Pseudoamphisiella

Pseudoamphisiella Song, 1996 (ref. ID; 4889)

Pseudoamphisiella lacazei (Maupas, 1883) (Song, 1996) Song, Warren & Hu, 1996/97 (ref. ID; 4889 redescribed paper)
Syn; Holosticha lacazei Maupas, 1883 (ref. ID; 4889)

Pseudoamphisiella lacazei (Maupas, 1883) (Song, 1996) Song, Warren & Hu, 1996/97 (ref. ID; 4889 redescribed paper)

Synonym

Holosticha lacazei Maupas, 1883 (ref. ID; 4889)

Improved diagnosis

Large, marine Pseudoamphisiella, in vivo 120-300 um x 40-80 um with numerous cortical granules. On average 50 adoral membranelles and 2 buccal cirri, 50 macronuclear segments, 20 transverse cirri extending to the anterior 1/2 of the body; two ventral rows, with 14-16 (VRI) and 16-21 (VR2) cirri respectively. 8-11 dorsal kineties and 8-11 caudal cirri; 21-34 and 20-31 cirri in left and right marginal rows respectively. (ref. ID; 4889)

Descriptions

[Tsingtao population]
Cells in vivo usually 150-250 um x 45-70 um, length to width 2.5-4:1. Body generally elongate, rather fragile and variable in shape, sometimes with an inconspicuous indent or fold on the surface, typically in starved individuals. Normally, left margin of anterior region ear-shaped, protruding to the left side. Adoral zone of membranelles (AZM) up to 1/3 of body length, extending far onto the right side, where the cell surface along the distal end of AZM is markedly indented (or depressed) and gives the appearance that the organism is more or less cephalized. Right side straight, left slightly convex. Posterior end of the cell only slightly narrowed. Cortical granules inconspicuous, bar-like, about 2 um long, irregularly arranged. Cytoplasm greyish, usually containing many granular inclusions 1 to 5 um in size, giving the cell a dark, opaque appearance. Food vacuoles of fresh isolates containing mainly small ciliates and flagellates. Cilia of AZM in cells in vivo ca. 25 um long. Frontal and transverse cirri ca. 25-30 um long. All other cirri ca. 20 um long, although the marginal cirri lie beneath the margin of cell (except those in the posterior region), do not protrude from the outline and are thus not discernible when observed dorso-laterally. Caudal cirri arranged in an oblique line lying slightly towards the left side of the body. Locomotion usually consists of slow crawling on the bottom of petri dish, but cells may react by crawling more quickly when disturbed. In its natural habitat this species evidently feeds on small ciliates or other protists, yet it could be maintained in culture with bacteria alone. (ref. ID; 4889)

