Leptodoras rogersae, Sabaj, 2005

Sabaj, Mark Henry, 2005, Taxonomic assessment of Leptodoras (Siluriformes: Doradidae) with descriptions of three new species, Neotropical Ichthyology 3 (4), pp. 637-678 : 665-667

Leptodoras rogersae , new species

Figs. 5c , 15c and 21

Holotype. USNM 226307 (1*, 180 mm), Venezuela, Bolivar, río Orinoco (Atlantic Dr.), river channel at Palua just below mouth of río Caroni , 181 nautical miles upstream from sea buoy (8°21’N, 62°43’W), 15 Feb 1978, J.G. Lundberg, J.N. Baskin et al., JGL 1-78.

Paratypes (13). Venezuela: Amazonas: MCNG 54110 [ex. ANSP 160742 ] (1*, 98.4 mm), río Orinoco (Atlantic dr.), shores of Isla de Ratón (5°5’N, 67°48’W), 14 Nov 1985 , V85-18 ; MNHN 2003- 0356 [ex. ANSP 160742 ] (1 + 1*, 90.9 mm), same data as MCNG 54110. Bolivar : AMNH 58175 (1, 66.4 mm), río Orinoco ( Atlantic dr.) (8°42’1"N, 62°5’4"W), 12 Nov 1979 , GM-T 79-43; ANSP 160885 (1*, 94.7 mm), río Cuchivero (Orinoco dr.), ca. 500 m from confluence with río Orinoco (7°38’N, 65°56’W), 18 Nov 1985 , V85-28 ; MBUCV-V 27136 (1, 80.76 mm), río Orinoco (Atlantic dr.), cerca de la boca río Caura , 22 Nov 1985 . Delta Amacuro: ANSP 179108 (1, 93.9 mm), río Orinoco ( Atlantic dr.), between nautical mile buoys 137.4 and 116.5, 12 Nov 1979 , T- 54-79; CAS 58077 (1*, 89.2 mm), río Orinoco ( Atlantic dr.), bottom drag in deep channel, 11 Nov 1979 ; FMNH 117084 [ex. MBUCV-V 13372 ] (1*, 116.7 mm), río Orinoco (Atlantic dr.), 137-138.5 nautical miles from sea buoy near Barrancas, 12 Feb 1978 ; MBUCV-V 13372 (1*, 128.8 mm), same data as FMNH 117084 ; LACM 43124 (1, 170 mm), deep river channel north of isla Tres Canos, 132 nautical miles upstream from sea, 19 Feb 1978 , JNB-36-78; MCZ 68120 (1, 78 mm), río Orinoco ( Atlantic dr.), deep channel bottom at river km 137, near Barrancas (8°42’N, 62°5’S), 12 Nov 1979 ; USNM 265710 (1*, 107.05 mm), channel of río Orinoco ( Atlantic dr.), at buoy 129.7 to buoy 130.4, at isla Tres Canos, downstream from el Consejo and Barrancas (8°39’48"N, 61°58’40"W), 14 Nov 1979 , T-55-79.

Non-types. Venezuela: ANSP 152863 (1, 85.3 mm), río Orinoco (Atlantic dr.), Orinoco delta region, Nov 1979 . Amazonas: ANSP 160742 (44 + 1*, 98.6 mm), río Orinoco (Atlantic dr.), shores of Isla de Ratón (5°5’N, 67°48’W), 14 Nov 1985 , V85-18 ; Bolivar: MBUCV-V 15843 (1, 79.6 mm), río Orinoco ( Atlantic dr.), 50 mts. de la boca de Cuchivero, Nov 1985 ; MBUCV-V 15939 (6), río Orinoco ( Atlantic dr.) playas, canales, lagunas y islas cerca puerto las Majadas, confluencial de Orinoco con el Caura, 23 Nov 1985 . Delta Amacuro: ANSP 179105 (1), río Orinoco (Atlantic dr.), sandy beach on Isla Paloma , 101 nautical miles from sea buoy (8°32’36"N, 61°32’12"W), 22 Nov 1979 , ECM-27-79; MBUCV-V 13724 (1, 72.8 mm), río Orinoco ( Atlantic dr.), cerca de la boca del Caño Arutaye, 20 Nov 1979 .

Diagnosis. Distinguished among Leptodoras by the following combination: sum of midlateral plates modally 83 or 84, plates moderately deep, covering 1/4 to 1/2 of body depth, adipose eye moderately developed, preadipose ridge weakly developed, distal medial margin of upper labial extension not forming enlarged or elongated triangular tip.

Description. Morphometrics summarized in Table 1. Overall shape similar to L. acipenserinus and L. nelsoni except body slightly more robust and snout comparatively shorter, distance from tip to posterior nares 33.8-35.9% of predorsal distance (vs. 36.1-40.3% and 36.4-40% in L. acipenserinus and L. nelsoni , respectively). Eye moderately sized, center distinctly anterior of midpoint between snout tip and origin of dorsal spine; adipose eyelid moderately developed.

