Neoperla Needham, 1905

Zwick, Peter & Zwick, Andreas, 2023, Revision of the African Neoperla Needham, 1905 (Plecoptera: Perlidae: Perlinae) based on morphological and molecular data, Zootaxa 5316 (1), pp. 1-194 : 15-17

Genus Neoperla Needham, 1905

Pseudoperla Banks, 1892 (no type designated), not Pseudoperla Pictet, 1856: 37 , pl. IV, figs. 9,10 (in Pictet & Hagen in Berendt, 1856, fossil Phasmatodea).

Neoperla Needham, 1905: 108 ; replacement name, type species (by original designation): Perla occipitalis Pictet, 1841 (redescriptions: Zwick 1987, Stark 1990).

Ochthopetina Enderlein, 1909b: 324 ; syn. fide Hynes (1952). Type species (by original designation): N. aeripennis (Enderlein, 1909) (redescription: Zwick 1973a: 496).

Javanita Klapálek, 1909: 224 ; type species (designated by Klapálek, 1923b): Neoperla caligata ( Burmeister, 1839) (syntypes lost; a synonym of Ochthopetina whose type species, N. aeripennis , was originally included).

Tropidogynoplax Enderlein, 1910: 141 ; type species (by monotypy): T. fuscipes Enderlein = N. aeripennis (Enderlein) , fide Klapálek 1923: 177. The type of T. fuscipes is not available and probably lost. Enderlein emphasised similarity of habitus between T. fuscipes and N. aeripennis . Klapálek’s interpretation of the name seemed doubtful ( Zwick 1973a: 499) but we follow him now assuming that the particular shape of the female subgenital plate was an artifact caused by drying.

Formosina Klapálek, 1913: 117 . No type designated. Preoccupied, not Becker, 1911.

Formosita Klapálek, 1914:118 ; nom. nov. for Formosina Klapálek, 1913 (not Becker, 1911); type species: Neoperla costalis ( Klapálek, 1913) (design. Zwick 2016).

Oodeia Klapálek, 1921: 321 ; type species (designated by Klapálek 1921): N. dolichocephala Klapálek, 1909 (redescription as Neoperla dolichocephala -complex: Uchida & Yamasaki, 1989).

The presence of only two ocelli was the key character of Enderlein’s (1909c) Neoperlinae . However, Peltoperlidae , several other Perlinae , especially the numerous very different Neotropical Anacroneuriini ( Perlidae : Acroneuriinae ) also share this character. Enderlein applied the name Neoperla only to American species and created new genera for Old World species.

A forthcoming study (P. Zwick, in prep.) will address the relations of Neoperla to the other genera of Perlinae and will revise the internal systematics of the genus which also occurs in South East Asia, Palaearctic Asia, and eastern North America.

In brief, males of Neoperla are distinguished from other Neoperlini by four primary apomorphies:

1. T7 is modified;

2. T9 has a median furrow between pilose lateral humps and bears sensilla basiconica (SB);

3. the anterior half of the hemitergites is slender and delicate as compared to the massive base and the large mediobasal callus (misinterpreted as the flattened hemitergite apex by Sivec et al. 1988);

and

4. a pair of hard rounded retractor sclerites projects laterally from the basal penis opening.

In many Plecoptera , also in most Perlinae , the membranous penis assumes its specific shape only temporarily while everted by hemolymph pressure. It collapses when the pressure is released. In the tribe Neoperlini , sclerites restricting the basal penis opening prevent this and penes of Neoperlini retain their shape at rest. The infolded endophallus (often simply called the sac) with its specific spine patterns is only for copula everted by hemolymph pressure.

Female Systellognatha share a uniform structure of genitalia. In sternite 7 (S7), the lateral oviducts turn mediad, merge, and form the common oviduct which enters the vagina in S8 on the underside. In preparations, the Y-shaped cuticular oviducal lining is often visible in front of the vagina and the spermatheca (sa) is dorsally attached via a narrow short unmodified spermathecal duct (SD).

Neoperla is the only exception, with several different types of connection between vagina and spermatheca. Three different morphs occurred among the types of Enderlein’s few African Neoperla ( Zwick 1973a) , while more were found in Asia ( Zwick 1977). The initial recognition of only two groups ( Zwick 1983) was unfortunate and partly erroneous. However, the distinction of a “ clymene-group ” and a “ montivaga-group ” is still accepted common practice (e.g., DeWalt et al. 2021).

