The World of Protozoa, Rotifera, Nematoda and Oligochaeta
Eutintinnus
From Dr. Inaki
[ref. ID; 4403]
The Kinetomes of Eutintinnus species were generally similar and characterized by: 1) the right and left fields being of similar length, kinetal spacing, and organization (i.e. kineties composed of an anterior dikinetid followed by a series of monokinetids); 2) two, rarely three, long dorsal kineties composed of monokinetids; 3) a ventral kinety; and 4) the absence of a true posterior kinety. (ref. ID; 4403)
Lorica: The goblet-shaped lorica of E. angustatus consisted of a long, roughly cylindrical upper portion, an abruptly constricted subequatorial region, and a short, narrow posterior cylinder. In our specimens, the upper shaft was usually tapered outward to form a slight posterior bulge. The subequatorial constriction was often asymmetrical and resulted in the longitudinal axis of the upper and lower cylinders forming an obtuse angle. The oral margin was not flared, but a faint brim was sometimes present; aboral margin was squarely cut. (ref. ID; 4403)
Zooid: The bell-shaped zooid of E. angustatus was attached to the constricted region of the lorica by a long (30-35 um) contractile pedicel. Contraction of the zooid during fixation often produced a more pronounced bulge in the upper cylinder and sometimes creased the lorica at the attachment site of the pedicel; this indentation may have contributed to the asymmetrical shape noted in some specimens. Zooids were twice as long as they were wide and occupied ca. 80% of the upper cylinder. The macronucleus consisted of four ovoid lobes with adjacent lobes connected by an argentophilic thread. The macronuclear lobes were typically arranged in a spiral with the first two lobes positioned transversely around the anterior dorsal curvature of the organisms. The third directed obliquely along the left side of the cell, and the fourth located near the posterior end of the zooid. One or two spherical micronuclei (1.0-1.5 um in diameter) were observed in most cells and were always closely apposed to the macronucleus. Somatic kineties of E. angustatus numbered from 50 to 64 and were usually distributed as ca. 16 kineties in the right field, ca. 36 in the left field, two (rarely three) dorsal kineties, and the ventral kinety; a posterior kinety was not observed. Most somatic cilia arose from monokinetids were relatively short (2-3 um long), and were directed anteriad and to the left. In addition, dikinetids were found at the anterior end of all kineties forming the RF and most of the those in the LF. The anterior cilium of dikinetids was 7-10 um long and directed anteriad along with the cilia of the OPk; the posterior cilium resembled those originating from monokinetids. The VK was relatively short, composed of ca. 14 monokinetids, and positioned posterior to OPk1. The anteriormost five to nine kinetids of the VK formed a tight row that slanted from the anterior right to posterior left and bore longer cilia (4-5 um) than other somatic monokinetids. The oral anlage for the opisthe developed posterior and to the left of the VK. Kineties of the RF were about the same length as the VK (usually 8-13 kinetosomes) and confined to the anterior third of the cortex. The dorsal kineties were located on the right dorsal surface of the cell posterior to OPk6 and began slightly below the kineties of the RF. Each extended just over half the cell length and was composed of ca. 16 monokinetids; the first DK sometimes had an anterior dikinetid. Kineties of the left field were of similar length and organization as the RF; however, the rightmost kinety of the LF (i.e. Kn) lacked an anterior dikinetid and was structurally indistinguishable from the VK. The shallow peristome of E. angustatus had a broad, low oral plug that channeled the infundibulum along the right curvature of the oral area as it descended toward the cytostome. The cilia of the paroral membrane were ca. 10 um long and their kinetosomes formed a densely staining line that extended along the wall of the infundibular channel from just above the cytostome to ca. OPk8. In some specimens, a more lightly staining row of granules extended from the left of the cytostome over the oral plug and along the left side of the peristome. These granules appeared to be ciliated and may represent an extension of the paroral membrane; however, we were unable to establish a connection between the two structures either along the right dorsal border of the infundibulum or near the cytostome. The 21 to 24 OPk of E. angustatus were composed of three rows of kinetosomes that were approximately equal in length. There were usually three infundibular OPk, the innermost of which (OPkn) was shorter than the others and located entirely within the infundibulum. When viewed through the ventral surface of the organism, OPkn was positioned just to the right of the ventral kinety and originated some distance from the cytostome-cytopharynx. The other infundibular OPk were to the left of the ventral kinety in longitudinal perspective, began inside the infundibulum, and extended progressively farther onto the peristomial lip. The cilia of OPkn were short and extended laterally; those of all other OPk were 15-20 um long and generally directed anteriad. (ref. ID; 4403)
Comments
