Triplectides gracilis (Burmeister 1839)

Sganga, Julieta V., Angrisano, Elisa B. & Asaroff, Pablo E., 2013, Preimaginal stages of Triplectides misionensis Holzenthal and Triplectides gracilis (Burmeister) (Trichoptera: Leptoceridae: Triplectidinae), with notes on the cases occupied by these species, Zootaxa 3616 (1) : -

Triplectides gracilis (Burmeister 1839)

Figs. 13–22 , 24

The larva and pupa of Triplectides gracilis were originally described by Müller (1921) as Tetracentron ramulorum . In his series of notes and letters Müller gave some characters of the immatures of this species, but these characters are so general and isolated that do not allow its identification nowadays. In this paper we provide a complete description of the larva, pupa and cases of this species and compare it with the other described Neotropical species in the genus.

Larva. Length up to 16 mm. Head coloration (in alcohol) homogeneous dark brown, with yellowish oval areas around stemmata. Muscle scars somewhat paler than rest of head, distributed characteristically as in Fig. 13 . Labrum stramineous, with 2 brown lateral stripes parallel to lateral borders. Ventral apotome subtriangular, with long constriction at mid-length; submentum oval ( Fig. 14 ).

Thorax with pronotum reddish brown; mesal half of anterior edge of each pronotal sclerite with 3 smooth, rounded crenulations; lateral half plain, slightly produced and rounded ( Figs. 15, 16 ); setal pattern as in Fig. 15 . Mesonotum stramineous; sa 1 each with single long seta, sa 2 each with 3 setae (1 long anteromesal, 1 short anterolateral and 1 short posterior) and sa 3 with 5 or 6 setae (1 long and others short) distributed as in Fig. 15 (when only 5 setae present, anterolateral seta absent); muscle scars as in Fig. 15 . Metanotum covered by 3 pairs of sclerites; sa 1 sclerites each subrectangular with single long seta, sa 2 with pair of small transverse sclerites (found in Triplectides species elsewhere in the world but this is the first record in a Neotropical species—e.g. see St Clair 2002); sclerites sa 3 slightly longer than sa 1 and sa 2 sclerites together ( Fig. 15 ). Prosternum rectangular, slightly produced anteriorly. Mesosternal sclerites subrectangular with both ends curved anteriorly. Metasternum with setal areas bearing 6–9 long setae, with a variable number of basal, circular sclerites ( Fig. 17 ). Foretrocantin with anterodorsal corner pointed and upturned and anteroventral corner rounded ( Fig. 16 ). Legs striped with alternate stramineous and reddish brown bands ( Fig. 21 ); setose (chaetotaxy as shown in Figs. 18–20 ).

Abdomen with gills simple, present on segments I–VIII (all segments with dorsolateral, lateral and ventrolateral gills, except segment I lacking lateral ones) ( Fig. 21 ). Segments II–VIII each with pair of long posteromesal setae (those of segments III–VII very thin). Segment IX dorsal sclerite with 6 long setae on its posterior margin and 2 pairs of very short, lateral setae anterior to them; with 2 lateroposterior setae at each side of sclerite ( Fig. 22 ).

Larval cases. Larva of this species occupying hollowed-out twigs as well as empty cases of Grumicha grumicha and Nectopsyche gemma . Contrary to our observations with T. misionensis , percentage of larvae occupying empty cases of G. grumicha and N. gemma representing only 16% of total (9% and 7%, respectively).

For both hollowed twigs and adopted cases, larva building cap of small twigs stuck together with silk threads covering dorsal portion of anterior opening ( Fig. 24 ). Most specimens (84%) occupying hollowed-out twigs of different sizes reaching 35 mm in length.

Pupa. Length up to 17.4 mm. Pupa of this species identical to that of T. misionensis Holzenthal (see description above), differing in length and in chaetotaxy of labrum. In T. gracilis , labrum similar to that of T. jaffueli Navás with 3 long setae at each basolateral corner and 3 pairs of long setae along its distal margin (1 mesal and 2 laterals).

