Hisonotus ringueleti, AQUINO & SCHAEFER & MIQUELARENA, 2001

AQUINO, ADRIANA E., SCHAEFER, SCOTT A. & MIQUELARENA, AMALIA M., 2001, A New Species of Hisonotus (Siluriformes, Loricariidae) of the Upper Río Uruguay Basin, American Museum Novitates 3333, pp. 1-12 : 3-8

Hisonotus ringueleti , new species

Figure 1

DIAGNOSIS: No autapomorphy was found for Hisonotus ringueleti . The new species can be distinguished from all other species of Hisonotus by the combination: (1) presence of serrae along distal two­thirds of posterior margin of pectoral spine (versus serrae absent, posterior margin smooth) (fig. 2B); (2) odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow odontode­free area (fig. 3, top); (3) caudal peduncle short (27–34% SL, versus> 31% SL) and deep (13–15 % SL, versus <13% SL); (4) eye large (15– 19% HL, versus <13% HL); and (5) caudalfin pigmentation, when well defined, dark brown with pair of whitish blotches on upper and lower lobes (fig. 4, top).

REMARKS: Among nominal species of Hisonotus , the presence of serrae along the posterior margin of the pectoral spine was also observed in Hisonotus taimensis Buckup, 1981 , and H. nigricauda (Boulenger, 1891) , which precludes this feature as autapomorphic for H. ringueleti among species of Hisonotus . However, the consistency of certain intrinsic features of the serrae in H. ringueleti are noteworthy. Specifically, serrae of H. ringueleti (1) are consistently present in individuals, versus variably present among individuals in other species, (2) are composed of robust ‘‘teeth’’ (tooth height approximately 40–50% of spine width at tip), versus teeth feeble and inconspicuous (tooth height <20% of spine width at tip), and (3) occupy the distal two­thirds of the pectoral­fin spine shaft, versus restricted to distal quarter of spine shaft in other species of Hisonotus .

DESCRIPTION: Descriptive morphometric and meristic data are provided in table 1 . Adult body size moderate (N = 126; mean 28.3 mm SL, range 26–39). Body relatively stocky, greatest body depth at supraoccipital, 17.7–19.6 [17.6]% SL, slightly deeper than depth at dorsal­fin origin; caudal peduncle deep, 13.0–14.9 [14.1]% SL. Head moderately narrow, cleithral width 21.8–25.4 [23.3]% SL. Dorsal profile of head from snout tip to supraoccipital convex, anterior to nostrils slightly depressed, between eyes slightly convex. Cross­sectional profile of supraoccipital gently convex. Snout tip rounded in dorsal view. Eyes placed dorsolaterally, horizontal eye diameter 5.6–6.8 [5.6]% SL, larger than suborbital depth. Iris diverticulum present, large, its length two­thirds of pupil diameter.

Lips papillose, posterior margin fimbriate. Maxillary barbels short. Jaw teeth bifid, major cusp slender, blade tip rounded; minor cusp minute, pointed. Relatively few jaw teeth, 11–16 (mode, 12) on premaxilla, 9–14 (mode, 12) on dentary; accessory teeth (sensu Reis and Schaefer, 1992) absent.

Body covered by dermal plates except for area around anus, skin covering lateral opening of swimbladder capsule, base of paired fins, area between pectoral girdle and lower lip, and snout anterior to nostrils. Lateral and anterior rostral plates reflected ventrally. Trunk plates arranged in five lateral series (fig. 2A): (1) dorsal series continuous; (2) mid­dorsal series discontinuous; (3) median series 23–24, incomplete, discontinuous, composed by anterior sector of 1–3 plates and posterior sector of 16–18 plates, separated by gap; (4) mid­ventral series incomplete, continuous; and (5) ventral series incomplete, continuous. Lateral­line canal incomplete, discontinuous, with anterior field of 1–4 [4] canal­bearing plates along anterior sector of median series, and posterior field of 1–3 [3] plates along posterior sector of median series. Abdomen partly covered by plates variable in size and shape, arranged in paired lateral series of 3–6 [6/4] plates each, and a median series of 3–6 [6] plates. Anal fin preceded by 4 paired lateral plates, variably contacting antimeres at midline. Coracoids and cleithra exposed ventrally, except for area at midline and surrounding arrector fossae.

Odontodes covering head, trunk, and fin rays. Head and trunk odontodes uniformly distributed, not arranged in distinct longitudinal lines or forming keels. Odontodes generally small, except for enlarged odontodes on ventral aspect of pelvic and pectoral spines, anterior rostral margin of snout, and tuft at posterior supraoccipital tip, not elevated above level of plate posterior to supraoccipital. Odontodes along anterior margin of snout biserially arranged, dorsad and ventrad series separated by narrow odontodefree area covered by pad of soft tissue; ventrad series composed of a continuous row of enlarged and laterally faceted odontodes and paired lateral patch of smaller, conical odontodes (fig. 3).

