Melanorivulus ofaie, Volcan, Matheus Vieira, Klotzel, Bruno & Lanés, Luis Esteban Krause, 2017

Volcan, Matheus Vieira, Klotzel, Bruno & Lanés, Luis Esteban Krause, 2017, Two new species of Melanorivulus (Cyprinodontiformes: Cynolebiidae) from Rio Verde drainage, Upper Rio Paraná basin, Brazil, Zootaxa 4236 (1) : -

Melanorivulus ofaie , new species

( Figs. 5–7 )

Holotype. MCP 50019, male, 30.5 mm SL, Brazil, Mato Grosso do Sul State, municipality of Ribas do Rio Pardo, stream tributary of right margin of Rio Verde , 20°25’27” S, 52°56’34” W, 347 meters a.s.l.; B. Klotzel, 29 Dec 2013.

Paratypes. All from Brazil, Mato Grosso do Sul, Ribas do Rio Pardo , upper Rio Verde drainage: MCP 50022, 5 males, 19.9 mm SL (1 C&S), 6 females, 17.3–24.3 mm SL (2 C&S), collected with the holotype . MCP 50020, 3 males, 17.2–23.3 mm SL, 4 females, 16.2–19.3 mm SL, stream tributary of right margin of Rio Verde , 20°01’50”S, 53°15’14” W, 354 meters a.s.l.; B. Klotzel, 11 Jul 2013 . MCP 50021, 4 juveniles, sex undetermined, 12.8–15.6 mm SL, stream tributary of right margin of Rio Verde , 20°02’11”S, 53°15’26”W, 357 meters a.s.l.; B. Klotzel, 11 Jul 2013 . ZUFMS-PIS 4736, 4 male, 21.5–23.3 mm SL, 3 females, 17.3–20.1 mm SL. same locality as holotype; B. Klotzel, 11 Jul 2013 .

Diagnosis. Melanorivulus ofaie is distinguished from all other species of Melanorivulus by color pattern of males, consisting of sides of body greenish blue above the anal fin base in males and by presence of an irregular black stripe between the postorbital region and the mid-length of the pectoral fin in both sexes, except from those of the M. pictus clade. Melanorivulus ofaie is distinguished from all other species of the M. pictus clade by dorsal fin yellow with 2–3 transverse broad red oblique stripes, distal region red or yellow, anterior region red (vs. never a similar color pattern), anal fin light orangish yellow with dark red margin (vs. dark red margin absent in other species of the M. pictus clade or presence of black margin in M. apiamici , M. egens , M. nigropunctatus , and M. polychromus ), caudal fin yellow or orangish yellow with 3–4 vertical red bars in the dorsal and middle portions of the fin, sometimes with an orange contour across the distal portion of the fin (vs. never a similar color pattern). Melanorivulus ofaie is also distinguished from other species of M. pictus clade (except of M. nigropunctatus , M. planaltinus , and M. polychromus ) by lower caudal fin length in males (28.1–31.2% SL vs 31.6–38.8% SL) and females (26.0–29.7% SL vs 28.7–38.9% SL, except in M. apiamici , M. nigropunctatus , M. giarettai , and M. polychromus ). Besides, the new species differs from all species of M. pictus clade by the following combination of characters: 9–10 scales in transversal series (vs. 7–8 scales in M. egens , M. faucireticulatus , M. illuminatus , M. kayapo , M. leali , M. litteratus , M. planaltinus , and M. polychromus ), anal fin origin between pleural ribs of 15th and 16th vertebrae (vs anal fin origin between the pleural ribs of the 13th and 15 th vertebrae in M. egens , M. faucireticulatus , M. giarettai , M. illuminatus , M. leali , M. litteratus , M. rutilicaudus and M. vittatus ), pre-pelvic length in females (50.5–55.3% SL vs 55.6–59.5 in M. apiamici , M. egens , M. faucireticulatus , M. giarettai , M. kayapo , M. litteratus , and M. pinima ). For additional morphometric and meristic characters distinguishing M. ofaie from congeners, see the Discussion, below.

