Moema juanderibaensis, Drawert, 2022

Drawert, Heinz Arno, 2022, A new species of the seasonal killifish genus Moema (Cyprinodontiformes: Rivulidae) from the Piraí watershed in the Southwest Amazon basin, Neotropical Ichthyology (e 220067) 20 (4), pp. 1-17 : 4-12

Moema juanderibaensis , new species

urn:lsid:zoobank.org:act:F84C7D9A-3BF2-4FF2-929F-CCD509D49BB5

( Figs. 1–5 ; Tab. 1 )

Holotype. MNKP 16539 , male, 41.9 mm SL, Bolivia, Santa Cruz, municipality of Santa Rosa del Sara, Juan Deriba ranch, temporary pool (“curichi”) within forest ca. 5 km southeast of Santa Rosa del Sara , hydrologic unit 6226987 (Pfafstetter), Piraí watershed , upper Madeira drainage, Amazon basin, 17°07’17.6”S 63°33’23.3”W, 20 Mar 2021, H. A. Drawert.

Paratypes. MNKP 16540 , 3 males, 38.2–42.6 mm SL, collected at same locality of holotype, 2 Apr 2021, H. A. Drawert . MNKP 16541 , 4 males, 41.3–46.1 mm SL, Bolivia, Santa Cruz, municipality of Santa Rosa del Sara, Juan Deriba ranch, temporary pool (“curichi”) within forest ca. 5 km southeast of Santa Rosa del Sara , hydrologic unit 6226987 (Pfafstetter), Piraí watershed , upper Madeira in the Amazon basin, 17°07’17.1”S 63°33’18.8”W, 2 Apr 2021, H. A. Drawert . MNKP 16543 , 8 females, 29.9–36.2 mm SL, collected at same locality of holotype, 2 Apr 2021, H. A. Drawert . MNKP 16545 , 2 males, 32.2–45.1 mm SL (2 females, 28.1–32.6 mm SL), Bolivia, Santa Cruz, municipality of Santa Rosa del Sara, Juan Deriba ranch, temporary pool (“curichi”) within forest ca. 5 km southeast of Santa Rosa del Sara , hydrologic unit 6226987 (Pfafstetter), Piraí watershed , upper Madeira in the Amazon basin, 17°07’19.5”S 63°33’19.3”W, 2 Apr 2021, H. A. Drawert .

Not-types. MNKP 16535 , 3 males, collected with holotype, 20 Mar 2021, H. A. Drawert.

Diagnosis. Moema juanderibaensis differs from congeners by a unique combination of the following characters on males: pattern of oblique, sometimes chevron-like, irregular rows of red and light blue double-dots on flanks; dark yellowish to golden pectoral fin with no visible markings (dots or spots); and ventral part of caudal-fin stripe pattern with very narrow black marginal line, intermittent or even absent (vs. never in this combination). The new species is distinguished from Moema apurinan , M. beucheyi , M. funkneri , M. hellneri , M. heterostigma , M. nudifrontata , M. pepotei , M. piriana , M. portugali , M. quiii , M. schleseri , and M. staecki by the oblique arrangement of red and light blue double-dots on flanks (vs. flank color pattern arranged in horizontal lines or rows of dots). It differs from M. manuensis , M. obliqua , M. peruensis , M. rubrocaudata , M. schleseri , and M. wischmanni by the presence of red dots on flanks mostly arranged in oblique, sometimes chevron-like, rows (vs. absence of dots, or arranged in vertical rows or randomly distributed). It is distinguishable from M. boticarioi , M. kenwoodi , and M. obliqua by the absence of dots, spots or any other markings on pectoral fins of males (vs. presence of dark reddish-brown dots, few dark green dots or longitudinally elongated dark brown spots); from M. claudiae by the absence of black humeral blotch in males (vs. presence); and from M. schleseri by the ground color of pectoral fins (brown-yellowish to golden vs. hyaline) and color pattern of ventral section of caudal fin (thin black marginal line, sometimes intermittent and inconspicuous or even absent, and broad deep orange to red stripe vs. ventralmost black stripe broad, and orange stripe with dark red dots). Additionally, it is also distinguished from M. boticarioi by the absence of brown dots or other marks on dorsum (vs. dorsum with brown dots).

