Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998

Cruz, Paulo Vilela, Boldrini, Rafael, De Lima, Cláudia R. T. & Hamada, Neusa, 2022, It is a mess! How many species are in Rivudiva trichobasis Lugo- Ortiz & McCafferty, 1998 (Ephemeroptera: Baetidae)?, European Journal of Taxonomy 789 (1), pp. 153-191 : 157-159

Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998

Figs 1–3

Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998: 64 (type material).

Rivudiva trichobasis – Cruz et al. 2018: 10, figs 23, 29. — Lugo-Ortiz & McCafferty 1998: 64 (with some doubt, partim). — Salles et al. 2020: 49 (with some doubt).

not Rivudiva trichobasis – Cruz et al. 2011: 60. — Falcão et al. 2011: 539. — Boldrini et al. 2012: 93.

— Boldrini & Cruz 2014: 5.

Diagnosis (adapted from Salles et al. 2020)

NYMPH. The combination of the characters: 1) labrum with medial emargination ( Fig. 1B); 2) labrum ventral surface with simple robust row of setae on distal margin ( Fig. 1B); 3) left mandible with incisors fused at middle length ( Fig. 1C); 4) maxillary palp segment II with robust apical lobe ( Fig. 1E); 5) ventral canine expanded, laterally folded over canines; 6) hypopharynx with small distomedial projection ( Fig. 1F); 7) outer arc of setae on glossa with apical half not sinuous, far from distal margin ( Fig. 1G–H); 8) labial palp segment III narrow and conical ( Fig. 1G); 9) dorsal margin of forefemur with one row of long spine-like setae from base to apex ( Fig. 2A); 10) forefemur on anterior surface with medial row of elongate blunt setae ( Fig. 2A); 11) patella-tibial suture absent; 12) distal margin of terga with wide marginal spines ( Fig. 3A).

Material examined

Paratype

BRAZIL • 1 nymph; Rio Grande do Sul State, Arroio dos Vargas; 30°50′ S, 53°10′ W; 120 m a.s.l.; Nov. 1964; F. Plaumann leg; IBN slide #270 .

Redescription

Nymph

HEAD. Antenna ( Fig. 1A). Flagellum with minute spines on apex of each segment. Labrum ( Fig. 1B). Rectangular, length about 0.7× 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, near distal margin, with many thin setae over surface. Left mandible ( Fig. 1C). Incisors partially cleft in two sets (fused at middle length); outer and inner set of incisors respectively with 4 + 3 denticles, outer incisor without 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; denticles of mola not constricted; mola with one large denticle; outer margin convex. Right mandible ( Fig. 1D). Incisors fused at base; outer and inner set of incisors respectively with 3 + 3 denticles, outer incisor with one spine-like process; prostheca stout, bifurcated at middle, inner lobe longer and pectinate; 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; first process of mola triangular, second expanded and straight; outer margin convex. Maxilla ( Fig. 1E). Maxillary palp 1.6× length of galea-lacinia; segment II 1.0× length of segment I, apex with robust apical lobe; ventral canine expanded, laterally folded over canines; set of distal setae of inner-ventral row clavate, base of maxilla broken. Hypopharynx ( Fig. 1F). Lingua longer than superlingua, sub-quadrangular with a small distomedial projection covered by tuft of simple setae; superlingua with rounded outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Labium ( Fig. 1G–H). Glossa slightly broad at base, with parallel margins, distal margin slightly rounded with small concavity and shorter than paraglossa; inner margin with two short spine-like setae on half; ventral surface covered by thin setae; dorsal surface with inner arc close to inner margin, outer arc basal half of row close to outer margin, apical half of row not sinuous, far from distal margin; one long robust blunt seta on apex. Paraglossa curved inward; apex with two rows of robust and long spine-like setae; outer margin with two 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 four setae near to ventral margin. Labial palp with segment I 0.8× 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 (folded in slide studied), covered by thin simple setae, dorsal surface with robust spine-like setae near inner margin.

THORAX. Foreleg ( Fig. 2A–C). Femur length about 3.2× maximum width; anterior surface with one medial row of elongate and blunt setae, one row of long spine-like setae near ventral margin not reaching apex; posterior surface with one row of long spine-like setae near dorsal margin not reaching apex, 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. Tarsal claws ( Fig. 2B) 0.3× length of tarsus, with two rows of conical denticles not reaching apex. Hind leg ( Fig. 2D–E). Femur anterior surface with one row of spine-like setae near dorsal margin on distal half, one row of long spine-like setae near ventral margin; posterior surface with one row of long spine-like setae near dorsal margin not reaching apex, one row of spine-like setae near ventral margin reaching apex. Tibia. Dorsally bare; ventral margin with one row of small blunt setae; patella-tibial suture present. Tarsus. Ventral margin with one row of small blunt setae. Tarsal claws ( Fig. 2D) 0.5× length of tarsus, with two rows of small conical denticles reaching apex.

ABDOMEN. Terga III and VI with large medium brown mark. Posterior margin of terga with small triangular spines ( Fig. 3A–B). Gills missing. Paraproct ( Fig. 3C) with nine to twelve wide marginal spines, posterolateral extension with spines. Cerci ( Fig. 3D) with lateral spines on every segment. Paracercus ( Fig. 3E) without spines.

Comments

Based on the study of type material, records from Brazil, Roraima ( Falcão et al. 2011), Rondônia ( Boldrini & Cruz 2012), Amazonas ( Cruz et al. 2011) and Maranhão (R. sp. X) ( Boldrini et al. 2012), are not R. trichobasis . The specimens from Espírito Santo ( Brazil) ( Salles et al. 2020) and Paraguay (Paraguarí) could not be evaluated.

Distribution

Brazil (Rio Grande do Sul). Paraguay (Paraguarí) is treated here as putative; records from Espírito Santo ( Brazil) ( Salles et al. 2020) are treated here as putative and must be evaluated.