Pagelmis mura, Polizei & Hamada, 2021

Polizei, Thiago T. S. & Hamada, Neusa, 2021, A new minute riffle beetle (Coleoptera: Elmidae: Pagelmis) from the Brazilian Amazon, Zootaxa 5061 (2), pp. 369-376 : 370-374

Pagelmis mura sp. nov.

( Figs 1–13 , 15–16 )

urn:lsid:zoobank.org:act:255E923D-08A8-417B-8D3E-FB8A998397E6

Material Examined: Holotype. Male. Pinned, genitalia, abdominal segments VIII and IX mounted on a slide. “ Brazil. Amazonas. Manacapuru / AM 352 - Km 75. Igarapé / pequeno no roçado. 30.III.2008. Jorge L. Nessimian et al. leg. 03°03’50.5”S 60°43’21.6”W, 45 m above s.l.” ( INPA) . Allotype. Pinned. “ Brazil. Amazonas. Manaus. / Reserva Ducke AM010 – Km 26 / Igarapé Bolívia . 26.V.2008 / 02°59’14.5”S 59°56’30.5”W, 75 m above s.l. Carlos A.S. Azevedo et al. leg. // MZSP 32999 ” ( MZSP) .

Diagnosis. The new species can be distinguished by having 1) body densely covered by distinct elongate granules; 2) pronotum with median area shiny and longitudinal, without plastron, creating a pattern in the middle third of posterior margin, that is almost straight from the base to posterior 1/3 of pronotum, then strongly narrowed into apical portion that is slightly widened into arrowhead-like shape, reaching slightly at anterior 1/3; 3) elytra with the intervals I–II without plastron; 4) anterior tibiae with a cleaning fringe; 5) males with an apicoventral tubercle on meso- and metatrochanter; 6) smaller size (1.31–1.33 mm length).

Description: Male. ( Figs 3–12 ) Body elongate, subparallel, flat. Cuticle reddish-brown, fully covered by opaque plastron except for the parts of head, median longitudinal area of pronotum, a longitudinal band on elytra near the suture, scutellum, and the legs. Surface with dense elongate granules and micropunctures. Total length (anterior margin of the pronotum to elytral apex) 1.31 mm, greatest width (elytra) 0.48 mm.

Head ( Figs 3–6 ) partly retractable into prothorax; dorsal surface with micropunctures. Eyes protruding laterally. Antennae filiform, 11-segmented, antennomere VI–XI with few, very short thin setae on apex. Frontoclypeal suture straight. Clypeus 4x wider than long. Labrum ( Fig. 3 ) subrectangular; anterolateral angles rounded; anterior margin bi-sinuate. Maxilla: maxillary palpus 4-segmented, palpomere IV subequal in length to the two-preceding ones combined. Labium: gula narrower than submentum and mentum, subrectangular, glabrous, with punctures; submentum and mentum flat, subrectangular, glabrous, with punctures; labial palpus 3-segmented; apical palpomere subequal in length to the two preceding ones combined; ligula weakly sclerotized, almost 2x longer than wide, anterior margin sinuous, anterolateral angles arcuate and raised. Gena covered by tomentum.

Thorax ( Figs 3–6 , 12 ). Pronotum ( Figs 3, 5–6 , 12 ) 1.2x longer than wide; anterior margin strongly arcuate and raised medially, with a distinct carinae not reaching the lateral margins ( Figs 3, 5 ); sides broadly convex, crenulated; posterior angles slightly acute; posterior margin tri-sinuate, without prescutellar fovea; pronotal surface ( Figs 3, 5 , 12 ) with median area shiny and longitudinal, without plastron, creating a pattern in the middle third of posterior margin, that is almost straight from the base to posterior 1/3 of pronotum, then strongly narrowed into apical portion that is slightly widened into arrowhead-like shape, reaching slightly at anterior 1/3; a median longitudinal impression distinct, from base to the posterior half, medially attenuated; integument with row of elongate granules, and micropunctures distanced by the equivalent of one or two times their diameter organized circular like. Scutellum ( Fig. 3 ) shield-like, glabrous. Elytra ( Figs 3, 5–6 ) 1.7x longer than wide; wider than pronotum; almost flat dorsally ( Fig. 6 ); anterior margin smooth, without plastron; subparallel in anterior 2/3, margins slightly crenulated, apices rounded; humeri rounded; elytra with the intervals I–II without plastron, intervals III–VII well marked by distinct rows of elongate granules, with micropunctures distanced by the equivalent of one or two times their diameters; first row of granules (between intervals I and II), less visible, and covered by plastron (better visible on female ( Fig. 1 )). Epipleura narrow, wider anteriorly, covered by plastron and micropunctures ( Figs 4, 6 ). Metathoracic wings absent (apterous). Hypomeron ( Figs 4, 6 ) broad, 2x longer than wide, with rows of elongate granules and covered by micropunctures. Prosternum 2x wider than long, anterior margin arcuate, disc covered by granules and micropunctures ( Fig. 4 ). Prosternal process narrow, with parallel sides, about 1/3 as wide as long, apex rounded ( Fig. 4 ). Proepimeron and proepisternum covered by plastron. Mesoventrite with mesal cavity for the reception of prosternal process; mesepimeron covered by plastron. Metaventrite longer than mesoventrite ( Fig. 4 ), mesaly strongly depressed; discrimen inconspicuous, surface with few setae, plastron and micropunctures, sides similar, but granulose. Legs ( Figs 3–6 ) without plastron. Pro and mesocoxae rounded, metacoxae transverse. Trochanter subtriangular; meso and metatrochanter with an apicoventral tubercle. Femora strongly narrowed basally, 3.5x longer than wide. Tibiae thin, 7x longer than wide, with spines on distal ¾; protibiae with short cleaning fringe on distal half, not reaching the apex ( Figs 3, 5 ). Tarsus elongated, with few thin setae on ventral surface; apical tarsomere shorter than the four preceding ones combined. Claws simple.

