Stylonychia ammermanni* sp. n., a New Oxytrichid (Ciliophora ...

76 R. Gupta et al.
Morphometric characterization was done on randomly selected
non-dividing cells after staining with the modified protargol method
(Kamra and Sapra 1990). The terminology employed was that of
Wallengren (1900), Borror (1972), Hemberger (1982) and Martin
(1982).
Most of the cells exhibiting better details have orientation with
their ventral sides facing downwards so that the AZM appears on
viewers left.
RESULTS
Stylonychia ammermanni sp. n. (Fig. 1) feeds voraciously
on the alga Chlorogonium elongatum and
healthy cells are very motile. With its rigid body and
broad anterior and narrow posterior ends it shows
morphological similarities to the S. mytilus-lemnae complex.
However, S. ammermanni sp. n. appears comparatively
flattened as it lacks the peristomial bulge. This
feature distinguishes it from the other two related species
viz. S. mytilus and S. lemnae (Fig. 2). On an
average S. ammermanni sp. n. measures 135 x 50 µm
with length to width ratio of 2.5:1. The generation time
under laboratory conditions is 11±0.5 hrs. Encystment
and excystment are occasional in the laboratory as well
as in wild cultures. Each cell possesses two macronuclei
and two to four micronuclei. The right and left marginal
cirral rows (RMC and LMC) are straight and posteriorly
well separated. Morphometric characterization of the
species is shown in Table 1.
Stylonychia ammermanni sp. n. (Fig. 1) has a large
peristome with the adoral zone of membranelles (AZM)
extending slightly more than fifty percent of the body
length. Two parallel undulating membranes (UMs) are
situated on the right wall of the peristome which appear
crossed in stained preparations due to flattening. Of the
18 FVT cirri, the eight frontals (F 1-8
) are disposed
characteristically. The posterior two pairs (F 5, 6
and F 7, 8
)
are separated from the anterior hypertrophied frontals
(F 1-4
) and also from each other by distinct gaps. Posterior
frontals (F 5, 6
) are in linear orientation and parallel to
the RMC. The posteriormost pair (F 7, 8
) is separated
apart from (F 5, 6
) and is situated near the cytostome. The
transverse cirri (T 1-5
) are placed in two groups of three
and two cirri. Among the five ventrals two are close to
the oral region and are termed the left (V 1
) and right
(V 2
) postoral ventral cirri, while the other three (V 3-5
)
are more posteriad. Marginal cirri are evenly spaced in
one row each near the right and left margins of the cell.
These right and left marginal cirral rows (RMC and
LMC) are widely separated posteriorly.
Dorsally, S. ammermanni sp. n. shows the presence
of six dorsal rows (DK 1-4
and DM 1, 2
) and three caudal
cirri. Three of the dorsal kineties (DK 1-3
) are curved
apically. The first dorsomarginal (DM 1
) terminates at the
posterior quarter region of the cell and the DM 2
before
the mid region. There are three caudal cirri (CC 1-3
), one
each at the end of dorsal kineties DK 1, 2, 4
and are equally
spaced (Fig.1). The right caudal cirrus (CC 3
) is positioned
between, terminal 2-3 cirri of the RMC row.
The morphogenetic pattern during division (Figs. 3-6)
is essentially similar to that in S. lemnae and S. mytilus
(Wirnsberger et al. 1986).
A small group of basal bodies evolves very close to
the uppermost transverse cirrus (T 1
). The kinetosomes
proliferate linearly to form an anarchic field, the oral
primordium (OP). A new AZM for the opisthe (posterior
daughter cell) is formed from the OP. The parental AZM
is retained for the proter (anterior daughter cell).
The FVT cirri for the two daughter cells develop from
two sets of six cirral primordia (I-VI) each. In the proter,
the parental UMs function as primordium I. The other
primordia originate from the OP (primordium II), F 8
(III),
F 7
(IV) and right postoral ventral cirrus (V and VI). In
the opisthe, three primordia (I-III) originate in conjunction
with the OP and the other three (IV-VI) from the
right postoral ventral cirrus.
The origin of the two sets of six primordia involves
three parental cirri (2 frontals and 1 ventral) and they
differentiate into 18 FVT cirri by the cleavage pattern 1,
3, 3, 3, 4, 4.
The marginal and dorsal ciliature are formed in a
manner similar to that described for other Stylonychia
species (Hemberger 1982; Wirnsberger et al. 1985,
1986; Berger and Foissner 1997).
In the proter, marginal primordia are formed at the
anterior ends of the marginal rows by reorganization of
2-3 parental marginal cirri. In the opisthe, marginal
primordia originate similarly slightly below the prospective
division furrow.
Dorsal kineties DK 1-3
are generated by intrakinetal
proliferation of kinetosomes in parental kineties
DK 1-3
. The kinety DK 4
originates by unequal
fragmentation of the third dorsal primordium (DP 3
).
Dorsomarginals (DM 1, 2
) are generated at the anterior
end of the new right marginal rows which shift to the