Encentrum psammophilum Althaus, 1957

De Smet, Willem H., 2015, Rotifera from the Mediterranean Sea, with description of ten new species, Zootaxa 4028 (2), pp. 151-196 : 187-188

Encentrum psammophilum Althaus, 1957

The specimens seen ( Fig. 29 A) largely conform to the original description, and only differ in minor aspects. The basal third of the toes is weakly swollen, and slightly offset from the tapering distal 2/3 part; the swelling of the toes is slightly unequal all around; two colourless frontal eyespots are present, not mentioned by Althaus (1957). The outer margin of the right toe is reported to be undulate (‘wellenförmig geschwungen’) in the original description, but this comes about when the basally, all around unequally swollen toes are not positioned in the same way. The vitellarium contains 8 nuclei instead of 4.

Encentrum psammophilum was a rather rare inhabitant of sublittoral psammon from the Costa Brava, Côte d’Azur and Tyrrhenian Sea, 20 m to 3.5 km off shore, depth 15−40 m, June, July, September, water temperature 17−22 °C. The species was to date only known from sublittoral mesopsammon (depth 2 m) of its type locality, the Central bath of Varna, Black Sea, Bulgaria ( Althaus 1957). The species reported sub E. psammophilum from the North Sea (island Sylt, Germany) is considered as a different species on basis of the morphology of the body and trophi ( De Smet 1997).

Redescription of trophi by SEM. Trophi ( Fig. 29 C −E) of subgenus Encentrum type; large, elongate, fairly slender. Rami outline longer than wide, ratio length:width of closed rami 1.7−1.9; outer margin of rami weakly concave dorso-laterally, rounded-angular posteriorly; outer ventral margin with carina rami near 3/7 from apical ramus tip; median rami opening elongate drop-shaped. Each ramus with single, slightly offset apical tooth set at right angle to trophi axis; cardal apophyses very small. Prior to apical teeth a preuncinal tooth set at a right angle to trophi axis; preuncinal teeth with elongate triangular head and short shaft forming obtuse angle; head with small cardal apophysis. Fulcrum longer than ramus, in dorsal/ventral view distal end slightly widening and indented dorsally; in lateral view with broad base, quickly tapering, continuing parallel-sided. Unci medium long, slightly curved, head slightly shorter than shaft, with dorsal and ventral apophyses. Intramallei long, sock-shaped, with relatively long, rounded medio-lateral basal expansion bearing medio-caudal opening; inner side expaned, fitting lateral concavity of rami. Supramanubria absent. Manubria slightly less incus length, stout, rod-shaped, proximal half straight, distal half incurving with crutched cauda, head short, rounded-triangular.

Measurements. Body (N=5): total length 175 µm, toe 25‒28 µm; trophi (N=3): length 25 µm, ramus 8.9 µm, fulcrum 10.4 µm, uncus 5.0 µm, intramalleus 5.0 µm, manubrium 16.0‒16.6 µm.

Figures

FIGURE 29. Encentrum psammophilum Althaus. A. Female, dorsal; B. toes, dorsal; C. trophi, complete set, dorsal; D. SEM photograph, complete set of trophi, dorsal; E. SEM, detail, dorsal. Scale bars: A: 50 µm; B − E: 10 µm.