Plumatella philippinensis Kraepelin 1887

Plumatella cf. philippinensis Kraepelin, 1887

(Figs. 8 a, b)

Plumatella philippinensis Kraepelin, 1887. P. 118, pl. 3, figs 81–83.

Plumatella fruticosa Marcus, 1942b. Pp. 65–69, figs. 2a–c.

Material examined. Holotype: Collected on Vallisneria leaves, Libmanan River, Luzon, Philippines by K. Kraepelin, Senckenburg Museum, No. 92–B–92 Frankfurt. Other material examined: ZUEC BRY No. 56, two individual floatoblasts collected 20 January 2016 by B. Okamura from Tapajós River (Site 2c), 2°26'19"S, 54°54'54"W, (see Table 2).

Description. Floatoblasts are elongate and oval in shape. Outer dimensions of the two intact statoblasts (length, width) are 445, 215 and 446, 222 micrometers, and the length is almost exactly twice the width (Figs. 8 a, b). The dorsal fenestra is elongate, irregular in outline, and about half the length of the entire statoblast. The width of the dorsal annulus at the poles is more than twice the width along the lateral edges of the statoblast. On the ventral valve the fenestra is broadly oval, matching the shape of the underlying capsule to leave an annular width at the poles more than three times the lateral annular width. Strong tubercules are evenly distributed across both dorsal and ventral fenestrae. Both valves are almost equally convex, giving the statoblast an even symmetry in lateral view.

Remarks. Plumatella philippinensis has not been reported from any site since the description from Libmanan River, Philippines was published by Kraepelin (1887). The holotype remains in good condition at the Senckenberg Museum, including both colonies and statoblasts (Figs. 8 c, d). Notable features of the floatoblast include an irregularly shaped dorsal fenestra occupying the central third of the dorsal valve. The ventral fenestra is a large oval. Both fenestrae are tuberculated.

This combination of features was not seen in any other species until Marcus (1942) encountered new material from Ribeira de Iguape River in Brazil, misidentifying it as P. fruticosa Allman, 1844. In contrast to the specimen from the Philippines, Marcus’ illustrated floatoblast shows a smooth outline of the dorsal fenestra and a uniform width to the ventral annulus (shown here in Figs. 8 e, f). These differences could be accepted as either normal variation or stylized drawing. Unfortunately, the type material that Marcus deposited at the NHMUK (No. 1942.2.16.1) is currently missing from the collection.

The floatoblast described here from Juá Lake is not a perfect match with the material from either Kraepelin or Marcus. Although the dorsal valve is similar and both fenestrae are tuberculated, the ventral fenestra is less elongate. There are no multiple specimens to indicate the range of morphological variation. It is possible that this specimen represents a new species yet to be described. However, with such scanty material we are placing it tentatively in a group that includes both Kraepelin’s P. philippinensis and Marcus’ material from Brazil. Future collections will no doubt clarify all of these relationships.

Distribution. Philippines: Camarines Sur Province, Libmanan River; Brazil: São Paulo State, Ribeira de Iguape River; Pará State, Juá Channel.