Halolepadella, 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 : 181-182

Genus Halolepadella gen. nov.

( Figs 24 , 25 )

Diagnosis. Lorica outline oval, compressed dorso-ventrally, closed laterally, with dorsal and ventral indentations for head and foot. Retractable head shield present. Foot with four pseudosegments; foot and toes completely retractable in trunk. Two slender, moderately long toes with acutely pointed claw. Trophi malleo-virgate. Rami reduced, triangular with lateral alulae. Fulcrum fairly short, thin, straight and less high, without distal expansion. Unci a thin plate with five slender teeth of decreasing length; head of teeth free, tiny additional linear teeth present. Manubria long, straight, head reduced; cauda strongly expanded.

Type species. Halolepadella pontica ( Althaus, 1957) nov. comb. for Lepadella pontica Althaus, 1957 ; junior synonym Lepadella psammophila Tzschaschel, 1978 .

Etymology. The prefix halo is derived from the Greek hals, salt, and refers to the saline environment the species lives in.

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 226.

Comments. The main features differentiating the species from the genus Lepadella Bory de St. Vincent, 1826, and considered here as significant enough to justify the erection of a new genus are: (1) the foot and toes which are retractable in the lorica, but not retractable in Lepadella , and (2) the trophi morphology which is malleo-virgate, instead of malleate in Lepadella . The assignment to Lepadellidae is questionable and the trophi rather conform to the Proales reinhardti species group of Proalidae , characterized by reduced rami with strong apophyses and rami teeth fused into few stout projections, long distally incurved manubria with small head, plate-shaped unci with 4−5 larger teeth with free head, and foot opening delimited by a ventral and dorsal lobe of the lorica. The species is provisionally kept in family Lepadellidae awaiting molecular analyses to evaluate its exact phylogenetic position.

Althaus (1957) erroneously interpreted the dorsal surface as being flat instead of arched, and described the toes as long and weakly incurved without mentioning the characteristic claws which, however, are clearly distinct in her microphotograph 13. The present author therefore opines that supposed differences between Lepadella pontica and L. psammophila result from inaccuracies in the original description, and the latter is here considered as subjective junior synonym. Koste (1978) synonymises L. pontica and L. psammophila with reserve, giving incorrectly priority to the second name.

Description of female. Loricate. Lorica outline oval ( Fig. 24 A, B); in cross-sectional view fairly convex and evenly arched dorsally, ventral margin flat to slightly concave; antero- dorsal sinus semi-hexangular, fairly narrow and shallow, with collar; antero-ventral sinus larger, semi-circular with small median indentation and slightly thickened border; head shield present ( Fig. 24 E), median margin rounded, slightly strengthened, lateral margins weakly concave; lorica dorsally often with two more or less pronounced shallow longitudinal ridges extending from the lateral margins of the collar of the dorsal sinus till the corners of the foot opening, or continuing on the medio-dorsal lobe. Foot opening heart-shaped ventrally, dorsally elongate, narrowing distally, ventral and dorsal proximal margins a semi-circular lobe. Lateral antennae dorsal, close set, near corners of foot opening. Foot with four pseudosegments, distal segment longest, others almost equally long. Toes ( Figs 24 D, F) slender, with long more or less cylindrical and distally tapering proximal part, and large, c. 3/4 of proximal part, lanceolate and movable distal spur; proximal part and spur with opening. Foot and toes completely retractable in trunk Four pedal glands. Two distinct pear-shaped, often dark-coloured salivary glands on mastax.

Trophi malleo-virgate ( Figs 24 G, 25). Rami strongly reduced, triangular, distal part recurved dorsally, very small; proximal part larger, with prominent distally rounded alulae and large dorsal opening; left ramus with strong basal apophysis, right ramus with at least three smaller sclerite elements, placed more apically; a fairly long cylindrical projection pointing antero-laterally ( Figs 25 B, F, G: cp), left inserted on basal apophysis, right inserted on margin of ramus; subbasifenestrae small, rounded. Two long strings of sclerite bodies connected distally to rami; proximal sclerite bodies cylindrical and rounded terminally, distal ones becoming spherical. Fulcrum slightly longer than rami, thin, straight and less high, proximal extremity only slightly higher than distal one. Unci a thin plate with 5 slender knobbed teeth of decreasing length, and 1−2 tiny, linear additional teeth; free margin of major teeth with prominence at c. 2/3 from tip; subuncus a bundle of slender, fusiform sclerite bodies; preuncinal tooth lanceolate. Manubria long, straight, head reduced, cauda strong, bird’s head in appearance: ventrally curved and pointed, dorsally with rounded expansion; dorsal chamber a very thin triangular lamella, ventral chamber small, elongate triangular with small opening; median chamber with small elongate opening.

Measurements. Body (N=10): lorica length 61‒80 µm, width 48‒60 µm, foot 18‒20 µm, toe 21‒28 µm, spur 10‒11 µm; trophi (N=5): length ~17−19 µm, ramus 2.6 µm, fulcrum 3.4 µm, uncus 5.2‒5.5 µm, manubrium 11.2‒11.4 µm.

Distribution and ecology. The species was described from sublittoral psammon at 2 m depth from Spatnite pjasatzi near Varna, Bulgaria, Black Sea ( Althaus 1957), and reported from the intertidal of a sandy beach at the island of Sylt, Germany, North Sea ( Tzschaschel 1979, 1980, 1983) and sublittoral of Elba Island, Tyrrhenian Sea ( De Smet 2007). The present observations extend its distribution to the sublittoral of the Costa Blanca and Côte d’Azur, at distances of 50 m to 8 km off shore and depth of 10−50 m; June, August, September, October, water temperature 15−23 °C.

Figures

FIGURE 24. Halolepadella pontica (Althaus). A. Female, dorsal; B. female, trunk, ventral; C. trunk, cross-sectional view; D. female, lateral view; E. detail head shield and dorsal sinus; F. toe, dorsal; G. trophi, lateral. Scale bars: A − D: 50 µm; F − G: 10 µm.

FIGURE 25. Halolepadella pontica (Althaus), SEM photographs of trophi. A. Complete set, ventral; B. complete set, lateral. C. complete set, mallei outer view, incus inner view; D. detail, oblique dorsal; E. detail, ventral; F. detail, oblique dorso-frontal left; G. detail, dorso-lateral right. cp: cylindrical projection; f: fulcrum; pt: preuncinal tooth. Scale bars: A − C, E: 10 µm; D, F, G: 1 µm.