Leptodoras hasemani ( Steindachner, 1915 )

Sabaj, Mark Henry, 2005, Taxonomic assessment of Leptodoras (Siluriformes: Doradidae) with descriptions of three new species, Neotropical Ichthyology 3 (4), pp. 637-678 : 653-654

Leptodoras hasemani ( Steindachner, 1915) Figs. 4d and 12

Hemidoras hasemani Steindachner 1915: 218 (type locality: rio Branco , Negro dr., Boa Vista, Roraima, Brazil).

Diagnosis. Uniquely distinguished among Leptodoras by having a large black blotch in the distal half of the anterior dorsal-fin rays and membranes.Also in L. hasemani the basal portion of the lower labial extension is uniformly widened and flat compared to other Leptodoras .

Description. Body elongate, weakly compressed; head comparatively short, deep, weakly compressed with bluntly pointed snout; ventrally flattened from snout to vent; caudal peduncle moderately elongate, depressed. Eye large with welldeveloped adipose eyelid.

Mouth subterminal, jaws edentulous in adults and juveniles as small as 39 mm SL. Oral hood comparatively large and somewhat unique in that origins of first secondary maxillary barbels and upper labial extensions occur well beyond distal margin of dentary. Maxillary barbel long, usually reaching to or slightly beyond ventromedial extent of gill opening. Secondary maxillary barbels 6-9 (modally 7 or 8), flattened, largely overlapping; proximal secondary maxillary barbels with fimbriate anterior margin and smooth posterior margin; distal ones smooth. Upper labial extension lanceolate (tapered distally), moderately elongate, usually straight with smooth ventral surface; lateral margin with small distal fimbriae. Lower labial extension finishing more or less even with upper labial extension, basal portion uniformly broad with conspicuously smooth surface, distal portion narrow, attenuate; margins smooth. Interlabial membrane narrow to moderate width (labial extensions parallel or convergent), comparatively thin with few very small papillae. Dorsolabial membrane weakly developed, evenly attenuate posteriorly. Two pairs of jaw barbels with comparatively few elongate papillae and broadly cojoined by basal membrane; outer pair only slightly longer than inner pair and shorter than maxillary barbel, cojoined with lower labial extension via narrow membrane. Branchiostegal membrane with greatly expanded fleshy margin that strongly overlaps ventral gill opening; fleshy inner flap along cleithrum well developed, reaching cleithral notch for pectoral spine insertion. Morphology of first gill arch similar to L. praelongus and L. copei .

Sum of midlateral plates 75-80 (modally 78, Table 3). Anterior midlateral plates deep, covering more than half of corresponding body depth; posterior margins of dorsal and ventral wings rounded with many small serrae. Tympanum usually with 3 small ossifications (plates or weak spines) along postotic laterosensory canal; small fixed spine usually visible along posterior margin of neurocranium where postotic laterosensory canal exits supracleithrum. Postcleithral process short, nearly uniform width or slightly expanded posteriorly. Middorsal groove on nuchal shield weakly defined. Nuchal foramina absent. Skin comparatively smooth, sometimes with minute papillae on head in region between eyes and posterior nares.

Dorsal-fin rays I,6; pectoral-fin rays I,10-11 (modally 10); pelvic-fin rays i,6; total anal-fin rays 14-16 (first 4 to 6 unbranched); caudal-fin rays i,8/9,i; dorsal procurrent caudalfin rays 14-17, ventral procurrent caudal-fin rays 13-17. Dorsal-fin spine of moderate length, rather sturdy, weakly curved for much of length, becoming straight near sharp tip; anterior denticulations antrorse, small, crowded basally and largely absent from distal third; posterior denticulations retrorse, moderately sized and regularly spaced to tip. Pectoral-fin spine sturdy, long, distinctly bowed with sharp tip; anterior denticulations antrorse, rather small, largely absent from distal third; posterior denticulations strong, retrorse, size rather uniform from midlength to tip; last denticulation subterminal. Pelvic fin of moderate length, very weakly pointed. Anal fin triangular, tip of longest branched ray more or less even with base of last ray, distal margin nearly straight. Caudal fin forked with rounded to bluntly pointed lobes.

Coloration in alcohol. Head and body weakly countershaded, upper sides relatively uniform tan or light gray, lower sides and ventral surfaces white to cream. Distal half of soft dorsal fin with large black blotch; melanophores concentrated on first two rays and three inter-radial membranes; remaining fin hyaline. Melanophores concentrated on skin covering dorsal-locking spine and posterior margin of nuchal shield. Dorsal spine depigmented or with few melanophores along anterior margin. Pectoral fin with few melanophores scattered along base and inter-radial membranes, remaining portions cream. Pelvic fins and anal fin relatively depigmented, cream, hyaline. Caudal fin with melanophores forming parallel pair of faint dusky stripes, one on lower rays and membranes of upper lobe and other on upper rays and membranes of lower lobe (portions of stripe overlying membranes appear darker); remaining portions of caudal fin light by comparison with sparsely scattered melanophores, particularly on rays.

