Lithogenes wahari, Schaefer & Provenzano, 2008

Schaefer, Scott A. & Provenzano, Francisco, 2008, The Lithogeninae (Siluriformes, Loricariidae): Anatomy, Interrelationships, and Description of a New Species, American Museum Novitates 3637 (1), pp. 1-52 : 11-24

Lithogenes wahari , new species

Figures 6–8 , table 1

HOLOTYPE: MBUCV-V-33738, 57.2 mm

SL, ♀, Venezuela, Amazonas, Caño Päwä ,

approximately 30 minutes by foot upstream from its mouth into Río Cuao, approximately 30 minutes by boat downstream from Puerto Nuevo, 05 ° 17.52 9 N, 67 ° 19.74 9 W, coll. S. Schaefer, F. Provenzano, J.N. Baskin, SAS 01-11, 8 March 2001.

PARATYPES: AMNH 233086 , 42 : 31.0– 76.7 mm SL (12 ♀, 24 ³) , CAS 226002 , 3 : 40.5–56.9 mm SL (1 ♀, 2 ³) ; FMNH 117747 , 3 : 45.3–66.4 mm SL (1 ♀, 2 ³); MBUCV-V- 29530, 35 (32, 3 cs): 34.0– 78.3 mm SL, (17 ♀; 15 ³) , MCP 41962, 3 : 41.4–54.6 mm SL (1 ♀, 2 ³) ; USNM 392583 , 3 : 45.7–63.3 mm SL (1 ♀, 2 ³) same data as holotype. MBUCV-V-27941, 62.1 mm. SL, ³, Venezuela, Amazonas, raudal in alto Río Cuao , aprox. 05 ° 30 9 N 67 ° 0 9 W, coll. S. Zent, 9 November 1986 .

DIAGNOSIS: Distinguished from all congeners by the absence of odontodes on the proximal portion of ventral surface of first pelvic-fin ray (vs. ventral pad covered with embedded odontodes along entire length, fig. 8); accessory premaxillary teeth absent; anal fin with intense pigment band along base and diffuse spot at midlength of fin rays (vs. pigment band at base absent, fin rays dusky, without distinct spot); adipose fin without ossified spine along anterior edge. Further distinguished from L. villosus by the presence of nine (vs. eight) branched pectoral-fin rays, absence of pigment band on snout lateral to nares; dermal plates on caudal peduncle small, irregular, plates of dorsal and ventral series not contacting plates of midline series (vs. plates large, regular in shape, dorsal and ventral series plates contacting those of midline series posteriorly). Further distinguished from L. valencia by the narrower, deeper head shape, head width 78% HL (vs. 80–95% HL), seven branched anal-fin rays (vs. five), 12 premaxillary teeth (vs. 25–28), tooth cusps asymmetrically bifid (vs. symmetrically bifid).

DESCRIPTION: Counts and measurements of holotype and paratypes given in table 1. Head and body moderately slender, not extremely depressed. Greatest head width (HW) at opercle, 18.8%–22.8% SL. Head shape bluntly triangular in dorsal view, snout gently rounded, margins tapered. Trunk elongate, slender, gently tapered posteriorly; greatest body width (BW) at pectoral-fin base, 23.4%–29.3% SL, greatest body depth (BD) at vertical through pelvic-fin origin, 15.6%– 19.3% SL. Dorsal aspect of head gently convex in lateral view, dorsal margin of trunk straight from dorsal-fin origin to caudal fin. Ventral profile of head straight, abdomen between pectoral and anal-fin origins gently convex, trunk distinctly concave along analfin base, caudal peduncle straight. Trunk extremely slender in region posterior to adipose fin, least caudal peduncle depth 33.3%–45.5% BD. Caudal peduncle elongate, terete, becoming slender posteriorly. Anus located midway between pelvic-fin origin and caudal-fin base, tubular. Urogenital papilla (see Body Size and Sexual Dimorphism, below) positioned immediately anterior to anal-fin origin.

Eyes moderately large, 7%–13% HL; posterior bony orbit margin positioned at vertical through opercle articulation with hyomandibula. Interorbit width broad, 35%–42% HW. Iris operculum absent. Nares ovoid, longer than wide, positioned midway between snout tip and posterior orbit margin; nares juxtaposed, separated by thin vertical skin flap, internaris width 15%–22% HW.

Premaxillary teeth 10–13 (12/13*) in single emergent row on each jaw element; asymmetrically bifid, cusps separated by V-shaped space, major (medial) cusp bluntly rounded, minor (lateral) cusp blunt to slightly pointed. Accessory premaxillary dentition absent. Dentary teeth 2–3 per jaw element; tooth and cusp shape bilobed and longer than the premaxillary, lobes of equal length and thickness. Replacement teeth as per emergent dentition, although cusps slightly more symmetric in size and shape.

