Tarumania walkerae, Pinna & Zuanon & Py-Daniel & Petry, 2018

TARUMANIA WALKERAE SP. NOV.

[ FIGS 1–3]

Holotype: INPA 33737 View Materials , 81.6 View Materials -mm SL, marginal pool of Igarapé Tarumã-Mirim (tributary to Rio Negro), Amazonas State, Manaus, Brazil (02.90965°S 60.22915°W), coll. L. Rapp Py-Daniel, J. Zuanon and M. de Pinna, 2 September 2006. GoogleMaps

Paratypes (all from Brazil, State of Amazonas): INPA 16563 View Materials , 1 View Materials ex, c. 23-mm SL, Igarapé do Camarão, Igarapé Tarumã-Mirim , col. Ilse Walker, 28 January 1999; INPA 25747 View Materials , 3 specimens (1 c&s), 87.3- to 151.2-mm SL, Rio Negro at Parque Nacional das Anavilhanas, paraná do Lago do Prato, Novo Airão (~ 02.72°S 60.75°W) GoogleMaps , coll. J. Zuanon, 22 August 2001; INPA 26241 View Materials , 3 View Materials ex, 44.9- to 51.2-mm SL, same data as holotype GoogleMaps , but at 2.90830°S 60.22873°W; INPA 26245 View Materials , 11 View Materials ex, 38.4- to 61.5-mm SL (56.35–62.02 mm), collected with holotype GoogleMaps ; INPA 26246 View Materials , 2 View Materials ex, 44.7- to 45.2-mm SL, collected with holotype GoogleMaps ; INPA 26248 View Materials , 1 View Materials ex, 63.5-mm SL, same data as holotype GoogleMaps , but 02.89637°S 60.22833°W; INPA 33733 View Materials , 3 View Materials ex, 58.5- to 102.8-mm SL same locality as holotype GoogleMaps , coll. J. Zuanon et al., 11 February 2002; 35585, 11 ex, 17.5- to 99.9-mm SL, Manaus, Igarapé Tarumã-Mirim , col. J. Zuanon, 3 February 2010; INPA 42299 View Materials , 7 View Materials ex, 57.5- to 87.0-mm SL, Manaus, Igarapé Tarumã-Mirim , pool inside forest , col. J. Zuanon et al., 20 December 2011; INPA 42302 View Materials , 6 View Materials ex, 26.7- to 37.6- mm SL, Manaus, Igarapé Tarumã-Mirim (02°54 ′ 35 ″ S 60°13 ′ 45 ″ W) GoogleMaps , col. J. Zuanon et al., 27 January 2010; INPA 52935 View Materials , 1 View Materials ex, 22.9-mm SL, Parque Nacional das Anavilhanas, Igarapé Açu (tributary to Rio Negro), Novo Airão (−2.8220100000 −60.8708600000) GoogleMaps , coll. D. Bastos et al., 4 May 2016; INPA 53174 View Materials , 1 View Materials ex, 73.0-mm SL, Manaus, pool near Rio Tarumã (−2.9016380000 −60.2292800000) GoogleMaps , col. D. Bastos et al., 12 October 2016; MZUSP 120543 View Materials , 11 View Materials ex (1 c&s), 42.2- to 76.1-mm SL, collected with holotype GoogleMaps ; MZUSP 120544 View Materials , 1 View Materials ex C&S, 98.4-mm SL, collected with holotype (preserved after 2 years in captivity) GoogleMaps ; MZUSP 120545 View Materials , 3 View Materials ex (1 c&s), 46.4- to 52.6-mm SL, same data as INPA GoogleMaps 26241.

Etymology: The specific name honours eminent limnologist Ilse Walker [Instituto Nacional de Pesquisas da Amazônia, Manaus (INPA)], not only for her lifelong contribution to the knowledge of Amazonian ecology but also for having collected the first (and for some years, only) known specimen. The epithet is a noun in the genitive feminine case.

Diagnosis: As for the family.

