Tapajosella elongata, 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 : 389

Tapajosella elongata n. sp.

( Fig. 4 )

Material examined. Holotype: ZUEC BRY 50 , individual statoblasts collected 25 January 2016 by B. Okamura from Juá Lake (Site 3), 2°26'0"S; 54°46'54"W, (see Table 2).

Etymology. Latin adjective, elongata (elongate) in reference to the statoblast shape.

Description. Floatoblasts are long and slender. They are widest in the middle, taper to pointed ends, and measure about 1 mm long by 0.27 mm wide and 0.25 mm in depth, giving a length/width ratio of 3.7 ( Figs. 4 a, c). Fenestrae of both valves are similar in size and present an unusually rectangular shape that contrasts to the more oval or circular fenestra that characterize floatoblasts of other known species. Polar grooves are absent. In lateral view one valve, which we designate as ventral, curves slightly inward at the poles. The other valve, designated dorsal, is correspondingly concave so that the ends of the suture are curved in a dorsal direction on either side of the capsule ( Fig. 4 b). SEM shows the so-called dorsal fenestra to have a finely wrinkled surface, while the presumed ventral fenestra is smooth ( Fig. 4 d). Low, rounded tubercles cover the annulus of both valves ( Fig. 4 c).

Remarks. At this time the species is known only by two floatoblasts. Neither colonies nor any other types of statoblasts have been observed.

The statoblast capsule alone exceeds the dimensions of many other whole phylactolaemate statoblasts ( Fig. 4 a). A similarly sized statoblast in the Neotropical region would be that of Asajirella gelatinosa ( Oka, 1891) which is disc-shaped and measures about 1.2 mm in diameter. Plumatella siolii , also known from Brazil, reaches nearly 800 µm in length, but the length to width ratio is well under 3 ( Fig. 4 c). In northern temperate regions P. fruticosa produces long and narrow floatoblasts with a length not more than 570 µm and a length to width ratio <2 ( Bushnell 1965, Wood & Okamura 2005).

Designating dorsal and ventral valves of the statoblasts is difficult using the criteria generally applied in other species. Because one valve is more convex than the other we have considered it as ventral, following the pattern of asymmetrical statoblasts in plumatellid species. However, this should be considered only tentative until it is known which valve attaches to the funiculus.

The statoblasts share basic structure with other phylactolaemate bryozoans, but their large size and uniquely elongated shape raise questions. More intensive searching may reveal the conditions to which this species is adapted as well as the type of colony capable of producing such large and oddly shaped statoblasts. Distribution. Unknown beyond the single site where statoblasts were collected.

Figures

FIGURE 4. Tapajosella elongata n. sp. a) Size comparison between floatoblasts of a well-known plumatellid, P. fungosa (left) and T. elongata (right), scale bar = 200 µm; b) Lateral view of two valves facing each other in their natural orientation, showing convex curvature of the ventral valve (left) and concave curvature of the dorsal valve (right); c) Scanning micrographs of the valves: ventral (left) and dorsal valve (right), scale bar = 300 µm; d) Scanning micrograph of the dorsal fenestra showing finely wrinkled-like texture, scale bar = 50 µm.