Oral disk ovoid, wider posteriorly; ventral surface smooth immediately anterior to premaxilla, upper lip bearing large circular papilla arranged in transverse rows to anterior margin; a wide, non-papillate zone immediately anterior to premaxillae. The upper lip less deep than lower lip, anterior margin smooth and diverging laterally as a short maxillary barbel located at confluence of upper and lower lips. Lower lip surface irregular; elongated papillae located distally near margin, more dispersed robust papillae distributed throughout lower lip surface, these more separate from one another relative to those of upper lip. Posterior lip margin bilaminar, consisting of thick ventral layer, overlain by thinner smooth layer of flesh that extends posteriorly beyond margin of ventral papillose layer. Dorsal layer fimbriate along margin, not continuous along posterior lip margin and separated by gap equal in width to premaxilla length. Region of lower lip at dentary immediately posterior to emergent teeth bearing paired raised cluster of 18–24 villiform papillae (fig. 3C); papillae elongate, slender, with pointed tips; paired papillae clusters separated from one another at midline, intervening region smooth. Maxillary barbels present, separated from lateral lip margin.

Odontodes present on cranial bones of dorsum, dermal plates of lateral cheek margin and trunk, and first unbranched rays of pectoral, pelvic, and caudal fins, on cleithrum near pectoral fin origin, on unbranched rays of all paired and median fins except dorsal and anal fins; absent from branched fin rays of all fins except caudal fin, where present along fourfifths length of branched rays; odontodes present on procurrent caudal-fin rays. Smaller odontodes variously distributed on trunk, associated with dermal plates between caudal fin and region at vertical through dorsal fin origin.

Postotic laterosensory canal with pterotic branch ( Schaefer and Aquino, 2000) present, skin-surface pore located on pterotic ventral process at vertical through or slightly posterior to gill aperture and posterior to origin of levator operculi muscle. Preoperculomandibular canal branching from temporal canal within pterotic, single pore located on ventral aspect of cheek at vertical through posterior orbit margin representing lateral branch of preoperculomandibular canal at its exit from preopercle bone. Antepreopercular canal segment of preoperculomandibular canal present as slender tubular ossified segment located anteroventral to canal exit from preopercle at posterior margin of second lateral cheek plate. Antepreopercular canal continuing anteriorly to terminate as skin-surface pore along ventrolateral margin of cheek. Temporal canal with posterodorsally directed short medial branch segment in frontal, its terminus a pore at frontal-pterotic junction. Infraorbital canal branching off within sphenotic, five or six paired infraorbital bones with expanded laminar ossification yielding platelike appearance, bearing complete infraorbital canal with five or six skin-surface pores. Supraorbital canal in frontal complete, terminating as canal within elongate nasal bone. Lateral line complete, continuous on trunk from pterotic to caudalfin base.

Three to five pairs of dermal plates on lateral cheek margin between opercle and maxilla; first two anteriormost plates elongate, rectangular; positioned above anterolateral corner of lower lip above and posterior to maxilla, bearing enlarged odontodes on lateral edges. Three or four small plates bearing odontodes in region between dorsal opercle margin and ventral pterotic margin.

Dorsal fin ii,6; first two rays segmented, thickened, bearing odontodes along anterior edge; second ray occasionally unbranched, first ray shorter, about half length of second ray; first dorsal fin spinelet absent. Fin margin straight. Pectoral fin i,9; first ray segmented for half length, unbranched and thickened, anterior edge rugose, bearing odontodes; remaining rays branched and without odontodes; fin emarginated; three radials, first rounded, second and third radials elongate, slender, distal margins expanded. Origin of pectoral fin about even with or slightly anterior to posterior edge of oral disc. Pectoral fin when depressed reaching to posterior third of length of first anal-fin ray. Pelvic fin i,5; first ray segmented, divided to base, greatly thickened, flattened dorsoventrally; flesh of ventral surface thickened, bearing numerous transverse ridges and without odontodes proximally (fig. 8A, B), remaining rays branched and without odontodes. Origin of pelvic fin at vertical through point midway between supraoccipital tip and dorsal-fin origin. Anal fin ii,6* or ii,6,i; first two rays segmented, unbranched without odontodes (except in mature males), last two segmented rays entirely separate, independent, and articulate on the same radial, seventh ray (when present) unbranched. Posterior anal-fin margin rounded, anterior fin margin concave. Anal fin when depressed reaching vertical through posterior third or slightly beyond adipose-fin base. Posterior edge of anal-fin base anterior to vertical through adipose-fin insertion. Adipose fin low, triangular, without well-ossified leading spine bearing odontodes except in larger males. Caudal fin i,14,i; three dorsal and five ventral procurrent rays, posteriormost procurrent rays elongate, odontodes on principal and procurrent rays. Caudal fin posterior margin deeply forked, upper and lower lobes equivalent in size and shape.

