Allodicranophorus, De Smet, Willem H., 2015

De Smet, Willem H., 2015, Rotifera from the Mediterranean Sea, with description of ten new species, Zootaxa 4028 (2), pp. 151-196 : 179-181

Genus Allodicranophorus gen. nov.

( Figs 22 , 23 )

Diagnosis. Trophi symmetrical. Incus flat. Rami elongate; opening of subbasal chambers lateral, opening of basal chambers dorsal; rami tips blunt with minute medially directed blunt toothlet; inner margins without teeth; alulae absent. Fulcrum short, strongly expanded distally. Unci each with two equally long teeth composed of head and shaft. Manubria ramus length, with large head and rod-shaped cauda. Epipharynx two more or less trapezoid and slightly asymmetrical robust plates with large ventral opening.

Type species. Allodicranophorus bulgaricus ( Althaus, 1957) nov. comb. for Dicranophorus bulgaricus Althaus, 1957 .

Etymology. The name Allodicranophorus combines the Greek allos, meaning different, and Dicranophorus , alluding to the differences in trophi structure with the latter.

Material. Several specimens from most of the study area (see Tab. 2 species list). A female in a permanent, glycerine glass slide mount deposited in the Royal Belgian Institute of Natural Sciences ( RBINS), Brussels, Belgium, No. IG 33082, RIR 225.

Comments. The external morphology of the species is typically dicranophorid-like, but the morphology of the trophi, which is the most important character state in the establishment of genera in Dicranophoridae ( De Smet 1997) , is completely aberrant. The unique combination of characters arguing for the establishment of a new genus of Dicranophoridae are: (1) the short distally enlarged fulcrum, (2) the manubria with large head of peculiar shape, (3) the two irregularly shaped hollow epipharyngeal plates, (4) the subbasifenestrae opening laterally, (5) the absence of distinct and medially projecting apical rami teeth, resulting in a wedge-shaped, distally open median rami opening.

Description of female. Body fusiform ( Fig. 22 ), sub-cylindrical, in lateral view weakly arched dorsally, almost straight ventrally. Head, trunk and foot distinctly offset by transversal folds; trunk with two additional transversal and two latero-dorsal folds. Rostrum small, rounded. Corona small, oblique frontal. Dorsal antenna near middle of head. Tail prominent, keeled, projecting beyond basal 1/3 of foot pseudosegment. Foot fairly long, conical-cylindrical, a single pseudosegment. Toes ( Fig. 22 C, D) fairly short, slender, almost cylindrical with short acute end; distal end in lateral view slightly decurving ventrally. Eyespots absent. Brain saccate, large. Retrocerebral organ present; cerebral sac large, hemispherical, posteriorly on brain; subcerebral glands present. Proventriculus, stomach and intestine very weakly demarcated. Gastric glands globular, weakly lobate, stalked, ventral. Pedal glands weakly stalked, foot length. Vitellarium with twelve nuclei. Oviparous.

Trophi ( Fig. 22 E, 23) modified forcipate, symmetrical. Incus flat. Rami elongate, alulae absent; basal chambers larger than subbasal ones, proximal margin broadly rounded; subbasal chambers somewhat projecting beyond basal ones caudally, proximal margin more or less angular laterally; ending distally in shallow blunt projection whereupon unci rest; subbasifenestrae lateral, small, rounded-triangular, basifenestrae dorsal, large, ellipsoid; median rami opening wedge-shaped, distally open; inner margins of rami without teeth, distinct apical rami teeth absent, basal chambers apically with very short blunt, medially directed knob. Fulcrum short, in dorsal/ ventral view narrow proximally, strongly expanded distally, in lateral view slightly narrowing towards expanded distal end. Unci each with two equally long teeth composed of head and shaft; head dorsal tooth c. ¼ tooth length, head of ventral tooth c. ½ tooth length. Manubria ramus length, with large head and rod-shaped cauda; outer side with large opening of median (?) chamber, other chambers reduced. Epipharynx ( Figs 22 F, 23D, E) two more or less trapezoid and slightly asymmetrical robust plates, with marginal extensions and large ventral opening.

Measurements. Body (N=5): total length 190‒260 µm, toe 28‒32 µm; trophi (N=5) length 14.3−16.0 µm, incus 13.3‒14.7 µm, ramus 9.6‒10.9 µm, fulcrum 3.1‒4.9 µm, uncus 8.7‒11.6 µm, manubrium 11.0‒14.6 µm, epipharynx 7.3‒9.0 × 5.3‒6.4 µm; amictic egg 63‒88 × 41‒53 µm.

Distribution and ecology. Allodicranophorus bulgaricus was to date only reported from the sublittoral (mesopsammon from 0.5 and 1 m) of its type locality, Varna, Sosopol, Bulgaria, Black Sea ( Althaus 1957) and the sublittoral of Elba Island ( De Smet 2007). In the present study it proved a rather common species of sublittoral psammon from the Costa Blanca, Golfe du Lion, Côte d’Azur, and Elba Island. It was found from 50 m to 5 km off shore, depth 15−50 m, June, August, September, October, water temperature 16−25 °C.

Figures

FIGURE 22. Allodicranophorus bulgaricus (Althaus). A. Female, dorsal; B. female, lateral; C. toe, dorsal; D. toe, lateral; E. trophi, dorsal; F. epipharynx, ventral. Scale bars: A, B: 50 µm; C − F: 10 µm.

FIGURE 23. Allodicranophorus bulgaricus (Althaus), SEM photographs of trophi. A. Complete set, dorsal; B. complete set, ventral; C. complete set, dorso-lateral; D, E. epipharyngeal elements, ventral; F. complete set, dorso-frontal. Scale bars: 10 µm.