Keronella
Keronella Wiackowski, 1985 (ref. ID; 7743 original paper)
[ref. ID; 7743]
Diagnosis; Frontal cirri form a corona parallel with the anterior part of the AZM. This structure originates as a cut off anterior fragment of the right midventral row. Midventral cirri in the posterior half of the organism consist of rows with a gradually increasing number of cirri in the posterior direction. Fronto-terminal (migratory) cirri form a row of more than 2 cirri. (ref. ID; 7743)
Type species; Keronella gracilis n. gen., n. spec. (ref. ID; 7743)
Type slide; Dept. Hydrobiology, Jagiellonian University, Krakow. (ref. ID; 7743)
Type locality; Mosses growing on calcareous rock in the region of the "Krakow Gate" in Ojcow National Park (Southern Poland). (ref. ID; 7743)
- Keronella gracilis Wiackowski, 1985 (ref. ID; 7743 original paper) reported author and year? (ref. ID; 191)
Keronella gracilis Wiackowski, 1985 (ref. ID; 7743 original paper) reported author and year? (ref. ID; 191)
Diagnosis
Corona of frontal cirri consists of 7-9 cirri; fronto-terminal (migrating) cirri: 7-15; dorsal kineties: 5; caudal cirri: 2-3; Ma: about 60 oval fragments. (ref. ID; 7743)
Descriptions
The ciliate is distinctly dorso-ventrally flattened with a slightly concave ventral surface. The cytoplasm is clear and has a greenish-yellow shadow. The contractile vacuole has the typical position on the left side of the cell. The macronucleus consists of numerous (about 60) oval fragments. In the impregnated specimens about 6 (up to 10) spherical micronuclei can be seen. The food vacuoles of the specimens cultivated in moss samples contained: fungal spores, fragments of Cyanophyta, occasionally Chilodonella uncinata and other unidentified small protozoans. Three different kinds of ciliature in Keronella can be distinguished: buccal, frontal (front-ventral-transverse complex) and somatic (Borror 1979). Buccal ciliature has a form typical for the majority of Hypotrichs. The peristome is bounded on the left by the adoral zone of membranelles (AZM) which curves to the right around the anterior border of the cell. Along the right side of the peristome the undulating membrane (UM) is located. The UM complex is composed of two paroral membranelles: inner (IP) and outer (OP). Both IP and OP consist of a double row of kinetosomes. The kinetosomes of the OP are arranged in a zigzag line and those of the IP form two parallel lines without such organisation.
FVT complex. seven to nine frontal cirri (FC) form a curved row (corona) parallel with the anterior part of the AZM. Midventral cirri (MV) typically have a characteristic zigzag line in the anterior part of the animal. Starting from about a half the cell length in the posterior direction the pattern of the MV gradually changes. Instead of diagonal pairs of cirri rows of more then two cirri begin to appear. There are usually 5 or 6 such rows with a successively increasing number of cirri from 3 up to 12 or more. The first rows are slightly diagonal. The last and longest row, which ends close to transverse cirri (TC) is always parallel with the antero-posterior axis of the animal. The anterior fragment of MV, a single row of usually 5-6 cirri is always distinctly curved in the direction of the UM end. Close to the UM there is always a single malar cirrus (m), (Borror and Wicklow 1983). There is an additional row of cirri in the frontal region. This row (FT) begins close to the distal end of the AZM and lies parallel to the MV on their right. It ends at about the level of the cytostome. Transverse cirri (TC) form a diagonal and somewhat curved row of about 8 cirri.
Somatic ciliature. there is one row of closely packed marginal cirri along the right and left sides of the cell (RMC and LMC). The posterior ends of marginal rows are not joined. The dorsal surface is covered by 5 longitudinal rows of bristles or dorsal cilia (Dc). These rows extend continuously from the animal's anterior to posterior end. Each bristle consists of a pair of kinetosomes the first of which bears a short stiff cilium. The animal has a group of caudal cirri (CC) on its posterior end. Generally there are 2 or 3, but some times up to 3 additional very small CC could be seen. Two dorsal cilia are also seen on the anterior end of the right marginal row. (ref. ID; 7743)
Morphogenesis:
- 1. Oral and FVT primordia of the opithe:
Small field of new kinetosomes are formed close to the left side of some cirri of the left MV row in the middle of the cell. This is the first sign of the beginning of cortical morphogenesis. The number of new kinetosomes increases, the old MV gradually disaggregate and a uniform longitudinal field of basal bodies appears. This is the AZM primordium. The new membranelles initially appear in the right anterior corner of the field. At the same time, parallel to the AZM primordium, on its right a long and narrow kinetosomal field is formed (UM primordium). The two fields are joined together in their posterior region. A ladder-like structure consisting of about 22 short diagonal streaks appears to the right of the future UM. The forming of new adoral membranelles proceeds in a posterior direction and to the left. The anterior end of the new AZM curves to the right and marks out the anterior end of the opisthe. A fork-like split appears on the anterior end of the UM field. A group of kinetosomes from the right part of the split forms the first frontal cirrus. The remaining kinetosomes of the UM field aggregate into two paroral membranelles. Differenciation of the new FVT cirri begins on the anterior and proceeds to the posterior end of the ladder-like primordium. Each of the steaks in the anterior part of primordium divides into two segments which condense and give two cirri. Thus the future MV appear (a zigzag line traced by the diagonal paires of cirri). The second cirrus originating from the first streak moves toward the UM and becomes the malar (m) cirrus. In the posterior part of the FVT primordium each successive diagonal streak gives rise to more and more cirri, from 3 to 12 per streak. The last cirrus of each of the 5-9 posterior streaks becomes a transverse cirrus. The row of 9-16 cirri originating from the last steak moves anteriorly and settles parallel to the MV on their right, at the level of the peristome. These are the fronto-terminal cirri (FT). In the last phase of the bipartition the anterior fragment of 6-8 cirri is separated from the right MV row and, together with the first frontal cirrus, form a corona of FC.