Abdomen ( Figs 4, 6–11 ) with five ventrites ( Fig. 4 ), covered by plastron, micropunctures and few granules and setae; intercoxal process of ventrite 1 depressed; posterolateral margins not produced. Tergite VIII ( Fig. 7 ) rounded posteriorly; anterior margin slightly arcuate medially; surface covered by few setae. Sternite VIII ( Fig. 8 ) with anterior apodeme about as long as rest of sternite, posterior margin arcuate, with long setae. Segment IX ( Fig. 9 ) forming a subrectangular genital capsule surrounding aedeagus with two long anterior median struts.

Male genitalia ( Figs 10–11 ) symmetrical. Phallobase tubular, approximately 3.7x longer than wide, 1.7x longer than penis. Parameres fused, narrowed towards the apex, wider at the base, approximately 5x longer than wide, apex slightly divergent; surface with sensorial pores on posterior ¾ and tufts of setae on apical 1/3; in ventral view inner margin arcuate ( Fig. 10 ), in dorsal view straight ( Fig. 11 ). Penis shorter than parameres, approximately reaching ¾ of the length of the parameres, 3x longer than wide at the base, constricted in the basal and apical 1/3, lateral margins sinuous, rounded apex, three basolateral apophyses; fibula narrow, approximately as long as 1/3 of penis; corona absent.

Female. ( Figs 1–2 , 13 ) 1.33 mm long, greatest width (elytra) 0.5 mm. External morphology similar to male, except for absence of deep depression on metaventrite and on intercoxal process of abdominal ventrite 1, and the lack of the apicoventral tubercle on meso- and metatrochanter. On the female specimen, shiny pronotal median area reaching from base to middle, not strongly narrowed on apex ( Figs 1 , 13 ).

Etymology. The specific epithet, mura is in honor of the Mura ethnic group that inhabits the hydrographic basins of the Madeira, Amazonas and Purus Rivers, in the Amazonas state. The Mura were known for their excellent knowledge of navigation in the different aquatic systems of the Amazon region. The name is a noun in apposition.

Habitat. Both specimens were found in typical slow-flowing Amazon streams, with black water and sandy streambed, with patches of leaf litter and roots of riparian vegetation ( Fig. 16 ). The holotype locality is a firstorder stream (sensu Strahler 1957), situated in the municipality of Manacapuru, Amazonas State, in a private rural property. The stream had a mean width of 1.2 m, a mean depth of 11 cm; its water temperature was 26.5°C, pH 4.6, and electrical conductivity 21.9 µS/cm. The allotype locality, Bolivia stream, is a second-order stream located in the Reserva Florestal Ducke , a biological reserve that belongs to the Instituto Nacional de Pesquisas da Amazônia, located adjacent to the city of Manaus, Amazonas. This stream was characterized by having mean width of 2 m, mean depth of 25.16 cm, water temperature 24.7°C; pH 4.92, and electrical conductivity 13.72 µS/cm.

Distribution: BRAZIL. Amazonas State.

Comparative notes. Pagelmis mura sp. nov. share to P. amazonica the structure of male genitalia, in which parameres are longer than penis. However, in P. amazonica the body is not covered by distinct elongate granulates; pronotum has the shiny, longitudinal, median area without plastron arcuate into apical portion; tibiae without cleaning fringes; metathoracic wings present; males with an apicoventral tubercle only on metatrochanter (very short in females) and the specimens are bigger (2.2 mm).

Holotype condition. It is slightly damaged. Missing parts include tarsomeres IV-V and the claws of the right foreleg and tarsomeres IV-V on the right hind leg. Genitalia, abdominal segments VIII and IX are preserved on a slide.

Figures

FIGURES 1–6. Pagelmis mura sp. nov. Habitus. 1–2. Female. Allotype. (1) Dorsal view. (2) Ventral view. 3–6. Male. Holotype. (3) Dorsal view. (4) Ventral view. (5) Frontal view. (6) Lateral view. Scale bar = 0.5mm.

FIGURES 7–11. Pagelmis mura sp. nov. Male. Holotype. (7) Sternite VIII. (8) Tergite VIII. (9) Segment IX. 10–11 Aedeagus. (10) Ventral view. (11) Dorsal view. Scale bar = 0.1mm.

FIGURES 12–14. Pattern of the median shiny longitudinal area without plastron on pronotum. 12–13 Pagelmis mura sp. nov. (12) Male. (13) Female. (14) Pagelmis amazonica Spangler, 1981, adapted from the original description.

FIGURES 15–16. (15) Geographical distribution map of Pagelmis (Coleoptera: Elmidae). (16) Stream in Manacapuru municipality, Amazonas state, Brazil, where the holotype of P. mura sp. nov. was collected.