Plumatella paltensis, Wood, 2022

Wood, Timothy S., 2022, Phylactolaemate bryozoans at the Zoological Survey of India and a taxonomic key to Indian Phylactolaemata, Zootaxa 5200 (2), pp. 401-435 : 420-421

Plumatella paltensis n. sp.

( Fig. 16 )

Holotype. ZEV 7546 /7, undated, collected at the Kshipra River near Ujjain, Madhya Pradesh, India by K.S. Rao.

Diagnosis. The colony grows as a loose tangle of branching tubules; the floatoblast dorsal fenestra is featureless while the ventral fenestra is more or less reticulated; the sessoblast is flamboyantly ornamented.

Etymology. The specific epithet recognizes the old Palta Waterworks near Kolkata where the species was first reported.

Description. Colonies consisting of interlacing tubules forming a loose mat up to 5 mm thick, the thin-walled tubules never fused; ectocyst ranging from clear to semi-opaque, with no indication of raphe or emargination. Floatoblasts roughly straight sided with broadly rounded ends, the dorsal fenestra length less than half the floatoblast length and lacking any ornamentation, ventral fenestra reticulated, but usually with only patches of a reticulated pattern encroaching from the periphery towards the center, floatoblast dimensions shown in Table 1 . Sessoblasts with variable morphology, but always with a strong reticulation across the frontal valve, often developing further into a heavy, sculpted meshwork across 80% of the frontal valve, with 10–12 narrow fingers radiating towards the annulus ( Fig. 16c ), the area between the fingers showing a uniform reticulation with a single small tubercle appearing in the center of each cell; sessoblast annulus smooth, fragile, and minutely toothed; sessoblast basal valve a stout ring with irregularly thickened sides.

Material examined. In addition to the holotype, recognized specimens include ZSI P1181 /1 collected 4 December 1949 in the filter beds of Palta Waterworks, West Bengal, by H.S. Rao; and P1198/1 collected 4 December 1949 at “Bagra,” Hoshangabad, Madyha Pradesh by F.H. Gravely .

Distribution. The species is known from a wide area within the borders of India.

Remarks. Although P. paltensis n. sp. was first noticed as P1181 at the ZSI, material from the Kshipra River (Z7546/7) is designated as the holotype because it is a much more complete specimen with many statoblasts.

The sessoblast is reminiscent of bizarre sessoblast morphologies occurring in two other species: Plumatella tanganyikae Rousselet, 1907 from Lake Tanganyika, and Varunella coronifera Wiebach, 1974 from Maharashtra, India (Nimbalkar et al. not yet published). In all three instances the sessoblasts appear to show a highly irregular secondary feature superimposed on a standard sessoblast design.

A similar species is P. bombayensis . Both species have a featureless floatoblast dorsal fenestra, and the floatoblast ventral fenestra can be more or less reticulated. However, the floatoblast in P. paltensis n. sp. is shorter and broader ( Table 1 ), and the sessoblast is completely different (compare Figs 4c and 16c ).

Figures

FIGURE 4. Plumatella bombayensis. Statoblasts from ZEV 3804, Zoological Gardens, Kolkata. (a) Floatoblast dorsal valve showing small, unmarked fenestra; (b) Floatoblast ventral valve showing pronounced fenestra reticulation; (c) Sessoblast showing reticulation in which each cell bears a single tubercle; (d) Partial enlargement of previous image. Scale bars for a–c = 100 µm, scale bar for d = 20 µm.

FIGURE 16. Plumatella paltensis n. sp. (a) Statoblasts from P1198 shown with light microscopy, from top to bottom:floatoblast dorsal valve, floatoblast ventral valve, sessoblast frontal valve; (b) SEM micrograph of floatoblasts from ZEV 4800, dorsal on left, ventral on right, scale bar = 100 µm; (c) SEM view of sessoblast from ZEV 4800 with magnified image on the right. Scale bars for all images = 100 µm.