Moema humaita, Nielsen & Hoetmer & Vandekerckhove, 2025

Moema humaita , new species

( Figs.1–2 View FIGURE 1 View FIGURE 2 ; Table I)

Holotype: ZUEC 18341 View Materials , male, 71.5 mm SL: Brazil, Amazonas , Humaitá , temporary pool near igarapé do 12, at road BR-230, rio Madeira basin, 7º34’26.1” S, 63º06’42.8” W; Willem Hoetmer and Eric Vandekerckhove, 29 January 2018. GoogleMaps

Paratypes: ZUEC 18342 View Materials , 3 males, 37.2–66.7 mm SL, 4 females, 36.6–42.8 mm SL, 2 c&s, 39.4–42.8 mm SL ; INPA 61195 View Materials , 1 male, 53.4 mm SL, 1 female, 39.8 mm SL: same date as holotype .

Diagnosis. Moema humaita differs from the remaining species of Moema by its unique color pattern on the flanks in males, which is light reddish beige, with three horizontal lines, formed by small red dots lying at the center of each scale, alternating with three bright yellow lines (vs. absence of horizontally-aligned red dots in M. beltramonorum , Moema boticarioi , M. claudiae , M. juanderibaensis , M. kenwoodi , M. manuensis , M. obliqua , M. peruensis , M. rubrocaudata , M. schleseri , and M. wischmanni ; color pattern composed by rows of dots arranged horizontally over vertical bars as background in M. funkneri , M. heterostigma and M. quiii ; overall color on flanks light brown to light grey, with red to dark reddish-brown dots, each preceded by vertically elongated, light blue-greenish dots forming a pattern of double-dots, arranged in incomplete oblique rows in M. apurinan ; overall color on flanks light metallic blue green, with five horizontal rows of dark reddish-brown dots alternating with four horizontal rows of orange dots in M. beucheyi ; overall color on flanks light metallic green with nine horizontal rows of brownish red dots in M. hellneri ; five horizontal lines composed by small dots in M. nudifrontata ; four horizontal lines composed by reddish-brown dots in M. piriana and M. pepotei ; 3–4 continuous red lines formed by spots in M. portugali ; and irregular lines formed by red dots in M. staecki . It can be additionally diagnosed from congeners by males presenting caudal fin with 3–4 elongated filamentous rays (vs. absence of filamentous rays in M. heterostigma , M. juanderibaensis , M. portugali , M. schleseri , and M. wischmanni ; a small elongation at the lower caudal-fin rays in M. beltramonorum , M. claudiae , M. manuensis , and M. nudifrontata ; short filamentous rays in M. beucheyi , M. hellneri , M. quiii , M. pepotei , M. piriana , and M. staecki ; and presence of two filamentous rays, each on the outer edges of the caudal fin in M. peruensis ). Moema humaita can be additionally diagnosed from congeners by males presenting an elongated anal fin, with the eleventh ray filamentous, its tip reaching vertical through near the end of the caudal fin, orange in color (vs. anal fin lacking filamentous rays in M. beltramonorum , M. boticarioi , M. claudiae , M. funkneri , M. hellneri , M. heterostigma , M. juanderibaensis , M. kenwoodi , M. manuensis , M. nudifrontata , M. obliqua , M. portugali , M. rubrocaudata , M. schleseri , and M. wischmanni ; anal fin pointed, reaching vertical through center of caudal fin in M. beucheyi , and M. staecki ; short filamentous rays, green in color, in M. pepotei , M. piriana , M. peruensis , and M. quiii ; anal-fin pointed, with filamentous rays yellow in color, reaching vertical through center of caudal fin in M. apurinan ). Additionally, M. humaita differs from all congeners by the absence of a dark vertical bar crossing the center of the eye (vs. presence in the remaining congeners).

Moema humaita differs from all remaining Moema species, except M. kenwoodi , by presenting a lower number of pelvic fin rays (6, vs. 7–8). It additionally differs from M. beucheyi , M. funkneri , M. hellneri , M. heterostigma , M. kenwoodi , and M. nudifrontata by presenting a lower number of caudal fin rays (28–30, vs. 31–35). Moema humaita additionally differs from M. beltramonorum , M. beucheyi , M. funkneri , M. hellneri , M. heterostigma , M. juanderibaensis , M. kenwoodi , M. nudifrontata , M. pepotoei , and M. quiii by presenting a lower number of scales transversal series (8, vs. 9–13). It differs from all congeners, except M. heterostigma and M. nudifrontata , by presenting dorsal-fin origin at vertical through base of 24th vertebrae (vs. 19 th –22 th). Moema humaita additionally differs from all congeners, except M. boticarioi , by females presenting a larger eye diameter length (37.8–38.6% HL, vs. 28.0–37.3% HL).

Description. Morphometric data presented in Table 1. Largest male specimen examined 71.5 mm SL, largest female 42.8 mm SL. Dorsal profile gently convex from snout to end of dorsal-fin base, approximately straight to slightly concave on caudal peduncle. Ventral profile slightly convex on head, almost straight from anterior portion of abdominal region to end of anal-fin base, nearly straight on caudal peduncle. Body slender, subcylindrical anteriorly, deeper than wide, to compressed posteriorly. Greatest body depth at level of pelvic-fin base. Jaws long, snout blunt.

