Encentrum liepolti ( Donner, 1964 ) De Smet & Verolet, 2009

De Smet, Willem H. & Verolet, Michel, 2009, On two new species of Proales from France, with reallocation of Dicranophorus liepolti Donner, 1964 and D. secretus Donner, 1951 (Rotifera, Monogononta), Zoosystema 31 (4), pp. 959-973 : 970-972

Encentrum liepolti ( Donner, 1964) n. comb. ( Figs 8 ; 9 )

Dicranophorus liepolti Donner, 1964: 281-283 , fig. 18a-k.

NEOTYPE. — A female in a permanent glycerine glass slide preparation deposited in MNHN ( AM 881 ). Additional type material: 9 females in slide mounts and 7 stubs each with trophi preparation for SEM in UA.

MATERIAL EXAMINED. — France. Rhône-Alpes, Ardèche, St-Julien-du-Serre, below outflow of spring “Source Jumel”, 25.V.2006, water temperature 13°C, pH 8.23, 17 ♀♀.

DESCRIPTION OF TROPHI ( FIG. 9 )

Trophi forcipate. Rami outline more or less hexagonal; rami opening more or less mushroom-shaped; rami broad, each with long drawn out and inwardly kinked dorsal apical ramus tooth, and a straight and shorter ventral apical ramus tooth ( Fig. 9C : at); latero-ventrally at the base of the dorsal apical ramus teeth is a socket ( Fig. 9C : s) wherein the base of the preuncinal teeth is articulating; rami mainly connected to fulcrum by basal chambers. Sub-basal chambers with rounded alula postero-laterally; their inner margins with long plate-shaped part extending beyond inner margins of basal chambers; oval sub-basifenestrae caudally. Basal chambers each with large drop-shaped fenestra dorso-caudally. Fulcrum very long, longer than rami, in lateral view straight, with broader basal part, gradually tapering distally. Unci single with well-developed head and shaft bearing ventral and dorsal rib, and a dorsally appressed ( Fig. 9G, H, J : vt), rod-shaped element (vestigial uncus tooth?); head with small basal knob and rib at the inner side. Preuncinal teeth composed of two fused elements consisting of tooth and shaft. Intramallei short, quadrangular with inwardly directed projection bearing supramanubria; at the base of the spine is a caudal opening. Supramanubria L-shaped. Manubria somewhat longer than incus, rod-shaped, in dorsal/ventral view incurved posteriorly, cauda crutched, head triangular with opening at inner side.

Measurements (N=5): ramus 6.0- 8.9 µm, fulcrum 8.3-9.4 µm, 4.0- 6.3 µm, manubrium 15.7- 17.1 µm, preuncinal tooth 3.2-3.8 µm, intramalleus 1.6-2.4 × 2.8-3.9 µm, supramanubrium 2.6-4.0 × 2.2-3.0 µm.

REMARKS

Donner (1964) probably assigned the species to the genus Dicranophorus because of its long toes, as was common practice formerly. However, the feature length of toes is a variable character and taxonomically irrelevant, as holds for several other rotifer genera. Jersabek (1994) stresses that several species with intramallei, and among them D. liepolti , have been incorrectly assigned to Dicranophorus . In his revision of the Dicranophoridae, De Smet (1997) considered the species incertae sedis in view of the presence of intramallei, a major character of the genus Encentrum . The results of the analysis of the trophi by SEM allows the reallocation of D. liepolti in the genus Encentrum .

The original description of the morphology of the body of the female ( Fig. 8A ) is fairly accurate, except for the toes which show a joint at ⅓ from the tip forming claw, not mentioned by Donner (1964) ( Fig. 8B, C ).

The trophi of Encentrum liepolti appear fairly derived, and due to their particular morphology, the species cannot be related to any other congener. It is distinguished by the very long fulcrum; the connection of the rami with the fulcrum which is mainly by the basal chambers and not by the subbasal chambers as in the other Encentrum species studied by SEM so far (see e.g., De Smet 1997); the preuncinal teeth composed of a pair of fused teeth articulating with the rami by a rami cavity, instead of singular preuncinal teeth more or less firmly attached or fused to the rami ventrally; the alulae present on the subbasal chambers (alulae only reported in the insufficiently described E. asellicola (Bartoš, 1947) and in E. frenoti De Smet, 2002 ; the alulae in E. frenoti and the angular postero-lateral corners, which could be interpreted as alulae,as found in E. kulmatyckii Wiszniewski, 1953 and members of the subgenus Encentrum always form part of the basal chambers; the single alula in E. kutikovae De Smet & Chernyshev, 2006 is part of an accessory right ramus chamber intercalated between the basal and sub-basal chambers; the implantation of the single alula on the right ramus in E. ussuriensis De Smet & Chernyshev, 2006 is unclear).

To date E. liepolti was only found in Austria, Europe, among submerged vegetation and both at the surface and in the bed sediments of running waters ( De Ridder & Segers 1997; Segers 2007). It belongs to the dominant species of the hyporheic zone (Schmid-Araya 1998).

Figures

FIG. 8. − Encentrum liepolti (Donner) n. comb., female: A, lateral view; B, foot and toes, with joint indicated (arrow); C, same as B, with kinked claw.

FIG. 9. — Encentrum liepolti (Donner, 1964) n. comb., SEM photographs of trophi: A, complete set, ventral view; B, rami, dorsal view; C, incus, ventral view; D, complete set, ventro-frontal view; E, same as D, lateral view; F, right manubrium; G, right uncus, outer view; H, left uncus, lateral view; I, same as H, inner view; J, left uncus, outer view; K, right preuncinal teeth, lateral view; L, same as K, oblique inner view; M, left preuncinal teeth,lateral view;N, supramanubria; O, right intramalleus, inner view; P, same as O, outer view. Abbreviations: at, apical ramus teeth; s, socket for preuncinal teeth; vt, vestigial tooth. Scale bars: A, 10 μm; B-F, 5 μm; G-P, 1 μm.