Material examined. Argentina: Misiones: arroyo Moreno, 26. x.2004, 3 larvae; arroyo Azul (puente quemado), 25–31. x.2004, 1 larva; arroyo Tamanduá, 25–31. x.2004, 3 larvae; arroyo Cuñá-Pirú (balneario), 6–11. xii.2004, 4 larvae; arroyo Azul (puente quemado), 6–11. xii.2004, 1 larva; arroyo Moreno, 6–11. xii.2004, 3 larvae; arroyo Tamanduá, 6–11. xii.2004, 3 larvae; arroyo Tamanduá (virgencita), 6–11. xii.2004, 6 larvae; arroyo Azul (puente quemado), 16–27. ii.2005, 5 larvae; arroyo Moreno, 16–27. ii.2005, 3 larvae; arroyo Tamanduá, 16–27. ii.2005, 6 larvae; arroyo Azul, 16–27. ii.2005, 1 larva; arroyo Tateto, 16–27. ii.2005, 2 larvae; arroyo Tamanduá, 8–14. i.2006, 1 larva; arroyo Tamanduá (virgencita), 8–14. i.2006, 1 male metamorphotype.

Habitat. The immatures of both species were found in almost all sites sampled, in 1st (arroyo Tamanduá and arroyo Azul) to 4th (arroyo Cuñá-Pirú) order streams that ranged from 161 to 403 m a.s.l. In all streams the substrate was composed of boulders, cobbles, gravel and sand, along with leaves and woody debris that comes from the gallery forest that develops on the margins. The larvae were collected in runs, riffles and pools in areas with accumulations of organic matter, especially woody debris.

Systematic considerations. The larvae of the 2 species of Triplectides described herein each have a series of distinctive features that allows their differentiation from those of the other known Neotropical species in the genus, T. jaffueli (see Holzenthal 1988) and T. egleri (see Sattler 1963) ( Table 1 ). Of this series of characters, the shape of the anterior border of the pronotum, the presence of sa2 sclerites in the mesonotum, the coloration of the legs and the number and distribution of the gills are the most important features in the identification of the larvae of these species.

Pupae of these species can be distinguished by the chaetotaxy of the vertex, antennal scape and labrum. The pupa of T. gracilis can be differentiated from that of T. misionensis by the chaetotaxy of the labrum, which is identical to that of T. jaffueli , bearing 3 pairs of long setae along its distal margin, and from T. jaffueli by the number of setae on the vertex (1 pair vs. 3) and on the antennal scape (5 setae vs. 4). There are no available data on the pupa T. egleri .

Triplectides gracilis Triplectides misionensis Triplectides jaffueli Triplectides egleri Acknowledgements

We are very grateful to the forest rangers from Salto Encantado Provincial Park, for their kindness and field assistance throughout the course of the investigation. We thank the Ministerio de Ecología y Recursos Naturales Renovables from Misiones Province for its support and for providing the permits to sample in the protected areas. We also thank Dr. Natalia Alberico (University of Buenos Aires) for her help in the translation of Müller’s paper and Dr. Silvina Menu-Marque (University of Buenos Aires) for the revision of an early version of the manuscript. We also thank the anonymous reviewer and Dr. John Morse for their critical comments that greatly improved the quality of the manuscript. This project received financial support from Agencia Nacional de Promoción Científica y Tecnológica (PICT 2002-12348), Universidad de Buenos Aires (UBACyT X836) and Universidad Nacional de Luján, Departamento de Ciencias Básicas. JVS was supported by a Postdoctoral Fellowship from CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas).

Figures

FIGURES 13 – 22. Triplectides gracilis larva. 13, head, dorsal; 14, head, ventral; 15, thorax, dorsal; 16, pronotum, left lateral; 17, thorax, ventral; 18 – 20, left fore-, mid- and hind legs, posterior; 21, habitus, left lateral; 22, segment IX and anal prolegs, dorsal.

FIGURES 23 – 24. 23, Triplectides misionensis, larval case, right lateral; 24, Triplectides gracilis, larva and larval case, right lateral.

Tables

TABLE 1. Diagnostic characters for Neotropical species of the known larvae of Triplectides. Sa = setal area;? = no data available.

Submentum	Oval	Pentagonal	Oval	Pentagonal
Ventral apotome	Subtriangular (constricted at mid- length)	Subtriangular (wide anteriorly in some specimens)	Triangular	Quadrate
Anterior edge of each pronotal plate	Mesal half with smooth crenulations, lateral half plain and slightly produced	Crenulate, anterolateral corners produced	Crenulate, anterolateral corners produced	Crenulate, anterolateral corners produced
Each mesothoracic sa 3	5–6 setae	8 setae	6 setae	?
Metathoracic sa 2	With pair of sclerites	Without sclerites	Without sclerites	Without sclerites
Prosternum	Rectangular	Triangular	?	Convex anteriorly, concave posteriorly
Legs	Striped	Homogeneous	Homogeneous	Striped
Abdominal gills	1-branched, on segments I–VIII	1-branched, on segments II–VI	1- to 3-branched, on segments II–VIII	1- to 3-branched, on segments II–VIII