Lophiobrycon weitzmani, Castro & Ribeiro & Benine & Melo, 2003

Castro, Ricardo M. C., Ribeiro, Alexandre C., Benine, Ricardo C. & Melo, Alex L. A., 2003, Lophiobrycon weitzmani, a new genus and species of glandulocaudine fish (Characiformes: Characidae) from the rio Grande drainage, upper rio Paraná system, southeastern Brazil, Neotropical Ichthyology 1 (1), pp. 11-19 : 14-16

Lophiobrycon weitzmani , new species

Figs. 1 and 2

Holotype: LIRP4366 ,male,26.0 mm SL, Brazil, Minas Gerais, rio Grande basin, Município de Delfinópolis, Estância Carmem Sílvia , córrego Bom Jesus (20º 12’10’’ S 46º 55’22” W), 18– 22 July 1998; A. C. Ribeiro, A. L. A. Melo & R. C. Benine.

Paratypes: LIRP 4337 , 8 spms, 20.4-27.3 mm SL (1 male, C&S, 25.8mm SL, 1 female, C&S, 27.0 mm SL, 6 females, 20.4-27.3 mm SL), collected with holotype . LIRP4338 , 31 spms, 9.8-28.9 mm SL (3males, 23.9-28.9mm SL, 3females, 23.8-25.5mm SL, 24juveniles, 9.8-25.5 mm SL), collected at type locality, 21 – 22 August 1998; A. C. Ribeiro & A.L. A. Melo . LIRP 4339 , 6 spms C&S, 16.8-25.3 mm SL, collected at type locality, 20 – 21 July 1999; A. C. Ribeiro, A. L.A. Melo & R. C. Benine . MZUSP 83353 , 30 spms, 10.9-25.3 mm SL (2 males, both 25.3 mm SL, 8 females, 18.6-21.4 mm SL, 20 juveniles 10.9-22.6 mm SL), collected at type locality, 20 – 21July 1999; A. C. Ribeiro, A. L. A. Melo & R. C. Benine . MCP 34194, 8 spms, 22.6-26.6mm SL (4 males, 25.5-26.6mm SL, 4 females, 22.3- 23.4 mm SL), collected at type locality, 20 – 21July 1999; A. C. Ribeiro, A. L. A. Melo & R. C. Benine .

Diagnosis. As for the genus.

Description. Table 1 presents morphometrics of holotype and paratypes.

Body compressed, moderately elongate; body deepest approximately in region between verticals through pelvic-fin origin and close to dorsal-fin origin. Dorsal profile of head and predorsal profile of body convex. Body profile slightly elevated at dorsal-fin origin, straight along dorsal-fin base and nearly straight to origin of dorsal procurrent caudal-fin rays. Dorsal-fin origin located nearer snout tip than to caudal-fin base. Ventral profile of body convex from tip of lower jaw approximately to origin of pelvic fin. Ventral profile slightly concave to straight between pelvic-fin origin and caudal-fin base.

Head and snout of moderate size in proportion to body length. Lower jaw protruding and extending anterior to tip of upper jaw. Mouth angled posteroventrally with maxilla extending posteriorly to point slightly anterior of vertical through anterior border of pupil.

Dorsal-fin rays ii,8 (i-ii, mode = ii; 6-9, mode = 8; n = 62). Adipose-fin with shape and size unique to the genus, the length of its base in adult males extending for almost the entire distance between the posterior termination of the base of the dorsal-fin and the base of the upper lobe of the caudal fin, its length averaging approximately 25% of SL. Anal-fin rays iv, 22 (iii-iv, mode = iv; 20-24, mode = 22; n = 62). Anal fin with moderately developed anterior lobe including four unbranched rays and first six branched rays. Anal fin of sexually mature males with hooks on last unbranched ray and anterior five branched rays. Anteriormost rays bearing small hooks and other rays each with single or sometimes a few more highly developed hooks.

Pectoral-fin rays i,12 (i,11-i,14; mode = i,12; n = 62) (very young individuals not included); posterior tips of longest pectoral-fin ray extends posteriorly to origin of pelvic fin and of approximately equal lengths in both sexes. Pectoral-fin rays without hooks; middle portions of the unbranched and first branched pectoral-fin rays of sexually mature males with globular expansions, formed by the lepidotrichia and hypertrophied soft tissue, a condition autapomorphic for genus ( Fig. 5 ). Pelvic-fin rays i,6 (in all specimens, n = 61). Pelvic-fin rays without hooks. Principal caudal-fin ray count 10/ 9 in all specimens (n = 62); sexually mature males with an anteriorly round soft tissue keel running below ventral procurrent caudal-fin rays ( Figs. 1A and 2 ), feature apparently also present in sexually mature Glandulocauda melanogenys ( Weitzman et al., 1988: 398-399, Figs. 13-14).

Scales cycloid; lateral line incomplete; perforated scales 4 (2-6; mode = 4; n = 58). Lateral series scales 35 (29-36; mode = 32; n = 59). Predorsal scales 10 (10-15; mode = 11; n = 60). Scale rows between dorsal-fin and anal-fin origin 12 in all specimens (n = 59). Scale rows around caudal peduncle 15 (11-15; mode = 14; n = 59).

