Rhinoglena texana, Segers, Hendrik & Walsh, Elizabeth J., 2017

Segers, Hendrik & Walsh, Elizabeth J., 2017, The genus Rhinoglena (Rotifera, Monogononta, Ephiphanidae) in North America, with the description of two new species, Zootaxa 4290 (1), pp. 113-122 : 119-120

Rhinoglena texana new species

( Figures 10–12 , 17–20 )

Holotype: one amictic female, in Royal Belgian Institute of Natural Sciences (KBIN, reg. no. IG 2 8556 RIR 106); Paratypes: one male allotype (RIR 107) and two slides containing female paratypes in KBIN (RIR 108, 109), further paratypes in UG and UTEP.

Type locality: ephemeral pond in Hueco Tanks State Park and Historic Site, El Paso, Co., Texas, USA. 31° 55' 09.26'' N, 106° 02' 28.02'' W, elevation 1379 m.

Additional material examined: numerous amictic females from the type locality; specimens of R. frontalis used in the present comparison are from Feather Lake , El Paso Co., Texas ( USA).

Differential diagnosis: Rhinoglena texana n. sp. can easily be confused with R. frontalis . The two differ by the number of nuclei in the vitellarium (10–14 in R. texana n. sp., 6–9 in R. frontalis ), and by the shape of their manubria (compare Figs 18 and 22 , see also Fig. 5 in De Smet & Gibson, 2008): the anterior lamella is smoothly rounded in R. texana n. sp., this margin is acute in R. frontalis . In addition, the openings to the proximal rami chambers are asymmetrical in R. texana n. sp. ( Fig. 17 ), symmetrical in R. frontalis ( Fig. 21 ), whereas the openings of the distal rami chambers are relatively smaller in R. texana n. sp. than in R. frontalis (compare Figs 20 and 24 ).

Description (of parthenogenetic female, mictic female unknown). Head with ventrally ciliated proboscis ( Fig. 10 ), bearing the dorsal antenna. Two red eyes, retrocerebral organ large, fused caudally. Corona a well-developed ring of cilia, mouth in a deep ventral gap. Body conical, illoricate, transparent. Tegument with variable number of weak pseudoannulations. Mastax small, with associated salivary glands. Stomach and intestine displaced to right, anus dorsally of the foot. Excretory system with distinct bladder. Vitellarium large, elongate, with 10–14 nuclei. Lateral antennae in posterior third, and dorsal half of body. Viviparous, developing embryos (up to two observed) can be seen inside body. Posterior part of body set off by transverse fold. Foot short, clearly separated from body, dorsally partly covered by a broad, rounded lobe. Foot nearly twice as long as the toes, pedal glands large, extending inside the posterior part of the body. Two well-developed and separate, elongate conical toes. Male similar to female, only slightly smaller.

Trophi malleate. Fulcrum short, rod-shaped, with basal plate. Rami triangular, no allulae, lateral margins notched. Inner margins with transversally oriented processi consisting of rows of relatively blunt, and almost completely fused rami scleropili. Openings of the proximal rami chambers asymmetrical ( Fig. 17 ), openings of the distal rami chambers relatively small ( Fig. 20 ). Dorsal end of rami rounded, denticulate. Unci with six large teeth each, these decreasing in size to dorsally. Additional groups of reduced unci teeth present dorsally. Head of each element robust ( Fig. 19 ). Manubria ( Fig. 18 ) with elongate and straight shaft, and large proximal and distal lamella; anterior margin of proximal lamella evenly rounded. Connection with uncus at an angle of ca. 35° with axis of manubrium shaft.

Dimensions (preserved material, of male between brackets): Total length 245–273 (222) µm, maximum body width 106 (75) µm, height 113 (68) µm, proboscis length 34–41 (25) µm, width 31–40 µm, foot length 21–30 (27) µm, toe length 8–11 (10) µm. Fulcrum length 7–8 (5) µm, rami width 22–23 (12) µm, major uncus tooth length 14– 16 (8) µm, manubrium length 18–20 (14) µm.

Etymology: The species name is derived from the name of the state where it occurs. It is to be treated as an indeclinable noun.

Ecology and distribution: Rhinoglena texana n. sp. was found in two ponds located at Hueco Tanks State Historic Site, El Paso, Co., TX. One is a shallow ephemeral pond (length:width:depth 42.1:15: 0.27 m) located near East Mountain behind a retention dam. The pond fills only after heavy seasonal rains. Rhinoglena were found on 22 February 1998, water temperature was 22.4 °C, pH 8.3. The second pond is larger, on the other side of the dam; this pond was sampled for over 17 years and the Rhinoglena was found there only on two occasions in 1998: February 2 (water temperature 14.4 °C, pH 8.9) and March 16 (water temp. 15.4 °C, pH 7.7). The species has not been found in the type locality or adjacent ponds on any other occasion.

Figures

FIGURES 6 – 12. Rhinoglena spp., amictic female. 6 – 9: R. ovigera n. sp. 6: ventral, 7: lateral, 8: trophi, frontal, 9: trophi, dorsal. 10 – 12: R. texana n. sp. 10: ventral, 11: trophi, frontal, 12: trophi, dorsal (trophi: manubria omitted)

FIGURES 17 – 20. Rhinoglena texana n. sp., trophi SEM photographs. 17: frontal, 18: manubrium, lateral, 19: right uncus and ramus, detail, 20: trophi, caudal. Scale bars: 10 µm (Figs 17, 20), 1 µm (Figs 18, 19).

FIGURES 21 – 24. Rhinoglena frontalis Ehrenberg, trophi SEM photographs. 21: frontal, 22: manubrium, lateral, 23: right uncus and ramus, detail, 24: trophi, caudal. Scale bars: 10 µm (Figs 21, 24), 1 µm (Figs 22, 23).

FIGURES 1 – 5. Rhinoglena ovigera n. sp. photomicrographs. 1: amictic female ventral, 2: lateral, 3, 4: males, 5: slightly contracted mictic female and resting egg, lateral.