Loricaria spinulifera, Thomas & Rapp Py-Daniel, 2008

Thomas, Matthew R. & Rapp Py-Daniel, Lúcia H., 2008, Three new species of the armored catfish genus Loricaria (Siluriformes: Loricariidae) from river channels of the Amazon basin, Neotropical Ichthyology 6 (3), pp. 379-394 : 381-386

Loricaria spinulifera , new species

Figs. 2 , 3 a-b, and 4b

Holotype. INPA 28849 (1, 137.7 mm SL), Brazil, Amazonas , rio Jauaperi (Negro dr.), 8.3 km upstream from confluence with rio Negro, 9.6 km upstream from S. Francisco (01º35’08.4”S, 61º28’34.9”W), 7 Dec 1993, J. P. Friel et al.

Paratypes (12). Brazil: Amazonas : ANSP 178690 (1, 123.0 mm SL), rio Negro (Amazonas dr.), 11.3 km downstream from Santa Maria, 18.6 km upstream from Leprosario (03º01’36.0”S, 60º24’12.0”W), 12 Dec 1993, J. G. Lundberg et al .; ANSP 178691 (1, 78.6 mm SL) rio Negro (Amazonas dr.), 10.6 km downstream from Leprosário, 14.8 km upstream from Manaus (03º06’36.0”S, 60º24’12.0”W), 10 Oct 1994, J. G. Lundberg et al .; INPA 28850 (1, 95.4 mm SL), rio Negro (Amazonas dr.), 12.6 km downstream from Santa Maria, 16.3 km upstream from Leprosário (03º02’01.8”S, 60º23’23.2”W), 12 Dec 1993, J. G. Lundberg et al .; INPA 28851 (3, 106.0- 125.4 mm SL), rio Negro (Amazonas dr.), 10.0 km downstream from Santa Maria , 18.9 km upstream from Leprosário (03º01’24.5”S, 60º24’19.6”W), 13 Dec 1993, J. G. Lundberg et al .; MZUSP 57447 (1, 60.9 mm SL), rio Negro (Amazonas dr.), near Santa Maria , (03º04’11.0”S, 60º11’03.0”W), 19 Jul 1996 ; MZUSP 57636 (3, 43.4-72.2 mm SL), rio Negro (Amazonas dr.), above Tarumã-mirim (03º04’04.0”S, 60º14’58.0”W), 17 Jul 1996. Roraima : ANSP 178687 (1 + 1 c&s, 116.9-120.6 mm SL), rio Branco (Negro dr.), 13.9 km upstream from confluence with rio Negro , between Atauba (town upstream) and Caruna (downstream) (01º17’24.0”S, 61º51’08.0”W), 8 Dec 1993, J. G. Lundberg et al .

Diagnosis. Loricaria spinulifera is distinguished from all congeners by the following unique characters: strongly developed crests on surfaces of head and predorsal plates bearing large thorn-like odontodes ( Fig. 3a ) vs. weakly developed crests on surfaces of head and predorsal plates without large thorn-like odontodes; a unique arrangement of oral papillae situated behind the premaxillary teeth consisting of approximately 20 papillae, all longer than premaxillary teeth, arranged in a dense cluster ( Fig. 3b ), vs. approximately 16 short papillae, no longer than premaxillary teeth ( Fig. 3d ); a unique arrangement of plates on the median abdominal area consisting of small round to diamond-shaped plates varying in size and spacing, with pre-anal shield absent or with few small plates distributed along the center and around anterior margin of anus ( Fig. 4b ); and a unique pigment pattern on the dorsal surface of the head consisting of solid dark brown extending from center of orbits to tip of snout with large irregular spots from center of orbits to middle of dorsal fin.

Description. Standard length of specimens examined 78.6- 137.7 mm SL. Other morphometric data presented in Table 1 . Meristic data for selected dermal plate characters in Table 2 .

