Brasilocaenis mendesi Malzacher, 1998

Brasilocaenis mendesi Malzacher, 1998 View in CoL

( Figs. 2–8 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

B. mendesi Malzacher, 1998: 2 View in CoL ; Domínguez et a l. 2006: 201; Lima et al. 2019: 91.

Diagnosis. This species can be characterized by the following combination of characters, male imago: 1) Body length 1.33–2.08 mm; 2) Base of antennal flagellum not dilated; 3) Forceps apically pointed, abruptly narrowing at the apex and slightly curved inward; basal half fused to the lateral margins of the styliger plate ( Fig. 3A–D View FIGURE 3 ); 4) Styliger plate as wide as long, with a deep median emargination forming two long lateral lobes ( Fig. 3A–D View FIGURE 3 ); 5) Presence of a dorsal structure associated with the penis ( Lima et al. 2019). Nymph: 1) Anterolateral corners of pronotum pointed ( Fig. 6A View FIGURE 6 ); 2) Middle coxa with well-developed semicircular projection, hind coxa with finger-like projection ( Fig. 8B–C View FIGURE 8 ); 3) Hind tarsal claws with 14 small denticles ( Fig. 8F View FIGURE 8 ); 4) Opercular gill with dorsal surface covered with microspines and short, simple bristles ( Fig. 6C View FIGURE 6 ); 5) Sternum IX with a truncated posterior margin.

Descriptions

Male imago ( Figs. 2–3 View FIGURE 2 View FIGURE 3 ). Length (in mm): Body 1.3–2.0 (n= 6); forewing: 1.4–2.0; foreleg: 1.1– 2.2; hind leg: 1.0–1.6; cercus: 4.8–6.6. Ratios. Foreleg 1.1–1.3× the length of hind leg. Ratio of first segment of the foretarsi length to 2nd:3rd:4th:5 th = 0.2:0.4–0.5:0.5:0.7–0.8. Genitalia: styliger plate length 0.47–0.70× width; forceps length 6.7–7.4× width at half length.

Coloration. Head light brown to yellowish, shaded with dark markings in dorsal view ( Fig. 2A View FIGURE 2 ); ventral surface yellowish ( Fig. 2C View FIGURE 2 ). Antennae: scape pale; pedicel pale with dark brown apex; flagellum grayish, with basal half dark brown ( Fig. 2A View FIGURE 2 ). Thorax. Prothorax light brown to yellowish, with black lateral margins. Meso- and metanotum light brown to yellowish, shaded with brown on the keels; pleura and sterna pale light brown. Wings. Forewings hyaline; veins translucent, except C, Sc, Rs, and MA, which are black. Legs. Yellowish brown, with femora and tibiae each bearing a black subapical spot. Abdomen. Terga whitish: segments I–II with a black medial stripe and darker lateral areas; segments III–VI whitish with subtle black pigmentation medially; segment VII whitish, faintly yellowish, with black lateral spots; segment VIII similar, but lateral black spots are more subtle; segments IX–X faintly yellowish ( Fig. 2A View FIGURE 2 ). Sterna pale, with segment IX yellowish ( Fig. 2C View FIGURE 2 ); pleura pale ( Fig. 2B View FIGURE 2 ). Genitalia. Sternum IX with distinctly yellow sclerites ( Fig. 2C View FIGURE 2 ). Forceps dark brown; penis yellowish ( Figs. 3A–D View FIGURE 3 ). Caudal filaments. Light and translucent.

Morphology. Antenna: Base of antennal flagellum dilated. Thorax. Pronotum with lateral margins rounded and broader posteriorly ( Fig. 2A View FIGURE 2 ); process on mesonotal membrane in lateral view triangular, pointed (shark-finshaped) ( Figs. 2B, E View FIGURE 2 ); prosternal longitudinal ridges forming a triangular structure, closed and rounded anteriorly and with straight lateral margins ( Fig. 2D View FIGURE 2 ). Abdomen. Lateral filaments and fingerlike process on tergum II lacking. Genitalia. Styliger plate sclerotized, with roundly projected lateroposterior margins, forming a variable broad and concave posterior margin in-between. Anterior margin roundly indented between the long and thick apophyses ( Fig. 3A–D View FIGURE 3 ), barely discernible basolateral and central sclerites, wide lateral sclerite. Forceps middle third fused with styliger plate, tapering progressively towards apex and curving slightly inwards; smaller, subequal or larger than styliger plate. Penis protruding dorsally and laterally, with apical notch, deeper in some individuals, with sclerotic penile fold.

Female imago ( Figs. 4A–E View FIGURE 4 , 5A–C View FIGURE 5 ). Body length: 2.3–2.9 mm (n = 7); forewing: 1.9–2.1 mm; foreleg: 1.3–1.4 mm; cercus, broken. Thorax: Similar to that of males, but with more evident dark brown spots on the mesonotum and metanotum. The process on the mesonotal membrane is less elevated and less developed compared to males. Katepisternum pale yellow; mesopleural sclerites brown ( Fig. 4B View FIGURE 4 ). Abdomen: similar to that of males, but with a distinct black line on the posterior margin of terga VII and VIII, more pronounced in some individuals. Abdominal sternum IX with the posterior margin slightly projected ( Fig. 4C View FIGURE 4 ). Lateral filaments absent.

Egg ( Figs. 5A–C View FIGURE 5 ). Length: 97–101 μm; width: 64–73 μm. Light yellow in color. Oval in shape. Chorion surface smooth. Micropyle funnel-shaped, narrow and elongated, without a sperm guide. Two rope-like polar caps, coiled with fine intertwined threads, located at the narrower end of the egg, each with approximately 12 terminal buttons.