In the forthcoming revised Neoperla system (P. Zwick in prep.), all African species are placed in Neoperla (Neoperla) with an armed spermathecal stalk (SSt) connecting the vagina and spermatheca instead of an unmodified cuticular duct. The shape of the stalk and its armature of scales, spinules, and microtrichia differ between groups (e. g., Figs 83, 84 ). In most African species, the SSt forms a ring or is coiled. The spermatheca itself is a delicate spiral or curled tube (e.g., Fig. 17 ) while in most Asian and in the North American species the spermatheca is ball-shaped or resembles a thick sausage with rather firm and often also rough cuticle.

Neoperla eggs are ovoid to subspherical; the firm chorion is sculptured by follicle cell impressions ( Rościszewska 1987). Punctures are often called aeropyles (e.g., Picker 1980, Rościszewska 1991, Stark & Szczytko 1988) which seems plausible but in Plecoptera there is no evidence of the suggested function. Aeropyles in the sense of Hinton (1981) are different. In the literature, the terms anterior—posterior for the structurally different egg poles vary. We use terms based on function and distinguish the anchor pole from the opposite opercular pole where larvae hatch. The anchor is an elastic attachment structure surrounded by a strongly sclerotised collar; vestigial character expressions and secondary reductions occur. The anchor pole leads the way out of the ovariole into the oviduct when eggs are ready. We use the term operculum for the opposite pole although we do not know if the larva indeed detaches a polar cap or if the larvae exit through some slit in the chorion. However, some African species have a visible opercular suture or a ring of specially shaped follicle cell impressions. Insemination occurs via several micropyles distributed in a ring between widest egg diameter and opercular pole.

Eggs of many Neoperla species are striate, which is unique among Perlidae . The plesiomorphic striation is longitudinal ridges on the entirely punctate chorion, with chorion surface differing at best gradually between the ridges and the wide concave interstices between them (e.g., Figs. 85, 87 ). Many of the species in question have opercula in the shape of a low cap. The apomorphic condition is differentiation of the chorion into alternating raised costae with impunctate usually flat back and punctate concave sulci, with one costa and one sulcus together constituting a stria (e. g., Fig. 86 ). In most species, striae are straight; spiral striae are apomorphic. The direction of spin is species-specific: striae are called levogyrous if in polar view spirals turn left (anticlockwise), in side view levogyrous striae run from top left to bottom right. Different types of punctation of the sulci are described under the respective species groups.

The most derived character expression is a secondary egg surface consisting only of wide bare costae separated by narrow fissures leading to sulci concealed in the depth of the chorion (e.g., Figs. 359 , 379 ). This is an extreme character expression in a group of species where even freely visible sulci have no punctures and only regular single rows of micropunctures separating sulcus and costa. Micropunctures are structures visible only in mounted eggs at high magnifications, but under transmitted light their structure remained unclear even at magnification 630X.

I. Keys to species groups and species of African Neoperla (Neoperla)

Dichotomous keys to taxa at various levels (e.g., species co-complexes) and to all species are provided. However, only one gender is known for several species. To be user-friendly, some species appear at several places in a given key or in several keys.

All characters used in a key couplet must be considered and identifications should be checked against the individual descriptions and illustrations. Specific identification of females without eggs may be impossible.

Males

1 T7 with an unpaired caudo-medial process; T8 variable....................................................... 2

1’ T7 without unpaired caudal process; T8 with a forward-curved process or hook........................................................................................... N. excisa and N. sjostedti -operational complex, p. 130

2 Caudal process of T7 flat (e.g., Figs. 1, 4 , 11 ); T8 not or only weakly sclerotised along midline, no humps or processes; penis soft, only basally sclerotised and, when contracted, short and flat; the endophallic armature is dispersed, dorsal and ventral sides are not much different (e.g., Figs. 2–3 , 12 )......................................... N. transvaalensis -group, p. 19

2' Caudal process of T7 variable but always three-dimensional, not flat; T8 distinctly sclerotised in midline (e.g., Figs. 76–77 ); penis tubular, sclerotised, endophallus variable.............................................................. 3