Description. Morphometric data presented in Table 2 . Males larger than females, largest male examined 30.5 mm SL, largest female 21.5 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, straight on caudal peduncle. Ventral profile slightly convex from lower jaw to origin of anal-fin, approximately straight to end of caudal peduncle. Body slender, approximately cylindrical and compressed, greatest body depth at level of pelvic-fin base. Snout short and rounded in lateral view. Jaws short.

Dorsal and anal fins short. Dorsal-fin rays 8–10. Dorsal fin slightly pointed in male, rounded in female. Dorsalfin origin on vertical through base of 8th to 10th anal-fin ray, and between neural spines of 19th to 21th vertebrae. Anal-fin rays 13–15. Anal fin slightly pointed in both males and females. Origin of anal fin at vertical through pleural ribs of 15th–16th vertebrae. Caudal fin oval-shaped, longer than deep, with 31–32 rays. Pectoral fin rays 12–14. Pectoral fins rounded, with its posterior margin reaching vertical at about 70–95 % of length between pectoral-fin and pelvic-fin bases. Pelvic-fin rays 7. Pelvic-fin posterior tip reaching vertical at anus to 1st anal-fin ray. Pelvic-fin bases in close proximity.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 18–23% of caudal-fin base. No contact organs on flanks and fins. No scales on dorsal and anal-fin bases. Frontal squamation E-patterned; E-scales not overlapping medially; scales arranged in regular circular pattern around A-scale without exposed margins; Longitudinal series of scales 30–33; transverse series of scales 9–10; scale rows around caudal peduncle 16. No contact organs on flanks and fins.

Cephalic neuromasts: supraorbital 3+3, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 1+11-12+1, preorbital 1–2, otic 1, postotic 1–2, supratemporal 1–2, median opercular 1–2, ventral opercular 1–2, preopercular 2+4-5, mandibular 3+1, lateral mandibular 1–2. Two neuromasts on caudal-fin base. Lateral line interrupted, alternating sets of 3–4 scales with one neuromast and without neuromasts.

Gill rakers in the first branchial arch 1+6-7. Six branchiostegal rays. Total number of vertebrae 30–31. Dermosphenotic present.

Coloration in life. Males ( Figs. 5–6 ): sides of head and flanks greenish blue to metallic blue, with 7–9 oblique red bars, forming narrow chevron-like bars with vertex forward-pointing, their tips along the midline. Irregular thin lines at the anterior half of the body, sometimes incomplete. Red dots on dorsal and anteroventral portions of flanks. Black melanophores irregularly extending between postorbital and tip of pectoral fin forming a broad midlateral dark stripe. Opercular region golden, with small dark brown spots. Dorsum greenish blue with scattered dark brown spots. Abdominal region whitish. Upper jaw greenish grey, lower jaw dark grey to brown. Ventral portion of head whitish with dark brown spots. Iris pale yellow to light brown, sometimes with broad black bar on anterior and posterior portions, close to pupil. Dorsal fin yellow with 2–3 wide transverse oblique red bars, distal portion red or yellow, anterior portion red. Anal fin light orangish yellow, basal area light blue with short red bars (sometimes these bars are coalesced, forming a sub-basal red line), distal portion with dark red margin. Caudal fin yellow or orangish yellow with 3–4 vertical red bars in the dorsal and middle portions of fin. In some specimens, an orange contour across the distal portion of the fin is present. Pectoral fins light yellow. Pelvic fins yellow, distal margin reddish.

Females ( Fig 7 ): side of head and flanks light brown, with 7–10 oblique dark red bars, forming narrow chevron-like bars with pattern similar to males. Broad mid-lateral dark stripe between postorbital region and tip of pectoral fin, sometimes going beyond the first chevron-like bar. Dorsum light brown, with scattered dark brown spots. Abdominal region whitish. Upper jaw greyish brown, lower jaw brown. Ventral portion of head whitish with dark brown spots, sometimes forming a reticulate pattern. Iris yellow to light brown. Opercular region golden with black stripes or black dots. Dorsal fin light yellow, with 1–2 oblique dark grey bars; distal margin dark grey. Anal fin light yellow, base light blue with dark red bars; distal margin dark grey. Caudal fin light orange with 3–4 vertical dark grey bars; sometimes the bars are interrumpted, forming spots; fin margin dark grey to black; rounded black spot on dorsal portion of caudal fin base, sometimes in contact with the dark grey dorsal margin of fin. Pectoral fin hyaline. Pelvic fin yellowish, with dark grey to black distal area.