Description of dentition based on eight C&S specimens. Premaxillary teeth in two distinct rows. Outer row teeth 2-3 (mode = 2, n = 8), tricuspid. Inner row teeth 3-6 (mode 5, n = 8), tricuspid. Maxillary teeth 4-6 (mode = 5, n = 8), all conic or anterior 1-3 teeth tricuspid and all 2-5 posterior teeth conic. Dentary teeth 10-13 (mode 12, n = 8) in single row with anterior 3-4 teeth largest and tricuspid and followed posteriorly by 7-9 tricuspid to conic teeth gradually diminishing in size posteriorly. Central cusp of premaxillary, maxillary, and dentary teeth larger than lateral cusps ( Fig. 6 ).

Vertebra 33-35 (mode 34, n = 8 C&S) and branchiostegal rays 4 (n = 8 C&S). Three branchiostegal rays originating from anterior ceratohyal and one from posterior ceratohyal. Color in alcohol. Ground coloration of preserved specimens tan. Slightly widened longitudinal stripe begins just posterior to opercle and extends to tip of medial caudal-fin rays. Several irregular dark vertical bars on body from just posterior of opercle to vertical line passing through posterior terminus of base of dorsal fin. First two bars more evident and posterior bars becoming thinner posteriorly. Dorsal portion of head dark brown. Dark mid-dorsal stripe extends from posterior tip of occipital bone to anterior region of caudal fin and passes through base of the dorsal fin. Dorsolateral portion of body darker than nearly unpigmented ventrolateral region. Dispersed dark pigment present on all fins. Base of anterior anal-fin rays darkly pigmented.

Color in life. Ground color greenish and dark pigmentation as in specimens in alcohol. Anterior two bar more obvious than others. Dorsal portion of body darker than yellowish-green ventral region. All fins yellowish, especially sexually dimorphic crest-shaped adipose-fin of mature males, with small black dots ( Fig. 2 ).

Sexual dimorphism. Overall body shape of the males differs from that of the females and juveniles ( Fig. 1 ). Mature, dominant and sexually active males (identified during observations of live wild specimens in aquaria) have deeper greater bodies and caudal peduncles and longer pectoral fins relative to mature and unequivocally identifiable females. Overlapping morphometric values in Table 1 between males, females, and juveniles possibly result of difficulties in distinguishing females and immature males.

Mature males with adipose fin much longer and more developed than females and/or juveniles and with middle portions of the unbranched and first branched pectoral-fin rays with globular expansions formed by the lepidotrichia and hypertrophied soft tissue ( Fig. 5 ) that may be used in courtship behavior. Mature males bear numerous hooks on the anal-fin rays that are absent in the females. Sexually mature males with anteriorly rounded soft tissue keel that runs below ventral procurrent caudal-fin rays ( Figs. 1A and 2 ).

Distribution. Known only from type locality ( Fig. 3 ).

Etymology. The specific epithet is named for Stanley H. Weitzman, in recognition of his seminal work on the systematics of Neotropical characiforms, particularly of the characid subfamily Glandulocaudinae .

Figures

Fig. 1. Lophiobrycon weitzmani, holotype (A), LIRP 4366, male, SL 26.0 mm; paratype (B), LIRP 4338, female, SL 27.0 mm; Brazil, Minas Gerais, rio Grande basin, Município de Delfinópolis, Estância Carmem Sílvia, córrego Bom Jesus (20º12’10’’S 46º55’22”W), showing the accentuated sexual dimorphism in general body shape and adipose-fin dimensions.

Fig. 2. Lophiobrycon weitzmani, paratype, LIRP 4338, male, SL 31.1 mm; Brazil, Minas Gerais, rio Grande basin, Município de Delfinópolis, Estância Carmem Sílvia, córrego Bom Jesus, (20º12’10’’S 46º55’22”W), aquarium field photograph.

Fig. 5. Lophiobrycon weitzmani, paratype, alizarin stained pectoral fin of adult male, ventral view, anteriormost fin ray at top, medial fin ray at bottom. Arrow indicates modified portions of the lepidotrichia supporting the diagnostic globular expansion, formed by the lepidotrichia and hypertrophied soft tissue (not represented in the illustration), in the middle portions of the unbranched (above) and first branched (below) pectoral-fin rays. LIRP 4338, 24.7 mm SL, same locality data as in Figs. 1 and 3.

Fig. 6. Lophiobrycon weitzmani, paratype, jaws and dentition of adult male, lateral view, anterior at right. LIRP 4339, 24.3 mm SL, same locality data as in Figs. 1 and 3.

Fig. 3. Map of part of the eastern coast of South America and adjoining regions showing the type locality and known distribution of Lophiobrycon weitzmani, new genus and species, in the upper rio Paraná system, southeastern Brazil (1 = rio Grande; 2 = rio Paraná; 3 = rio São Francisco).