Tip of dorsal fin pointed, without filamentous ray in males, rounded in females.Anal fin approximately trapezoid in shape, longer than deep; eleventh ray filamentous, reaching vertical through near the end of the caudal fin in males, rounded and short in females. Caudal fin elliptical and long, acuminate, with 3–4 elongated filamentous rays in males, rounded in females. Pectoral fin elongated and lanceolate, terminating in a long tip, reaching between base of 7th and 10th anal fin rays in males, slightly pointed and short, reaching between pelvic-fin base and anus in females. Pelvic fin rounded, its tip reaching between base of 1 st and 3 rd anal-fin rays in males, and between anus and urogenital papilla in females. Pelvic-fin bases in close proximity. Dorsal-fin origin at vertical through base of 10 th anal-fin ray, and neural spines of 24 th vertebrae. Anal-fin origin at level of pleural rib of 18 th vertebrae. Dorsal-fin rays 9–10 (10); anal-fin rays 15–16(10); caudal-fin rays 28–30 (10); pectoral-fin rays 14 (10); pelvic-fin rays 6(10).

Scales large, cycloid. Body and head entirely scaled, except anteroventral surface of head. Body scales extending 10% over caudal-fin base; no scales on dorsal and anal fins. Frontal squamation E-patterned; E-scales not overlapping medially; scales arranged in irregular circular pattern around A-scale without exposed margins. Longitudinal series of scales 34–35(10); transverse series of scales 8(10); scale rows around caudal peduncle 16(10).

Ventral process of post-temporal present. Supraorbital neuromasts 3+3; infraorbital neuromasts 18. Contact organ on each scale of median ventral portion of male flank. One neuromast on each scale of lateral line. Six branchiostegal rays. Second pharyngobranchial with 0–2 small teeth. Gill rakers of first branchial arch 10. Vomerine teeth 5–10. Total vertebrae 33(2).

Coloration in life. Males. Side of body light reddish beige, with three longitudinal lines, composed by small red dots positioned in the center of each scale, alternating with three bright yellow longitudinal stripes. Dorsum light brown, with dark dots. Venter whitish. Sides of head and jaws light reddish beige, with bright yellow pigmentation in the opercular area. Iris yellowish brown. Dorsal fin light brown with small dark reddish-brown spots. Anal fin light greenish with small dark brown spots, basal area with a blue iridescent stripe, fin tip orange. Caudal fin light reddish beige with variously-sized dark brown spots on dorsal portion, three longitudinal dark brown lines, formed by the coalescence of spots, beginning at the caudal fin base and extending to the end of the filamentous rays; ventral portion presenting a black longitudinal bar below the third, lowermost filamentous ray, followed by a thinner, light stripe; lower portion of caudal fin reddish, with some greenish iridescence. Pelvic fin light greenish, with small reddish-brown spots. Pectoral fin hyaline, with a reddish tint.

Females. Side of body light brown, with two pale longitudinal rows of red dots alternating with three bright green thin lines. Dorsum light brown. Venter whitish. Side of head pale brown. Jaws grey. Iris yellowish brown. Dorsal fin hyaline, with small dark brown spots. Anal fin hyaline, with small dark brown spots, basal area with a thin blue iridescent stripe, and distal portion with an orange bar. Caudal fin hyaline, distal portion with orange bar. Caudal fin hyaline, with diffuse brown spots on the upper portion of the fin and an orange band on the lower portion of the fin. Pectoral fin hyaline. Pelvic fins hyaline with brown spots on the middle and distal part of the fin.

Coloration in alcohol. Body ground color light brown; dorsal region darker; ventral area whitish. Flanks with small dark brown spots, arranged in incomplete longitudinal rows. Sides of head brown. Head ventrally whitish. Dorsal fin light brown to light grey, with small brown blotches. Anal fin light beige. Caudal fin light brown, caudal fin rays dark brown; ventral portion clear. Pectoral and pelvic fins hyaline.

Distribution. Known only from the type locality, a flooded area near the Rio Madeira , next to the road BR 319, about 12 km west from Humaitá, Amazonas state, Brazil ( Fig. 3 View FIGURE 3 ).

Ecological notes. The type locality of Moema humaita is an annual pool close to a stream, near the road between Humaitá and Lábrea. The flooded area consisted in many puddles near a bamboo grove. The puddle where Moema humaita was found was 20 cm deep, with a layer of silt more than a meter thick. The color of the water was light brown, and the puddle was entirely devoid of aquatic vegetation. Moema humaita was the only fish species recorded in the pool ( Fig. 4 View FIGURE 4 ).

Etymology. In reference to the city of Humaitá, state of Amazonas, which was named in honor of the battle that Brazil and Argentina fought against Paraguay at the Fortress of Humaitá, during the Paraguayan War (1864– 1870). Humaitá in Guarani language means old rock (“yma”, antiquity; “itá”, rock).