Distribution. The new species is only known from the wetlands along a c. 50 km stretch on the right bank of the Rio Verde, Ribas do Rio Pardo municipality, Mato Grosso do Sul State, Brazil ( Fig. 4 ).

Etymology. The specific epithet ofaie is a reference to a name of an indigenous ethnicity ( Ofaié ), which formerly inhabited the region of the right bank of Paraná River in central Brazil, including the region where the species was discovered.

Habitat notes. The new species was found in sun-lit, shallow swamp grasslands (depth <15 cm), associated with small direct tributaries of the Rio Verde ( Fig. 8 ). Melanorivulus ofaie occurs in either standing water or gently flowing water, with muddy substrates, within the savannah-like Cerrado domain of central Brazil. The only fish species recorded co-occurring with M. ofaie was the lebiasinid Pyrrhulina australis .

Conservation status. The species was recorded in disturbed areas, mainly due to changes in hydrology and physical structure of their habitats through the construction of small water reservoirs for livestock, similar to those recorded for M. nigropunctatus . Furthermore, populations were probably lost due to the establishment of the hydroelectric power plant of São Domingos, since both margins of the Rio Verde were flooded. In accordance with IUCN Red List (IUCN 2001), due to the relatively wide area of distribution of the species (along a 50 km river stretch) and the high probability of occurrence in other locations along this stretch, M. ofaie was considered “Endangered”, in accordance with criteria EN B2ab (ii, iii). The species presents a reduced area of occupancy (AOO less than 500 km ²), occurs in less than 5 locations (a) and presents a continued decline (b) in area of occupancy (ii) and quality of habitat (iii).

Figures

FIGURE 4. Distribution of Melanorivulus nigropunctatus (star) and Melanorivulus ofaie (circles), Rio Verde drainage, upper Rio Paraná basin, Mato Grosso do Sul, Brazil. Black symbols indicate the type localities.

FIGURE 5. Melanorivulus ofaie, new species, MCP 50019, holotype, 30.5 mm SL, Brazil, Mato Grosso do Sul, Ribas do Rio Pardo. Photo by Matheus V. Volcan

FIGURE 6. Melanorivulus ofaie, new species, living males, Brazil, Mato Grosso do Sul, Ribas do Rio Pardo: A – B: paratypes (MCP 50022); C: male, not preserved. Photos by Matheus V. Volcan.

FIGURE 7. Melanorivulus ofaie, new species, MCP 50022, paratypes, living females, Rio Verde drainage, upper Rio Paraná basin, Mato Grosso do Sul State, Brazil, Brazil. Photos by Matheus V. Volcan.

FIGURE 8. Type-locality of Melanorivulus ofaie, Ribas do Rio Pardo, Mato Grosso do Sul State, Brazil. Photo by Bruno Klotzel.

Tables

TABLE 2. Morphometric data for the holotype and paratypes of Melanorivulus ofaie.

	Holotype	Males (n=5)	Females (n=8)
Standard Length	30.5	17.2–28.5	16.2–21.5
Percentages of standard length
Body depth	23.6	22.8–24.6	20.7–26.5
Caudal peduncle depth	13.8	13.0–15.1	13.0–14.4
Predorsal length	79.3	74.5–78.5	76.4–81.7
Prepelvic length	55.1	50.6–55.7	50.5–55.3
Dorsal fin base length	10.8	10.6–12.6	10.5–14.1
Anal fin base length	19.6	19.7–21.4	17.0–22.0
Caudal fin length	28.6	28.1–31.2	26.0–29.7
Pectoral fin length	18.8	15.8–21.2	15.6–19.3
Pelvic fin length	11.9	9.4–12.9	6.6–9.4
Head length	25.4	26.5–30.6	25.6–30.4
Percentages of head length
Head depth	73.4	62.2–72.3	66.3–72.1
Head width	75.5	63.1–74.2	69.0–73.2
Snout length	17.3	11.4–21.3	13.9–18.5
Lower jaw length	15.0	15.7–20.7	14.4–20.0
Eye diameter	30.8	30.1–33.0	31.3–37.3