Rivudiva watu De Lima & Massariol & Cruz & Hamada 2022, sp. nov.

Rivudiva watu sp. nov.

urn:lsid:zoobank.org:act: BEAE7E30-6067-4856-80A5-B64BFB8F516E

(Figures 6A–G; 7A–D; 8A–F)

Material examined. Holotype. Larva (on slide), BRAZIL, Minas Gerais State, Resplendor, 41º21′35″W, 19º13′57″S, 28.II. 2019, 148 m. a.s.l., coll. Bramuth A.C., Massariol, F.C., INPA. Paratypes: Larva (on slide), same data as holotype, INPA; 2 larvae (in alcohol), same data as holotype, INPA.

Description. Larva. Body length 3.0–4.0 mm. Coloration of light yellow, with light brown mark over terga VI.

Head. Antenna: flagellum with minute spines and setae on apex of each flagellomere. Labrum (Fig. 6A). Rectangular, length about 0.6 × maximum width; distal margin with medial emargination, one row of robust, eventually pectinated, setae from lateral to middle; one row of thin bifid setae on distal margin not reaching distolateral margin; dorsal surface with many thin setae near distal margin. Left mandible (Fig. 6B): incisors partially cleft in two sets (fused at middle length); outer and inner set of incisors respectively with 4+2 denticles, outer incisor with spine-like process; prostheca robust and apically pectinate; margin between prostheca and mola straight; tuft of spine-like setae at base of mola absent; subtriangular process wide and pointed; denticles of mola constricted; mola with one large denticle; outer margin convex. Right mandible (Fig. 6C): incisors cleft in two sets; outer and inner set of incisors respectively with 3+2 denticles, outer incisor with one spine-like process; prostheca stout, bifurcated at middle; margin between prostheca and mola straight; tuft of spine-like setae at base of mola present; denticles of mola not constricted; apex of mola with one simple setae; process of mola triangular; outer margin convex. Maxilla (Fig. 6D). Maxillary palp 2.0 × length of galea-lacinia; segment II 1.0 × length of segment I, apex with robust apical lobe; ventral canine expanded, not laterally folded over canines (see Fig. 1E in Cruz et al. 2022); two sets of distal setae of inner-ventral, one row clavate and one pectinate; base of maxilla broken. Hypopharynx (Fig. 6E): lingua 1.2× longer than superlingua, rounded without distomedial projection or tuft of setae and lateral simple setae; superlingua with rounded outer margin and with short, thin, simple setae scattered over distal margin. Labium (Figs 6F–G): glossa slightly broad at base, with parallel margins, distal margin slightly rounded with inner part oblique, with one stout blunt setae, shorter than paraglossa; inner margin with one short spine-like setae on half; ventral surface covered by thin setae; dorsal surface with inner arc close to inner margin, outer arc not sinuous, far from distal margin. Paraglossa curved inward; apex almost straight, with two rows of robust and long spine-like setae; outer margin with 3 long setae; dorsal surface with three longitudinal rows of setae, first row near inner margin longer than half of length, with long robust setae; second with half of length of the inner row, with long robust setae; and third near to outer-distal margin, with long setae; ventral surface with one row of 4 setae near to inner margin. Labial palp with segment I 1.0 × length of segments II and III combined; inner distal protuberance of segment II rounded, covered with thin, long simple setae; segment III narrow and conical, covered by thin simple setae, dorsal surface with robust spine-like setae.