Inflaciliature: Base of membranelles about 10 um long, distal end of zone of membranelles distinctly bent towards the posterior end of the cell. Paroral membrane (PM) short, slightly arched and crossing the long endoral membrane (EM). Pharyngeal fibres pronounced after protargol impregnation. Three large frontal cirri (FC) typical of the genus. Two medium-large buccal cirri (BC). Ventral row 1 (VR1) long, extending to about the posterior 1/5 of the body. The anterior end of ventral row 2 (VR 2) immediately below distal end of AZM. Highly developed transverse cirri (TC) arranged in J-shaped row and terminating near posterior end of right marginal row. The well developed caudal cirri (CC) connect the left and right marginal rows completely, and hence, it is almost impossible to distinguish where the marginal rows terminate. Very characteristic are the fibrils associated with the ventral, marginal, and transverse cirri, the latter ones being particularly conspicuous and recognizable even in the very late morphogenetic stages. Dorsal cilia 3-5 um long, usually arranged in 11 kineties (DK), of which 1 or 2 might be on the lateral side. Macronuclear segments (Ma) spherical, about 5 um in diameter, distributed in the whole body. Micronuclei difficult to recognize. (ref. ID; 4889)
Divisional morphogenesis: Morphogenesis commences apokinetally with the appearance of loosely arranged basal bodies around and next to the anterior cirri of the transverse row. The proliferation of these basal bodies appears to occur below the cortex and thus all old cirri and fibres nearby remain intact. Then, two oral fields (primordia) are formed with further proliferation of more basal bodies (we unfortunately field to find an intermediate stage between the first and the next phase). Evidently, the proter's oral primordium develops de novo below the buccal cavity. The parental paroral and endoral membranes begin to dissolve and obviously not incorporated in the formation of the primordium. The primordium in the opisthe is not arched and develops at the same place where it originates, posterior to that of the proter. Slightly later, membranelles differentiate at the left anterior end of the enlarged oral primordia in both proter and opisthe. Two groups of cirral anlagen (FVT-anlagen) develop to the right of oral primordia, each of which has about 20-25 oblique streaks. The left marginal primordium in both dividers could be seen at this time within the old structure, several cirri of which are involved in the formation of the new anlagen. By contrast, the right marginal primordia, which lie to the right of the FVT-streaks, are only slightly longer than those next to it and are obviously separated from the parental structure. Dorsal kineties develop from two anlagen within each parental kinety which by now consist of short, close-set rows of basal bodies, the macronuclear segments are somewhat enlarged with no recognizable replication band. Micronuclei remain unchanged. Development in both dividers is very similar and takes place at about the same pace. Nevertheless, the entire field of the proter migrates to the frontal portion of the cell while opisthe's primordium still develops clearly beneath the cortex. Hence the old fibrils and cirri could be observed in this region. In both dividers, the anterior end of the primordium arches strongly. The new adoral membranelles and the anlage of the undulating membranes differentiate in a posterior direction. A single (paroral) cirrus develops from the anterior end of the undulating membrane anlage, later becoming the rightmost frontal cirrus. FVT-anlagen begin to segregate into cirri with the exception of the right most one (anlage for right marginal row) which is only enlarged and becomes markedly longer. Subsequently, about half of the membranelles are differentiated. The segregation of cirri from FVT-anlagen is complete. Each anlage, except the UM-streak, develops into 3 cirri, all of which are placed in three oblique rows. The anlagen of the left marginal row develop anteriorly from disaggregating parental cirri. The fusion of macronuclear segments is completed by this time, forming a single large mass with ca. 7 enlarged micronuclei attached to it. Cortical morphogenesis proceeds with further cirral segregation from the marginal anlagen. Some parental ciliary organelles are disaggregated. The anlage for the undulating membrane splits in both proter and opisthe, giving rise to the paroral and endoral membranes. The formation of the adoral zone of membranelles in both dividers is completed and each has acquired its definitive shape. The new cirral rows begin to extend as the cell elongates and migrates to form the mature cortical pattern. At this stage it could be seen that one or two cirri from the right most anlagen sometimes become resorbed so that the number of cirri in each longitudinal row, ventral or transverse, are not always equal. The parental dorsal kineties are completely resorbed. The anlagen of dorsal primordia stretch continuously in both directions across almost the whole dorsal surface. A single caudal cirrus develops from the posterior end of each dorsal kinety each of which consists of ca. 6 basal bodies. The micronuclei and macronuclear segments begin to divide. The final process is just before the cell divides. The frontal, transverse and ventral cirri have migrated to their final position. The separation of the undulating membranes is already completed. The caudal cirri become confluent with the marginal rows. By this time, some old membranelles, marginal and transversal cirri are still not completely resorbed. The remaining morphogenetic events are very similar to those known for other hypotrichous ciliates: the daughter-cells separate and then, with the completion of the cytostome become once again trophic cells. Compared with those of other known hypotrichs, the morphogenesis of this species is characterized by the following particulars: 1) Only the left marginal row derives from the disintegrated parental structure in the usual fashion. The right marginal row originates homologously with the cirri of FVT-complex. 2) The numerous oblique FVT-anlagen develop only to 2 frontal and buccal cirri, one transverse and 2 ventral (untypical midventral) rows. 3) Frontoterminal cirri, i.e. deriving from the rightmost streak of FVT-anlagen, absent. 4) With the exception of the dorsal kineties and the left marginal row, the old ciliature is generally not involved in the formation of new primordia. Even in the proter, unlike most other known types, there is no indication that the old undulating membrane is joined to the origin of the oral primordium, viz. the site of the oral primordium of the proter is not within the buccal field by posterior to it. 5) All parental ciliature, including the adoral zone of membranelles, is entirely renewed during the cytogenesis. (ref. ID; 4889)

Comments

The population described here is almost certainly conspecific with the organism of Maupas (1883). The forms as depicted in Figs. 5 and 6 in the original report (Maupas 1883), which have a characteristic indention to the left of the buccal field, were not observed among cells in culture. A likely explanation for this is that field specimens are more likely to be starved and to exhibit the characteristic folding or indentation described by Maupas (1883). Furthermore, the spherical macronuclei, cortical structure, cirral arrangement, dark-grey cytoplasm, body size and shape, and biotope are all consistent with those described by Maupas (1883) indicating that the identification is correct. The systematic position of this species has been uncertain since the original report by Maupas (1883). Though several authors mentioned it thereafter (Kahl 1932; Gelei 1936; Kattar 1970; Borror 1972), its ciliary pattern remained unknown until it was reinvestigated and excluded from the genus Holosticha (Song 1996). The species found by Patsch (1974) from a freshwater stream in the nature park Wildenrath in Germany is almost certainly a misidentification as Hemberger (1982) noted in his generic revision. (ref. ID; 4889)