Plumatella jariensis, Wood & Okamura, 2017

Wood, Timothy S. & Okamura, Beth, 2017, New species, genera, families, and range extensions of freshwater bryozoans in Brazil: the tip of the iceberg?, Zootaxa 4306 (3), pp. 383-400 : 392

Plumatella jariensis n. sp.

( Fig. 7 )

Material examined. Holotype: ZUEC BRY 49, colony, including statoblasts, collected 22 January 2017 by B. Okamura on submerged, uprooted tree at Jari Channel (Site 4a), 2°14'40"S; 54°50'23"W, (see Table 2).

Etymology. Specific name is derived from the site name, Jari Channel.

Description. The colony is robust with a dark, heavily sclerotized outer cuticle. At the tip of each zooid the stiff ectocyst ends abruptly and is continued by a colorless and more flexible portion of the body wall ( Figs. 7 d, e). The entire colony is firmly attached to the substratum with no free branches. However, the zooids bend outwards away from the substratum, and under crowded conditions the colony takes on a shrubby appearance.

In floatoblasts the ventral valve is highly convex, and the dorsal valve is much less so. Separated valves are shown in Fig 7 a, and dimensions in Table 3. The entire statoblast periphery reveals a line of tiny projections from the suture ( Fig. 7 b). In lateral view the dorsal and ventral valves taper at the periphery to form an acute angle ( Fig. 7 c). Dorsal and ventral fenestrae are strongly tuberculated with the tubercles more widely spaced on the ventral valve. Sessoblasts have not been observed.

Remarks. The minute knobs on the periphery of the floatoblast would be sufficient to place this species in the genus Swarupella Shrivastava, 1981 . Shrivastava (1981) introduced this genus to accommodate Swarupella andamanensis , a species from the Andaman Islands having very small spines at the poles of the floatoblast. Two species from Thailand were further added to Swarupella : Swarupella divina, Wood, Anurakpongsatorn & Mahujchariyawong 2006 and Swaruella kasartensis, Wood, Anurakpongsatorn & Mahujchariyawong 2006 ( Wood et al. 2006b), both with small processes around the entire statoblast periphery. However, it is uncertain whether the species showing this diminutive feature truly share a common ancestry that would unify them within the Family Plumatellidae . Other species in Brazil showing the same peripheral feature include Stolella evelina e ( Marcus, 1941), Stolella agilis tica Marcus, 1942 , and Stolella iheringi ( Marcus, 1942) (Wood, unpublished, based on examinations of paratype specimens at the NHMUK). For now we consider a prominent suture with an irregular edge, shown in P. jariensis n. sp., to be a useful taxonomic character with little systematic significance.

The acute taper of dorsal and ventral valves toward the periphery ( Fig 7 b) is unusual feature that contrasts with the more rounded statoblast edges found in most other plumatellids.

Distribution. Unknown beyond the single site where this species was collected.

Figures

FIGURE 7. Plumatella jariensis n. sp. a) floatolast valves: dorsal (left) and ventral (right), scale bar = 100 µm.; b) Detail of floatoblast periphery showing small projections, scale bar = 25 µm; c) Lateral view of floatoblast showing the taper to an acute angle, scale bar = 20 µm. d) Portion of a colony showing well sclerotized curitula, scale bar = 2 cm; e) Detail showing abrupt transition from sclerotized to soft parts, scale bar = 0.5 mm.