Thorax. Foreleg (Figs 7A–B): femur length about 2.8 ×maximum width; dorsal margin with one row of long and robust setae reaching apex; ventral margin with few setae at base; anterior surface with one medial row of elongate setae, one row of long spine-like setae near ventral margin not reaching apex; posterior surface with one medial row of long spine-like setae, and one row of long spine-like setae near ventral margin reaching apex. Tibia dorsally bare; ventral margin with one row of long spine-like setae increasing in length to apex; patella-tibial suture absent. Tarsus: ventral margin with one row of spine-like setae. Claws 0.5 × length of tarsus, with two rows of conical denticles not reaching apex. Middle and hind legs (Figs 7C–D): femur anterior surface with one row of spine-like setae near dorsal margin, one row of long spine-like setae near ventral margin, and one medial row of long spine-like setae; posterior surface with one row of long spine-like setae near dorsal margin reaching apex, and one row of spine-like setae near ventral margin not reaching apex. Tibia dorsally bare; ventral margin without row of small blunt setae; patella-tibial suture present. Tarsus. Ventral margin with one row of small blunt setae. Claws 0.5 × length of tarsus, with two rows of small conical denticles reaching apex.

Abdomen (Figs 8A–F). Coloration of light yellow with tergum VI with large medium brown mark; sternum IX posterior margin with transversal dark mark. Posterior margin of terga with triangular spines (Fig. 8C). Gills oblong, longer than next segment, with one medial trachea pigmented. Paraproct (Fig. 8D) with four wide marginal spines, posterolateral extension with spines. Cerci (Fig. 8F) with lateral spines on every segment, longer on every longer on 2 nd segment. Paracercus (Fig. 8E) without spines.

Imagoes: Unknown.

Etymology. The Krénak people, the indigenous group who inhabits the region, named the Doce River as Watu; the specific epithet should be considered a noun in apposition.

Diagnosis. Larva: 1) labrum with medial emargination (Fig. 6A); 2) labrum ventral surface with simple robust row of setae on distal margin (Fig. 6A); 3) left mandible with incisors fused at middle length (Fig. 6B); 4) subtriangular process of left mandible pointed (Fig. 6B); 5) ventral canine of maxilla expanded, not laterally folded over canines (Fig. 6D); 6) maxilla with two sets of distal setae on inner-ventral row, one clavate and one pectinate (Fig. 6D); 7) hypopharynx without distomedial projection (Fig. 6E); 8) glossa distal margin with inner part oblique (Fig. 6G); 9) outer arc of setae on glossae not sinuous, far from distal margin (Fig. 6F); 10) labial palp segment III conical (Fig. 6F); 11) ventral margin of hind tibiae without row of setae (Fig. 7C); 12) patella-tibial suture absent (Fig. 7A); 13) paraproct with four spines (Fig. 8D).

Comments. The distal shape of glossa, distal set of inner-ventral row of maxilla, the absence of row of setae on hind tibiae and hypopharynx without distomedial projection or tuft of setae are unique characteristics from Rivudiva watu sp. nov., distinguishing it from all other species of the genus.

Rivudiva watu sp. nov., in Cruz et al. (2022) key, can be identified as R. trichobasis Lugo-Ortiz & McCafferty or R. uiara Cruz, Boldrini, De Lima & Hamada, 2022. Rivudiva watu sp. nov. can be differentiated from R. trichobasis by left mandible with pointed subtriangular process, rounded in R. trichobasis; maxillary palp segment II with small apical lobe, larger in R. trichobasis; ventral canine expanded, not laterally folded over canines (Fig. 6D), folded in R. trichobasis (Fig. 1E in Cruz et al. 2022); maxilla with two sets of distal setae of inner-ventral row, one clavate and one pectinate (Fig. 6D), only clavate in R. trichobasis (Fig. 1E in Cruz et al. 2022); hypopharynx without distomedial projection or tuft of setae, with projection and tuft of setae in R. trichobasis; glossa distal margin with inner part oblique, with one stout blunt seta, distal margin rounded in R. trichobasis; row of setae on ventral margin of hind tibiae absent, present in R. trichobasis; paraproct with four spines, nine in R. trichobasis. The same feature set presented distinguishes Rivudiva watu sp. nov. from R. uiara. Additionally, the new species can be differentiated by the segment III of labial palp, complete conical in R. watu sp. nov., apex concave in R. uiara; and outer arc of setae on glossa not sinuous, far from distal margin in R. watu sp. nov., sinuous in R. uiara.