Dorsal­fin origin slightly posterior to vertical through pelvic­fin origin. Adipose fin absent. Pectoral fin, when depressed, overlapping nearly two­thirds of pelvic­fin length; serrae along distal two­thirds of posterior margin of pectoral­fin spine, robust (tooth height approximately 40 –50% of spine width at tip) (fig. 2B). Pelvic fin, when depressed, reaching beyond anal­fin origin only in males (see SEXUAL DIMORPHISM, below).

OSTEOLOGY: The following is not an exhaustive description, but an account of character states present in the new species for features that have been treated in recent phylogenetic analyses ( Schaefer, 1991, 1998). Mesethmoid tip bearing small, uncinate process directed ventrally; mesethmoid disk separated from mesethmoid tip by one­quarter disk width. Parasphenoid shaft, posterior to lateral processes, laterally constricted. Pterotic bone fenestrae relatively few in number, expanded and rounded, restricted to anteroventral part of compound pterotic. Swimbladder­capsule lateral opening wide.

Upper pharyngeal tooth­ plate dentition with narrow extension anteriorly. Total vertebrae 27. Vertebral centra 10–15 with bifid neural spines, 15–18 with bifid hemal spines; distal portions of neural and hemal spines tapering distally, widely separated from one another. Seventh vertebral centrum not expanded anterior to dorsal­fin first proximal radial; anterior margin of seventh vertebral centrum simple.

Posterior margin of caudal­fin skeleton straight or with slight median notch. Dorsalfin spinelet small, roughly triangular; dorsalfin locking mechanism absent. Dorsal­fin first three proximal radials with transverse process expanded.

COLOR IN ALCOHOL: Ground color of dorsolateral surfaces of head and body light brown, lighter on rostral margin of snout, ventrolateral edge of cheek, area anterior to nostrils, and opercular region. Nostril flap dark brown. Dorsum of body with brown pigmentation, having irregular patchy pattern. Trunk with irregular blotches. Ventral surface of head and trunk whitish, with clumped melanophores on abdomen, area surrounding anus, and lips. Pad of soft tissue between dorsad and ventrad series variably pigmented. Pectoral­fin spine with six dark blotches. Branched rays of pectoral, dorsal, and anal fins mostly unpigmented. Caudalfin pigmentation of unbranched rays with series of dark blotches variable in number. Pigmentation of caudal­fin branched rays variable, ranging from a well­defined pattern of ground color dark brown and a pair of lighter blotches of moderate size placed symmetrically relative to longitudinal axis (fig. 4, top), to a pattern of ground color dark brown, with a series of small light blotches on dorsal and ventral lobes variably connected between lobes forming light transverse bars (fig. 4, bottom).

DISTRIBUTION: Known only from the type locality, a creek in the río Quaraı´ , a tributary of the upper río Uruguay.

HABITAT: This species was collected from a small creek, ca. 0.5 m depth, with rapid current and clear water, bottom composed of rocks and sand, and with vegetated margins. Specimens of the new species were collected from around submerged rocks and aquatic plants (C. Roldán, personal commun.).

SEXUAL DIMORPHISM: Males smaller than females, mean standard length 26.9 (N = 58) versus 29.3 (N = 66). Genital papilla of males pointed; fleshy flap along posterior margin of pelvic­fin spine of males. Males with longer pelvic fins (longest pelvic­fin ray length 19.6–23.7% SL, versus 14.9–19.1% SL); distance from anus to anal­fin origin shorter (16.3–18.6%, versus 19.8–22.8% SL SL; fig. 2C, D). Pelvic fin not reaching anal fin origin in 85% of females (versus 7% of males); reaching first anal­fin ray in 15% of females (versus 35% of males); reaching beyond first anal­fin rays in no females (versus 58% of males).

ETYMOLOGY: Named after Dr. Raúl A. Ringuelet (1914–1982), researcher and professor of the Museum of Natural Sciences of La Plata, Buenos Aires. Dr. Ringuelet’s vast career includes the publication of the book Los Peces de Agua Dulce de la República Argentina ( Ringuelet et al., 1967), which set the standard for systematics research conducted during the last decades of the 20th century in the Austral region of the Neotropics.

MATERIAL EXAMINED: Holotype: ILPLA 886 (35.8 mm, female), Uruguay, Rivera State, upper Uruguay River basin, Quaraí River drainage, creek at Km 18 of route joining Santana do Livramento , Brazil, and Rivera, Uruguay; close to border (ca. 31° 00' S, 55° 30'W). Coll. R. A. Ringuelet and C. Roldán, 24 July 1981.