Nymph ( Figs. 6A–F View FIGURE 6 , 7A–F View FIGURE 7 , 8A–F View FIGURE 8 ). Length (in mm): Body, 3.2–3.3 mm (n = 2), cercus, broken. Ratios. Mouthparts. Width of maxillary palp segment I 2.4 width of segment II; length of maxillary palp segment I 2.0× length of segment II; length of maxillary palp segment I 1.3× length of segment III; length of labrum 0.3× its maximum width. Foreleg. Length of fore femur 3.0× its maximum width.

Coloration and Morphology. Head. Light brown with black spots, shaded black posterior to eyes; mouthparts light brown to translucent yellowish. Antennae with pedicel and flagellum pale. Labrum broad, with shallow anteromedial emargination and rounded lateral margins; dorsal surface with long bristles along the margin and serrated/denticulate apical edge. Linguae of hypopharynx rounded ( Fig. 7B View FIGURE 7 ). Right mandible with subapical bristles of varying size on the inner margin and long, thin setae at the median area ( Fig. 7F View FIGURE 7 ). Thorax. Nota light brown with dark brown sutures. Pronotum with light brown anterior margin and black-shaded areas; anterolateral corners pointed ( Fig. 6A View FIGURE 6 ). Mesonotum with yellowish white spot anterior to wing bud bases and dark brown medial lines ( Fig. 6A View FIGURE 6 ). Thoracic sternum yellowish with brownish outer margins; metasternum with a dark brown posterior line. Legs brownish yellow: femora yellowish-brown with subapical black spots; tibiae yellowish-brown, slightly darkened medially; tarsi yellowish-brown. Fore femur well-developed, without projection; middle and hind femora developed and pointed ( Figs. 8A–C View FIGURE 8 ). Coxae without bristles externally; middle coxa with well-developed semicircular projection, hind coxa with finger-like projection. Femora with few, variably sized bristles along dorsal, internal, and external margins ( Figs. 8A–C View FIGURE 8 ), anterior and middle femora in the dorsal region with bifid setae ( Figs. 8A–B View FIGURE 8 ). Tibiae with simple setae of variable size along the inner margins and with few simple setae on the outer margin ( Figs. 8A–C View FIGURE 8 ). Anterior and middle tarsi with a single row of simple setae on the inner margin ( Figs. 8A–C View FIGURE 8 ). Hind tarsus with two rows of setae, one simple and the other serrated ( Fig. 8C View FIGURE 8 ). Anterior and middle tarsal claws without denticles; posterior tarsal claws with approximately 14 small denticles ( Fig. 8F View FIGURE 8 ). Abdomen. Terga light brown, segments I–II with medial black band; III–VI subtly pigmented medially; VII–IX whitish with lateral black spots, more distinct on segment VII; segment X slightly yellowish ( Figs. 6A–B View FIGURE 6 ). Sterna light brown to grayish ( Fig. 6B View FIGURE 6 ). Operculate gills light brown, nearly entirely shaded with black, and with three lateral black spots; dorsal surface covered by microspines and short, simple setae; medial crest Y-shaped, complete and well-developed; ventral surface with elongated, apically fringed microtrichia ( Figs. 6C–E View FIGURE 6 ). Posterolateral projections on segments III–IX long and pointed ( Figs. 6A–B View FIGURE 6 ). Sternum IX with a truncated posterior margin, bearing short, simple setae laterally and posteriorly. Caudal filaments brownish ( Figs. 6A–B View FIGURE 6 ).

Life cycle association. The association was established based on shared morphological characteristics and coloration patterns among specimens collected from the same water body.Although five male imagos of Brasilocaenis elidioi were collected at the same location, the nymphs collected from the same habitat do not match the described morphological characteristics of B. elidioi , indicating that they likely belong to a different species. Additionally, coloration characteristics were used to assist in associating nymphs with adults, the main ones being: yellowish-brown legs; yellowish-brown femora with subapical black spots; and yellowish-brown tibiae, slightly darkened in the median region, patterns that can also be observed in both male and female adults. The alates of Brasilocaenis elidioi generally exhibit a whitish body coloration; however, the specimens we analyzed showed a yellowish hue.

Distribution and Biology. This species is known from Bolivia, Brazil (states of Mato Grosso and Pará), and Colombia. The specimens analyzed in this study were collected from tributaries of the Curuá-Una (Moju River) and Tapajós (Juá stream) river basins. These habitats are characterized by moderate rapids and vary in width from 6 to 12 meters depending on the season. Notably, both environments have been subjected to significant anthropogenic pressure, particularly Juá stream, which flows through an urbanized area.

Material examined. Fourteen ♂ imagos, 2 ♂ subimagos, 1 ♀ imago, 2 ♀ subimagos from Brazil, Pará state, Santarém city, Júa-Casa Stream , 02°26’4”S; 54°47’21”W, 27–28.ix.2023, Oliveira L.A. col. ( UFOPA) GoogleMaps ; 100 ♂ imagos, 19 ♀ imagos, from Brazil, Pará state, Mojuí do Campos city, Moju river , 02°42’03”S, 54°41’01”W, 11.xi.2020, Oliveira L.A. col. ( UFOPA) GoogleMaps ; 1 nymph, same data except date 21.i.2020 ( UFOPA) GoogleMaps ; 1 nymph, same data except date 05.vii.2020 ( UFOPA) GoogleMaps .