Tyttobrycon marajoara, Marinho & Bastos & Menezes, 2013

Marinho, Manoela M. F., Bastos, Douglas A. & Menezes, Naércio A., 2013, New species of miniature fish from Marajó Island, Pará, Brazil, with comments on its relationships (Characiformes: Characidae), Neotropical Ichthyology 11 (4), pp. 739-746 : 740-745

Tyttobrycon marajoara , new species

Figs. 1-2

Holotype. MZUSP 109196 , 17.9 mm SL, male, Brazil, Pará State, Marajó Island, Salvaterra, Vila União , igarapé Olho d’água, 0º50’51”S 48º34’1”W, 10 Apr 2010, M. M. F. Marinho & D. A. Bastos.

Paratypes. Brazil. Pará State, Marajó Island. ANSP 193488 , 4 , 17.5-19.2 mm SL ; DZSJRP 18179 , 4 , 16.8-18.6 mm SL ; INPA 39504 , 4 , 18.2-20.4 mm SL ; MCP 47859 , 4 , 17.2-19.9 mm SL ; MPEG 27051 , 4 , 17.5 - 19.5 ; MZUSP 106110 , 68 , 16.8-19.7 mm SL (19, 16.8-19.7 mm SL), 6 c&s, 1 mol, igarapé in the balneário Olho no Olho , 0º51’53”S 48º34’16”W, 10 Apr 2010, M. M. F. Marinho & D.A. Bastos . MZUSP 108820 , 24 , 17.3-22.1 mm SL (15, 17.3-21.1 mm SL), collected with holotype . MZUSP 109197 , 21 , 9.9-12.3 mm SL, balneário Olho no Olho in igarapé, 0º51’53”S 48º34’16”W, 23 Aug 2010, D. A. Bastos .

Diagnosis. Tyttobrycon marajoara can be readily distinguished from all congeners by having tricuspid premaxillary teeth, tri- or pentacuspid maxillary teeth and four broad tricuspid anterior dentary teeth (vs. all teeth conical in the jaws).Additionally, it can be distinguished from all congeners, except T.dorsimaculatus , by having 5-7 premaxillary teeth (vs. 8-9), and from T.dorsimaculatus by having only scattered melanophores on the dorsal fin (vs. dorsal fin with a conspicuous black spot). Furthermore, Tyttobrycon marajoara can be distinguished from T. hamatus and T. spinosus by having an adipose fin (vs. adipose fin absent).

Description. Morphometrics in Table 1. Largest specimen examined 21.1 mm SL. Body compressed, greatest body depth slightly anterior to dorsal-fin origin. Dorsal body profile convex from tip of snout to nostrils; straight from nostrils to tip of supraoccipital spine, slightly depressed at fontanels; almost straight from supraoccipital spine to dorsal-fin origin on males, convex on females; posteroventrally inclined along dorsal-fin base; slightly convex from base of last dorsal-fin ray to adipose fin; straight along caudal peduncle. Ventral body profile convex from tip of lower jaw to vertical through pectoral-fin origin; straight from pectoral-fin origin to pelvic-fin origin on males, convex on females; slightly concave from pectoral-fin origin to anal-fin origin on males, straight on females; posterodorsally inclined along anal-fin base; straight along caudal peduncle.

Mouth upturned. Premaxillary with 5(2), 6(4), or 7(1) tricuspid teeth, in a regular row; some specimens with third tooth slightly ahead from remaining. Maxilla with 1(6) or 2(1) tri- or pentacuspid teeth, posterior tip beyond vertical through anterior border of orbit. Dentary with four broad tricuspid teeth anteriorly; one male and one female with largest teeth pentacuspidate; 3(1) or 4(6) smaller teeth tricuspid or conical, laterally located ( Fig. 3 ). Infraorbital bones reduced in number: infraorbital four, five and six absent.

Pseudotympanum large, muscle hiatus anterior to first pleural rib and between first and second pleural ribs, dorsally limited by lateralis superficialis muscle. The anterior hiatus is limited anteroventrally by obliquus superioris and posteriorly by first pleural rib. Posterior hiatus limited anteroventrally by obliquus superioris and posteriorly by second pleural rib ( Fig. 4 ).

