Fredericella tenax, 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 : 394-395

Fredericella tenax , n. sp.

( Fig. 9 )

Fredericella australiensis browni DuBois-Reymond Marcus, 1953 , p. 152, pl. 2; not Fredericella australiensis browni Rogick, 1945 .

Material examined. Holotype: ZUEC BRY 51 , collected 19 January 2016 by B. Okamura at Jari Channel (Site 4b), 2°14'40"S; 54°50'23"W, and Tapajós River (Site 2a), 2°26'30"S, 54°53'38"W 21 and 23 January 2016 (see Table 2). Colonies include statoblasts attached to wood. Also examined for comparison was F. toriumii Hirose & Mawatari, 2011b , T. Wood personal collection No. 1464, collected 22 July 1998, Garrison Lake, Curry Co., Oregon, USA by T.G. Marsh.

Etymology. The specific name is from the Latin adjective, tenax , meaning tenacious, holding fast, clinging, referring to the tight adherence of statoblasts to the substratum.

Description. The specimen includes statoblasts, and only short portions of the colony without polypides. Statoblasts are variable in shape ( Fig. 9 a) but are mostly roughly circular with a diameter of about 300 µm. They are firmly attached to the substratum along the entire basal valve. Weak pitting of the frontal valve is easily seen when the clean, isolated valve is viewed with transmitted light microscopy ( Fig. 9 b). SEM also shows the pitting clearly ( Fig. 9 c). However, when a dry statoblast is viewed with reflected light the surface of the frontal valve appears shiny.

Remarks. A combination of three morphological features of the statoblast characterize the specimen from Brazil: surface topography, shape, and strong adherence to the substratum.

The lightly pitted texture of the statoblast frontal valve is very similar to that of Fredericella toriumii Hirose & Mawatari, 2011b . All other fredericellid species have statoblasts that are either smooth or heavily pitted, or in the case of Fredericella browni ( Rogick, 1945) smooth but covered with a cornified membrane (Hartikainen et al., 2013b; Wood 2015). Among the known fredericellids only the statoblasts of F. toriumii have an unmistakable but consistent lightly pitted texture.

The round statoblast shape is a feature also seen in Fredericella australiensis Goddard, 1909 and F. browni . In all other fredericellids the statoblast is longer than wide, often at a ratio approaching 2:1 ( Toriumi 1951; Wood & Backus 1992). Toriumi (1951) suggested that statoblast shape in F. sultana is controlled largely by the diameter of the zooecial tube, which in turn may be a function of environmental conditions. The correlation between zooecium diameter and statoblast breadth has been noted in other fredericellids as well ( Wood & Backus 1992). Hartikainen et al. (2013a) showed that F. sultana statoblasts become malformed and take on more rounded dimensions in colonies infected by the myxozoan parasite, Tetracapsuloides bryosalmonae . All of the fredericellid statoblasts in our collection from Brazil are rounded, and many are malformed ( Fig 9 a). Based solely on statoblast dimensions this could be either a new species or else F. toriumii with a myxozoan infection.

However, the third feature of the statoblasts of the specimen from Brazil is an unusually firm adherence to the substratum. Most other fredericellid species may have traces of an attachment ring on the basal valve. In F. browni the ring is quite well developed. How this compares to F. toriumii from Japan is inconclusive (Hirose, personal communication), but F. toriumii from Oregon has no special attachment structures. On balance, the combined three morphological features seen in the fredericellid statoblasts from the Jari Channel are sufficient, in our opinion, to justify the new species, F. tenax n. sp..

Distribution. Known only in South America from the vicinity of Lake Titicaca, and the Jari Channel reported here.

Figures

FIGURE 9. Fredericella tenax n. sp. Statoblasts, scale bars = 100 µm. a) Three separate statoblasts showing round or irregular shapes; b) Statoblast valve showing faint pitted pattern; c) Scanning micrograph showing pitted pattern and abundant adhesive material securing statoblast to the substratum.