Amazonspinther dalmata, Bührnheim & Carvalho & Malabarba & Weitzman, 2008

Bührnheim, Cristina M., Carvalho, Tiago P., Malabarba, Luiz R. & Weitzman, Stanley H., 2008, A new genus and species of characid fish from the Amazon basin - the recognition of a relictual lineage of characid fishes (Ostariophysi: Cheirodontinae: Cheirodontini), Neotropical Ichthyology 6 (4), pp. 663-678 : 665-668

Amazonspinther dalmata , new species

Fig. 1

Holotype. MCP 38623 (1 unsexed 19.63 mm SL), Brazil, Amazonas, Humaitá-Canutama, stream crossing road Transamazônica about 12 km west of Humaitá to Lábrea , rio Madeira basin, 07°34’25”S 63°06’39”W, 27 July 2004, P. Lehman, F. T. Lima, P. A. Buckup, V. A. Bertaco & J. Pezzi da Silva.

Paratypes. All from Brazil, Amazonas: ANSP 187154 (1 unsexed 13.68 mm SL), INPA 28199 (1 unsexed 13.93 mm SL), MCP 37571 (1 female 14.05 mm SL c&s), MNRJ 31096 (2 unsexed 12.79-13.56 mm SL), collected with holotype. INPA 28659 (2 unsexed 14.49 mm SL & 14.74 mm SL), Autazes, stream of rio Tupana , rio Madeira basin, around 48 km southeast to the municipality of Careiro , 04°09’24”S 60°08’40”W, 3 July 2007, H. M. V. Espírito Santo, A. V. Galuch & D. Barros. INPA 28660 (2 unsexed 16.32 mm SL & 16.73 mm SL), same locality and collectors as INPA 28659 , 5 July 2007. INPA 28661 (3 unsexed 14.72-15.41 mm SL), same locality and collectors as INPA 28659 , 7 July 2007. INPA 28662 (1 female 19.68 mm SL, 2 unsexed 11.02 mm SL & 12.14 mm SL), Canutama, stream of upper rio Mucuim , about 50 km west of Porto Velho , 08°39’16”S 64°22’02”W, 25 April 2007, F. P. Mendonça & D. Barros. INPA 28663 (1 unsexed 13.86 mm SL), same locality and collectors as INPA 28662 , 2 May 2007. INPA 28664 (7 unsexed 11.28-19.79 mm SL), same locality and collectors as INPA 28662 , 3 May 2007. INPA 28665 (1 female 15.39 mm, 37 unsexed 12.18-15.77 mm SL), MCP 42017 (1 female 15.73 mm SL, 9 unsexed 12.24-15.82 mm SL), same locality and collectors as INPA 28662 , 29 April 2007. MCP 37572, 2 (1 unsexed 14.98 mm SL c&s, 1 unsexed 14.85 mm SL), Canutama, stream of rio Açuá , rio Mucuim drainage, about 136 km southwest of Humaitá on road BR-319, rio Purus basin, 08°12’13”S 63°53’01”W, 28 July 2004, R. Reis, E. Pereira, F. Langeani & A. Cardoso .

Diagnosis. The same as for the genus.

Description. Morphometric and meristic data given in Table 1 . Largest specimen 19.79 mm SL, possibly a female. General body shape relatively elongate. Greatest body depth at dorsal-fin origin corresponding to most elevated point in dorsal profile; greatest body depth slightly ahead of dorsal fin in females. Dorsal body profile slightly convex from snout to dorsal-fin origin, slightly concave to caudal peduncle. Ventral profile almost straight from isthmus to anal-fin origin.Anal-fin base slightly concave. Caudal peduncle very long, not deep. Two pseudotympanums, one anterior to first pleural rib and another between first and second pleural ribs ( Fig. 1 ).

Head short, snout blunt, mouth subterminal. Posterior margin of opercle sinusoidal, with upper portion concave and lower portion convex. Obliquely positioned maxilla; posterior tip at vertical through anterior eye border and below projected longitudinal line through ventral eye border. Dentition examined in two c&s specimens ( Fig. 5 ). Premaxillary teeth 6 or 7, conical. Maxillary teeth 3 or 4, conical. Dentary teeth 7 or 9, 4 or 5 largest tricuspid, 1 bicuspid and 2 or 3 smallest conical.

Dorsal-fin rays ii,9(8). Dorsal-fin origin at middle body length, slightly posterior to vertical through pelvic-fin ori- gin. Posterior margin of dorsal-fin almost straight or slightly concave. Anal-fin rays iii, 8 (7), 9(1). Anal-fin border concave with 3 rd unbranched and anterior 1 st- 3 rd branched rays longer, decreasing moderately in length from 4 th- 8 th branched ray. Pectoral-fin rays i,10(9). Pectoral fin pointed, 1 st- 3 rd branched fin ray longer, lateral margin straight, posterior margin oblique and straight. Pectoral fin reaching to or slightly beyond pelvicfin origin. Pelvic-fin rays i,5,i(9). Pelvic fin slightly rounded at tip, reaching anal-fin origin. Principal caudal-fin rays 17(1), 18(4), 19 (3). Procurrent caudal-fin rays: dorsal 7(2), 8 (5), 9(1), ventral 7 (4), 8(3), 9(1). Adipose fin at vertical through middle of caudal peduncle. Caudal-fin lobes equal, somewhat pointed. No hooks on fins.

Scales cycloid. Counts estimated on scale pockets: lateral line incomplete with 4(1), 5 (5) scales, row of longitudinal scales 32, 34(1); predorsal row 9 (6), 10(1); scales between lateral line and dorsal-fin origin 4 (8); scales between lateral line and pelvic-fin origin 3(1), 4 (2).

