Hyrtanella pascalae, Jacobus, Luke M. & Sartori, Michel, 2004

Jacobus, Luke M. & Sartori, Michel, 2004, Review of the genus Hyrtanella (Ephemeroptera: Ephemerellidae), Zootaxa 785, pp. 1-12 : 3-10

Hyrtanella pascalae , new species

Figs. 1–8 , 10–19

Descriptions. Larva ( Figs. 1–8 , 10–14 )—Length: body 4.0– 4.4 mm; caudal filaments 1.4–2.1 mm. Body color light brown.

Head: vertex with two pairs of short suboccipital spines. No ocellar bumps. Inner margin of antennal base with short projections. Frontal shelf not expanded. Genae slightly produced. Long hairlike setae present along anterior margin of frontal shelf and sparsely present below compound eye. Clypeus with anterior row of long hairlike setae. Labrum ( Fig. 1 ) width nearly 2x length, with shallow, very broad notch anteriorly; dorsal face with scattered long hairlike setae on lateral margin and with several rows of brushlike setae anteriorly ( Fig. 2 ); ventral face with simple or fimbriate setae on lateral margins and dense transverse row of 7–9 long, stout setae ( Fig. 3 ). Hypopharynx with superlinguae size nearly subequal to linguae size ( Fig. 4 ); lingua with row of short setae on anterior margin; superlingua with row of long, thin setae on margin, with setae decreasing in length anteriorly. Mandibles ( Figs. 5, 6 ) with lateral setae relatively long. Maxilla ( Fig. 7 ) with palp reduced; apex of galea relatively sharp with 3 incisors, and with no setae distally on outer margin; lacinia with 2 stout spinous processes (dentisetae) and with double row of 4 stout setae. Labium ( Fig. 8 ) reduced; palp segments short; terminal segment length about 3 times basal width.

Thorax: Prothorax width subequal to head width, with no anterolateral projections and no dorsal spines; anterior margin upturned and not receded; ventral spines absent. Mesonotum with forewingpads base darkly pigmented and no spine between forewingpads. Coxae with slight dorsolateral projections; projections with hairlike setae. Legs with marginal long hairlike setae; femora generally flattened. Forefemur ( Fig. 10 ) with incomplete narrow transverse band of dorsally projecting bristlelike setae; dorsal edge with single stout bristlelike seta medially; ventral edge with few chalazae medially; anterior face with no dorsal projections; foretibial projection short ( Fig. 11 ). Claws bent, with short subdistal setae; palisade of elongate denticles on inner distolateral margin and few denticles present proximally ( Fig. 12 ). Dorsal edge of midfemur ( Fig. 13 ) with single stout bristlelike seta, but seta situated more distally than similar seta of forefemora; ventral edge with numerous chalazae, with proximal chalazae bearing long, bristlelike setae and distal chalazae with blunt, stout setae. Dorsal edge of hindfemur ( Fig. 14 ) with 6–8 chalazae bearing long, bristlelike setae; ventral edge with only blunt and stout chalazae on distal half.

Abdomen: Gills similar to those of H. christineae (see Kluge 2004: Figs. 94a–e). Gills 3 brown with no apparent distal pigmentation; gills 4–7 translucent. Gills 3 operculate, with medial transverse weak band; gills 4 operculate. Dorsal lamellae of gills 4–6 with strong projection on inner proximal margin; projection folded dorsally; gills with slight projection on outer proximal margin. Dorsal lamellae truncate apically. Gills 3–6 ventral lamellae bifid, with dorsal and ventral lobules; lobules tips acute. Gills 7 narrow; point of attachment medial. Terga 1 and 2 with long hairlike setae on posterior margins. Terga 3–7 or 4–7 with pair of blunt oblique ridges and with short, blunt, paired spines on posterior margins; spines and ridges form inner portion of prominent gill chamber. Tergum 8 sculpted posterolaterally, and with single, short, blunt, median spine and blunt posterolateral projections. Tergum 9 with single, short, blunt, median spine and weak oblique ridges. Segments 6–8 with lateral margins strongly upturned, forming outer portion of prominent gill chamber. Abdominal sterna flattened, with no maculation and no long setae. Caudal filaments pale, with dense whorls of long hairlike setae.

Male Subimago ( Figs. 15–18 )—Length: body (excluding caudal filaments) 5.5 mm; forewing 5.0 mm; hindwing 0.9 mm.

Head: Vertex yellow­brown; antennae with scape and pedicel light yellow, flagellar segments light brown. Ocelli light yellow; median ocellus tinted with grey on posterior margin and lateral ocelli tinted with grey on inner magin. Compound eye with upper part yellow, lower part black.

