Leptohyphes kukenan, Molineri & Derka, 2020

Molineri, Carlos & Derka, Tomáš, 2020, A rare new species of Leptohyphes Eaton (Ephemeroptera: Leptohyphidae) from the Lost World, Zootaxa 4786 (2), pp. 261-268 : 262-267

Leptohyphes kukenan sp. nov.

( Figs. 1–20 )

Type material: Holotype female mature nymph ( MLBV) from VENEZUELA, Est. Bolívar, Kukenán river below Kukenán Tepui , N 05.15601º, W 60.82507º, 1631 m a.s.l., 25/xi/2015, T. Derka col. Paratypes: 6 female and 1 male nymphs, same data as holotype (1 female in MLBV, rest in IBN) ; 1 female nymph ( IBN, slide IBN833 CM) from VENEZUELA, Est. Bolívar, small creek in Kukenán Tepui base camp, N 05.16636º, W 60.82384º, 1875 m a.s.l., 25/xi/2015, T. Derka col.

Diagnosis: 1) male compound eyes enlarged and divided ( Figs. 3–4 ); 2) tubercles on body absent ( Figs. 1, 3 ); 3) forefemur length/maximum width 2.1 ( Fig. 10 ); 4) fore and hind margin of middle and hind femora with spines on strong elevated sockets ( Fig. 12 ); 5) small pale spots (”pale pits”) cover the surface of head, thorax and femora (dorsally) and submentum (ventrally); 6) dorsum of hind femora with a mediolongitudinal ridge and a row of 16–20 minute spines ( Fig. 12 ); 7) tarsal claws with 4–5 marginal denticles and 2 subapical denticles ( Fig. 11 ); 8) pronotum with large rounded lateral projection ( Figs. 1–2 ); 9) hind wing pads absent in female; 10) gill formula 8/7/7/4/1, gill V without ventral extension on dorsal lamella ( Figs. 13–20 ).

Mature nymph: Length of female (mm) (n=3): body, 8.9–9.1; caudal filaments, 7.0–8.0. Length of male (mm) (n=1): body, 8.5; caudal filaments (broken at base). General coloration whitish to yellowish light brown, with small pale spots on head, thorax and legs ( Figs. 1, 3 ). Head: shaded with black widely except anteriorly to each ocellus, on occiput forming a net-like pattern ( Fig. 2, 4 ); and with small pale spots. Antennae yellowish white. Compound eyes of female rounded and small as usual, male eyes enlarged and divided in two portions ( Figs. 3–4 ), line between both parts hardly visible. Mouthparts ( Figs. 5–9 ): labrum with single long setae dorsally, some of them forming a transverse submedian row ( Fig. 5 ); anteromedian emargination shallow, with a row of bifid micro-setae along ventral edge of fore margin ( Fig. 5 , detail); hypopharynx with rounded small superlinguae and lingua; maxilla with well-developed 3-segmented palpus ( Fig. 8 ); mandibles relatively stout ( Figs. 6–7 ); labium with large and elongated submentum, completely covered with pale spots ventrally ( Fig. 9 ). Thorax. Nota brownish shaded with black widely except median area paler, wingbuds grayish on costal margin; sterna paler. Pronotum with rounded lateral projection ( Figs. 1, 3 ). Mesonotum with subtriangular blunt anterolateral projection ( Figs. 1, 3 ). Hind wingpad absent in female. Legs yellowish slightly shaded gray dorsally except mediolongitudinal pale line on middle of femora, dorsum of all femora completely covered by small pale spots. Ratio length fore femur/hind femur = 0.55. Foreleg ( Fig. 10 ): ratio femur length/maximum width 2.1; transversal row at 0.6 from base to apex; fore margin with small spines, hind margin with fringed rounded spines ( Fig. 10 , detail) distally to transversal row, all spines mounted on elevated sockets. Foretibia slightly longer than femur, with tiny spines along inner margin and a longitudinal ridge along outer margin. Tarsus 1/2 the length of tibia with row of setae in inner margin; tarsal claw with five marginal denticles, and 2 subapical submarginal denticles ( Fig. 11 ). Middle and hind legs ( Fig. 12 ) similar in form and setation to each other (middle leg smaller). Ratio hind femur length/maximum width 2.0; fore margin with row of tiny rounded spines mounted on large sockets (on basal half this row is double), hind margin with 38–40 rounded small spines on very elevated sockets (see detail in Fig. 12 ), dorsal surface with longitudinal ridge covered by 18–20 small spines. Tibia slightly longer than femur, with dorsal ridge, inner and outer margins with spines, those on hind margin stronger and mounted on elevated sockets. Tarsus 0.25 the length of tibia, inner margin with setae, tarsal claw as in foreleg. Abdomen ( Figs. 2, 3 , 13 ) yellowish diffusely shaded with gray on terga as in Figure 2 ; terga glabrous, except rounded small paired spines submedially on terga VI–IX ( Fig. 13 ); segments III–VI forming lateral flanges; small posterolateral projections present on VII–IX. Gills ( Figs. 14–20 ): operculate gill light brownish-gray with whitish margins, ventrally with membranous and relatively short ”basal spine” and two fringed lamellae ( Figs. 14–16 ); other gills grayish to hyaline, gills III–IV also with fringed lamellae ( Figs. 17–18 ). Gill formula 8/7/7/4/1. Caudal filaments with whorl of short setae at joinings, with darker annuli at base on females (broken off and lost in male).

