Hubbardipes, Molineri, Carlos, Salles, Frederico F. & Peters, Janice G., 2015

Molineri, Carlos, Salles, Frederico F. & Peters, Janice G., 2015, Phylogeny and biogeography of Asthenopodinae with a revision of Asthenopus, reinstatement of Asthenopodes, and the description of the new genera Hubbardipes and Priasthenopus (Ephemeroptera, Polymitarcyidae), ZooKeys 478, pp. 45-128 : 61-62

Taxon classification Animalia Ephemeroptera Polymitarcyidae

Hubbardipes gen. n. Figs 4A, 5, 6, 7, 20D

Asthenopus (partim) Molineri et al. 2011: 34.

Type species.

Asthenopus crenulatus Molineri, Cruz & Emmerich, 2011 (original designation).

Species included.

Hubbardipes crenulatus (Molineri, Cruz & Emmerich) comb. n.

Diagnosis.

Eight autapomorphies define the genus Hubbardipes in our cladistic analysis (Appendix 2), some of them are: 1) male foretibia very wide apically (Fig. 20D), first tarsal segment partially fused with second tarsal segment (Fig. 7B); 2) thumb (inner basal projection) of penes reduced, indistinguishable (Fig. 7A); 3) apex of penis lobe wider than base and with many marginal spines (Fig. 7A); and 4) nymphal mandibular tusk with smooth to slightly crenulated inner margin, without submedian tubercles (Figs 5B, D). Additionally, the following combination of characters is useful to distinguish Hubbardipes from other genera in Polymitarcyidae : 1) ratio length male FW/foreleg = 1.1; 2) male foreleg with large and apically widening tibia, tarsal segment 1 small and partially fused to tarsal segment 2, tarsal claws slender slightly wider at apex; 3) pronotum width/length ratio: 1.5 (male), 2.2 (female); 4) marginal intercalary veins present on the entire margin of fore and hind wings, generally shorter than distance between longitudinal veins in male, but longer and anastomosed in female; 5) in both sexes FW with 3-4 crossveins between R and M, basally to R fork; 6) basal relation of FW veins IMP-MP1 variable (IMP joined to MP1, or basally free), MP2 curved toward CuA and fused to CuA and MP1 by cross veins (forming a characteristic oblique Y); 7) median remnant of styliger plate subquadrate and small, pedestals short also subquadrate and relatively small; 8) forceps slender, ratio length/basal width = 8.5-9.0 (Fig. 7A); 9) penes relatively thin, with many spines near the apex on outer edge, slightly curved inward (Fig. 7A); 10) female abdominal sternum VIII with anteromedian paired sockets on a protruding subcircular structure; 11) eggs with relatively large polar caps (almost as wide as egg, ratio width egg/cap 1.2-1.4), each cap formed by 4-7 threads, chorion completely covered by large disk-like plates and smaller irregular plates (Figs 7 D–E); 12) nymphal head with a small median projection on the frons (arrow in Fig. 5C); 13) nymphs with long robust tusks, without inner tubercles, with 2 or 3-pointed apex (right and left mandible respectively) (Figs 5 A–B, D); 14) nymphal foretarsal claw with single row of about 14 denticles, denticles are small basally, and larger medially, 3 denticles are closer together near the apex, and the last one is much smaller (Fig. 6D); 15) nymphal dorsal apex of hind femur with ca. 20 stout spines (Fig. 6E).

Male imago. Length (mm): body, 7.0-7.8; FW, 7.5-8.6; HW, 3.1-3.7; foreleg, 6.2-6.9; cerci, 21.6. Antennae: scape slightly longer than pedicel; flagellum bristle-like. Thorax. Pronotum width/length: 1.5-2.5. Legs. Forelegs relatively long, ratio length FW/foreleg = 1.1; tarsal segment 1 fused to tarsal segment 2 (Fig. 20D), longest segment is tibia, ratio length tarsal segment 2/tibia = 0.8; tarsal segments long decreasing in length from 2>3>4>5 (Fig. 7B); claws different in size, one long the other short, not strongly widened distally (Fig. 7C). Wings. FW with 14 marginal intercalaries along hind margin, also present along entire hind margin of HW; these intercalaries present relatively numerous connections with other cross and longitudinal veins but they are not very anastomosed; 3-4 crossveins between R and M sectors basally to R fork; Rs stem length/Rs from fork to margin = 0.24; ratio MA from fork to margin/stem length = 9-12; IMP fused basally to MP1; MP2 fused to CuA. Genitalia (Fig. 7A): median remnant of styliger plate present, and with pedestals short and subquadrate with inner apical corner slightly protruding distally; forceps relatively long and slender, ratio length/basal-width = 9. Terminal filament reduced, cerci long (ratio length FW/cercus = 0.35).

