Chloroniella peringueyi Esben-Petersen, 1924

Martins, Caleb Califre & Contreras-Ramos, Atilano, 2020, Redescription of larva of the South African endemic dobsonfly genus Chloroniella Esben-Petersen, 1924 (Megaloptera, Corydalidae), with a proposed terminology for Corydalidae larval sclerites, Zootaxa 4820 (1), pp. 134-146 : 136-145

Larva of Chloroniella peringueyi Esben-Petersen, 1924

( Figs. 1–8 )

Material examined. Late-instar larva: “ South Africa, Western Cape, Jonkershoek St. For. Nat. Reserve nr. Stellenbosch, Langrivier and adjacent area, 33”58.598’S, 18”58.660’E, el. 700 ft., 21–23.i.2000, K. Kjer & R. Blahnik ” .

Diagnosis. Body yellowish. Labrum ovate with anterior margin rounded. Mandible with three preapical teeth, second one with an indentation producing an M-shaped apex; basal tooth longer than second. Antennae with four articles. First abdominal segment with shorter lateral filaments than lateral filaments of segments II–VIII; filaments of segment VIII longer and narrower than other filaments.

Description. Measures. Body ( Fig. 1 ) Ca. 29.0 mm length. Head 4.2 mm length, 4.0 mm width. Mandibles 1.8 mm length, 0.6 mm width. Prothorax 5.2 mm length, 3.6 mm width.

Coloration. Body generally yellow ( Fig. 1 ); head dark yellow with sutures and stemmata black; legs pale yellow with dark yellow claws; all sclerites pale yellow, except for prothoracic ventral sclerites, which are dark yellow; membrane on and between segments pale yellow; lateral filaments dark brown dorsally and pale yellow ventrally; prolegs pale yellow with dark brown claws.

Head ( Figs. 2–3 ). Labrum ovate with anterior margin rounded, a group of preapical, tapered and yellowish setae present on each side, two of them longer and located on lateral edge; general coloration dark amber, with two preapical black spots. Anteclypeus subquadrate, narrower at apex, pale amber, laterally dark amber. Gena amber with lateral margins black; small and yellow setae present. Frontal region subtriangular, amber with small yellowish setae; without muscles scars; epistosomal suture black, frontal suture inconspicuous. Mandible long, with middle and base dark amber, black on lateral and apical margins, including teeth; apical tooth long and subtriangular, third preapical tooth similar to apical tooth but shorter, second preapical tooth trapezoidal with an indentation so apex appears M-shaped, first (basal) preapical tooth subtriangular and longer than second. Antenna short, with four amber antennomeres; second antennomere almost three times longer than first. Area between frontal sclerite and stemmata amber. Dorsal area of head adjacent to coronal suture amber, with small yellowish setae present; without muscle scars. Ocular region with six stemmata, arranged as a pentagon, with single central stemma; small and yellow setae present between stemmata; area adjacent to corneal lenses black. Postocular area amber; postocular keel black, with short and thick pale amber setae; area between gular plate and post ocular area pale amber. Maxilla dark amber; cardo semicircular, covered with minute, thick yellowish setae; lacinia subrectangular, four times longer than wide, covered with minute and thick setae on medial region, a row of tapered thick setae present at internal lateral margin; galea small, finger-shaped, with small yellow setae; maxillary palpus five-segmented, finger-shaped, with small yellowish setae. Labium mostly dark amber, covered with minute yellowish setae; ligula subglobose; lapial palpus three-segmented and cylindrical, base of palpomeres black; prementum dark amber, subrectangular; mentum pale amber, with four mental plates dark amber, basal mental plates subquadrangular, apical mental plates rectangular. Submentum amber; submental projections, subtriangular and dark amber, surpassing the anterior margin of mental plates. Gular plate amber, covered with minute yellow setae.