Cleared and stained specimens (2): branchiostegal rays 4; supraneurals 4(1); precaudal vertebrae, including Weberian apparatus, 15; caudal vertebrae 18-19, including posterior half centrum. Anteriormost proximal radial of anal fin with an anteriorly extended lamina slightly entering abdominal cavity unique to A. dalmata , among all known Cheirodontinae ( Fig. 2 ). Upper gill rakers 3, short; lower gill rakers absent ( Fig. 6a ).

Color in alcohol. General ground body color pale beige. Dorsal midline scales with few black chromatophores on scale borders reaching to caudal peduncle. Scarce or no chromatophores on pseudotympanum area; no humeral blotch. Black chromatophores on mid ventral line between anal-fin base termination and caudal peduncle, forming dotted line.

Three conspicuous black blotches on base of dorsal, anal, and caudal fins ( Fig. 1 ). Dorsal blotch formed by black chro- matophores on 1 st and 2 nd unbranched and 1 st to 4 th branched dorsal-fin rays, positioned on base and middle of fin rays, and laterally on body surface close to dorsal-fin base, forming nearly triangular blotch. Anal blotch formed by black chromatophores on 3 rd unbranched and 1 st to 7 th branched anal-fin rays, on middle of anteriormost fin rays, decreasing in size to base of posterior pigmented branched rays, and laterally on body surface close to anal-fin base forming elongated blotch. Caudal black blotch rounded centered at posterior end of caudal peduncle and base of median caudal-fin rays, not reaching upper and lower border of caudal peduncle. Few scattered black chromatophores sometimes present along 2 nd unbranched and 1 st branched dorsal-fin rays. Scarce black chromatophores on base of 1 st branched pectoral fins and 1 st unbranched pelvic fin ray in a few specimens. Adipose fin hyaline. Caudal fin with few scattered black chromatophores on upper and lower lobes, clearer area just behind caudal blotch.

Snout with scarce black chromatophores; few chromatophores on upper lip. Epidermis covering fontanels wellpigmented; epidermis covering frontals and parietals, with deep-lying black chromatophores over brain underneath to frontals and parietals.

Color in life. Body translucent, allowing view of glass blad- der and vertebral column ( Fig. 7 ). A greenish metallic yellow iridescent line along vertebral column more evident depending on angle of light incidence. Proximal portion of pleural ribs and opercle iridescent ( Fig. 7 ).

Sexual dimorphism. No external sexual dimorphism was observed. Four sexed specimens are females, two with immature gonads (MCP 37571, 1 c&s, 14.05 mm SL; INPA 28665, 1,

15.39 mm SL), two with mature gonads ( MCP 42017, 1 , 15.73 mm SL; INPA 28662 , 1 , 19.68 mm SL). A small incision was made on left side of abdominal region of holotype (19.63 mm SL), but no discernible gonads were found .

Distribution. Amazonspinther dalmata is known from small streams of middle rio Purus (rio Açuá) and middle and lower rio Madeira basins, State of Amazonas, Brazil ( Fig. 8 ).

Ecological notes. The holotype of Amazonspinther dalmata was collected syntopically with several characid species, such as Axelrodia lindeae, Iguanodectes spp., Microschemobrycon geisleri , Tyttocharax madeirae , Gnathocharax steindachneri , Phenacogaster beni , Hemigrammus sp., Knodus sp., and with the crenuchids Odontocharacidium aphanes , Elachocharax pulcher , Ammocryptocharax elegans , and Microcharacidium sp. The type locality was characterized by possessing slow current, muddy substratum, and silty, turbid water. There was abundant riparian vegetation, and the maximum depth was 1.3 m ( Fig. 9 ). The site of collection in the tributary of rio Purus (MCP 37572) had perceptible current, some submerged vegetation, transparent water, sandy and muddy substratum, riparian vegetation, and a maximum depth of 1 m.

Etymology. The epithet refers to the Portuguese word “dalmata”, in allusion to the color pattern of the skin of the dogs of the Dalmatian breed which resembles the color of A. dalmata . The origin of this word is linked to the Dalmatia region currently in Croatia, where the dog breed was possibly developed. A noun in apposition.

Figures

Fig. 1. Holotype of Amazonspinther dalmata, new species, MCP 38623, undetermined sex, 19.63 mm SL.

Fig. 5. Premaxilla, maxilla, and dentary (right side) of Amazonspinther dalmata (MCP 37572, unsexed 14.98 mm SL c&s).

Fig. 2. Lateral view (left side) of the anteriormost proximal radial of the anal fin of Amazonspinther dalmata, showing the anteriorly extended lamina entering the abdominal cavity (MCP 37572, 14.98 mm SL, c&s).

Fig. 6a-f. First branchial arches, left side, external view: (a) Amazonspinther dalmata, MCP 37571, female 14.05 mm SL, (b) Spintherobolus papilliferus, MZUSP 51022, unsexed 23,79 mm SL, (c) Spintherobolus broccae, MCP 19196, unsexed 17.43 mm SL, and (d) Spintherobolus ankoseion, MCP 19280, female 23.10 mm SL. Below cheirodontines: (e) Cheirodon ibicuhiensis, MCP 13663, male 36.10 mm SL, and (f) Serrapinnus heterodon, MZUSP 16740, male 30.20 mm SL.

Fig. 7. Live specimens of Amazonspinther dalmata. In detail a specimen on the left and a school of specimens as observed in the field on the right (photos by Fernando Mendonça).

Fig. 8. Distribution of Amazonspinther dalmata in northern South America, rio Purus and rio Madeira basins. Circles represent more than one lot, and more than one locality. Star indicates the type locality.

Fig. 9. Type locality of Amazonspinther dalmata. Stream crossing road Transamazônica about 12 km west of Humaitá to Lábrea, rio Madeira basin, 07°34’25”S 63°06’39”W.