Operculigera inornata, Clamp & Kane, 2003

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 : 158-161

Operculigera inornata n.sp.

Figs. 13–15 ; Tables 4–7

Description. Lorica hemispheroidal, suboval to subcircular in dorsal view, slightly longer than wide. 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 not thickened. Dorsal surface of lorica without curved ridge. Posterior part of vallum reduced to slightly thickened ridge.Anterior and lateral parts of vallum moderately tall; posterior edges of lateral parts sloping abruptly to posterior part of vallum, posterior edges nearly vertical. Free edge of vallum smooth, even, lacking projections of any sort. Long strip near base of inner wall of each anterolateral part of vallum moderately thickened and projecting inward to form prominent, protruding fold. Rim of lorica aperture moderately thickened. Operculum

n.sp. from the type locality and host (n=20). subcuneate in dorsal view. Anterior edge of operculum moderately thickened to form narrow, ventral shelf; ventral shelf smooth, lacking processes. Macronucleus short to moderately elongate, cylindroid, usually folded to make compact mass. Macronucleus located in left half of body. Micronucleus ovoid, located more frequently near centre of macronucleus rather than near either end.

Etymology. The specific name (Latin: unadorned, simple) refers to the plain appearance of the lorica and its vallum.

Type material. HOLOTYPE, AUSTRALIA, Victoria, Otway Range ; 24 Dec 1963, J. R. Kane; on Phreatoicopsis terricola Spencer & Hall, 1896 , pleopods . Holotype slide with holotype organism marked by inscribed circle (Delafield’s hematoxylin), AM P62816. P ARATYPE slide (Delafield’s hematoxylin), IPTC USNM 1004289 . Victoria, Grampian Range, swamp near Fyan’s Creek; 20 Nov 1963, J. R. Kane ; on Phreatoicopsis sp., pleopods . Paratype slides (Delafield’s hematoxylin), AM P62817 and IPTC USNM 1004290 . Tasmania, Great Lake , 1914, W.M. Tattersall; on Colubotelson chiltoni (Sheppard, 1927) , pleopods ( NMNH-CC USNM 60657 ) . PARATYPE slides (Heidenhain’s hematoxylin), AM P62818 and IPTC USNM 1004291 (the latter comprises 2 slides) .

Remarks. The vallum of O. inornata lacks the spines or other types of processes so characteristic of some other species of Operculigera ( Jankowski, 1986; Clamp, 1991), but so do three other species of Operculigera that are hosted by various species of phreatoicid isopods ( Figs. 1, 2 ; Table 6; Clamp, 1991). At first glance, this appears to create the potential for taxonomic confusion; however, two of these species, O. obstipa Clamp, 1991 and O. montanea ( Fig. 1 ), are easily distinguished from O. inornata ( Figs. 14, 15 ) by differences in shape and symmetry of the anterolateral part of the vallum, proportions of the lorica, and (in the case of O. montanea ) presence of a prominent ridge in the dorsal surface of the lorica ( Table 6).

The third species with a plain vallum, O. zeehanensis ( Fig. 2 ), is much closer to O. inornata ( Figs. 14, 15 ) in appearance but is separated from it by differences in the shape of the anterolateral part of the vallum and, especially, proportions of the lorica ( Table 6). The lorica of O. inornata is subcircular to moderately longer than wide in dorsal view ( Figs. 13–15 ; Tables 4, 5, 7). Only four individuals in the sample of O. inornata from Tasmania and none in the sample from Victoria had loricae that were slightly wider than they were long. By contrast, all but one individual in the sample of O. zeehanensis had loricae that were at least 5% wider than they were long

n.sp. from the type locality and host (n=25).

n.sp. from Great Lake, Tasmania (n=19).

( Table 7). In addition, the width of the vallum in comparison to the width of the lorica was markedly greater in both samples of O. inornata than in the single sample of O. zeehanensis ( Table 7). Only one individual in the sample of O. inornata from Tasmania fell within the range seen in O. zeehanensis in regard to this proportion. Otherwise, the two species did not overlap. Finally, one characteristic of the cell body clearly differed between O. inornata and O. zeehanensis . The epistomial disk of O. zeehanensis was, on the average, 30% wider than the epistomial disk of O. inornata ( Figs. 2 , 14, 15 ; Tables 2, 4, 5).

The same type of intracellular parasite that was found in one sample of O. montanea was observed in the sample of O. inornata from Tasmania ( Fig. 13 ); the percentage of infected individuals (approximately 8%), however, was much lower in the latter. No parasites were seen in the samples of O. inornata from Victoria.

Figures

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.

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.