Nemoura jejudoensis, Zwick & Baumann, 2011

Zwick, Peter & Baumann, Richard W., 2011, Nemoura Jejudoensis A New Species Of Stonefly And The Redescription Of Amphinemura Baei Ham And Lee (Plecoptera, Nemouridae) From Jeju Island, Korea, Illiesia 7 (15), pp. 148-155 : 149-150

Nemoura jejudoensis sp. n.

( Figs. 1-6 )

Material examined. Holotype ♂, 3♂ paratypes, Republic of Korea, Cheju Island, Chungmoon City, Chonyeon waterfalls , 1 December 1986, M.F. Whiting [Jeju Island, Seogwipo City, Jungmun, Cheonjeyeon falls] Additional material with the same collection data: 13♀ plus 1♂ and 2♀ used for SEM study .

Size and habitus. Front wing length 6.4-7.4 (mean 6.8) mm in ♂, 8.4-9.9 (mean 9.2) mm in ♀. Habitus typical of genus, not characteristic. Body and antennae brown, legs and palpi paler, yellowish brown. Wing veins brown, membrane of front wing with faint brownish tinge.

Male. Tergite 9 medially short, otherwise unmodified. T10 forms the medially largely membranous base plate of the epiproct. Epiproct closely appressed to base plate, basally firmly connected, difficult to detach for study. The epiproct consists of a short body and a long anterior rostrumlike process.

Body of epiproct short, wider than long ( Fig. 1 ). The transverse anterodorsal sclerite supports two backwardly turned claw-like plates each with four marginal bare teeth. There is an additional anteromedian tooth whose mediodorsal face is beset with cuticular spicules ( Fig. 4 ). A short distance behind the anterodorsal sclerite lies another slender transverse sclerite which is laterally angled backward. Other sclerites are seen only in slidemounted epriprocts, by transparency ( Fig. 1 ). There are no ventral setae or teeth. The basolateral earshaped structures that provide the normally-shaped epiprocts of other Nemoura -species with some mobility can be recognized but seem rigid, nonfunctional.

Rostrum rising from a bulb-like base connected to the medial ends of the anterolateral sclerites. A central sclerite with median division line appears by transparency. Basal half of rostrum with several oblique folds, in side view seen to be triangularly raised near midlength ( Fig. 2 ).

Sternite 9 almost circular, with short pointed caudal tip. The club-shaped vesicle occupies 4/5 of the sternite length. The short blade-like median sclerites of the paraprocts lie alongside the tip of S9. A membranous section separates them from the triangular, apically quite narrow outer lobe.

Cerci curved forward and mediad, partly concealing the epiproct in dorsal view ( Fig. 3 ). Medial flat face pale and convex outer face brown, and pilose. The tiny rudiment of segment 2 is at the top of the curved cercus, on the soft medial face. There is an inconspicuous subterminal point on the front side of the cercus.

Female. Similar to the female of N. geei as illustrated by Shimizu (1997, his fig. 48). The almost circular pregenital plate on S7 covers the middle of S8 almost completely, the curved edges of the unpigmented vaginal lobes may be faintly visible ( Fig. 5 ). Sides of S9 with a poorly defined elongate pigmented strip. Triangular sclerites in the dorsal wall of the genital opening and the end of the oviduct, respectively, may be visible by transparency.

In cleared genitalia ( Fig. 6 ), two anterolateral caplike brown sclerites are seen at the side of a long carrot-shaped transparent tube connecting to the receptacula. Behind it the dorsal wall of the vagina has two paramedian areas with concentric cuticular rings, probably extensible pouches.

Diagnosis. A member of the East Asian Nemoura ovocercia -group (sensu Shimizu 1997). N. geei Wu 1929 occurs on the Asian mainland ( China, Korea, Russian Far East) as well as on Hokkaido and Honshu. Nemoura pekinensis Claassen 1929 and N. brevicercia Zhiltzova 1982 are junior synonyms ( Shimizu 1997). We studied some specimens from mainland Korea. Excellent illustrations of N. geei are also available ( Zhiltzova 1982, 2003, Shimizu 1997, Teslenko & Zhiltzova 2007). Several additional species occur in Japan, the surrounding islands, Taiwan ( Shimizu 1997), and China ( Li & Yang 2007). Nemoura geei , the present species, N. quadrituberata Shimizu 1997 (Tsushima Island), N. longilobata Shimizu 1997 (Hokkaido) , and N. atristrigata Li & Yang 2007 (Henan) share a very long rostrum of the epiproct in combination with large, dentate, claw- or hand-shaped anterolateral sclerites. Nemoura jejudoensis possesses an anteromedial rough process above these toothed sclerites which is absent in N. geei . The shape of the transverse dorsal epiproct sclerites also differs between the two species.

Details of epiproct structure distinguish also the other two similar species but they differ in additional characters from N. geei : N. quadrituberata by four hairy swellings on tergites 9 and 10, toothless cerci, and broad paraprocts; N. longilobata and N. atristrigata by a large hook on the cercus and broad, tongue-shaped paraprocts.

Nemoura jejudoensis differs from N. geei only in the epiproct. We imagine that N. jejudoensis developed fairly recently from a small founder population of N. geei that ventured to the off-shore island of Jeju-do. Etymology. The specific name is a noun in apposition after Jeju Island where the specimens were collected that represent this new species.

Figures

Figs.1-4. Nemoura jejudoensis sp. n., male. 1. Epiproct in dorsal (right half of figure) and ventral view (left half of figure), respectively. 2. Slightly oblique lateral view of male epiproct, diagrammatic, (not to scale). 3. Dorsal view of abdominal tip. 4. Anterior view of the apical epiproct sclerites. Note that figures 3 and 4 show a strongly contracted specimen with the epiproct pulled down and the paraprocts forward. The normally barely noticed blade-like inner paraproct lobes appear as sharp spines between the cerci and the epiproct while the obtuse pilose apex of the outer lobe is concealed between the epiproct and base of the cercus.

Figs. 5-6. Nemoura jejudoensis, female. 5. Ventral view of abdominal tip. 6. Dorsal view of cleared vagina.