Figures

FIGURES83–90.Neoperladidita(Enderlein)andN.juxtadiditan.sp.:N.didita:83,spermathecalstalkofthefemalefromMamfe; 84,fragment ofan eggfromthe lectotype;85,eggof thespecimenfrom Mamfe;86,anchor poleofsame,opticalsectionandsurface view combined (diagrammatic, from a photograph). N.juxtadidita: 87, genital situs of holotype female from Belinga; 88, spinules from inside the spermathecal stalk; 89, egg; 90, anchor pole with anchor.Scales are 100µm, 84, 85 to the same, others not to scale. a, anchor; c, collar; r, ridges on egg; sa, spermatheca; SSt, spermathecal stalk; V, vagina.

FIGURES 16–17. Female genital situs: 16, N. lujana Navás, not to scale; 17, N. costata n. sp. (Liberia, near Tapeta). co, common oviduct; scl, sclerite in vagina; sd, spermathecal duct; SSt, spermathecal stalk; V, vagina.

FIGURES 351–361. Neoperla conradti (Enderlein): 351–354, male from Baré, abdominal tip and contracted penis; 355–356, male from Matadi, everted penis and detail near midlength of endophallus; 357, 358, ♀ genital situs and anchor pole of egg (from Bangem, Cameroon); the arrow points at spine patches in the vagina; 359, SEM, egg from holotype (courtesy of MPI for Limnology). Figs 353–355 to the same scale. Tergites, HT10 and cercus labeled; a, anchor; ac, anchor cavity; Mi = pores between costae above a concealed micropyle.

FIGURES 373–385. Neoperla heideae n. sp. and N. larvata n. sp. N. heideae: 373, 374, abdominal tip and contracted penis of a misassociated paralectotype of N. excisa Klap. from Lolodorf (to the same scale), with the label in Sütterlin script; 375, contracted penis, dorsal view, 376, everted endophallus (from Libamba); 377, ♀ situs from near Kama (D. R. Congo); 378, ♀ situs (D. R. Congo, Odzala N.P., NEOP242); 379, egg (Sangmelina,Cameroon). N. larvata: 380, everted endophallus (CAR, Bayanga, NEOP240); 381, ♀ situs, sternites 8 and 9 labeled (Ghana, Ankasa Res.); 382, ♀ situs (Togo, Kati); 383, ♀ situs (Ghana, Volta R., Z21.41); 384, egg with detail, Guinea, Simbareya (NEOP237); 385, aberrant contracted penis, ♁ from Ivory Coast, Boa. The scales are 100µm; tergites, HT10 and cercus labeled. a, anchor; mi, micropyle; n, nail; sa, spermatheca; SSt, spemathecal stalk; V, vagina.

FIGURES 1–5. Neoperla transvaalensis (Enderlein) (1–3) and N. laticollis Klapálek (4, 5): 1, male tergites 7–10, dorsal and lateral views; 2, penis, dorsoventral; 3, artificially everted penis, the retractor apodemes (sclerotised knob) are on the dorsal side; 4, male tergites 7–10; 5, artificially everted penis. The scales are 100µm, other figures not to scale. bs, bare strip; ce, cercus; gp, gonopore; vlb, ventrolateral spine bands.

FIGURES 11–15. Males in the N. lujana-complex. N. costata n. sp.: 11, male tergites 7–10, dorsal view; 12, artificially everted penis. N. lujana Navás, artificially everted penes: 13, from Cameroon, Etambo R.; 14, from Bayanga (CAR). 15, N. serrula paratype from Ghana (NEOP009).

FIGURES 76–82. Neoperla duodeviginti n. sp.: 76–78, ♁ abdominal tip and contracted penis, specimen from Bui Camp, Ghana (not to scale, tergites and HT10 labeled; modified from Zwick, 1973b); 79, penis with everted endophallus, specimen from Ghana, river Mensu; 80, endophallus of holotype (NEOP048) from Cameroon; 81, 82, genital situs and egg, ♀ from Belefuanai. Scales are 100µm unless differently indicated. a, anchor; c, collar: od, oviduct; sa, spermatheca; SSt, spermathecal stalk; V, vagina.