- 2. Oral and FVT ciliature of the proter:
The process begins with a slight delay in regard to the opisthe. New kinetosomes appear first, close to the anterior end of paroral membranelles. The process of disaggregation of both inner and outer paroral membranelles begins and proceeds in the direction of the cytostome. The malar cirrus and the first cirrus of the left MV row become disorganized. The remaining MV along the peristome are disorganized somewhat later. The UM and FVT primordia appear. The right wall of the peristome and the region of the cytostome become filled up with basal bodies. Some membranelles close to the cytostome disaggregate and form a kinetosomal field, together with the kinetosomes which fill the peristome. Not one of the dividing specimens found on the slides provides evidence that the remaining membranelles are changed. It may be that this process is completed in a very short time and was not recorded, or rather the proter receives the old AZM in which only a few membranelles close to the cytostome ar renewed. The development of the UM and FVT primordia proceeds in the same way as in the opisthe.
- 3. Development of somatic ciliature:
The primordia of new marginal cirri are formed within old marginal rows on each side at two levels corresponding to the FVT primordia. The old cirri gradually disaggregate and long kinetosome streaks are formed. The differentiation of the new marginal cirri from the streaks begins from the anteiror end of each streak. The dorsal primordia are formed at two levels within each of the five kineties. The new kineties elongate and overlap the remaining parts of the old ones. On the end of the right most kinety up to three distinct caudal cirri are formed. No CC appear on the ends of the remaining four kineties. However, in a few cases additional very small single CC could be observed on the ends of other kineties.
- 4. Nuclei:
Nuclear events which occur during bipartition of Keronella gracilis n. gen., n. spec. are very similar to what can be seen in other Urostylide Hypotrichs (Jerka-Dziadosz 1972; Hemberger 1982).
The replication band can be observed in all fragments of Ma during the first stage of morphogenesis. Later each Ma fragment rounds up. When the new MV cirri become to appear the macronuclear material is fused. The first division of the Ma occurs when all new MV cirri are formed. Then the process of farther segmentation of Ma takes place and is finished after the separation occurs. The micronuclear mitosis can be seen during the first divisions of Ma. The offspring of each Mi fragment follow different cell. (ref. ID; 7743)
Notes
The most remarkable characteristic of the new taxon is a corona of frontal cirri. Such pattern of FC has not yet been described in Hypotrichs possessing MV. A very similar pattern can be found in the genera Kerona and Keronopsis (Keronidae). However, in spite of the great similarity of the two structures, which perhaps perform the same function, their way of development is quite different. The corona in Keronella n. gen. originates as a cut off anterior fragment of the right MV row while the analogical structure in Keronidae corresponds to the first frontal (paroral) cirrus of the other Hypotrichs (Hemberger and Wilbert 1982; Tuffrau and Fryd-Versavel 1977). The pattern of newly developing MV in the anterior part of the cell just before the coronal cirri become cut off is exactly the same as in Pseudourosyla (Jerka-Dziadosz 1972), Thigmokeronopsis (Wicklow 1981), and Pseudokeronopsis (Wiackowski in preparation). Each streak gives a pair of cirri which are all of comparable size. The coronal cirri can therefore be considered as an evolutionary novelty originating directly from the pattern existing in the three mentioned genera. The second important characteristic is the pattern of the MV in the posterior half of the organism. The development of more than two MV from some of the posterior streaks of the FVT primordium has been considered as a characteristic of the genus Bakuella Agamaliev and Alekperov, 1976. Although, in Bakuella this is particularly remarkable, it exists, however, in much less striking form also in other genera. Besides the new genus, the author observed such a pattern of MV in Urostyla sp. (in preparation). Probably it exits in Urostyla grandis (Jerka-Dziadosz 1972). In many Holosticha the last two streaks give not three (2 MV and 1 TC) but four cirri (Hemberger 1982). The additional cirri usually remain close to the TC. Foissner (1982) calls them "ventral cirren". The number of cirri developing from the last streaks of the FVT primordium, as a taxonomic character, has therefore many different states. Perhaps these states could be arranged as an evolutionary continuity with Bakuella on one extremity and with forms possessing their MV as a typical zigzag line till TC on another. According to Agamaliev and Alekperov (1976), the development of many cirri from one FVT streak should be considered as a rudimentary character state. The third important morphological characteristic of the new ciliate is the additiontal row of cirri originating from the last FVT streak and migrating anteriorly to the frontal region. This phenomenon was recently described by Hill (1980) and Hemberger (1982), who coined the term fronto-terminal cirri (FT). There was a pair of migrating cirri in all cases described hitherto. The new ciliate has a row of 7-15 such cirri. This is probably due to the large number of cirri developing from the last FVT streak. The additional cirral row in the frontal region of Bakuella is probably of the same origin but Agamaliev and Alekperov (1976) give no information on the pattern of morphogenesis. The FVT primordium of Keronella n. gen. is typical for the suborder Urostylina, Jankowski, 1979. In spite of the similarity between posterior fragments of MV, the frontal region ciliature of Keronella n. gen. is quite different of that of Bakuella. The genus Bakuella which has three hypertrophied frontal cirri and a row of malar cirri, was placed by Borror and Wicklow (1983) in the family Urostylidae Butschli, subfamily Holostichinae Faure-Fremiet. Keronella n. gen. owning to its MV pattern in the frontal region, should be placed in the family Pseudokeronopsidae Borror and Wicklow. (ref. ID; 7743)