Distribution and habitat. Leptodoras hasemani is known from the río Orinoco, rio Branco (Negro dr.) and Essequibo river in Venezuela, Brazil and Guyana, respectively ( Fig. 13 ). It also occurs in the lower rio Demini, a tributary of the rio Negro. This species appears to favor whitewater habitats. Collections are from the main channels of large rivers and often associated with large sandy beaches.

FMNH 109976 (2, 76.8, 152.5 mm), río Caura (Orinoco dr.), sand island 1 km upstream from mouth of caño Mato (7°11’49"N, 65°8’53"W), 9 Dec 2000 ; LACM 43011 (1), río Orinoco ( Atlantic dr.), river channel between Palua and San Felix, 180 nautical miles upstream from sea buoy, 15 Feb 1978 ; MCNG 19239 (2, 39.2, 43.6 mm), puente del río Orocopiche (Orinoco Dr.), near Ciudad Bolivar, 23 Sep 1988 , ABD87-33 .

Type-material examined. Hemidoras hasemani : lectotype by present designation, NMW 46381 (82 mm, largest), rio Branco (Negro dr.), Boa Vista, Brazil, J. D. Haseman . Paralectotypes: NMW ex. 46381 (3, 77.2-80.1 mm), NMW 46382 (4, 73.1-80.5 mm), same data as lectotype; NMW 46383 (5, 66.0- 76.6 mm), rio Branco (Negro dr.), Serra Grande, Brazil, J. D. Haseman; NMW 46384 (1, 46.9 mm), rio Negro (Amazonas dr.), delta of río Negro, Brazil, J. D. Haseman (not this species and reidentified here as Hemidoras stenopeltis [Kner 1855]); NMW 46385 (1, 68.6), Conceição, below Boa Vista, Brazil, J. D. Haseman; NMW 46470 (3, 58.8-64.5 mm), same data as NMW 46383 .

Non-typematerial. Brazil: Amazonas: INPA 17705 (12) , rioDemini (Negro dr.), near mouth of rio Aracá , 21 Jun 1993. Roraima: ANSP 178533 (1) , rio Branco, 9.3 km upstream from confluence with rio Negro , between Atauba and Caruna (1°19’34"S, 61°52’13"W), 8 Dec 1993, JGL-93-171 . Guyana: ANSP 175884 (4, 89.0- 167 mm) , Essequibo River (Atlantic Dr.), sandbars in vicinity of Maipuri campsite (4°34’17"N, 58°35’17"W), 31 Jan 1997, WGS97-28; ANSP 175885 (1, 157 mm) , Essequibo river (Atlantic dr.), 180 yards upstream from Essequibo campsite (Maipuri) (4°45’43"N, 58°45’52"W), 27 Jan 1997, WGS97-23; ANSP 175886 (5) , Essequibo river (Atlantic dr.), Essequibo campsite (4°45’41"N, 58°45’53"W), 26 Jan 1997, WGS97-19; ANSP 175887 (3) , Essequibo river (Atlantic dr.), sandbars in vicinity of Maipuri campsite (4°34’17"N, 58°35’17"W), 2 Feb 1997, WGS97-31; ANSP 175888 (4) , same data asANSP 175887; ANSP 175889 (1, 86.7 mm) , Essequibo river ( Atlantic dr.), sandbar ca. 800 m downstream from Essequibo campsite (Maipuri) (4°45’43"N, 58°45’52"W), 29 Jan 1997, WGS 97-25; ROM 62633 (43) , Essequibo river (Atlantic dr.), at southern tip of Indian House Island just north of Kurupukari (4°40’23"N, 58°40’50"W), 15 Oct 1990, H90-78; ROM 62643 (2) , Essequibo river (Atlantic dr.), inlet and beach downstream from Kurupukari (4°42’57"N, 58°42’40"W), 10 Oct 1990, H90-43 . Venezuela: Amazonas: ANSP 165788 (1, 57.1 mm) , río Orinoco (Atlantic dr.), shores of Isla de Raton (5°05’N, 67°48’W), 14 Nov 1985, V85-18 ; ANSP 180897 (2) , río Orinoco (Atlantic dr.), island west of Puerto Venado, 4.5 km south of Samariapo , 56.5 km SW of Puerto Ayacucho (5°12’25"N, 67°48’32"W), 28 Feb 2005, VEN 05-04 . Bolivar:

Figures

Fig. 4. Variation in oral-hood morphology in Anduzedoras and Leptodoras. a. A. oxyrhynchus,ANSP 160628 (SL 124.6 mm). b. L.praelongus,ANSP162464 (SL 124.9 mm).c.L.copei,ANSP 162461 (SL95.9 mm).d. L.hasemani,ANSP 175889(SL86.7 mm). e. L. linnelli,ANSP 175883 (SL 94 mm). f. L. nelsoni, MCNG 13167 (SL 93 mm). g. L. cataniai,ANSP 161533 (SL 162.5 mm).h. L. juruensis, INHS 39465 (SL 117.4 mm). i. L. myersi,ANSP 112319 (SL 72.6 mm).

Fig. 12. Leptodoras hasemani, ANSP 175885 (SL 156.4 mm), Essequibo river (Atlantic dr.), Guyana.

Fig. 13. Distributions of Leptodoras hasemani (open circles, blue star denotes type locality) and L. myersi (red star denotes type locality).