Mouth subterminal, jaws edentulous in adults, juveniles under 75 mm SL with few thin acicular teeth near distal medial symphysis of dentaries. Maxillary barbel long, usually reaching ventromedial extent of gill opening. Secondary maxillary barbels 9-13 (modally 11), flattened, overlapping proximally, separated distally; proximal secondary maxillary barbels with fimbriate anterior margin and smooth posterior margin; distal ones smooth. Oral hood as in L. acipenserinus and L. nelsoni except comparatively longer, distance from jaw margin to tip of upper labial extension 29.2-35.5% of predorsal distance (vs. 20.9-29% and 19.1-28% in L. acipenserinus and L. nelsoni , respectively); dorsolabial membrane moderately developed. Branchiostegal membrane with moderately expanded fleshy margin overlapping ventral gill opening; fleshy inner flap along cleithrum usually complete, nearly reaching cleithral notch. Morphology of first gill arch similar to L. linnelli .

Sum of midlateral plates 82-86 (modally 83 and 84, Table 3). Anterior midlateral plates of moderate depth, covering less than half of corresponding body depth; posterior margins of dorsal and ventral wings rounded with many small serrae. Tympanum without conspicuous ossifications or with 2 or 3 very small spines along postotic laterosensory canal; small fixed spine usually present (but inconspicuous) where postotic laterosensory canal exits supracleithrum. Postcleithral process short, moderately expanded posteriorly. Middorsal groove on nuchal shield usually well-defined. Subrectangular nuchal foramina present, replacing suture between epioccipital and anterior nuchal plate. Skin with very small fleshy papillae on snout; papillae scattered, not forming conspicuous ridges.

Dorsal-fin rays I,6; pectoral-fin rays I,10; pelvic-fin rays i,6; total anal-fin rays 15-17 (first 4 or 5 unbranched); caudalfin rays i,8/9,i; dorsal procurrent caudal-fin rays 15-16, ventral procurrent caudal-fin rays about 14. Dorsal-fin spine of moderate length, nearly straight, rather thin and evenly attenuate with sharp tip; anterior denticulations antrorse, moderately sized, absent from distal tip; posterior denticulations small, retrorse basally, becoming straight towards tip. Pectoral-fin spine as described for L. acipenserinus . Pelvic fin weakly pointed and slightly longer (average length 17.1% of SL) than in L. acipenserinus (15%) and L. nelsoni (15.4%). Anal fin triangular with elongate base; tip of longest branched ray falls well short of vertical through base of last branched ray when fin extended. Adipose fin usually with weak preadipose ridge (not as well developed as in L. acipenserinus and L. linnelli ). Caudal fin deeply forked with elongate and pointed lobes.

Coloration in alcohol. Pattern on body and fins similar to that of L. acipenserinus and L. nelsoni , but more faintly expressed overall. Weakly countershaded, upper sides tan or gray, lower sides and undersurfaces white. Broad dusky middorsal and midlateral stripes faint. Divergent dusky stripes on caudal fin distinct as in L. nelsoni .

Distribution and habitat. Leptodoras rogersae is known from the río Orinoco from Isla Ratón (near mouth of río Vichada, northwestern Amazonas) to the delta, Venezuela ( Fig. 16 ). Nearly all collections are from the main channel of the río Orinoco. One is from the río Cuchivero near its confluence with the Orinoco. Many specimens were collected via bottom trawls as deep as 14 m. This species is probably restricted to the main channel of the lower to middle Orinoco and the mouths of its largest tributaries.

Etymology. Named in honor of Mary Anne Rogers, for her dedicated service to the ichthyological community since 1988 as Collection Manager of Fishes, Field Museum of Natural History.

Figures

Fig. 5. Ventral views of heads in Leptodoras. a. L. linnelli, MBUCV-V 16602 (SL 157 mm). b. L. nelsoni, MBUCV-V 14769 (SL 135.8 mm). c. L. rogersae, USNM 226307 (SL 180 mm). d. L. acipenserinus, FMNH 92385 (SL 155 mm). e. L. acipenserinus, FMNH97140 (SL 113.3 mm).f.L.acipenserinus,ANSP 178467 (SL 107.9 mm). g. L.cataniai,ANSP 161532 (SL 142.6 mm).h. L. cf. cataniaiAmazon form,ANSP 180925 (SL 194 mm). i. L. cf.cataniai Nanay form,ANSP 178438 (SL 164.2 mm).

Fig. 15. Juvenile and subadult Leptodoras (Orinoco and Essequibo basins). a. L. linnelli, ANSP 175881 (SL 100.1 mm), Essequibo river, Guyana. b. L. linnelli, MBUCV-V 19689 (SL 100.5 mm), río Mavaca (Orinoco dr.), Amazonas, Venezuela.c. L. rogersae, paratype, MBUCV-V 13372 (SL 128.8 mm), río Orinoco, DeltaAmacuro, Venezuela. d. L. nelsoni, paratype, MBUCV- V 14769 (SL 104.5 mm), ríoApure,Apure, Venezuela.

Fig. 21. Leptodoras rogersae, holotype USNM 226307 (SL 180 mm), río Orinoco (Atlantic dr.), Palua just below mouth of río Caroni, Bolivar, Venezuela.

Fig. 16. Distributions of Leptodoras acipenserinus (solid red circles), L. linnelli (solid green circles), L. nelsoni (open red circles) and L. rogersae (open blue circles) (stars denote type localities).