Bioacoustics of Smicridea (Rhyacophylax) gladiator

Head . Subrectangular in dorsal view; pale yellow except for darker anterior margin of frontoclypeus and labrum; each stemmata surrounded by pale oval spot; frontoclypeus with two oblique, dark brown, oval spots laterally over mesolateral depressions and anterior tentorial pits; and frontoclypeal suture dark posteriorly (forming V-shaped spot); oval spot on each side connected to its dark frontoclypeal arm by broad, curved light brown stripe; muscle scars conspicuous, oval and pale, grouped on posteromesal region of frontoclypeus and posteriorly on parietal apotomes: Two parallel series each with four scars and group of three scars in medial region ( Fig. 1A ). Chaetotaxy consisting of #01, #03, #09, #17 [dorsal setae]; #07, #12 [lateral setae]; and #08, #18 [ventral setae]. Primary setae mostly long, thick and dark; secondary setae short, fine, tapered, and black, covering dorsal and lateral surfaces of head, except for transverse occipital region. Dorsal carina absent. Coronal suture short, about 1/ 10 as long as frontoclypeus. Frontoclypeus with anterior margin symmetrical, convex; with three crenulae at each side of anteromedian depression, lateral notches inconspicuous, lateral lobes absent; frontoclypeal suture lyreshaped, equally conspicuous throughout its length ( Fig. 1A ); slightly constricted at 1/3 its length. Labrum yellowish brown, with pair of dark, oval, posterolateral spots; with pair of long, golden brushes of pectinate setae anterolaterally, directed anterad; dorsal surface with short, dark setae; fringe of short, very fine setae on anteromesal margin and one pair of long, parallel, submarginal setae ( Fig. 1D ). Mandibles asymmetrical, each with external margin bearing fine, pale setae. Left mandible ventromesal edge with 1 indistinct molar tooth and 3 obtuse, subequal, subapical teeth; 1 truncate, apical tooth; 1 subapicodorsal tooth; and mesal tuft of fine setae. Right mandible ventromesal edge with 1 small molar tooth and 3 subapical teeth with basal subapical tooth (1st) truncate and larger than obtuse 2nd or 3rd; 1 obtuse, apical tooth; and 1 subapicodorsal tooth; without mesal tuft of setae ( Fig. 1E ). Lateral sides of head each with 3 longitudinal rows of pale brown muscle scars arising posterior to stemmata and extending posterad to occipital margin at posterior tentorial pit ( Fig. 1C ). Genae ventrally each with conspicuous patch of thick, strongly marked, transverse stridulatory lines; dark brown L-shaped mark covering stridulatory lines and extending posterolaterad almost to postgenae; muscle scars oval and pale and scarcely discernible, with one present on posterior region of each patch of stridulatory lines ( Fig. 1B ). Submentum without median cleft. Anterior ventral apotome triangular, twice as wide as long; posterior ventral apotome absent ( Fig. 1B ). Thorax . Nota sclerotized and densely covered by short, slender, dark, acuminate peg-like setae, mixed with pair of long, slender setae on mid-region of pro- and mesonota ( Fig. 2C ). Pronotum with longitudinal ecdysial line, yellow, darker posteriorly, muscle scars barely visible, grouped posterolaterally. Meso- and metanota not divided by ecdysial lines, pale yellow, lateral diagonal grooves slightly visible, muscle scars inconspicuous ( Fig. 2C ). Gills on prosternum absent; mesosternum with 1 pair of ventrolateral gills; metasternum with 1 pair of ventromesal gills and 1 pair of simple ventrolateral gills, each with long stalk and few irregularly distributed lateral filaments. Legs yellowish brown ( Fig. 2B1–2B 3 ). Foreleg coxae with short, pale, thick, spike-like setae on external surfaces and dark, long, slender setae posteroventrally; trochanters and femora each with numerous yellowish, long, slender setae on ventral margin, mixed with row of 10–12 dark, long, slender setae; tibiae and tarsi with median, pale, thick, spike-like setae on ventral margins and long, pale setae on dorsal margins ( Fig. 2B 1 ). Mid- and hind legs similar in size, shape, and structure; femora each with short, pale, spike-like setae on ventral margin and 2 dark, long, slender apical setae: 1 apicoventral and 1 apicodorsal; tibiae and tarsi each with short, pale, spike-like setae and 1 dark, long, slender seta on apicodorsal margin of tarsus ( Figs. 2B2, 2B 3 ). Foretrochantins each simple, tapered to acute apex, with 3–5 short, stout, dark, acuminate peg-like setae on dorsal margin ( Fig. 2A ). Abdomen . Abdominal segments densely covered by flattened scale-like setae with few long, thin, dark, hairlike setae among them; with light depression on cuticle ( Fig. 2A ). Segments I–VI each with 1 pair of ventral gills; segments I–VII each with 2 pairs of ventrolateral