Paratypes: collected with holotype. ILPLA 883 (51 ♀ + 44 ♂, 26.0– 39.2 mm SL). AMNH 230702 (3 ♀ + 2 ♂ + 3 cs, 23.3– 33.2 mm SL); ANSP 177878 (1 ♀ + 2 ♂ + 1 cs, 22.9–32.4 mm SL); FMNH 108806 (2 ♀ + 2 ♂, 25.7–32.2 mm SL); MCP 26154 (2 ♀ + 1 ♂ + 1 cs, 26.4–31.3 mm SL); MLP 9536 (2 ♀ + 2 ♂, 27.9–33.4 mm SL); MZUSP 62788 (1 ♀ + 2 ♂, 23.3–31.1 mm SL); USNM 362665 (2 ♀ + 2 ♂, 27.2–32.0 mm SL).

COMPARATIVE MATERIAL: Hisonotus sp. : FMNH 59635; USNM 206204, 297971, 235073, 300968, 235072, 345698, 345937. Hisonotus laevior: USNM 235075, 285894, 326112. Hisonotus leucofrenatus: FMNH 59628. Hisonotus maculipinnis: UMMZ 206297; USNM 176024. Hisonotus nigricauda: USNM 181550, 177537 (2 cs). Hisonotus notatus: FMNH 59636. Hisonotus paulinus: FMNH 59636. Hisonotus punctatus: MHNG 240825 (1 cs); UMMZ 206204 (1 cs). Hisonotus taimensis: ANSP 168949 (1 cs); USNM 235062. Microlepidogaster perforatus: ANSP 174718 (1 cs).

Figures

Fig. 1. Hisonotus ringueleti, holotype, ILPLA 886, female, 35.8 mm SL.

Tables

TABLE 1 Morphometric and Meristic Data for Hisonotus ringueleti

			Males (N = 10)				Females (N = 10)
	Holotype	Min	Max	Mean	SD	Min	Max	Mean	SD
Standard length	35.8	26.8	30.1	28.4	1.12	27.5	35.5	31.93	2.56
PERCENT OF STANDARD LENGTH
Predorsal length	45.5	46.4	48.0	46.9	0.47	46.8	49.5	47.63	0.94
Head length	33.8	34.9	37.5	36.2	0.89	35.2	39.2	36.80	1.15
Cleithral width	23.3	22.1	23.8	23.0	0.64	21.8	25.4	23.47	1.09
Dorsal­fin spine length	25.9	26.0	31.2	27.9	1.75	25.4	29.0	27.30	1.09
Trunk length	16.2	15.2	19.0	17.0	1.07	15.1	18.6	16.61	1.10
Pectoral­fin spine length	25.6	23.9	27.9	26.3	1.41	25.9	28.2	27.09	0.70
Pelvic­fin spine length	14.6	19.6	23.7	21.2	1.41	14.9	19.1	17.56	1.36
Abdominal length	17.2	17.5	21.4	19.6	1.19	17.4	20.1	19.02	0.83
Caudal peduncle length	31.2	28.8	32.0	30.9	1.08	27.3	33.8	30.63	1.71
Caudal peduncle depth	14.1	13.0	14.9	13.7	0.58	13.0	14.9	13.65	0.56
Head depth	17.6	18.0	19.4	8.4	0.39	17.7	19.6	18.67	0.65
Snout length	10.5	9.3	11.5	10.5	0.60	10.5	11.7	11.08	0.44
Horizontal eye diameter	5.6	5.7	6.6	6.2	0.29	5.6	6.8	6.08	0.33
Least interorbital diameter	13.9	13.5	16.4	15.0	0.99	14.2	17.0	15.19	0.83
PERCENT OF HEAD LENGTH
Head depth	52.1	49.5	53.4	50.9	1.61	48.1	53.0	50.76	1.89
Snout length	31.1	26.7	30.7	28.9	1.29	28.7	32.8	30.12	1.32
Horizontal eye diameter	16.7	15.8	18.8	17.1	0.97	15.3	17.5	16.52	0.73
Least interorbital diameter	41.0	38.2	44.9	41.5	2.41	38.7	44.4	41.28	1.71
COUNTS
Left lateral plates	24	23	25	24.1	0.57	24	24	24.0	0
Right lateral plates	23	24	25	24.1	0.32	23	25	24.0	0.67
Predorsal plates	3	3	3	3.0	0	3	3	3.0	0
Left premaxillary teeth	13	11	14	12.4	0.84	12	16	13.3	1.25
Right premaxillary teeth	12	11	15	12.3	1.49	12	16	13.8	1.14
Left dentary teeth	11	9	12	11.2	1.14	10	14	12.2	1.40
Right dentary teetha	14	9	13	11.0	1.33	11	15	12.6	1.24
Dorsal­fin branched rays	6	6	7	6.4	0.52	6	7	6.4	0.52
Pectoral­fin branched rays	5	5	5	5.0	0	5	5	5.0	0
Pelvic­fin branched rays	5	5	5	5.0	0	5	5	5.0	0
Anal­fin branched rays	4	4	4	4.0	0	4	4	4.0	0
Caudal­fin branched rays	14	14	14	14.0	0	14	14	14.0	0

TABLE 1

Morphometric and Meristic Data for Hisonotus ringueleti

a N = 9 for females.