Dermal plates on trunk consisting of single regularly arranged paired series of plates along median lateral line caudally, plus few small, isolated platelets irregularly arranged above and below median series plates in region of caudal peduncle between dorsal and ventral procurrent rays. A few small, irregularly arranged and isolated platelets along dorsal and ventral midline immediately anterior to procurrent rays; these platelets variable in number and extent, 3–7 in dorsal series and 1– 3 or none in ventral series. Plate series extending anteriorly to vertical through anus. Plates on head restricted to region of lateral snout between opercle and maxilla, above the infraorbital series of plates, small plates surrounding nares and along lateral margin of frontals. A few small isolated platelets on body in region between pterotic margin, lateral line, and dorsal-fin origin; plates otherwise absent on head and trunk. All plates bearing odontodes.

COLORATION: Pigmentation generally consisting of dark brown melanophores on an underlying tan ground coloration dorsally, cream yellow ventrally (fig. 6). Dorsum of head overall dark brown, melanophores arranged as diffuse clusters yielding slight mottled appearance, with lighter underlying ground coloration prominent above opercle, between nares, and in form of thin V-shaped mark between nares and anterior snout margin. Ventral surface unpigmented, except for pectoral fins, genital papilla, and area surrounding anal fin. Melanophores on dorsum of trunk generally diffuse, concentrated as three broad saddles along base of dorsal fin, between dorsal and adipose fins, and through posterior half of adipose fin to caudal-fin base. Dark pigmentation tending toward indigo blue in bright sunlight prior to preservation. Lateral surface of trunk with 5–6 diffuse irregular blotches between pectoralfin origin and caudal fin; melanophores becoming progressively more diffuse ventrally. Intense concentration of melanophores in form of narrow band along anal-fin base. Fins uniformly dusky, pigment concentrated along segmented fin rays, interradial membranes unpigmented. Caudal fin with concentration of melanophores at base and broad diffuse, irregular vertical band across fin rays; anal fin with broad pigment band across median portion of rays, pelvic fin with pigment concentrated along length of first branched ray; dorsal fin with multiple irregular bands; pectoral fin with diffuse concentration of melanophores along fin rays.

BODY SIZE AND SEXUAL DIMORPHISM: Sexual dimorphism is here defined as those external morphological characteristics that allow an unambiguous determination of sex. Differences between males and females can be of two types, depending on the life stage of first appearance of the morphology. In the first type, sexual dimorphism is evident at hatching. In the second type, morphological differences between males and females do not become evident until individuals reach sexual maturity. Additionally, morphological differences between males and females can be permanent, that is, independent of developmental stage, season of the year, and reproductive condition of the gonads, such that sex can be determined without difficulty. In other cases, differences between males and females can be temporary because these morphologies appear only when gonads are developed, during a certain developmental phase, or a particular season of the year (as when reproductive activities occur). The specimens of Lithogenes wahari reported upon herein were captured in March, and because of their relative abundance, we are able to describe morphological differences that permit sex determination relatively easily. Morphological differences between sexes are observed in the head, anal fin, and urogenital papilla.

Males are larger than females on average (fig. 9). Average standard length for males (59.9 mm) is significantly larger than that for females (46.3; t 5 3.314, Bonferroni-adjusted P 5 0.009); the same relationship was observed for centroid size (males 29.5, females 24.1; t 5 2.619, Bonferroni-adjusted P 5 0.038). MANCOVA based on 11 variables describing aspects of shape in dorsal view (fig. 1A) plus body depth showed no significant difference in overall shape between sexes (Wilk’s Lambda 5 0.207, F 5 2.791, df 5 11, 8; P 5 0.078). However, similar analysis of 12 variables describing aspects of shape in ventral view (fig. 1C) revealed significant sexual dimorphism overall (Wilk’s Lambda 5 0.049, F 5 11.423, df 5 12, 7; P 5 0.002), with four measures responsible for the difference (snout width, anus to anal-fin origin, oral-disk length, and pectoral to pelvic-fin distance; fig. 10), all without an interaction with size, except for mouth width (F 5 6.083, P 5 0.025). In males the anus, genital papilla, and anal fin are positioned further caudad relative to the pelvic fin, and the pelvic fin is positioned more caudad relative to the pectoral fin (fig. 10). Females generally have a wider mouth than males at all sizes (fig. 10). Relative warps analysis of body shape revealed substantial differentiation between sexes. Separate principal components analyses of the partial warp scores on both dorsal and ventral unilateral landmark datasets yielded segregation of the sexes along the first relative warp axis (figs. 11, 12). The pattern of landmark deformations represent- ed by the relative warps is consistent with the findings based on analysis of distance data in showing posterior displacement of the anus region relative to the pelvic fin in males and the narrowing of the space between anus and anal fin in females (fig. 10). Compared to aspects of ventral shape, the deformation implied by the first relative warp from the analysis of dorsal landmark data (fig. 12) is more subtle.

