Nilssondytes diversus, Miller & Michat & Ferreira Jr, 2024

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Reclassification of Cybistrinae Sharp, 1880 in the Neotropical Region (Coleoptera, Adephaga, Dytiscidae), with description of new taxa, ZooKeys 1188, pp. 125-168 : 125

Nilssondytes diversus sp. nov.

Figs 11 , 19 , 20 , 36-38 , 53 , 61 , 73, 74

Type locality.

Venezuela, Amazonas State, roadside pond ca. 7 km S Samariapo 5°10.900'N, 67°46.078'W, 95 m elev.

Diagnosis.

This is the only species in the genus and is characterized by its diagnostic combination (see above). Typically, species-level features include the shape of the male median lobe which is unique. In ventral aspect the apex is abruptly constricted with the apex narrowly truncate with laterally pointed processes (Fig. 37 ). In lateral aspect, the median lobe is moderately evenly curved on the dorsal margin, lobe apically abruptly narrowed with the apex elongate and slender, apically narrowly rounded (Fig. 36 ).

Description.

Measurements. TL = 16.7-19.4 mm, GW = 9.6-10.7 mm, PW = 7.0-8.1 mm, HW = 4.2-4.7 mm, EW = 2.7-2.9 mm, TL/GW = 1.7-1.8, HW/EW = 1.6-1.7, WC/WV = 3.1-3.2. Body shape suboval, slightly expanded posteriorly, widest at ~ 3/5 of length; lateral margins evenly, continuously curved between pronotum and elytron. Depressed and somewhat flattened in lateral aspect (Figs 11 , 73).

Coloration (Figs 11 , 73). Head dark green, anterior clypeal margin yellow, more so laterally, testaceous near eyes. Pronotum dark green with broad lateral yellow margin, posteriorly interrupted and green in one of the four examined specimens, in other specimen yellow extending to posterior angle. Elytron dark green with broad lateral yellow band, separated narrowly from lateral margin, slightly expanded near apex. Ventral surfaces largely black, testaceous on head, basal leg segments and elytral epipleuron.

Sculpture and structure. Head broad, frontoclypeal lines elongate, straight, strongly oblique; anterior clypeal margin broadly, shallowly, and evenly concave; dorsal surface evenly covered with fine microsculpture and micropunctures. Pronotum with lateral margins evenly and broadly curved; surface similar to surface of head in microsculpture and micropunctation. Elytral lateral margin evenly and slightly curved for most of length, apically broadly curved; surface of elytron similar to surface of head in microsculpture and micropunctation. Prosternal process apically rounded, ventral surface distinctly sulcate, apex robust, acutely pointed. Metaventral wing broad, slightly less than 1/3 width of lateral portion of metacoxa (WC/WV = 3.1-3.2); surface smooth, without sculpturing. Lateral portion of metacoxa large, broad, surface smooth, without sculpturing; metacoxal lines short, extending less than half distance across metacoxa. Abdominal ventrites smooth, unsculptured.

Male genitalia. Male median lobe in lateral aspect shallowly curved, apically abruptly narrowed, apex narrowed, slightly curved, apically narrowly rounded, broad medially (Fig. 36 ). In dorsal aspect broad throughout most of length, apically abruptly narrowed, apex laterally produced, submedially with broad, elongate lobes on each side, ventral sclerite short, apically sharp, acuminate, extending to 3/5 length of median lobe, apex sharply pointed (Fig. 37 ). Lateral lobe broad in basal half, apically distinctly narrowed, apex narrowly rounded, with series of elongate setae along more than apical half of dorsal margin of lateral lobe (Fig. 38 ).

Female genitalia. With a single genital opening, vagina elongate, slender, with enlarged, bulbous region at base of common oviduct; spermatheca short, curved, at apex of enlarged region, with soft tissue region on each side of enlarged region (Fig. 61 ); gonocoxae together broad, apically broadly pointed (Fig. 61 ); gonocoxosternite broad, with elongate anterolateral lobe, with medial margin sublinear, without conspicuous setae (Fig. 61 ).

Sexual dimorphism. Males have a characteristic broad protarsal palette with ventral adhesive setae. Males also have mesotarsomeres with clumps of posteroventral setae. Females lack pro- and mesotarsal expansions or adhesive setae. Both males and females have two metatarsal claws with the posterior shorter than the anterior, but females have the posterior somewhat more curved than in males (Figs 19 , 20 ). Females have distinctive microsculpture on the surface of the elytron anteriorly in the form of a field of short striae which is absent in males.

Variation. Five specimens were examined. One specimen has the lateral pronotal yellow band extending to the posterior margin of the pronotum, the others have a narrow dark green separation from the posterior margin.

Distribution.