Thorax: Prothorax brown with purple band on proximal margin. Mesoscutellum yellow­brown with light yellow maculae. Mesosterna light yellow with purple narrow longitudinal band medially. Legs yellow­brown, with tarsi pale; each leg with claws dissimilar (one blunt and paddlelike and one hooklike). Forewing ( Figs. 15, 16 ) brown, with dark brown basally in subcostal field; few crossveins, mainly in radial and median fields; posterior margin with some irregular intercalaries; one intercalary between IMP and MP2, and one between MP2 and CuA; 3 intercalaries between CuA and CuP. Axillary cords (plumidia) long. Hindwing ( Figs. 15, 17 ) brown with dark brown basally in subcostal and radial fields; crossveins absent; costa with well­developed process at middle; tip of process angled away from wing base.

Abdomen: Terga 1–3 and 8–10 yellow; terga 4–7 light brown; each with thin black band on anterior and posterior margins. Tergum 3 with pair of brown spots. Sterna brown, but with sterna 8 and 9 yellow. Gill socket vestiges on segments 3–7, decreasing in size posteriorly. Genitalia ( Fig. 18 ) with posterior margin of subgenital plate convex; forceps three­segmented; forceps segment 3 elongate. Penes fused and compact, with small median incision; outer, lateral margins subparallel distally and concave proximally. Caudal filaments broken and missing.

Female Subimago— Unknown.

Adults— Unknown.

Egg ( Fig. 19 )—shape ovoid; one polar cap; chorion generally smooth, without reticulations; micropyles in equatorial position; large KCTs between equator and poles.

Diagnosis. Larvae of H. pascalae differ from those of H. christineae by being much smaller and by having bluntly expanded genae, no basal projections on the mandibles, the third segment of the labial palp ( Fig. 8 ) more slender than that of H. christineae ( Fig. 9 ), no dorsal projections on the upper surface of the forefemur, and no ventral projections on the thoracic and abdominal sterna.

Male subimagos ( Fig. 15 ) of H. pascalae differ from Hyrtanella female adults beyond the usual sexual differences by having an abdomen that is not constricted, one small intercalary between MP2 and CuA ( Fig. 16 ), and the costal process of the hindwing with the tip angled away from the body ( Fig. 17 ).

Male adults very likely have genital forceps segment 3 much longer than wide and penes lobes that are compact and nearly fused. This probable diagnosis is based on our examination of the male subimago.

Etymology. This species is named in honor of Dr. Pascale Derleth ( Swiss Federal Institute of Technology, Lausanne), who collected much of the type material.

Larval variability. General color patterns vary from the typical light brown to dark brown. This variation appears to be between populations, and it is not dependent on the instar number. The number, relative development, and placement of chalazae on the ventral edge of the femora varies slightly between populations.

Ecology. Hyrtanella pascalae was collected commonly in the study areas of Indonesia, and sometimes it was locally abundant. It was sampled from stream riffles and runs with different substrate compositions, including silt, gravel, cobble, and boulders. Flow velocity at these sites ranged from 0.2–2.0 m/s; water depth was between 0.3–3.0 m; and at least some sites had a moderate silt load. Water temperature during the sampling period varied from 24.1°–26.4°C (Derleth 2003; Danuta Zaranko, pers. comm.). Multivariate analyses have shown that H. pascalae is more abundant in larger streams, and its distribution is positively correlated with the opening of the canopy, stream width, and water temperature (Derleth 2003). With respect to the influence of logging activities in the area, H. pascalae is characterised by population density increasing during, and until six months after, logging. However, the population density decreases one to three years after logging activity (Derleth 2003).

All localities where H. pascalae has been collected are situated between 100 and 400 meters above sea level, whereas collecting locales of H. christineae in Sabah are located between 900 and 1600 m. These species may represent altitudinal vicariants.

Material examined. Holotype: Island of Borneo—INDONESIA, East Kalimantan: Malinau Basin— Seturan River tributary: Temalat (Sungai Guang) trib., Loc. Seturan (2000­petak 43), 2°59'29" N, 116°33'29" E, 18/VI/2000, P Derleth, J­L Gattolliat, (B0811), 1 female larva [ MZL].