Body form of males is somewhat more slender than in M. boticarioi , M. manuensis , M. obliqua , and M. wischmanni (body depth 17.7–21.6% SL vs. 23.4–26.1%, 22.2–23.6%, 22–23.6%, and 23.2%, respectively). Caudal fin of males shorter than in M. boticarioi , M. claudiae , and M. manuensis (27.8–36.9% SL vs. 39.4% or more of SL); and pectoral fins shorter than in M. boticarioi and M. kenwoodi (maximum 27.5% vs. minimum 29.2% SL). Males differ by having more scales in longitudinal series than M. manuensis and M. rubrocaudata (34–36 vs. 32 and 33 respectively); and more scales in transversal series than M. boticarioi , M. claudiae , M. manuensis , and M. obliqua (9–10 vs. 8). They also differ by having more pelvic-fin rays than M. kenwoodi (7 vs. 6), and more anal-fin rays than M. rubrocaudata (14–16 vs. 13); but fewer anal-fin rays than M. kenwoodi and M. manuensis (14–16 vs. 17 and 17–18, respectively), and caudal-fin rays than M. claudiae and M. kenwoodi (25–27 vs. 28–29 and 31, respectively).

Description. Morphometric and meristic data of holotype and paratypes are presented in Tab. 1 . Males larger than females, largest male examined 46.06 mm SL, largest female 36.24 mm SL. Dorsal profile on lateral view straight on head, slightly convex to convex from nape to just anterior to caudal-fin base, in females straighter than in males. Ventral profile on lateral view convex on head, approximately straight to slightly convex from end of lower jaw to end of anal-fin base, section of anal-fin base more convex in females. Caudal peduncle slightly concave. Body slender, subcylindrical, body depth about 1.2 times body width. Greatest body depth on vertical through pelvic-fin base in males, more posterior between vertical through pelvic-fin base and vertical through anal-fin origin in some females. Snout blunt, mouth superior and jaws short.

Dorsal-fin distal section in males slightly pointed to rounded, rounded in females. Dorsal-fin origin at vertical through 7 th to 9 th anal-fin rays in males and through 7 th to 10 th anal-fin rays in females. Postero-median anal-fin rays of males longer than posterior and anterior rays, forming pointed tip of anal fin with membrane; anal-fin distal border rounded in females. Caudal fin elliptical; in males with posterior extension forming short sword in ventral part, occasionally barely visible extension in dorsal section. Pectoral fin lanceolate; tip pointed and reaching vertical between pelvic-fin base and 2 nd anal-fin ray in males, tip rounded and not reaching vertical through pelvic-fin base in females. Pelvic fin lanceolate and short; tip pointed and reaching between base of 1 st and 3 rd anal-fin ray in males; in females rounded to slightly pointed reaching between anus and 3 rd anal-fin ray. Dorsal-fin rays 8(1), 9(17), or 10*(2); anal-fin rays 14(3), 15*(11) or 16(6); caudal-fin rays 25(6), 26*(6), 27(6), or 28(2); pectoral-fin rays 14(1), 15(9), 16*(8) or17(2); pelvic-fin rays 7*(20).

Scales large, cycloid. Head fully scaled, except on ventral surface at jaws and gular region. Frontal squamation E-patterned; E-scales not overlapping medially, scales arranged in irregular circular pattern around A-scale, which has no exposed margins. Body completely scaled with scales extending over caudal-fin base approximately on anterior 20–25% of caudal-fin length. No scales extending over other fins. Longitudinal series of scales 34(3), 35*(4) or 36(3) in males and 33(2), 34(4), 35(3) or 36(1) in females; transverse series of scales 9*(17) or 10(3); scale rows around caudal peduncle 16*(7), 17(2) or 18(11). Lateral line on body in older males and females complete, with one neuromast per scale. Contact organs on scales of median section of adult male flank, not more than one per scale; no contact organs on fins or fin-rays. Supraorbital neuromasts 3; Infraorbital neuromasts 18, preopercular and mandibular series present ( Fig. 5 ).