This species is known from few localities in Venezuela along the northwestern margins of the Guiana Shield craton (Fig. 74 ).

Natural history.

The only natural history information available from labels is "roadside pond," "river margin," and "rock outcropping."

Etymology.

The species is named from the Latin Nilssondytes diversus , meaning “different,” in recognition of the different lengths of the metatarsal claws in both males and females (Figs 19 , 20 ).

Material examined.

Holotype, male labeled, " VENEZUELA: Amazonas State 5°10.900'N, 67°46.078'W, 95 m ca. 7 km S. Samariapo 15.i.2009; leg. Short, Miller, García, Camacho, Joly VZ09-0115-02X: roadside pond/ SM0846115 KUNHM-ENT [barcode label]/ HOLOTYPE: Nilssondytes diversus Miller, Michat and Ferreira-Jr., 2023 [red label with double black line border]." Paratypes, 1 male labeled, " Suapure VENEZ. Caura River 4.20.1900 [handwritten] E.A. Klages. " , 1 female labeled " VENEZUELA: Bolivar State 7°41'23.6"N, 64°1'56.0"W, 134 m ca. 14 km E Rio Aro ; 5.viii.2008 leg. A. Short $ M. García AS-08-073; rock outcropping/ SM0829328 KUNMH-ENT [barcode label]," 1 female labeled " VENEZUELA: Guárico State 8°6.226'N, 66°26.228'W, 52 m UCV San Nicolasito Field Station: Rio Aguaro ; 10.i.2009 leg. Short, Miller, Joly, García, Camacho; VZ09-0110-01A/ SEMC0852602 KUNHM-ENT," 1 male labeled " VENEZUELA: Bolivar State 6.58694°N; 67.02912°W Rio Caripito 12.i.2009; leg. Short Miller VZ 09-0112-02A: river margin/ SM0844405 KUNHM-ENT [barcode label]." All paratypes with, “… PARATYPE Nilssondytes diversus Miller, Michat and Ferreira-Jr., 2023 [blue label with black line border]."

Figures

Figure 74. Distribution of Nilssondytes diversus in northern South America.

Figures 9 - 14. Neotropical Cybistrinae species, habitus 9 Cybister festae 10 Cybister puncticollis 11 Nilssondytes diversus 12 Megadytes parvus 13 Megadytes latus 14 species " IR 57 " (Ribera et al. 2008). Scale bar: 10.0 mm.

Figures 15 - 29. Neotropical Cybistrinae species, metatarsal claws and tarsomere VI of males and females 15, 16 Cybister festae 17, 18 Cybister puncticollis 19, 20 Nilssondytes diversus 21, 22 Megadytes latus 23, 24 Megadytes parvus 25 species " IR 57 " (Ribera et al. 2008) 26, 27 Paramegadytes glaucus 28, 29 Metaxydytes fraternus. Scale bars: 1.0 mm.

Figures 30 - 50. Neotropical Cybistrinae species, male genitalia 30 - 32 Cybister festae: 30 median lobe, right lateral aspect 31 median lobe, ventral aspect 32 right lateral lobe, right lateral aspect 33 - 35 Cybister puncticollis: 33 median lobe, right lateral aspect 34 median lobe, ventral aspect 35 right lateral lobe, right lateral aspect 36 - 38 Nilssondytes diversus: 36 median lobe, right lateral aspect 37 median lobe, ventral aspect 38 right lateral lobe, right lateral aspect 39 - 43 Megadytes parvus: 39 median lobe, right lateral aspect 40 median lobe, ventral aspect 41 right lateral lobe, right lateral aspect 42 apex of median lobe, right lateral aspect 43 apex of median lobe, ventral aspect 44 - 47 Megadytes latus: 44 median lobe, right lateral aspect 45 median lobe, ventral aspect 46 right lateral lobe, right lateral aspect 47 apex of median lobe, ventral aspect 48 - 50 species " IR 57 " (Ribera et al. 2008): 48 median lobe, right lateral aspect 49 median lobe, ventral aspect 50 right lateral lobe, right lateral aspect.

Figures 51 - 57. Neotropical Cybistrinae species, male sternite IX, ventral aspect 51 Cybister festae 52 Cybister puncticollis 53 Nilssondytes diversus 54 Megadytes latus 55 Megadytes parvus 56 Paramegadytes glaucus 57 Metaxydytes fraternus. Scale bars: 1.0 mm.

Figures 58 - 61. Neotropical Cybistrinae species, female genitalia including left gonocoxosternite, ventral aspect, except Fig. 60 without internal genitalia 58 Cybister festae 59 Cybister puncticollis 60 Megadytes latus 61 Nilssondytes diversus. Scale bars: 1.0 mm.