Operculigera montanea Kane, 1969

Clamp, John C. & Kane, John R., 2003, Redescription of Four Species of Lagenophryid Peritrichs (Ciliophora) from Australia and New Guinea, With Descriptions of Two New Species, Records of the Australian Museum 55 (2), pp. 153-168 : 155-157

Operculigera montanea Kane, 1969

Figs. 1 , 8–11 ; Tables 1, 6

Operculigera montanea Kane, 1969: 369 .– Jankowski, 1986: 82, 83; Clamp, 1991: 365.

Redescription. Lorica hemispheroidal, suboval in dorsal view, moderately wider than long. Lorica asymmetrical in dorsal view; width of right half from midline to edge noticeably greater than width of left half from midline to edge. Rim of lorica moderately thickened. Dorsal surface of lorica with prominent, curved ridge extending across entire width of lorica and encircling concave depression in surface surrounding lorica aperture. Because of dorsal ridge, lorica with acuminate, nearly triangular profile in lateral view. Posterior part of vallum reduced to slightly thickened ridge. Anterior and lateral parts of vallum moderately tall, sloping abruptly to posterior part of vallum; posterior edges of lateral parts nearly vertical. Vallum symmetrical in height; free edge straight, even, lacking projections of any sort. Long strip near base of inner wall of each anterolateral part of vallum heavily thickened to form slightly protruding fold. Rim of lorica aperture moderately thickened. Operculum subcuneate in dorsal view. Anterior edge of operculum moderately thickened to form narrow, ventral shelf; ventral shelf smooth, lacking processes.

Macronucleus short, cylindroid; ends flexed upon centre to create compact, folded shape. Macronucleus located in left half of body. Micronucleus ovoid, located more frequently near centre of macronucleus than near either end.

Etymology. The specific name refers to the montane habitat of the type host.

Type material. LECTOTYPE, AUSTRALIA, Victoria, summit of Mt Baw Baw (1850 m elevation); 13 Oct 1963, J. R. Kane; on Colubotelson searlei Nicholls, 1944 , pleopods . Lectotype slide with lectotype organism marked by inscribed circle (Erlich’s hematoxylin), AM P62810 .

PARALECTOTYPE slide (Erlich’s hematoxylin), International Protozoan Type Collection (hereafter abbreviated IPTC) USNM 1004287 . AUSTRALIA, Victoria, Kiewa; J. R. Kane ; on Colubotelson sp., pleopods . Paralectotype slide (Erlich’s hematoxylin), AM P62811 .

Other material examined. Victoria, Mt Buffalo ; Feb 1926, G.E. Nicholls; on C. joyneri (Nicholls, 1926) , pleopods ( AM Z6189 ). Voucher slides (3 Heidenhain’s hematoxylin, 2 protargol) AM P62812, P62880, P62881, P62882, P62883 .

Nomenclatural note. No type species was explicitly fixed for Operculigera in Kane (1969); consequently, this name was not yet available because such fixation was required for genus-group names published after 1930 ( ICZN, 1999). Clamp (1991) designated O. montanea as the type species of the genus, making the name Operculigera available and (inadvertently as it turned out) becoming the author of the genus. The authorship of species of Operculigera described in Kane (1969) and Jankowski (1986) was not affected by this action (Article 11.9.3.1 of the current Code).

Remarks. The curved ridge in the dorsal surface of the lorica ( Figs. 1 , 9 ) is a distinctive characteristic of O. montanea that does not occur, even in reduced form, in any other known species within the genus ( Jankowski, 1986; Clamp, 1991). Indeed, this ridge has no real equivalent in any other lagenophryid species.

Operculigera montanea has a simple vallum ( Fig. 1 ), lacking the spines or other processes so characteristic of most other species in the genus ( Jankowski, 1986; Clamp, 1991). Its shape resembles that of O. zeehanensis Kane, 1969 , O. inornata n.sp., and O. obstipa Clamp, 1991 ; nevertheless, its distinctive proportions make it relatively easy to recognize. The vallum of O. montanea is markedly shorter in relation to its width than those of either O. zeehanensis or O. inornata ( Figs. 1, 2 , 14, 15 ; Tables 1, 2, 4–6). The vallums of O. montanea and O. obstipa are both short in relation to their widths but the vallum of the former is uniform in height compared to that of the latter, which diminishes in height from left to right ( Table 6; Clamp, 1991).

Approximately 50% of the ciliates in the sample of O. montanea from the type locality contained one or more individuals of an unknown type of spherical, unicellular parasite in their cytoplasm ( Fig. 10 ). Neither of the other samples examined showed any evidence of infection. The mean diameter of a sample of 15 parasites was 9.5±3.2 µm (4.8–13.9 µm). Each parasite had a single, dense nucleus ( Fig. 10 ), eliminating the possibility that they could be ciliates of any kind, such as the suctorians that parasitise some peritrich ciliates. In addition, none of the distinctive stages in the life cycle of parasitic suctorians (Lynch & Noble, 1931; Matthes, 1971) were evident.

