Eatonigenia zhangi Sun, Luo & Zhou, 2016, sp. nov.
Creators: name: Sun, Jun-Zhi
name: Luo, Juan-Yan
name: Zhou, Chang-Fa
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Ephemeridae
Eatonigenia
Eatonigenia zhangi

description: Eatonigenia zhangi sp. nov.
Eatonigenia chaperi Zhang, 1988: 68 (male, female, subimago) (nec. Hexagenia chaperi Navás, 1935: 99, misidentification); Zhang et al., 1995: 74; She et al., 1995: 80; You and Gui, 1995: 91.
Diagnosis. The new species can be distinguished from the other species of the genus based on the following characteristics: in males, larger and more colorful body, slightly projected apex of penis and three tips of gonopores; in nymphs, larger and paler body, smaller fore-claw and asymmetrical labrum.
Nymph (in alcohol, not mature, Figs. 1, 3 A): Body length 20.0 mm, cerci 4.0–6.0 mm, terminal filament 3.0 mm. Body ivory pale, with golden setae on most parts of body.
Head (Figs. 1, 3 A, 5A): Length of frontal processes slightly shorter than width, its anterior margin smoothly convex and narrower than posterior margin; all free margins with dense golden setae; base of antenna projected forwards with relatively long setae on supra-antennal surface; scape of antenna slightly longer than pedicel, the latter with setae on basal half; flagella with sparse setae; length of antenna subequal to head width; compound eyes dark, surrounded with a row of setae; upper half of ocelli pale, lower half dark; area between 3 ocelli slightly pigmented grey; vertex pale (Fig. 5 A).
Mouthparts: Labrum generally heart-shaped, asymmetrical; free margins and dorsal surface with long anteriorly directed setae (Figs. 2 A, 5F), ventral surface with short mesally directed setae but no long setae (Fig. 5 G). Mandibles asymmetrical, tusk of left mandible shorter than right in dorsal view; triangular mandibular tusks densely setaceous dorsally and laterally with setae progressively shorter toward apex; outer incisor of left mandible much stronger than inner incisor; apex of both incisors of left mandible divided into 3 denticles; prostheca of left mandible modified into a thick spine, with 2 denticles near apex and a small setal tuft next to prostheca (Fig. 2 B); outer incisor of right mandible slightly stronger than inner incisor, apex of both incisors divided into 3 denticles; prostheca represented as 2 spines, one near inner incisor, other close to mola, an additional small setal tuft between them (Fig. 2 C). Maxillae slender, outer margin with relatively long hair distally, inner margin with long spines and hair, apex of galea-lacinia extended to form 2 large spines (canine and dentiseta) (Fig. 2 D), apex of distal spine (canine) bifurcate (Fig. 2 E); maxillary palp 3-segmented although segmentation between second and third segment indistinct; basal and second segment subequal in length, apical segment slightly longer; basal segment with only 2 long setae on outer margin near apex but other segments with long setae over entire surface, those on inner margin longer; cardo with small spine-like setae (Figs.2 D, 5H). Hypopharynx with lingua slightly emarginated to straight on free margin; surface of lingua and superlinguae with setae, setae more abundant on dorsoapical surface and free margin (Fig. 2 F). Labium with dense setae on paraglossae forming brush-like setal tuft; labial palp 2-segmented, apical segment ca. 2× length of basal segment, basal segment with a thumb-like protuberance, apical segment with fan of long setae and dense spines on surface near apex (Fig. 2 G).
