Smicridea (Smicridea) truncata, Flint, Flint

Description of the immature stages View in CoL

Larva. Length 5.7–6.9 mm (n = 9), lateral habitus as in Fig. 1 View FIGURES 1–9 ; body covered with short, scale-like hairs.

Head. Dorsum: yellowish-brown, pattern of dark spots darker on anterior region than posterior; mandibles asymmetrical, left one with 5 internal teeth and one subapicodorsal tooth, brush of hairs in middle region going beyond mesal edge; right mandible with 4 internal teeth, no hairs present in middle region, with 1 tooth ( Fig. 5 View FIGURES 1–9 ); labrum darkly sclerotized anterolaterally, with long hairs anterolaterally, being more dense anteriorly ( Fig. 4 View FIGURES 1–9 ), dorsal surface with two setae long and short setae; frontoclypeus, anterior region asymmetrical, left side with shallow crenulations, 2 rounded lobes, right side being larger than left side, anterolateral ends straight, without lateral expansion, median region with transverse dark concave line, anterior region becoming depressed from this point ( Fig. 2 View FIGURES 1–9 ); venter: transverse stridulatory file ridges decreasing in length anteriorly and posteriorly, with short ridges posteriorly in ventrolateral area of head ( Fig. 3 View FIGURES 1–9 ); submentum without median cleft; ventral apotome divided, anterior apotome wider than long, triangular in shape, posterior apotome small, sclerotized anteriorly.

Thorax. Dorsum: pronotum with longitudinal ecdysial line, several dark spots posterolaterally, highly sclerotized and dark posterolaterally ( Fig. 6 View FIGURES 1–9 ); meso and metanota entire, with dark spots forming arcuate line in lateral view, dark spot in middle of posterior edge, highly sclerotized and dark anterolaterally ( Figs. 7 and 8 View FIGURES 1–9 ); cuticle between pronotum-mesonotun and mesonotum-metanotum laterally bearing small tubercles; venter: gills each with elongate stalk, few (4–6) filaments not arising uniformly, absent on prosternum, 1 pair on mesosternum and 2 pairs on metasternum; tibia of forelegs each bearing ventrally at least 8 pinnate hairs; trochantin not forked, with 4 dorsal spines; sclerites posterior to prosternal minute.

Abdomen. Gills with elongate stalk, few (4–6) filaments not arising uniformly, 2 pairs on segments I–VI, 1 pair on segment VII; single median sclerite on segment VIII ventrally; segment VIII bearing dorsolaterally 1 pair of tubular structures ( Fig. 1 View FIGURES 1–9 ), each with apical tuft of setae; anal claw without ventral teeth, brush well developed. Abdominal sternum VIII with circular sclerite bearing numerous setae on posterior margin ( Fig. 9 View FIGURES 1–9 ).

Pupa. Length 5 mm (n=3), dorsal habitus ( Fig. 10 View FIGURES 10–14 ), labrum with distinct basolateral lobes, each with 5 long hairs, anterior region with 2 long hairs on each side and 5 short hairs on median region ( Fig. 10 View FIGURES 10–14 ).

Mandibles inflated basally, bearing long hairs posterolaterally, each tapering to pointed apex, inner margin with large teeth near base (3 on left mandible, 4 on right) and small serrations beyond; 4 hairs dorsally in middle near base ( Fig. 12 View FIGURES 10–14 ). Thorax and abdomen with sparse setae, lacking lateral fringe. Hook plates anteriorly on segments II–VIII, posteriorly on segments III–VI ( Fig. 13 View FIGURES 10–14 ); each posterior plate 3 (3p) wider than longer, bearing 6 large teeth and 10 smaller teeth, distributed in two irregular rows. Apical processes straight, widely separated, each with apical brush of hairs (4 very long), shorter hairs on first third of process, no hair beyond this area until base of process ( Fig. 14 View FIGURES 10–14 ).

Diagnosis

Larva. Larvae of S. truncata can be distinguished from the other known larvae of subgenus Smicridea by the concave line on the median region of the frontoclypeus. This line is curved in S. fasciatella McLachlan , S. bivittata (Hagen) and S. travertinera Paprocki, Holzenthal and Cressa. Smicridea truncata can also be distinguished from S. travertinera because the latter species has a U-shaped marginal carina in the head ( Paprocki et al. 2003). The frontoclypeus of S. truncata can be distinguished from that of the other species by the shape of the frontoclypeus. It is the only species in which the anterolateral region of the frontoclypeus is not expanded, and the anterior region has two rounded projections (the right one being slightly larger than the left one) ( Fig. 8 View FIGURES 1–9 ). Another distinct character of S. truncata is the tubular structures ( Fig. 1 View FIGURES 1–9 ), located in the dorsolateral region of abdominal segment VIII, that were not observed in any of the described larvae of S. ( Smicridea ), including S. frequens (Nav á s), and S. annulicornis (Blanchard) ( Sganga and Fontanarrosa 2006) .