Thorax ( Fig. 4 ). Cervix bears a lateral and long sclerite (Cv), forming a bar anterior to VM+VP. Prothorax three times longer than meso- and metathorax. Pronotum composed by single, large and subrectangular sclerite (DM), latter longer than wide, with yellowish to brown margins; lateral and anterior margins covered by numerous minute, dark-amber setae; medial area with few long setae. Propleura pale yellow, mostly membranous except for two lateral sclerites; LPa long and triangular, bearing numerous minute setae, anterior to LPm and located above the VM+VP sclerite, separated from latter by an inconspicuous suture; LPm small and subtriangular free and anterior to LPp, latter narrow-subtriangular, both sclerites above base of coxa. Prosternum mostly membranous and pale yellow; bearing a large, dark amber and subtriangular sclerite, fused from two minor sclerites, VM (basisternum) and VP (sternellum). A large spiracle present between pro- and mesothorax, margins sclerotized and dark amber. Mesothorax similar in color to prothorax. Mesonotum bearing a large sclerite (DM), almost two times as wide as long; covered with numerous minute setae, especially on lateral margins. Mesopleura membranous except for a long, narrow and subtriangular sclerite fused from LPm+LPp, covered with numerous minute setae; mesosternum mostly membranous, except for a small and subtriangular sclerite (VP), located on inner side of coxal base. Small spiracle between meso- and metathorax, margins sclerotized and dark amber. Metathorax similar to mesothorax, including number, distribution and shape of sclerites, bearing long setae on DM.

Legs. Legs ( Fig. 1 ) pale yellow. Coxa basally pale brown, with few short and amber setae. Trochanter pale yellow, exterior surface with small group of long amber setae near base and few amber spines distally interspersed with long amber setae; interior surface covered with minute amber setae. Femur long, pale yellow with apex dark brown, both interior and exterior surfaces covered with amber long setae interspersed with pale minute setae and dark amber long spines. Tibia pale yellow with dark brown apex, covered by numerous dark-amber spine-like setae and long amber setae, especially on apex of ventral surface. Tarsi yellow, ventrally with amber spine-like setae; tarsal claws brown, darker at apex.

Abdomen. Abdomen ( Figs. 1 , 5–7 ) longer than head and thorax together. Tergites yellow to pale brown bearing three types of setae ( Fig. 5A ), all of them dark amber: 1) very long, erect, cylindrical, smooth and tapering macrosetae, which are found in lesser number on the abdominal dorsal region ( Figs. 5 A–B); 2) small, rounded, decumbent and smooth microsetae, with tip apparently closed, which are frequent and dispersed over the entire surface of the tergum ( Figs. 5A, C ); 3) medium size macrosetae, scattered and very frequent on the tergum, each has a smooth outer surface and a tubular shape with the apex wider than the base and with an opening ( Figs. 5A , D–E). Intersegmental membranes yellow; spiracles positioned anterolaterally, dark amber. Middle region of abdominal tergites with numerous small dark amber microsetae. Lateral filaments ( Figs. 1 , 6 ) of segments I–VIII amber, long and tapering; filaments of first segment shorter than other filaments, apex without long setae; filaments of segments II–VII similar in size, color and distribution of setae; filaments of eighth segment longer, narrower and bearing less setae than other filaments, especially on apical region. All lateral filaments bearing dark amber, long and tapering macrosetae on dorsal surface ( Figs. 6 A–B), on which substrate of larval habitat is attached ( Fig. 6D ); ventral surface covered with mid-sized, narrow, erect and tapering macrosetae interspersed with small, wide, decumbent and ovate microsetae ( Figs. 5 A–C). Tracheal gills present on segments I–VII, whitish. Sternites have a central sclerite ( VM), segments I–VII bearing a sclerite ( VM) shaped as two semicircles connected to a V-shaped line ( Figs. 7 A–B), semicircles distant from each other on first abdominal segment but close on distal segments; on segment VIII semicircles fully fused forming a subquadrate sclerite; on segment IX sclerite inconspicuous.Anal prolegs ( Figs. 1 , 7 C–F) yellow, covered with black decumbent microsetae interspersed with tapered amber macrosetae and long, fine amber macrosetae. Terminal filament (cerci) covered with amber, long and tapering macrosetae interspersed with small, decumbent and amber microsetae; terminal filament little longer than proleg. Claws dark brown, darker and curved at apex .

