Rhinoglena ovigera, 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 : 115-119

Rhinoglena ovigera new species

( Figures 1–9 , 13–16 )

Holotype: one amictic female, in Royal Belgian Institute for Natural Sciences ( KBIN, reg. no. I.G. 28556 RIR 103 A) ; Paratypes: one paratype at UTEP, two paratypes in UG and KBIN (RIR 103B) each.

Type locality: Album Pond, a temporary water body in a depression in Eastwood City Park lawn, located at N 31°46'59.12'', W 106°20'45.36'' (elevation 1202 m) in El Paso, El Paso Co., Texas, USA.

Additional material examined: numerous amictic females and males from the type locality. In addition amictic females, mictic females (unfertilized and fertilized) and males were collected live or re-hydrated from sediments from Anthony Gap pond, a temporary pond located at N32°00'44.66'', W106°31'20.89'' (elevation 1339 m), in Doña Ana County, New Mexico, USA . Sediments rehydrated from Peccary Tank (30°45'20''N, 105° 00'15''W; 1210 m) and Red Tank (30°43'48''N, 104° 59'18''W; 1186 m) located at UTEP’s Indio Mountains Research Station ( IMRS), Hudspeth County, Texas yielded additional material. These are both seasonally dry impoundments along River Road, south of the IMRS headquarters . A few amictic females were found in a plankton sample taken from the shallow Caballo Lake , Sierra County, New Mexico (32° 58' 40''N, 107° 16' 50'' W; 1277 m). Interestingly , females emerged from a rehydrated dust sample collected at Yellow Lake Playa , Texas (33° 48' 54''N, 102° 27' 24'' W; 1045 m; for additional details of the site see Stout 2003, 2007).

Differential diagnosis: R. ovigera n. sp. can be distinguished from its congeners by its relatively large proboscis, its well-delimited foot with inconspicuously small tubercles bearing the openings of the pedal glands, and by the large number of nuclei in its vitellarium (16 in R. ovigera , n. sp., 6–9 in Rhinoglena frontalis , 8–12 in R. fertoeensis : see Althaus (1957), 8 in R. kutikovae , unknown for R. tokioensis ). Reproducing females are oviparous (viviparous in all other Rhinoglena ) and carry one or two eggs attached antero-dorsally on the foot. Its trophi, with six particularly slender unci teeth, and recurved end of manubrium shaft, can not be confused with that of any other Rhinoglena .

Description of the female. Head with large proboscis ( Figs 1–2 ). Two dark eyes, retrocerebral organ large, fused caudally. Dorsal antenna on proboscis ( Fig. 6 ). Corona a well-developed ring of cilia, mouth in a deep ventral gap. Body fusiform, illoricate, transparent. Tegument with variable number of weak pseudoannulations. Mastax small, with associated glands. Stomach and intestine straight, anus dorsally of the foot. Excretory system with four pairs of flame cells and large bladder. Vitellarium large, with 16 nuclei. Lateral antennae in posterior third and dorsal half of body. Parthenogenetic and sexual eggs attached caudally and dorsally on the trunk. Unfertilized mictic females typically carry 2– 3 eggs, while fertilized females carry only one egg. Foot clearly separated from body, elongate conical, not pseudosegmented. Pedal glands large, almost as long as foot, elongate, opening on small tubercles. No toes.

Trophi ( Figs 8, 9 , 13–16 ) malleate. Fulcrum short, rod-shaped, slightly dilated distally in dorso-ventral plane. Rami triangular, no allulae, lateral edges notched. Inner margins with transversally oriented, well-developed and sharp processes consisting of rows of incompletely fused rami scleropili. Dorsal end of rami with weak fan-shaped projections. Unci with six large teeth each, these decreasing in size dorsally. Groups of fused remnants of uncus elements present dorsally. Heads of elements relatively slender, with a large, frontal tooth covering a minute accessory denticule ( Fig. 13 ). Manubria ( Fig. 15 ) with elongate and distally recurved shaft, and large, characteristic proximal lamella. Connection with uncus at an angle of ca. 20° with axis of manubrium shaft.

Description of the male. The male is similar to that described for Rhinoglena frontalis ( Melone 2001) . However, no trophi were evident in 10 males examined.

Dimensions (preserved material): Total length 197–201 µm, maximum body width 78 µm, height 70 µm, proboscis length 33 µm, width 34 µm, foot length 42–52 µm. Amictic egg length 73 µm, width 41.5 µm. Unfertilized mictic egg length 60 µm, width 34 µm. Diapausing embryo length 98.5 µm, width 59 µm. Male 100 µm. Fulcrum length 1.2 µm, rami width 2.4–7.2 µm, major uncus tooth length 18–20 µm, manubrium length 5 µm.

Etymology: The species name is derived by combining the words ovum (egg) and gero (carry), and refers to this species’ unique feature of carrying its parthenogenetic and sexually produced eggs. It is to be treated as an indeclinable noun.

Ecology and distribution: Rhinoglena ovigera n. sp. was found in 6 locations. The type locality is a temporary pool in Eastwood City Park (Album Park) lawn. Its elevation is 1150 m and maximum dimensions are North/South 71 m by 82.6 m, East/West with a maximum depth of 1.5 m. The pool is fed by rainwater and excess irrigation water, and receives fertiliser surface run-off during rainy periods. Samples from Album Park where collected on October 2, 1997. Water temperature was 33.7°C and the pH was 10.6.

The second location is Anthony Gap pond, a temporary pond located in Doña Ana County, New Mexico, at N 32°00'44.66'', W106°31'20.89'', elevation 1339 m . Maximum pond dimensions are N/ S 46.8 m by E/ W 23.5 m, maximum depth is approximately 0.5 m . This pond is frequented by cattle, it is surrounded by a 6.5 m wide ring of grasses ( Panicum obtusum , Echinochloa colonum (L.), Echinochloa crus-galli (L.), Eragrositis pedtinacea (Michx.), Leptochloa fascicularis (Lam.) also Verbena bracteata and Solanum rostratum ) then Chihuahuan desert scrub. Both ponds contain other organisms associated with temporary ponds, including a variety of other rotifer species, tadpole shrimp ( Triops longicaudatus (Le Conte, 1846)) , clam shrimp ( Eulimnadia texana ), fairy shrimp ( Thamnocephalus platyurus Packard, 1877 and T. mexicanus Linder, 1941 ) and tadpoles of Scaphiopus .

The third and fourth locations are former cattle tanks (Peccary Tank and Red Tank) that fill after seasonal rainfall events. They are located at UTEP’s Indio Mountains Research Station , Hudspeth Co., Texas. Both contain organisms associated with temporary ponds as noted above . Caballo Lake , the fifth location, is a shallow, reservoir on the Rio Grande in southern New Mexico, United States . It has a surface area of 46.4 sq km and mean depth of 7 m. Water levels fluctuate seasonally and with releases from the upstream Elephant Butte dam. Finally , R. ovigera n. sp. was found in a rehydrated dust sample collected at Yellow Lake playa, Lubbock Co., Texas using a passive dust collector. The dust sample had been stored for>10 years before rehydration.

Figures

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.

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 13 – 16. Rhinoglena ovigera n. sp., trophi SEM photographs. 13, 14: frontal, 15: manubrium, lateral, 16: trophi, caudal. Scale bars: 5 µm.