Pupa. Flint (1978) reported that the pupae of species of subgenus Smicridea (Smicridea) cannot be distinguished at the morphological level, but the known species of this subgenus can be distinguished from the known species of the subgenus S. ( Rhyacophylax ) by the distribution of the teeth on 3p, which in the former subgenus are distributed irregularly over its surface rather than in one anterior row.

Some Smicridea pupae have been poorly described ( S. frequens (Nav á s), S. jamaicensis Flint , S. grandis Flint , S. minima Flint ) or only figured ( S. fasciatella , S. annulicornis , S. caribae Flint , S. simmonsi Flint ), making morphological comparison among species in this subgenus difficult and limited. Based on descriptions and figures included in published papers ( Flint 1968a, 1968b, 1974b, 1989, Sganga and Fontanarrosa 2006), the S. truncata pupa can be distinguished from that of S. faciatella by differences in the labrum; in the first species the labrum is rounded while in S. faciatella it has a squared shape. Also, these two species can be distinguished by differences in hook plate 3p, which in S. truncata is as wide as it is long and has six large teeth, while in S. fasciatella it is three times wider than it is long, with nine large teeth. Smicridea truncata can be distinguished from S. grandis and S. minima by having hook plate 4p quadrangular with strong teeth, while in the latter two species this plate has a lanceolate shape and is four and five times, respectively, longer than wide, with a serrated edge. The S. truncata pupa can be distinguished from that of S. annulicornis by having paired hook plate 4p while in the latter species this plate is single.

Distribution

Flint (1978) listed the adults of this species for Surinam, Guyana (Georgetown), and Brazil (Manaus municipality - Amazonas; Santar é m municipality- Par á). The specimens for the present study were collected in Itacoatiara and Presidente Figueiredo municipalities, Amazonas, Brazil.

Bionomics

The immatures of this species are found throughout the year; they colonize artificial substrates as well as the lateral wall of the wooden water trough (human-made habitat) in Itacoatiara. In Presidente Figueiredo this species also was found in streams affected by human action, because they were artificially dammed. The habitat where the immatures were found is located in an open area, has acidic water (pH=4.0–5.9), water temperature varying daily from 24–31 o C, electrical conductivity of lees than 10µS/cm, air temperature varying daily from 26–35 o C, and humidity varying from 80–100%.

Larval specimens of S. truncata collected in Itacoatiara municipality fed mainly on green algae, diatoms and dinoflagelates ( Table 1 View TABLE 1 ), of which the most abundant species were Bambusina brebissonii K ü etz (Chlorophyta) and Peridinium sp. (Dinoflagelates) . Oliveira and Froehlich (1996) reported that in Leptonema and Smicridea diatoms were the most frequent item in the larval gut contents in the State of São Paulo.

Note: R=rare (1–3 per field); S=some (10–20 per field); F=frequent (over 20 per field).

In Itacoatiara, the immatures were found in association with immatures of Simulium perflavum Roubaud ( Diptera : Simuliidae ), a black fly species occupying characteristically open, disturbed areas, associated with artificial dams ( Hamada and McCreadie 1999). In Presidente Figueiredo, this species also was found in streams associated with a dam (due to road construction), suggesting that both species have similar environmental requirements.

Material examined

BRAZIL: Amazonas, Itacoatiara municipality, Fazenda Aruanã AM 010 Highway km 215, 03°00’S 58°49’W, Hamada, N., 27.iii.1993 —1 pharate female, 1 pharate male, 2 pupae and 5 larvae (INPA); 29.vi.1993 —1 pharate female, 1 pharate male, 1 pupae and 4 larvae (INPA); Presidente Figueiredo municipality, São Jos é do Uatumã, Igarap é [small stream] on Estrada [road] da Morena km 17, #1 02°04'S / 59°20'W, 23.ii.2000, Pes, A.M.O, U.C. Barbosa, J. Bosco, Y. B. Alencar - 4 larvae (INPA); BR 174 Highway km 9, Igarap é [small stream] das Lages, Camping Sr. N é zinho, 01°59'38"S / 60°01'40”W, 27.ix.2000, Pes, A.M.O., J. Bosco, J. O. da Silva— 1 larvae (INPA); Igarap   GoogleMaps é [small stream] of the Ramal do Cemit é rio, 02°02'S / 59°59'W, 27.ii.2000, Pes, A.M.O., U.C. Barbosa, J. Bosco, Y. B. Alencar— 1 larvae, 30.ix.2000, 22 larvae and 5 pupae; Igarap é [small stream] BR 174 Highway, km 121, 01°55'S / 60°03'W, 26.ix.2000, Pes, A.M.O., J. Bosco, J. O. da Silva – 48 larvae (INPA).