Paratypes: same locale and date, 11 larvae [ MZL]; same locale, but 16/VIII/2000, P Derleth, R Schlaepfer, (B0812), two larvae [ MZL]; same locale, but 16/IV/2001, P Derleth, (B0813) one larva [ MZL]; other Seturan River tributaries: Tamalang trib., Loc. Seturan (2001­petak 57), 2°59'22"N, 116°30'29" E, 18/VII/2000, P Derleth, F Béboux, (B0511), two larvae [ MZL]; Tamalang trib., Loc. Seturan (2001­petak 57), 2°59'22"N, 116°30'46" E, 10/IV/2001, P Derleth, (B0513), 16 larvae [ MZL]; Tamalang trib., Loc. Seturan (2001­petak 57), 2°59'50"N, 116°30'29" E, 19/VII/2000, P Derleth, F Béboux, (B0521), 14 larvae [ MZL]; same locale, but 5/VIII/2000, P Derleth, (B0521PLS), one male subimago [ MZL]; Bengahau trib., Loc. Seturan (2001­petak 57), 2°59'22"N, 116°30'46"E, 8/VIII/2000, P Derleth, (B0531), five larvae [ MZL]; same locale, but 11/IV/ 2001, P Derleth, B Feldmeyer, (B0533), seven larvae [ MZL]; Bengahau trib., Loc. Seturan (2001­petak 57), 2°59'22"N, 116°30'46" E, 19/VIII/2000, P Derleth, R Schlaepfer (B0541), ten larvae [ BMNH, FAMU, MZL]; Kipah trib., Loc. Seturan (1998­petak 28), 3°01'48" N, 116°29'48" E, 29/III/2001, P Derleth, (B0913), one larva [ MZL]; Seturan riv., Loc. Seturan (unlogged), 3°00'05" N, 116°30'48" E, 28/III/2001, P Derleth, B Feldmeyer, (B1313), 50 larvae [ MZL]; Riv. Seturan, Loc. Seturan, Aff. cours principal, 3°00’05”N, 116°30’48”E, 28/III/2001, P Derleth, B Feldmeyer, three larvae [ PERC]; unnamed trib., Loc. Seturan (unlogged), 2°59'49" N, 116°31'22" E, 17/IV/2001, P Derleth, M Sartori, B Feldmeyer, (B1513), one larva [ MZL]. Rian River tributaries: Belakau trib., Loc. Langap Sud (1997­petak 6), 3°04'04" N, 116°30'26" E, Alt. 100 m, 20/IV/2001, P Derleth, M Sartori, (B0113), one larva [ MZL]; Ngayo trib., Loc. Langap Sud (1995), 3°01'48" N, 116°29'48" E, Alt. 160 m, 14/VI/2000, (B0410), seven larvae [ LIPI, MZL]; same locale, but 8/VII/2000, P Derleth, (B0411), two larvae [ MZL]; Ngayo trib., Loc. Langap Sud (1995), 3°04'56" N, 116°30'58" E, Alt. 160 m, 13/VII/2000, P Derleth, (B0431), four larvae [ MZL].

Other Material (not paratypes):

Island of Borneo—INDONESIA, East Kalimantan: Kelinjau R., about 10km upstream of Atan R., at logging staging area above rapids, 0°45’N, 116°15’E, 23/I/1997, one larva [ PERC]. Island of Borneo—MALAYSIA (east), Sabah: Liwagu R at bridge, Ranau, 335m elev., 11–16/VIII/1972, GF&CG Edmunds, WL&JG Peters, four larvae [ PERC]; Mantukungan R, S of Poring Hot Springs Station, 365m elev., 12/VIII/1972, WL&JG Peters, five larvae [ PERC]; Sungai Moyog (26°C), 3 mi E of Penampung, 27–29/ IX/1978, GF& CH Edmunds, seven larvae [ PERC]; Sungai Moyog at tributary 8 mi E of Penampung, 2/X/1978, GF& CH Edmunds, one larva (mouthparts on slide) [ PERC]; Penompange River, Crocher National Park, 8/VIII/2003, M Whiting team, seven larvae [ MZL].

Figures

FIGURES 1 – 9. Figs 1 – 8. Hyrtanella pascalae, n. sp., larvae: 1. Labrum (left, dorsal view; right, ventral view). 2. Detail of brushlike setae on dorsal surface of labrum. 3. Detail of transverse row of setae on ventral surface of labrum. 4. Hypopharynx (right half). 5. Right mandible. 6. Left mandible. 7. Maxilla. 8. Labium. Fig. 9. Hyrtanella christineae, larva: Detail of labial palp.

FIGURES 10 – 14. Hyrtanella pascalae, n. sp., larvae: Fig 10. Foreleg. Fig. 11. Detail of apex of tibia. Fig. 12. Detail of foreclaw. Fig. 13. Middle femur. Fig. 14. Hind femur.

FIGURES 15 – 18. Hyrtanella pascalae, n. sp., male subimago: 15 Photograph of specimen in alcohol. 16. Forewing. 17. Hindwing. 18. Genitalia, ventral view.

FIGURES 19 – 20. Eggs (scale bars = 10 m): 19. Hyrtanella pascalae, n. sp. 20. Undetermined Ephemerellinae, West Malaysia.