In both males and females, the region between the anus and anal-fin origin forms a depressed trough between the paired retractor ischii muscles of the midtrunk. The trough is shallower in males, which have hypertrophied paired retractor ischii muscles relative to females. In females, the region within the trough between the anus and anal-fin origin is developed as a deep, blind pocket formed by multiple skin folds surrounding a central aperture (fig. 13). A small genital papilla with acute tip and orifice with a small fleshy projection occupies a skin fold forming the posterior wall of the skin pocket; the anal-fin origin is positioned caudally and is separated from the genital pocket by a deep recess. In males, the region homologous with the genital pocket of females is developed as a large, oblate spherical papilla. The structure is conspicuous, projects well beyond the boundaries of the trough, and is positively allometric with respect to body size. The papilla tip is acutely pointed, darkly pigmented, and projects caudally beyond a vertical through the anal-fin origin. The skin at the base of the anal fin is hypertrophied as a thickened fleshy pad along the anterior edge of the first anal-fin ray and separated from the expanded flesh surrounding the second ray by a deep channel (fig. 13). The genital papilla of males is separated from the fleshy pad forming the anterior margin of the first anal-fin ray, but the two structures closely abut one another. Dimorphism is present even in small-sized individuals (juveniles) that lack well-developed odontodes and skin papillae relative to larger, presumably mature individuals.

The skin on the dorsal and lateral surfaces of the head of males is adorned with small papillae, except for the area from the nostrils to the tip of the snout. Additionally, there are well developed odontodes on the dermal plates of the lateral head and snout. Females also possess odontodes and papillae in the same arrangement, but are not as extensively developed as in males. Males have thickened proximal portions of both the first and second anal-fin rays. These fin rays are curved slightly ventrad and have concave proximal margins, then become straight distally. A single mature specimen captured in November shares these distinctive morphological traits with male specimens captured in March, suggesting that the dimorphisms involving the urogenital papilla, anal fin, and head ornamentation represent permanent features, rather than seasonal or temporary conditions related solely to reproductive activity.

DIGESTIVE AND REPRODUCTIVE ANATOMY: The anatomy of the digestive tract in Lithogenes differs from that of most other loricariids in lacking an extremely elongate, coiled intestine; however, they have a coiled intestine nonetheless. Instead, the morphology is somewhat intermediate between the typical loricariid gut, described in detail for the subfamily Hypoptopomatinae in Schaefer (1997), and that of the Astroblepidae , which possess a fairly simple, single-loop mid- and hind gut. In Lithogenes , the organs of the digestive system form a compact elongate spheroid mass within the body cavity between the pectoral girdle and anal fin. The digestive tract lies on either side of the urogenital organs, which occupy the midline immediately ventral to the vertebral column. The stomach and intestines form a series of loops around a central coil (fig. 14), which then passes to the hindgut and terminates at the anus. Pyloric cecae are absent.

Dorsal and ventral pharyngeal tooth plates covered with small conical, sharp teeth. Esophagus short, thin, and straight; connection with pharynx at the branchial apparatus clear, as it is its boundary with stomach. Esophagus located superior to remainder of the digestive tract. Liver extensive, covering to a great extent the entire anterior region and most of the ventral surface of digestive organs.