Supraneurals 3(2) or 4(5), I-shaped. Dorsal-fin rays ii,8(1) or 9*(36); first unbranched ray almost one-half length of second unbranched ray. Tiny spines laterally positioned on both lobes about equally developed. Principal caudal-fin rays i,9,8,i*. Scales on caudal fin restricted to base of fin. Dorsal procurrent rays 8(2), 9(3), or 10(1), and ventral procurrent rays 6(1), 7(2), or 8(3).

last unbranched dorsal-fin ray of males ( Fig. 5). Adiposefin origin slightly posterior to vertical through anal-fin base end. Pectoral-fin rays i,8(4), 9(6), or 10*(26), its tip reaching pelvic-fin origin. Pelvic-fin rays i,7*. Pelvic-fin origin slightly anterior to vertical through dorsal-fin origin; tip of pelvic fin extending to bases of first three branched anal-fin rays in adult males, and first two unbranched anal-fin rays, or not reaching anal fin, in adult females ( Fig. 1 ). Bony hooks on all pelvic-fin rays of males ( Fig. 6 ). Anal-fin rays iii(3) or iv(3), 12(3), 13(10), or 14*(18).Anal-fin origin slightly posterior to vertical through base of last dorsal-fin ray. Last unbranched anal-fin ray and first four or five branched anal-fin rays longer than remaining rays. Bony hooks on last unbranched and first five or six branched anal-fin rays of males ( Fig. 7 ). Caudal-fin forked,

Scales cycloid. Lateral line incomplete, pored scales 3(1), 4(11), or 5*(17). Longitudinal scale row, including pored scales 28(4), 29(8), 30*(10), or 31(4). Predorsal scales 9*(8), 10(20), or 11(1). Longitudinal scale rows above lateral line 4**; longitudinal scale rows below lateral line at pelvic-fin origin 3**. Single row of 1-3 scales overlying base of anteriormost anal-fin rays. Scales around caudal peduncle 12**. Axillary scale present.

Precaudal vertebrae 13 (1), 14 (6), caudal vertebrae 17 (1), 18 (5), or 19 (1). Total vertebrae 31(2), 32(4), or 33(1). First gill arch with 1(1) or 2(5) hypobranchial, 1(5) on cartilage between hypobranchial and ceratobranchial, 8(1) or 9(5) ceratobranchial, 1(6) on cartilage between ceratobranchial and epibranchial, and 6(2) or 7(4) epibranchial gill-rakers. Four branchiostegal rays: three located on anterior ceratohyal and one on posterior ceratohyal.

Color in alcohol. Overall ground coloration pale. Dorsal portion of head and upper and lower lips with dense concentration of melanophores. First and second infraorbitals, maxilla and dorsal portion of opercle with scattered dark cromatophores. Infraorbital, opercular and gular areas silvery. Dorsal portion of body with scales bordered by melanophores; predorsal area with dark brown stripe. Humeral spot absent. Scattered melanophores from opercle to near vertical through dorsal-fin origin, united to a conspicuous longitudinal black stripe from later point to base of middle caudal-fin rays. Series of oblique and parallel black lines at anal-fin base. Middle caudal-fin rays dark, as an extension of the longitudinal black stripe; caudal-fin lobes with scattered melanophores. Scattered melanophores on distal margins of first seven dorsal-fin rays; on distal margins of largest unbranched and first six anal-fin rays; on first three or four pectoral-fin rays; and on fist four pelvic-fin rays.

Color in life. Dorsolateral portion of body from head to base of caudal fin translucent. Iridescent yellow to green stripe, from opercle to base of caudal fin; black stripe below it, from vertical through dorsal-fin origin to base of middle caudal-fin rays. Iridescent pigmentation yellow to green over posterodorsal region of head, opercle areas and upper lateral portions of abdominal region. Ventrolateral portion of body from anal-fin origin to base of caudal fin translucent.All fins hyaline, except for a yellowish area at base of dorsal and caudal fin, and a white area on the distal portion of the anterior dorsal-fin rays ( Fig. 2 ). Sexual dimorphism. Spines and hooks on fins present only in males ( Figs. 5-7). Tiny spines laterally located on unbranched dorsal-fin rays; hooks on all pelvic-fin rays and on last unbranched and first five or six branched anal-fin rays. Males with shallower body depth and longer pectoral and pelvic fins than females ( Fig. 8 ). Medial portion of pelvic bone of males expanded and dorsally projected ( Fig. 9 ).