Body elongate and slender, dorsoventrally depressed, widest at cleithrum. Head evenly convex in transverse profile; triangular in frontal profile, lateral margins from snout tip to operculum straight to slightly concave, snout pointed. Dorsal profile of head from snout tip to parieto-supraoccipital tip slightly convex, straight from parieto-supraoccipital tip to dorsal-fin origin. Dorsal profile of body from dorsal-fin origin to caudal peduncle slightly concave. Greatest body depth at dorsal-fin origin, 8.0-9.4% SL. Eye small, maximum orbital diameter 16.0-19.3% HL; iris operculum absent. Postorbital notch moderately developed, angular.

Entire body covered with dermal plates except for ventral surface of head anterior to branchiostegals, various portions of median abdominal area, around bases of pelvic fins, and Vshaped area surrounding anus. Dermal plates on dorsum of body from snout tip to dorsal-fin origin with well-developed odontode crests. Large thorn-like odontodes present on lateral margins of head from snout tip to opercle; several large odontodes concentrated on dorsal and ventral margin of snout tip and along anterodorsal margin of orbit. Two prominent odontode crests originating at snout tip converge between nares, at single large odontode, becoming divergent on frontals, continuing in parallel to posterior parieto-supraoccipital tip, each terminating in 2-3 large odontodes. Dorsal and dorsolateral plates between pterotic-supracleithrum and dorsal-fin origin each with single crest terminating posteriorly in single large odontode. Lateral surface of exposed cleithrum with conspicuous median keel consisting of 3-5 large odontodes.

Upper lip narrow with numerous marginal fringe barbels, each with multiple branches. Maxillary barbel long, extending to branchiostegals, with numerous secondary barbels, each with multiple tertiary branches. Lower lip well developed with conspicuous median notch; surface covered with numerous elongate filaments; and marginal fringe barbels with multiple branches. Premaxillary teeth 3-4 on each side; each tooth consisting of slender stalk ending in enlarged bilobed crown; outer lobe small, rounded or conical; inner lobe large, rounded or conical. Buccal papillae behind premaxillary teeth elongate and thin, longer than premaxillary teeth, tightly arranged in dense cluster of approximately 20. Dentary teeth 6-9 on each side; less than half the length of premaxillary teeth; structure similar to that of premaxillary teeth except lobes usually shorter, more rounded.

Total plates in lateral series 34-35 (modally 34). Anterior 16-18 lateral plates with two parallel odontode keels widely separated, converging at midline on caudal peduncle; posterior (coalesced) lateral plates 16-18 (modally 17). Post-anal plates 21. Lateral abdominal plates 6-9 (modally 7), sickle shaped and slightly bent at center with odontodes forming inconspicuous keel anterior to pelvic-fin origin. Median abdominal area naked or with small round to diamond-shaped plates varying in number, size, and spacing; thin line of small plates usually present posterior to gill openings; pre-anal shield absent or with few small plates distributed along the center and around anterior margin of anus ( Fig. 4b ).

Dorsal fin when depressed reaching ninth plate posterior to its origin; distal margin slightly concave when erected. Pectoral fin, when depressed, reaching sixth or seventh lateral plate posterior to cleithrum; distal margin straight to slightly concave when erected. Unbranched pelvic-fin ray (spine) longest, reaching to anterior third of anal-fin length. Anal fin when depressed reaching seventh or eighth plate posterior to its origin; distal margin convex when erected. Distal margin of caudal fin concave, upper unbranched ray produced into long filament (usually damaged or broken) at least two-thirds of standard length.

Color in alcohol. Ground color tan to pale yellow. Solid dark brown covering dorsal surface of head from snout tip to center of orbit; large brown blotches irregularly distributed on dorsal surface of remaining head and trunk. Four or five dark brown transverse bands on dorsal surface from middle of dorsal fin to caudal peduncle usually conspicuous. Dorsal surfaces of upper lip and maxillary barbel with heavy sprinkling of melanophores. Ventral surfaces pale yellow or with light scattering of melanophores between pectoral fin and on lateral abdominal plates. Pectoral and dorsal fins with evenly distributed dark brown melanophores, becoming more intense near distal edge. Pelvic fin opaque, hyaline or with light sprinkling of brown melanophores on interradial membranes.Anal fin hyaline or opaque. Caudal fin opaque, hyaline, or with light brown surrounding edges of basicaudal plate and along distal edge of lower lobe.