Daday (1887) described the lorica of E. angustatus as forming a uniformly thick-walled cylinder with a sharply constricted posterior quarter. His loricae were 135-144 um long, had an oral diameter of 48 um, and an aboral aperture of 10-12 um. The oral margin had a small horizontal rim, whereas the posterior opening was squarely cut. Hada (1938) emended the description of E. angustatus to include specimens measuring 85-100 um in length, 38-45 um in oral diameter, and 14-16 um in aboral diameter. The oral margin of Hada's specimens was thickened to form a faint brim, but lacked a distinct horizontal rim. The loricae of our specimens most closely resemble those of Hada (1938) as they were of comparable proportions, uniformly thick walled, roughly cylindrical in both the upper and lower portions, and lacked an oral rim; however, the upper cylinder was usually widest posterior to the oral aperture, and the longitudinal axis of the lower cylinder was typically not aligned with that of upper shaft. Only one other species, E. apertus Kofoid & Campbell, 1929, has a lorica that closely resembles that of E. angustatus; however, it differs from E. angustatus by having an oral flare, a less distinct posterior tube, and a conical rather than cylindrical upper lorica. (ref. ID; 4403)
Measurements
General lorica dimensions: maximum diameter of upper cylinder, 37-50 um (44+/-0.6); length of upper shaft/total length, 0.6-0.9 um (0.69+/-0.01); length of posterior shaft/total length, 0.1-0.2 um (0.12+/-0.01). (ref. ID; 4403)
E. inquilinus has a characteristic tapering lorica at the aboral end. The morphology of the lorica is similar to that of E. apertus (Kofoid & Campbell, 1929). However, the lorica oral diameter (LOD) of our E. inquilinus (21+/-1.7 um) was significantly smaller than those in previous reports for E. apertus. Kofoid & Campbell (1939) listed the LOD of E. apertus as 36-39 um, with a mean of 33 um. Furthermore, E. inquilinus attached to surfaces by the aboral end of the lorica but did not appear to attach Chaetoceros cells or other particles to the oral end of the lorica, as has frequently been described for E. apertus. E. inquilinus is probably identical to the T. inquilinum revised in Kofoid & Campbell (1929). (ref. ID; 4963)
Measurements
The lorica oral diameter (LOD) was 21+/-1.7 um, the width of the aboral end was 13+/-1.2 um, and the length of the lorica was 97+/-6.6 um (mean+/-SD, n=22). (ref. ID; 4963)
Chesapeake Bay specimens of E. pectinis had a tubular lorica that was slightly flared at the oral and aboral openings. The shaft tapered gradually from the oral flare and had a noticeable ca. 1-um constriction 5-10 um anterior of the aboral flare. The oral margin was serrated with 20 to 26 (22.2+/-0.19; n=33) teeth that measured ca. 4 um in length. (ref. ID; 4403)
Zooid: A long (30-35 um) pedicel attached the cylindrical zooid to the posterior quarter of the lorica wall. The pedicel of E. pectinis appeared less contractile than other species as it was readily visible following contraction of the zooid. Zooids were approximately four times longer than wide and occupied ca. 40% of the lorica. The macronucleus usually consisted of four ovoid lobes. These lobes were connected by an argentophilic thread and were positioned along the longitudinal axis of the cell. The two, rarely three, spherical micronuclei were set close to the macronuclear lobes and had a diameter of 1.0-1.3 um. Somatic ciliation of this species consisted of 18 to 24 kineties usually arranged as seven in the RF, 11 in the LF, two DK, and the VK; except where noted, cilia were of similar length and orientation as in the preceding species. In addition, a highly variable number of kinetal fragments (one to eight kinetids each) often formed a diagonal series running posteriad from dorsal to ventral beneath the left field. These fragments may represent the posterior kinety as previously suggested (Brownlee 1977); however, they were most conspicuous during cell division (i.e. in the cells that had begun stomatogenesis), eventually formed that left field of the opisthe, and were greatly reduced or absent in recently formed daughter cells. Thus, E. pectinis appears to lack a true posterior kinety. The VK was located mid-ventrally between the right and left fields, and was broken into one to four fragments each containing a highly variable number (one to 10) of monokinetids. During division, the opisthe oral primordium formed immediately to the left to these fragments. Unlike the kinetal fragments located posterior to the left field, the segmented ventral kinety was always present in recently formed daughter cells and only contributed to the formation of the opisthe VK. The kineties of the RF and LF were of similar length (5-11 kinetosomes) and each kinety was composed of a dikinetid followed by a series of monokinetids. The two dorsal kineties, located posterior to OPk6-7, were set close to the LF, but removed from the RF by a wide gap. Both were composed of ca. 24 monokinetids and had noticeably longer cilia (ca. 5 um) than the other somatic kineties; however, differences in kinetids spacings resulted in the DK being of unequal length. The first dorsal kinety (DK1) began the same level as the LF and ran about half way down the zooid. The second (DK2) originated several microns posterior to DK1 and