Distribution. Tyttobrycon marajoara is known from two small streams located on the east portion of Marajó Island ( Fig. 10 ).

Ecological notes. The two sampled streams are temporary, drying completely during the dry season, from September to February, and flowing on the rainy season, from March to August ( Fig. 11 ). Specimens of Tyttobrycon marajoara were the bottom and marginal portions of the streams. In August, large schools of juveniles were observed and captured along the bottom of the stream.

Species collected with Tyttobrycon marajoara were Aequidens tetramerus (Heckel) , Apistogramma agassizii (Steindachner) , Acaronia nassa (Heckel) , Bryconops melanurus (Bloch) , Copella arnoldi (Regan) , Crenuchus spilurus Günther , Curimatopsis crypticus Vari , Hemigrammus levis Durbin , Hemigrammus ocellifer (Steindachner) , Hemigrammus rhodostomus Ahl , Hemigrammus rodwayi Durbin , Hoplerythrinus unitaeniatus (Spix &Agassiz) , Hoplias malabaricus (Bloch) , Hyphessobrycon heterorhabdus (Ulrey) , Megalechis sp. , Microcharacidium weitzmani Buckup , Moenkhausia collettii (Steindachner) , Nannostomus eques Steindachner , Nannostomus nitidus Weitzman , Pyrrhulina sp. and Rivulus sp.

observed (during snorkeling) and/or captured in April and August of 2010, at the rainy season. In April, small groups of 10 to 15 adult specimens were observed and captured on

Etymology. The specific name, marajoara , refers to the type locality, Marajó Island, Brazil. An adjective.

Figures

Fig. 1. Tyttobrycon marajoara: (a) Holotype, MZUSP 109196, 17.9 mm SL, mature male, igarapé Olho d’água, Vila União, Salvaterra, Pará, Brazil; (b) Paratype, MZUSP 108820, 20.9 mm SL, mature female, collected with holotype.

Fig. 2. Tyttobrycon marajoara alive. Female above, male below, collected with paratypes in a small stream (igarapé) at balneário Olho no Olho, Marajó Island, Pará State, Brazil. Not preserved.

Fig. 3. Jaws of Tyttobrycon marajoara, paratype, MZUSP 106110, 20.5 mm SL. Scale bar = 1 mm, left side.

Fig. 4.External view of muscle covering the anterior portion of the swim bladder of Tyttobrycon marajoara,paratype, MZUSP 106110, 19.6 mm SL, mature female. Skin and adipose tissue removed, left side. 5plr = fifth pleural rib; 6plr = sixth pleural rib; ls = lateralis superficialis; os = obliquus superioris.

Fig. 6. Bony hooks on pelvic fin of a male of Tyttobrycon marajoara, paratype, MZUSP 106110, 18.9 mm SL. Ventral view, left side.

Fig. 7. First anal-fin rays of a male of Tyttobrycon marajoara, paratype, MZUSP 106110, 18.9 mm SL, with bony hooks. Lateral view, left side.

Fig. 8. Fin lengths and body depth as a function of standard length by sex for Tyttobrycon marajoara: (a) body depth, (b) pectoral fin, (c) pelvic fin.

Fig. 9. Lateral view of left pelvic bone of male (a) and anterior portion of pelvic-fin rays of female (b) of Tyttobrycon marajoara, paratype, MZUSP 106110.

Fig. 10. Distribution of Tyttobrycon marajoara on the east portion of Marajó Island, Pará State, Brazil. Red dot represents two localities.

Fig. 11. Type locality ofTyttobrycon marajoara, Igarapé Olho d’água:(a) wet season at June, 2009; (b) dry season at October, 2009.