Thorax: totally pale to pale grey; pronotum slightly produced laterally, forming a lobe-like structure on anterolateral corners with additional hooked projection and cluster of golden setae, lateral margins with golden setae (Figs. 3 A, 3I, 5A). Length ratio of femur, tibia and tarsus of foreleg 7: 5: 3.6, ratio of midleg 2: 2: 1, hindleg 9.2: 8: 3, midleg shorter than other legs; ventral margin of coxa and trochanter of foreleg with setae, those on trochanter longer and more abundant; forefemur rounded, dorsal surface with 3 longitudinal rows of setae (one median row and rows near margins); foretibia greatly expanded with curved, pointed apex and long setae on margins, sparse and short setae on surfaces (Figs. 3 B, 5C); foretarsus with setae on dorsal surface, apex with cleft, vestigial claw recessed in cleft (Figs. 3 C, 5B); femur and tibia of midleg expanded slightly, tarsi without apical cleft but with slender claw, setal pattern similar to that of foreleg (Figs. 3 D, 5D); all segments of hindleg longer than midleg, coxa with setae on margins and surface, trochanter with very sparse short setae, other segments with longer, and denser setae (Figs. 3 E, 5E); apex of tibia expanded to form large curved projection, its length subequal to tarsus; claw similar to that of midleg but slightly longer and stronger (Fig. 3 F).
Abdomen: ivory or pale, with golden hair on lateral margins of terga; gills I forked deeply to one third distance from base (Figs. 3 G, 5I); gills II–VII similar in shape, each of them divided into two lamellae, dorsal lamella broader at base and ventral lamella slender and tapered (Figs. 3 H, 5J); each lamella of gills further divided into large number of fringed filaments; main trachea of gills II–VII clear to pigmented grey to brown; gills VII smaller than anterior pairs; margins of 3 caudal filaments with dense setae, terminal filament shorter than cerci.
Male imago (in alcohol, additional characters to those provided by Zhang 1988): Body length 20.0–23.0 mm; forewings 14.0–15.0 mm (Figs. 4 A, 6A), hindwings 6.0–7.0 mm (Figs. 4 B, 6B); body general yellowish brown.
Genitalia (Figs. 4 D, 6C): basal segment of forceps broader than distal segments, chestnut pigmented; second segment about 6× length of basal segment, curved with basal one-third light purplish red; apical segment very small, length slightly longer than broad. Apical two-thirds of fused penes slightly sclerotized and reddish brown. except for pale median groove; posterolateral corners of penes expanded apically forming trapezoidal shape (Figs. 4 C, 6D); basal third of penes membranous; sclerotized projections of gonopores with 3 tips, ventral tip slightly smaller than two dorsal tips (Figs. 4 C, 4D, 6E).
Eggs (Figs. 8 A, 8B, dissected from female body): Length 0.2 mm, width 0.1 mm; oval, chorionic surface without distinct structure, surface made up of many polygons; small micropyle with long sperm guide visible on equatorial area.
Material examined and collecting information. Holotype: 6, Wan-quan River, near Jia-ji Bridge, Qonghai County, Hainan Province, China, leg. Shu-Sheng SHE and Jun ZHANG, 23-V-1986; Paratypes: 3 66, 5 ♀♀, same as the holotype. Others: 10♀♀ subimagos, 22-V-1986; 10♀♀, 13-V-1986, other information same as types; 1 male subimago, 13-VII-2014, about 2 km downstream Jia-ji Bridge, 13-VII-2014, Jian-Hua DAI, Dan ZHOU and Jun- Zhi SUN; 16 larvae, Qionghai, Wan-quan River (110.465784°E, 19.226526°N), 4 km upstream of Jia-ji Bridge, 6- I-2015, Leg. Chang-Fa ZHOU, Jun-Zhi SUN and Yi-Ke HAN. All specimens are deposited in the Institute of Genetic Resources, College of Life Sciences, Nanjing Normal University, P. R. China.
The nymphs described here were collected from fine silt and sand substrates of Wan-quan River, Hainan Island, southern China. The river is wide, averaging at least 80 m in width, and more than 300 m at some sections visited (Fig. 7). It has deep water current in all seasons. Other mayflies collected at the same habitat and time include Ephemera and Caenis. This is consistent with the information provided by McCafferty (1973, 1979).
description: Published as part of Sun, Jun-Zhi, Luo, Juan-Yan & Zhou, Chang-Fa, 2016, The nymph, habitat, and status of Eatonigenia in China (Ephemeroptera: Ephemeridae), pp. 381-389 in Zootaxa 4193 (2) on pages 381-386, DOI: 10.11646/zootaxa.4193.2.12, http://zenodo.org/record/166992