A closely fitting, thin-walled cyst or cell wall encapsulated the cell body of the parasite. Several ruptured, empty examples of these capsules were seen ( Fig. 11 ), and a sample of 5 of them was measured. They had a mean diameter of 14.0±0.9 µm (12.7–15.3 µm). All empty capsules were in hosts that appeared either moribund or dead and disintegrating. One such capsule had a cluster of 16 small, oval cells nearby that may have been recently escaped swarmers of some kind. Each of these small cells had a single, dense, spherical nucleus similar to that of larger, encysted cells. A sample of 5 of the small cells had a mean length of 8.2±0.5 µm (7.4–8.7 µm) and a mean width of 5.7±0.6 µm (5.0–6.3 µm). The general appearance of the parasites suggests that they are either a species of chytrid fungus or amoeboid protozoan; however, positive identification will require more material than we had and observation of living parasites to elucidate their life cycle.

Note on the lorica aperture of Operculigera . Until now, functioning of the lorica aperture has not been described in living individuals of any species of Operculigera . Clamp

from the type locality and host (n=9).

from the type locality and host (n=11). All individuals measured were on the holotype slide.

(1991) described the operculum as being attached to the anterior edge of the aperture, based on sections of fixed material, and as opening toward the anterior, based on a short statement in Kane (1969). In this paper, we are able to draw on Kane’s personal observations of living O. montanea that were more fully described and illustrated in his MSc thesis ( Kane, 1964) than in the 1969 publication. In O. montanea , the operculum opens toward the posterior to lie against the dorsal surface of the lorica posteriad of the aperture. This allows the epistomial disk to protrude from the aperture anteriad of the reflected operculum instead of posteriad to it if Clamp (1991) were correct. To accomplish this, the operculum would have to be attached to the dorsum of the cell immediately posteriad of the peristomial lip instead of to the anterior edge of the aperture. The sagittal sections of two species of Operculigera illustrated in Clamp (1991) do not show this, but the lack of contact between the cell body and the operculum could have been a fixation artefact. Further observations of living material and sections of freshly fixed material are needed to resolve this ambiguity.

Figures

Figs. 1, 2. (1) Operculigera montanea, Erlich’s hematoxylin preparation. Dorsal view of lectotype individual from the type locality and host, AM P62810. (AD) thickened ridge that bounds anterior depression in dorsal surface of lorica; (AR) rim of lorica aperture; (AV) anterior and lateral parts of vallum; (C) peristomial cilia originating from epistomial disk (shown in outline only); (Cy) cytoplasm (sparsely stippled areas—food vacuoles and other taxonomically irrelevant structures are omitted); (ED) epistomial disk; (EM) myonemes that retract epistomial disk (densely stippled column anchored to ED); (I) infundibulum—this is a passageway through which food particles pass to reach the cytostomal area (the bulbous ampulla leading to a tubular cytopharynx that lies beyond the constriction at the end of the infundibulum); (LR) rim of lorica—the localized areas with large accumulations of lorica material (large arrow) are not typical; (MaN) macronucleus—the micronucleus is the small, dense, darkly stained body nestled in the central area of the macronucleus; (Op) operculum (the slightly displaced left side of the closed operculum is an artefact); (PM) myoneme in edge of peristomial lip that effects closure of the operculum; (TV) thickened strip in the anterolateral wall of the vallum; small arrow, vestigial posterior part of the vallum—to see species of Operculigera with this part of the vallum fully developed, consult Clamp (1991). (2) Operculigera zeehanensis, Erlich’s hematoxylin preparation. Dorsal view of lectotype individual from the type locality and host, AM P62813. The folding o ver of the left edge of the vallum (small arrow) is an artefact. The micronucleus was hidden underneath the macronucleus and is therefore not shown. The unfolded macronucleus indicates that this individual was probably approaching cell division when it was fixed. Most individuals in the sample examined had the ends of the macronucleus folded together.

Figs. 8–13. (8–11) Operculigera montanea from the type locality and host; Erlich’s hematoxylin preparations, AM P62810. (8) Heavily infested pleopod of host at low magnification. Arrow, lateral view showing triangular profile of lorica. (9) Dorsal view of single individual. See Fig. 1 for explanation of symbols. (10) Dorsal view of individual with intracellular parasite (arrow). (11) Dorsal view of individual with empty, ruptured cyst of intracellular parasite (arrow). (12) Dorsal view of Operculigera haswelli n.sp. from the type locality and host; Heidenhain’s hematoxylin preparation, AM P62814. Arrow, spine on left margin of vallum. (13) Dorsal view of two individuals of Operculigera inornata n.sp. from Great Lake, Tasmania; Heidenhain’s hematoxylin preparation, IPTC USNM 1004291. Arrow, intracellular parasite.

Figs. 14, 15. Operculigera inornata n.sp. (14) Dorsal view of holotype individual from type locality and host; Delafield’s hematoxylin preparation, AM P62816. (15) Dorsal view of individual from Great Lake, Tasmania; Heidenhain’s hematoxylin preparation,AM P62818.