Coloration in alcohol. Body ground color brownish-grey, darker on head and dorsal region, paler on ventral region and fins; venter whitish. Head on infraorbital and lower opercle regions usually with some dark blotches in males. Dorsal fin with dark dots, sometimes fused to form oblique lines. Anal fin darker on distal border and with dark spots on basal and posterior sections. Caudal fin at medial and dorsal section with dark dots, more conspicuous anterior-dorsally, ventral section with pale stripe sometimes outlined dorsally and ventrally by darker narrow line in males; fin rays darker than membrane. Pectoral fins hyaline, with darker distal border in males. Pelvic fins whitish. Females with less conspicuous markings on fins.

Coloration in life. Males ( Figs. 1–2 , 4 ). Body ground color pale light brown to light grey; dorsum darker, brown-greenish; venter white. Flanks with red to dark reddish-brown dots, each preceded by close light blue greenish vertically elongated dot forming “double-dots”; arranged in incomplete oblique rows in some specimens, usually descending forwards below lateral line where they change angle to ascendant forwards forming chevron-like pattern, at least on anterior flank. Side of head brown to dark brown; with golden to metallic green irregular blotches, mostly merged together or connected, forming irregular pattern on opercular region and irregular line following edge of eye in postorbital and suborbital region, usually interrupted in suborbital region. Head ventrally white to pale grey with greenish-brown to dark gray spots, usually fused in reticulated pattern. Iris blue greenish, with dark brown oblique bar crossing center of eye. Dorsal fin light brown to light gray with medial and posterior-basal section lighter, usually pale blue to white; red to dark reddish-brown dots, usually fused to form backwards descending lines, mainly on basal and posterior section of fin. Anal fin dark yellow to greenish-yellow or pale grayish-green in some individuals, which darkens towards distal section; subbasal and posterior-basal parts white to pale light blue; red to dark reddish-brown dots all over the fin, some fused to form 4 to 6 vertically elongated spots on subbasal part and usually also present on posterior section; distal border darker, usually with dark brown to black narrow marginal line. Background coloration of caudal peduncle continues on caudal-fin proximal part covered by scales. Medial and dorsal section of caudal fin reddish-brown fading into hyaline towards distal edge with greenish-light blue dots, greener towards posterior-distal section, usually fused in parallel curved lines on medial and proximal dorsal part. Caudal-fin coloration more intense and darker on dorsal section, sometimes forming dark brown to black border on distal part. Caudal-fin ventral section generally extends posteriorly forming small “sword”, with pattern of horizontal stripes with narrow black marginal line, sometimes inconspicuous or absent; broad deep orange to red stripe, less intense ventrally in most specimens; narrow white to yellow stripe; and narrow reddish-brown to red stripe, approximately continuing line given by the ventral profile of caudal peduncle and dorsally delimiting stripe pattern from medial section of fin. Pectoral fin dark yellowish-brown to golden, without dots or spots. Pelvic fin yellow to yellowish-brown, paler on basal and basal-posterior section; with few red to dark reddish-brown dots.

Females ( Fig. 3 ). Body background color light brown to pale greenish-brown; dorsum darker and venter white. Dark reddish-brown dots on flanks preceded by light brown to yellowish-brown dots forming double-dots, arranged as male pattern but more irregular and spaced. Side of head brown to light brown; with golden to greenish-yellow metallic spots, generally merged or connected on preopercular and opercular region. Head ventrally white. Iris green to greenish-yellow, with dark brown oblique bar crossing center of eye. Dorsal fin hyaline, basal section pale yellowish-brown; with dark brown dots, usually fused in basal section into 2 to 4 elongated spots. Anal fin hyaline, somewhat darker on distal section; with reddish-brown to dark brown dots, usually fused in basal section forming 4 to 6 vertically elongated spots. Caudal fin hyaline, sometimes with inconspicuous reddish-brown to dark brown dots. Pectoral and pelvic fins hyaline with dark golden to pastel yellow basal section.