extended almost the entire length of the cell. Eutintinnus pectinis had a slight oral plug situated on the ventral wall of the narrow, but rather deep peristome. The paroral membrane began to the right and a few microns anterior the cytostome, extended along the right wall of the peristome, and terminated interior to OPk6. The 15 to 16 OPk were composed of three kinetosomal rows of comparable length. There were typically 11 peristomial and four infundibular OPk. The last two oral polykinetids, OPkn and OPkn-1, originated deep in the infundibulum, very near the cytostome. OPkn never emerged from the infundibulum, whereas OPkn-1 was slightly longer and curved onto the peristomial lip. The remaining infundibular OPk began at successively shallower depths and extended progressively farther out of the infundibulum. Of the peristomial OPk, OPk1 (sometimes OPk2) was unique, as its proximal end extended over the edge of the peristome and down into the infundibulum toward the cytostome. The cilia of the OPk, including OPkn, were 10-20 um long and directed anteriad. (ref. ID; 4403)
Comments
As originally described by Kofoid (1905), the tubular lorica of E. pectinis is slightly flared at the oral and aboral ends, has 20 serrated teeth along the oral margin, and measures 150 um in length, 25 um in oral diameter, and 15 um at the aboral opening. Subsequent studies have shown that lorica size in E. pectinis is considerably more variable than originally recognized: length 115-172 um; oral diameter 22-27 um; aboral diameter 14-16 um. E. turris Kofoid & Campbell, 1929, closely resembles E. pectinis. Lorica size and shape in these latter species are indeed very similar, and the two appear to be distinguished primarily by the number of oral serrations: 24 in E. turris vs. 20 in E. pectinis. Loricae of specimens from Chesapeake Bay conformed to Kofoid's (1905) description of E. pectinis except for a more variable number of oral teeth (range 20-26). Our observations, coupled with great similarity in the original description of E. pectinis and E. turris, raise doubts regarding the validity of two species separate species. Since E. turris would fall as a junior synonym should the two species be united, we have chosen to refer to our specimens as E. pectinis. (ref. ID; 4403)
The lorica of our specimens formed a gradually tapered tube that had a slightly flared oral margin with a faint brim. The aboral margin was squarely cut, but had a very slight flare in some specimens. (ref. ID; 4403)
Zooid: The cylindrical zooid of E. tenuis had an average length to width ratio of 3.2 and occupied about 22% of the lorica. This species had 4-6 ovoid macronuclear lobes that were arranged along the length of the cell and connected by fine argentophilic strands. Two spherical micronuclei (1-2 um dia.) were appressed to the macronucleus. Somatic kineties varied in number from 30 to 35 and were partitioned as ca. 10 in the RF, ca. 20 in the LF, 2DK, and the VK; there was no true posterior kinety, but a diagonal series of kinetal fragments was present posterior to the LF of dividing specimens. The VK was formed by a short row of 8-21 ciliated monokinetids situated well posterior of the peristomial lip, between the right and left fields; the opisthe oral anlage formed to the left of the VK. All, kineties of the RF and most of those in the LF had an anterior dikinetid followed by 6-13 monokinetids; ciliary length and direction were comparable to that of the preceding species. Generally, the last three to four kineties of the LF (i.e. those nearest the VK) lacked an anterior dikinetids. The rightmost two to three of these kineties had their anterior kinetosomes (three to seven) arranged in a tightly spaced file that slanted from right to left, as noted in E. angustatus, and bore 5-6 um long cilia. The two dorsal kineties were located posterior to OPk7-8 and composed entirely of monokinetids; ciliary length was ca. 7 um. The DK bordered the LF, but were separated from the RF by several kinetal widths. DK1 began at the level of the anterior dikinetids of the LF, contained ca. 55 kinetids, and reached the posterior a quarter of the cell. The second dorsal kinety (DK2) started several micron posterior to the first, contained ca. 36 kinetids, and, in contracted specimens, curved around the posterior end of the cell. The buccal area of E. tenuis was similar in shape to that of E. pectinis. The paroral membrane encircled about a third of the infundibulum as it ran from near cytostome to OPk6. There were 18 (rarely 19) OPk composed of three kinetosomal rows of approximately equal length. The last four or five OPk were infundibular with OPkn and OPkn-1 originating deep in the infundibulum near the cytostome. The distal tip of OPkn just reached the peristomial lip, while OPkn-1 extended onto the rim of the peristome. As in E. pectinis, the proximal end of OPk1 and sometimes OPk2 curved down into the infundibulum. Cilia of the OPk were 15-20 um long; those of the paroral membrane were ca. 5 um. (ref. ID; 4403)
Comments
Morphological attributes of E. tenuis loricae from Chesapeake Bay were for the most part consistent with previous reports. Minor differences included a broader range in the ratio of total lorica length of oral diameter, and a slight flare at the aboral opening. (ref. ID; 4403)
