height of lorica 70.0(61-78); breadth of lorica 57.0(49-64); distance from the front of lorica to the hindmost end of the ligaments 122.8(110-138); length of toe 41.3(36-52) µm. (ref. ID; 3573)
Tvarminne specimens: Length of lorica 128.7(122-132); height of lorica 67.0(64-70); breadth of lorica 49.0; distance from the front of lorica to the hindmost end of the ligaments 120.0(118-122); length of toe 40.0(38-42) µm. (ref. ID; 3573)