Adults: unknown.

Etymology: The species is named after Kukenán tepui, a table mountain in southeastern Venezuela, on which talus it was found.

Distribution. Only known from Kukenán tepui ( Figs. 21–22 ), Pantepui region, Venezuela.

Discussion: Leptohyphes kukenan sp. nov. can be distinguished from all its congeners by the list of characters given in the diagnosis. It is similar to L. populus Allen (1973) because of the uncommon division of male eyes in a dorsal and a ventral portion. Other characters common to both species may also appear in other species of the genus, for example the large elevated sockets on femoral spines. The new species can be separated from L. populus because the spines on femora and tibia of the new species are relatively smaller and fewer; the form of the submentum (longer in the new species), and the paired subapical denticles on tarsal claws (absent in L. populus ). Gills are not described for L. populus , but in the new species, although preserving the general shape and aspect of the genus, they are different in their structure from other Leptohyphes : smaller ventral lobes arise consecutively from larger ones, so they are imbricated. This pattern (as well as the divided eyes) is plesiomorphic in Leptohyphidae , being present only in Amanahyphes Salles & Molineri (2006) , and also in related families Melanemerellidae and Coryphoridae ( Molineri 2006) . Another character that can be interpreted as plesiomorphic in the new species is the presence of paired subapical denticles on the tarsal claws, which is widespread in the family but in Leptohyphes it is almost always single and asymmetrical ( Molineri 2003, 2006). Small pale spots have been described in other species of Leptohyphes : L. liniti Wang et al. (1998) , L. petersi Allen (1967) , L. murdochi Allen (1967) , L. alleni Brusca (1971) , and L. andina Molineri et al. (2016) , but their function is unknown ( Baumgardner & McCafferty 2010). We have observed in other species of the genus some intraspecific variation on the number and extent of such pale pits.

Ecological notes: Both sites were located on mountain watercourses with relatively cool water ( Figs. 21–22 ). The type locality is situated on a cascading, 5–6 m wide river with bottom formed by boulders and stones, the water temperature oscillated around 17 ºC. The surrounding area was a secondary savanna, trees were preserved on the banks. The stream originates on the plateau of Kukenán tepui at an altitude about 2,600 m a.s.l. The second site was a stream 0.4 m wide, with gravel bottom with many tree roots and debris. The water temperature 15.4 ºC indicates that the sampling site was situated near the spring. The surrounding area was a dense young forest regenerating after a fire.

Figures

FIGURES 1–4. Leptohyphes kukenan sp. nov. 1, female mature nymph, habitus; 2, female head, dorsal view; 3, male nearly mature nymph, habitus; 4, male head, dorsal view.

FIGURES 5–9. Leptohyphes kukenan sp. nov., mouthparts. 5, labrum dorsal view (setae on right side omitted), with detail of bifid microsetae on fore margin; 6, left mandible with detail of prostheca, dorsal view;; 7, right mandible with detail of prostheca, dorsal view; 8, maxilla, ventral view of distal part; 9, labium, ventral view with detail of microsetae and pits.

FIGURES 10–20. Leptohyphes kukenan sp. nov. 10, foreleg, dorsal view with detail of spine; 11, fore tarsal claw; 12, hind leg with detail of spine, dorsal view; 13, schematic representation of abdominal terga setation; 14–16, operculate gill in dorsal, lateral and ventral view; 17–20, abdominal gills III–VI, ventral view.

FIGURES 21–22. 21, Landscape of Kukenán tepui foothills where sampling localities are situated; 22, type locality. Photographs by Daniel Grul’a.