Description: Body greatly elongate (BD ~9% of SL) and approximately oval in cross-section, ending in highly compressed, spatulate caudal peduncle deeper than rest of body. Proportional measurements provided in Table 1. Anal and urogenital openings located immediately anterior to origin of anal fin. Myotomes narrow and numerous. Head small (~15% of SL), its profile continuous with that of the body in live and recently preserved specimens (partly dehydrated specimens with well-defined groove dorsally between head and trunk). Dorsal trunk musculature produced anteriorly to cover posterior part of cranium. Snout blunt, ending anteriorly in large and slightly upturned mouth, with lower jaw longer than upper one. Posterior margin of upper jaw reaching to vertical through posterior margin of eye. Eye small, located on anterior fifth of head in lateral view. Anterior and posterior nares not juxtaposed, separated from each other by considerable distance, longer than eye diameter. Anterior naris positioned immediately dorsal to upper lip and produced on surface of the head as small mound. Branchiostegal membranes united to each other, free from isthmus, forming wide branchial opening. Maxilla with two rows of conical teeth, straight or slightly curved, for part of its dentate surface. Jaw dentition described in ‘Selected osteological features’. Infraorbital latero-sensory canal absent. Skull roof without cranial fontanels. Part of frontal and parietal bones prominent and exposed on dorsal surface of the head in large specimens. Numerous neuromast lines over head and anterior part of the body. Body neuromasts mostly arranged as short vertical rows of five or six elements. Supraoccipital spine invisible externally. Dorsal fin short-based and lanceolate, i or ii + 4–6, its origin at ~70% of SL. Pectoral fin short, i or ii + 7–10, its length approximately half of HL, attached on ventral fourth of thorax. First pectoral-fin ray approximately half as long as others, adpressed to second ray. Pelvic fin large, i + 5 or 6 (i.e. all rays branched), extending posteriorly to vertical through base of dorsal fin. Anal fin ii + 9 + i, its base more than twice as long as that of dorsal fin and its origin slightly anterior to vertical through tip of adducted dorsal fin. Caudal fin lanceolate or oblong and no differentiation between upper and lower lobes, with 8 + 10 principal rays plus four accessory rays in lower lobe. Caudal-fin attachment area more extensive ventrally than dorsally. Adipose fin absent. Squamation fine and extremely uniform in size, covering entire body in regular narrow rows, as well as most of the head (including entire perimeter of orbit), except lips and exposed top of skull. Scales on head similar in morphology to those on body, but with different imbrication, that is free margins not directed posteriorly. Imbrication pattern changes along limit between trunk musculature and head. Scales at interface with free margins directed laterally or ventrally. Such orientation maintained in scales over gill covers and posterior portion of cheeks. Free scale margins shifting to progressively more anterior orientation over anterior portion of cheeks, until completely reversed on dorsal part of head ( Fig. 5). Scales in midlateral series of body 244–267, none perforated by lateral-line pores, 21 or 22 scale rows between origins of dorsal and pelvic fins. Modally 25 series of scales on caudal peduncle. Pre-dorsal scales 168–193. Vertebrae 64 or 65 (43–45 precaudal and 21–22 caudal). Pleural ribs 41–44. Anterior branchial arch with 11 or 12 gill rakers, 3 or 4 upper and 8 lower (posterior lower one sometimes at limit).

Swimbladder subdivided into 11 compartments, positioned in longitudinal series immediately ventral to vertebral column ( Fig. 4). Series arranged in anterior row of three and posterior row of eight, connected by sinuous duct. Individual compartments varying in shape and size. Size of compartments increasing towards anterior and posterior ends, with smallest ones approximately in middle of abdominal cavity. First compartment corresponding in position and shape to anterior chamber of swimbladder in other characiforms. All other compartments represent subdivisions of the posterior chamber. Anterior chamber largest of all in volume, with wide cordiform shape in ventral view. All subsequent chambers narrower than first one. Second chamber cylindrical, longer than first one. Third chamber conical, bottle shaped and markedly smaller in volume than its predecessors, with posterior atrium-like region tapering posteriorly into narrow sinusoid duct expanding slightly into fourth chamber, smallest of all. Constriction separates fourth from slightly larger fifth chamber. Sixth chamber larger still. All subsequent chambers similar in shape, although progressively larger posteriorly, except for last chamber, slightly smaller and more roundish than its predecessor, and abutting against posterior limit of abdominal cavity, dorsally to anterior anal-fin pterygiophores. All swimbladder chambers connected via short ducts, except third and fourth, connected via long sinusoid duct described above. Wall of anterior chamber noticeably thicker than that of subsequent chambers, otherwise uniformly thin and delicate. Ductus pneumaticus opening ventrally from second chamber, close to limit with first one. Swimbladder configuration described is constant in four specimens dissected.

Pigmentation: Overall ground colour dark brownish, slightly less dark ventrally. Subtle differences in the density of pigment forming irregular small blotches on the dorsum and flanks, partly merging into irregular vertical or slanted bars on anterior third of trunk, sometimes extending across dorsum. Barred pattern more intense on caudal peduncle, sometimes changing into irregular blotches. Areas of procurrent caudal-fin rays dorsally and ventrally on caudal peduncle darker than rest of peduncle in small specimens, but indistinguishable in larger individuals. Dorsal and ventral edges of caudal peduncle outlined as very dark thin line. Scales with dark exposed portions collectively forming pattern of fine longitudinal stripes covering entire body, visible under close examination. Dark slanted lines on lower half of flanks outlining limits of myomeres. Head as dark as body. Snout and area of opercle darker than rest of the head, with sides of cheeks slightly lighter. Dorsal and lateral sides of head with numerous short thin light lines corresponding to neuromast lines. Central portion of isthmus with same colour as abdomen, with adjacent portion of branchiostegal membrane distinctly darker than rest of ventral aspect of head. Caudal fin with very dark posteriorly convex semilunar mark across base, covering ~15% of length of longest (central) rays at its widest. Heavy dark pigment covering basal third of anal fin, more intense at its ventral limit, forming very dark stripe in some specimens. Rest of fin abruptly hyaline. Dorsal fin with dark field over its basal 10–20%, otherwise hyaline. Pectoral and pelvic fins with dark fields at bases, more pronounced on former, forming dark spot with elongate dark fields radiating alongside fin rays. Remainder of both fins hyaline. Colour of small individuals (up to 6.0-cm SL) very dark and uniform, nearly black. In life, colour pattern obviously mimics dead leaves in habitat, with hyaline portions of fins practically invisible.

Maximum size: 151.2-mm SL (a specimen from INPA 25747).

Geographical distribution: So far endemic to the Rio Negro basin, from the Rio Tarumã-Mirim, tributary to the Rio Negro near the city of Manaus, and from the Anavilhanas archipelago, on the main Rio Negro ( Fig. 11). The two localities are ~ 60 km apart in straight line.