Female adult. Length (mm): body, 10.2-10.8; FW, 11.1; HW, 4.3. Thorax. Pronotum width/length = 1.5-2.3. Wings with more crossveins and intercalaries than male. Abdominal sternum VIII with paired anteromedian sockets on an oval and ventrally protruding structure, sockets small, shallow and contiguous. Terminal filament reduced, shorter than tergum VIII, with few thin annuli; cercus 0.5-0.6 times the length of abdomen.

Eggs (Fig. 7 D–E). Length, 221-266 μ; width, 143-152 μ. Oval (ratio maximum length / maximum width = 1.5-1.7), with two medium sized polar caps on apices (ratio maximum with of egg/maximum width of coiled polar cap = 1.2-1.4), each cap formed by 4-7 very long filaments. Chorionic surface completely covered by plates: large disk-like structures frequently 3-partited with a fine microsculpture forming a dashed pattern, and many small (and irregular in shape) plates covering completely the spaces between the large plates.

Nymphs (Fig. 4A). Length (mm): body, 11.0-14.5; cerci, 4.5-5.5; terminal filament, 6.0. Head (Figs 5A, C) subquadrate in dorsal view, smooth (without pilose area), antennae 1.7-2.0 times length of head. Occipital region well developed, convex (Fig. 5A). Head capsule dorsally projected at bases of antennae. Frontal ridge marked only by a dense transversal row of setae; frons acutely projected medially (Fig. 5C); clypeus and labrum membranous and small, labrum densely covered with long setae on dorsum. Mandibular tusks (Figs 5A, B, D) relatively long and slender, similar in length to head capsule, dorso-ventrally flattened, left tusk apically with 3 tubercles (the median is reduced in length), right tusk with 2 tubercles; dorsal surface of tusks wide, with crenulated inner margin bearing long setae; outer margin with a small dorsal tubercle near base ( “b” in Figs 5 A–B) and densely covered with stout setae along entire margin; the small basal tubercle ( “b”) forms an additional articulation between mandible and head capsule ( “a” in Fig. 5A). Body of mandible: molae and canines present but small, margin between them sharp-edged (acutely protruding in right mandible, Fig. 5D); with basal U-row of long filtering setae in both mandibles. Thorax. Pronotum with short anterior ring (collar), 1/3 the length of posterior ring (length taken at the medio-longitudinal line), anterolateral corners projected, spine-like. Legs (Fig. 6). Leg I (Fig. 6A): femora very wide, well developed, with a double ventro-basal row of long filtering setae; tibio-tarsus (fused) with 3 rows of filtering setae (2 on anterior face and 1 on inner margin), roundly projected apically; tarsal claw long and slender with a row of marginal denticles (Fig. 6 D). Leg II (Fig. 6B): smaller, with thinner femora, with scattered long setae, mostly basally and along hind margin; tibia and tarsi with row of long setae on outer (dorsal) margin, ventrally with many stout spines on apical half, with a distal brush of thick setae; tarsal claw weaker, without denticles. Leg III (Fig. 6C): as leg II except larger and with anterior margin of femur densely covered with thick setae, femur distally with a group of acute stout spines (Fig. 6E), tibia without distal brush. Coxae I and II directed ventrally, coxae III directed laterally. Abdomen. Sternite I stronger and partially fused with metasternum. Gill I reduced in size, dark gray, double, both portions of a similar length, but the dorsal is wider (arrow in Fig. 5E). Gills II–VII well developed, ventral portion smaller than dorsal portion. Tergum X with short and blunt, poorly developed posterolateral spine. Cerci slightly shorter than terminal filament, with long setae at joinings.

Etymology.

Hubbardipes from “Hubbard” and “pes”, Latin, masculine, meaning “foot”. We dedicate the genus to Mike Hubbard, mayfly specialist, who devoted many of his works to the Polymitarcyids.

Distribution.

Amazonas subregion (Amazonas river in Colombia and Brazil).

Discussion.

Hubbardipes was recovered as sister to a larger clade containing Priasthenopus , Asthenopus , Povilla and Languidipes (see synapomorphies in Appendix 2), not related with Asthenopodes , as previously thought ( Molineri et al. 2011). Hubbardipes shows many differences in the adult stage and, more markedly in the nymph and egg here described for the first time. Male genitalia is unique in form and structure ( Molineri et al. 2011), nymphal tusks and microsculpture on disk-like structures of the egg are exceptional as well.