Geographical distribution. Known only from type locality and surrounding temporary pools in the Piraí watershed (hydrologic unit 6226987), upper Madeira basin, in the southwest Amazon ecoregion ( Fig. 6 ).

Ecological notes. Collected in shallow temporary pools within dense forest, a biotope type locally known as “Curichi”. The water was typically “black-water”, dark brown color and slightly acid (pH 6.4–6.6) probably due to the presence of organic dissolved matter, of pluvial origin without detectable flow or fluvial connection. The extension of the pools were not determined (some over 100 m 2), largely flooding the surrounding forest; mostly shallow (about 0.05–0.20 m deep) with the deepest sections about 0.40 to 0.50 m deep. The surface was partially covered (about 5–10 %) by floating leaves and plant litter, and poorly lit due to forest canopy coverage shadow. The substratum was composed by a 0.05–0.10 m layer of leaves, other plant litter and mud over compact, dark brown to blackish clay. Aquatic vegetation found was Nymphaea aff. amazonum ( Nymphaeaceae ), which grows with submerged leaves in the deeper and better illuminated sections of the pools, and Heliconia aff. marginata ( Heliconiaceae ) was found as riparian and “standing” emergent vegetation in the shallow sections. Surrounding vegetation corresponds to a tropical pluvistational semideciduos forest. The only sympatric fish species found was another rivulid of the same genus: Moema cf. beucheyi .

Only one or two dominant males preserve the whole ventral section of caudal fin with the stripes pattern visible under spatial stress (e.g., collecting bucket, aquarium) in groups of several males or males and females mixed, after a few hours. In other males, this part is mutilated or severely damaged. When this color character is absent (i.e., mutilated fin, juvenile males or females), the aggressions reduces dramaticaly and are less harmful. In the aquarium, specimens were observed staying attached to the glass above water surface or resting on floating leaves of aquatic plants for several hours, especially at high temperatures or under stress factors (e.g., intraspecific aggression).

Etymology. Named juanderibaensis in reference to the name of the ranch “Juan Deriba” where the type locality is situated. An adjective.

Conservation status. Moema juanderibaensis is known only from temporary pools within forests in good conservation status and in the vicinity of the type locality. The advance of the agricultural frontier in recent decades and the associated ecological degradation that still persists should be considered as threats to this species. There is no information on distribution, biology, and population trends, so its extinction risk cannot be adequately assessed. Therefore , Moema juanderibaensis can be categorized as Data Deficient ( DD) according to the International Union for Conservation of Nature ( IUCN) categories and criteria ( IUCN Standards and Petitions Subcommittee, 2022).

Figures

FIGURE 1 | Moema juanderibaensis, MNKP 16539, holotype, male, 41.9 mm SL (24 days after collection, left side), Bolivia, Santa Cruz, Santa Rosa del Sara.

FIGURE 2 | Moema juanderibaensis, MNKP 16539, holotype, male, 41.9 mm SL (2 days after collection, right side), Bolivia, Santa Cruz, Santa Rosa del Sara.

FIGURE 3 | Moema juanderibaensis, MNKP 16543, paratype, female, 36.1 mm SL (1 day after collection, left side), Bolivia, Santa Cruz, Santa Rosa del Sara.

FIGURE 4 | Moema juanderibaensis, MNKP 16541, paratypes, males, 41.3–46.1 mm SL (2 days after collection, left side), Bolivia, Santa Cruz, Santa Rosa del Sara.

FIGURE 5 | Moema juanderibaensis, MNKP 16541, paratype, male, 46.1 mm SL, Bolivia, Santa Cruz, Santa Rosa del Sara. Detail of infraorbital, preopercular and mandibular neuromast series.

FIGURE 6 | Occurrence localities of Moema species in Bolivia and surroundings. Sources: Hydrologic Units from Lehner, Grill (2013); Basemap ESRI World Topo (2022).