Remarks. The species identity of the larva studied was established as C. peringueyi , both because it was collected near the type locality of the species, and because its dobsonfly ( Corydalinae ) traits guaranteed it belongs to the only dobsonfly species recorded from the Afrotropical region, particularly from South Africa. As a dobsonfly, C. peringueyi ’s larva bears ventral gill tufts near the base of the lateral filaments, as well as spiracles of abdominal segment VIII positioned laterally, anterior to the segment’s lateral filaments, respectively. In fishfly larvae ( Chauliodinae ), spiracles of abdominal segment VIII are dorsal, sessile or in short to long respiratory tubes ( Cuyler 1958, Neunzig & Baker 1991). Moreover, the ovate labrum, 4-segmented antennae, slightly notched second preapical tooth of the mandible, and the hydrofuge pile on venter of abdominal segments IX and X ( Neunzig & Baker 1991) apparently absent, would separate Chloroniella larvae from all other dobsonfly genera. Interestingly, 4-segmented antennae ( Cuyler 1958, Ardila-Camacho & Contreras-Ramos 2018) and absence of a hydrofuge pile, are shared characters with fishfly larvae. An anteclypeus subtly separated from postclypeus ( Fig. 2A, B ), appears to correlate with adult traits shared with Chauliodinae . Chloroniella ’s relict biogeographic distribution and its unique morphology pose questions about the phylogenetic and evolutionary significance of this enigmatic species.

Distribution. This species has only been recorded from the Western Cape Province, South Africa ( Fig. 8 ): Dwaars River, Groot Drakenstein; Keeromsberg, Hex River District; Witte River on Wellington Mountains; Stellenbosch and Jonkershoek Nature Reserve near Stellenbosch; Knysna ( Esben-Petersen 1924; Barnard 1931; Penny 1993; Mansell 2003; this study).

Biology. C. peringueyi is a seasonal species, occurring during the summer, when adults are probably found close to vegetation and rocks in the vicinity of fast-flowing mountain streams and rivers, or they may be attracted to lights during warm evenings ( Mansell 2003). The specimens of this and other studies, such as Esben-Petersen (1924), Barnard (1931), Penny (1993), and Mansell (2003) were collected in January, March, November, and December, and were found in mountain regions at mid elevations, from 700– 915 m.

Figures

FIGURE 1. Late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A) habitus dorsal; B) habitus ventral.

FIGURE 2. Head of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A–B) dorsal view; C–D) ventral view. Abbreviations: ant, antenna; atg, anterior tentorial grooves; cri, nearly circular ridge delimiting neck region; cs, coronal suture; fs, frontal suture; ge, gena; gu, gula; pgscl, postgular sclerite; ptg, posterior tentorial grooves; sen, sensorium; smt, submentum; sri, secondary parietal ridge; ste, stemmata.

FIGURE 3. Mouthparts of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A) labrum and clypeus, dorsal view; B) right mandible, dorsal view; C) labium, ventral view; D) maxilla, ventral view. Abbreviations: atcly, anteclypeus; a tooth, apical tooth; crd, cardo; ga, galea; lbp, labial palp; lbr, labrum; lig, ligula; mt, mentum; mtpls, mental plates; mxp, maxillar palp; pmt, prementum; ptcly, postclypeus; p teeth, preapical teeth; smt, submentum; smpro, submental projection; sti, stipes.

FIGURE 4. Thorax of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A) dorsal view; B) ventral view; C) lateral view. Abbreviations: DM, dorsal medial sclerite; Cv, cervical sclerite; LPa, lateral posterior anterior sclerite; LPm, lateral posterior medial sclerite; LPp, lateral posterior posterior sclerite; sp, spiracle; VM, ventral medial sclerite; VP, ventral posterior sclerite.

FIGURE 5. Setae of abdominal terga of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A) Dorsal surface of an abdominal tergite with three distinct types of setae; B) Long, slender, smooth, erect and tapering macrosetae, with inconspicuous openings; C) Small, smooth, decumbent and rounded microsetae, with inconspicuous opening; D–E) Medial, smooth, erect and tubular macrosetae, with widened and upper portion and open tip.

FIGURE 6. Abdominal lateral filament of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A–B) Lateral view; (C) Detail of the small macrosetae and microsetae on ventral surface; D) Detail of the long macrosetae of dorsal surface with substrate.

FIGURE 7. Abdominal detail of late-instar larva of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A–B) Seventh abdominal segment, ventral view; C–D) Abdominal apex, dorsal view; E–F) Abdominal apex, ventral view. VM, ventral medial sclerite.

FIGURE 8. Distribution of Chloroniella peringueyi Esben-Petersen, 1924 (Megaloptera: Corydalinae). A) African Continent, overview; B) South Africa; C) Western Cape.This map was made with data from Esben-Petersen (1924), Barnard (1931), Penny (1993), Mansell (2003), and this study.