gills; lateral gills absent ( Fig. 2A ). Sternum VIII with 2 small subtriangular sclerites bearing short, yellowish, spike-like setae; each sclerite with 6–8 dark, long slender setae on posterior margin ( Fig. 2D ). Sternum IX with 2 subtriangular sclerites each longer than width of its posterior margin, bearing moderate-sized, yellowish, spike-like setae with spines emanating from prominent sockets; with 12–15 dark, long slender setae on posterior margin; lateral sclerites absent ( Fig. 2D ). Segment X with membranous anal papillae (may be retracted). Anal prolegs each with bent simple claw and tuft of numerous, long, hair-like apicodorsal setae; without spine-like setae on ventral surface ( Figs. 2A, 2D ). Pupa ( Fig. 3 ). Length 5.0– 6.1 mm (mean = 5.58 mm , SD = 0.41 mm , n = 7). Head . Labrum with anterior margin rounded; anteromesal region with 12–14 medium-sized setae; basolateral lobes distinct, each with 6–7 long setae ( Fig. 3B ). Mandibles asymmetrical, broad basally, tapering to apex, each with brush of long setae posterolaterally; inner margin with acute teeth mesally, 4 on left mandible and 3 on right mandible, and finely serrate distally ( Fig. 3C ). Thorax . Pale yellow, without conspicuous features other than those of adult specimens of Smicridea (Rhyacophylax) ( Fig. 3A ). Abdomen . Covered with sparse setae. Lateral fringe absent. Abdominal terga with pairs of anterior hook plates (a) on segments II–VIII with hooks directed posterad; pairs of posterior hook plates (p) on segments III–IV with hooks directed anterad ( Figs. 3A, 3D ); hook-plate pair IIa each with 3–5 pointed, stout hooks and 3 smaller; hookplate pair IIIa each with 5–6 pointed, stout hooks and 6–7 smaller; hook-plate pair IIIp each with 9–13 sharply pointed, long hooks; hook-plate pair IVa each with 4–6 pointed, stout hooks and 5–11 smaller; hook-plate pair IVp each with 5–6 pointed, upturned hooks; hook-plate pair Va each with 4 pointed, stout hooks and 5–10 smaller; hook-plate pair VIa each with 3–4 pointed, stout hooks and 4–7 smaller; hook-plate pair VIIa each with 3 pointed, stout hooks and 6–8 smaller; hook-plate pair VIIIa each with 3–4 pointed, stout hooks and 8–9 smaller hooks ( Fig. 3D ). Apical processes of segments IX–X long, slender, widely separated, each with apical brush of setae (5–6 short and 9–12 long setae) ( Fig. 3E ).

Remarks . Considering that immature stages of most Smicridea species are undescribed or illustrated, and some are not accurately associated with the adults, proposing morphological comparisons among species of the genus is difficult and limited. Based on species with known immature stages, the last-instar larva of S . gladiator is similar to that of S . ( R .) thermophila Rueda-Martín & Sganga 2011 by the anterior margin of the frontoclypeus, convex or rounded, not crenulated, and with dark coloration, but S . gladiator can be distinguished from this and all other described congeners by the presence of the following characters: (1) two dark brown diagonal spots on the mesal depressions of the frontoclypeus [also seen in S . ( R .) thermophila ] and a V-shaped mark over the frontoclypeal suture in its median posterior portion; (2) mandibles each with 1 indistinct or an undeveloped molar tooth and 3 subapical teeth; (3) genae with transverse stridulatory lines conspicuous, strongly marked, evenly dark brown and with L-shaped posterolateral extension of dark brown color not reaching the postgenae posterolaterally. The pupa of S . gladiator differs from those described for other species in the genus mainly by the characters mentioned above by Sganga & Fontanarrosa (2006) . The pupa is similar to those of S . ( R .) helenae and S . ( R .) dithyra Flint 1974a based on shape and number of teeth of the mandibles. However, S . gladiator , differs from those species by having 6–7 long setae on each of the basolateral lobes of the labrum, whereas in S . helenae and S . dithyra there are 4 long setae on these lobes. The anteromesal region of the labrum of S . gladiator has 12–14 long setae, whereas this region in S . helenae has 5 medium-sized setae and in S . dithyra has 21 short and long setae. The pupae of these three species can also be easily distinguished by the number and shape of hooks on the hook-plates of the abdominal terga, a number and shape that is unique for each species. For example, as observed for each hook-plate IIIp, S . gladiator has 9–13 long pointed hooks, while in S . helenae it has 7 strong hooks and, in S . dithyra it bears 18 large hooks. The pupa of S . gladiator bears hooks that vary in number between the right and left plates of the same individual, while in S . helenae and S . dithyra the number of hooks is the same on the two plates.