The stomach is large diameter, thick walled, and elongate. Its diameter is at least twice that of the intestine. Its origin at the esophagus lies immediately ventral to the heart, from which point it passes to the right side of the body cavity, extends along the body wall to loop across the midline below the hindgut, and then turns back upon itself once again (fig. 14). There, the stomach narrows slightly at the pyloric transition to the intestine. The proximal intestine is large, its diameter equal to the greatest diameter of the stomach. It passes rostrally along the right side of the body cavity ventral to the stomach to the liver, where it turns dorsally and then caudally to loop back over the dorsum of the stomach along the right side of the body cavity. It then makes a loop across the midline dorsal to the loop formed by the stomach, and then passes rostrally along the left side of the body cavity. Anteriorly at a point posterior to the ventral lobe of the liver, the intestine forms a coil in the form of a quadruple loop with a reverse turn. The proximal portion of the coil turns clockwise (in dorsal perspective) to form two compact 360 ° loops, the second of which has a somewhat smaller radius and lies dorsal to the first. At the center of the coil on the midline, the intestine turns back on itself to reverse direction, with the resulting counterclockwise coiling distal portion forming another pair of loops continuing dorsally. The coil terminates at a transition to an expanded and elongate hindgut, which turns toward the left to pass caudally along the dorsum of the gut to its terminus at the anus.

Stomach contents of dissected specimens consist of fairly nondescript fibrous material that appears to be vegetable matter. No animal material was observed. Intestine contents consist of amorphous flocculent materials.

Gonads in one female and one male were observed in an advanced stage of maturity (fig. 15). There is no evidence of hermaphroditism or sex reversal with size. Ovaries are paired structures above the digestive tract and liver and below the kidney, extend for approximately half of the visceral chamber, are cylinder shaped, and without any type of deformation, branching, or compartmentalization. Their anterior margin is rounded and their posterior margin is similar, attenuated only at the convergence with the urogenital papilla, where it seems both ovaries join (fig. 15A). No dermarkation between ovaries and oviducts was observed, and there is no structure that can be inferred as a receptacle for the urogenital papilla or sperm of the male. Ovaries are yellow due to the amount of vellum present in the mature ova, which are easily observed through the transparent ovarian walls (possibly due to extreme distension caused by the large size and advanced developmental stage of the eggs), the latter appearing granular and heterogeneous.

Counts and measurements of ova were made by direct observation through the transparent ovarian walls and without dissection. We observed a total of eight ova in the right lobe and seven in the left. Additionally we observed about 60 atresic ova, the largest ones creamy or yellow in color, the smallest ones almost transparent. The largest eggs were 3.2–3.5 mm in diameter; developing eggs ranged from 0.3 to 0.8 mm diameter. The near uniform size of developing ova, combined with the disparity in size between largest and smallest ova, suggest that egg maturity in this species is approximately synchronous. As with other members of the Loricariidae having similarly low fecundity, a high degree of parental care is suspected but unconfirmed at present. Low fecundity, restricted habitat requirements, and limited geographic distribution are characteristics of populations under potentially severe environmental risk. Consequent extinction seems to have occurred for Lithogenes valencia , a congeneric species that has not been observed in the field since the 1970s.

Testes of the two studied specimens are paired structures located dorsally above the digestive tract and liver, below the kidney, are ribbon shaped, without any type of branching or compartmentalization (fig. 15B). Their rostral margin terminates as a sharp tip; the caudal end is attenuated proximal to the urogenital papilla. There are no limits with the spermatic ducts, and it is remarkable that both testes appear to join before reaching the urogenital papilla. Testes are creamy white in coloration, homogeneous and fibrous in appearance.

DISTRIBUTION: Known only from the middle section of the Río Cuao, a clear-water tributary of the Río Sipapo of the Orinoco River basin of southwestern Venezuela (fig. 4).

HABITAT: Inhabitant of moderately highgradient forest streams with clear water, swift current, and exposed bedrock substratum. The water color of the Río Cuao at the time of collection was clear to light green.

ETYMOLOGY: The specific name wahari is taken from the Piaroa name Rúa-Wahari, the god of the creation according to the Piaroa peoples, here treated as a noun in apposition to the generic name. According to legend, one day Rúa-Wahari created the first man from a mass of fish flesh at the place called Mariuek’a. Unattended for a period of time, the crabs came and consumed the flesh he had prepared. Rúa-Wahari fished once again and with each fish captured from the lake, he fashioned the eyes, the hair, the ears, the mouth, and the nose. In this way, Rúa-Wahari completed the first man and first woman.

Figures

Fig. 6. Lithogenes wahari, male, preserved approximately 30 min after capture, showing coloration pattern against exposed Rio Cuao bedrock substratum.

Fig. 7. Lithogenes wahari, holotype, MBUCV V-33738, 57.2 mm SL, female, Venezuela, Amazonas, Caño Päwä, Río Cuao basin.

Fig. 8. Pelvic-fin pad, left side, ventral view. A, B, Lithogenes wahari AMNH 233086, female; C, D, L. villosus AUM 28152, female; E, F, L. valencia holotype, MBUCV V-30740, male; G, H, Astroblepus sp. MEPN 1599. Scale bar is 5 mm in A, C, E, G; 1 mm otherwise.