Variation. Specimens collected in deep channels have smaller eyes that are more recessed in the orbits ( Fig. 3a ) than individuals from shallower depths ( Fig. 2 ) and tend to be less boldly pigmented, with dark patterns on the head, body and fins more diffuse or faded. Minimum orbital diameter measurements as proportions of HL were plotted against average capture depths calculated from reported maximum and minimum trawling depths for each collection. Bivariate regression analyses revealed a significant relationship between minimum orbital diameter and average capture depth for Loricaria spinulifera (R 2 = 0.515, F 1,6 = 6.37, P <0.05; Fig. 5 ).

Sexual dimorphism. Two specimens examined (ANSP 178687, 116.9 and 120.6 mm SL) possess traits observed in breeding males of other Loricaria and other putatively derived members of the tribe Loricariini ( Isbrücker, 1981; Isbrücker & Nijssen, 1992). In each of these specimens, filaments on the lower lip are reduced in length, with an increase in number and development of globular papillae on lip surfaces surrounding bases of filaments. Surface area of lower lip enlarged through expansion of membranous connections between lower lip and rictal barbel and at the median cleft. Both the enlarged apical lobe and smaller outer lobe of premaxillary and dentary teeth are much shorter and more broadly rounded (mitten-shaped) than in other specimens. Pectoral spines are slightly thickened from the base to approximately threefourths the length of each spine; thickening is even throughout, rather than the distally expanded or club-like condition reported in certain other species (e.g., L. clavipinna ). Odontodes on pelvic- and anal-fin spines are blunt rather than pointed and conical in shape as seen in non-nuptial males and females. Dissection of one specimen (120.6 mm SL) revealed enlarged mature testes, flattened and white in color.

Distribution and ecology. Loricaria spinulifera is known from the rio Negro of Brazil, and from the lower rio Branco downstream to the mouth of the rio Negro, including the lower rio Jauaperi ( Fig. 6 ). This species appears to favor deep channels of large black water rivers. All specimens were collected in bottom trawls at depths ranging from 1.5 to 28 m and at distances of 10 to 750 m from the shoreline (J. G. Lundberg et al., unpubl. data). Some specimens were reportedly collected over substrates of sand, mud, and organic debris. Stomach contents of a single dissected specimen (ANSP 178687, 120.6 mm SL) collected in depths of 1.5 to 8.7 m contained sclerotized body parts of aquatic insect larvae of the orders Trichoptera and Diptera , as well as organic detritus and sand.

Etymology. From the Latin word spinula meaning “a small thorn, spine” and the adjective suffix fero meaning “to bear, carry, bring”. The specific name implies “bearing little thorns”, in reference to the conspicuous thorn-like odontodes on the dorsal and lateral surfaces of the head.

Figures

Fig. 2. Loricaria spinulifera, paratype,ANSP 178690 (123.0 mm SL), rio Negro (Amazonas dr.), 11.3 km downstream from Santa Maria, 18.6 km upstream from Leprosário,Amazonas, Brazil.

Fig. 3. Odontode ornamentation on the dorsal surface of the head and buccal papillae development in the oral cavity. a-b. L. spinulifera, INPA 28851 (106.0 mm SL); c-d. L. pumila, holotype,INPA 28852 [ex.ANSP178685] (74.6 mm SL).

Fig. 4. Variation in abdominal plate development and configuration in Loricaria. a. L. pumila; b. L. spinulifera; c. L. lundbergi; d. L. simillima.

Fig. 5. Relationship between minimum orbital diameter (as % of HL) and average capture depth for specimens of Loricaria pumila (R2 = 0.692, P <0.05) and L. spinulifera (R2 = 0.515, P <0.05).

Fig. 6. Geographic distributions of Loricaria lundbergi (type locality = 1), L. spinulifera (type locality = 2), and L. pumila (type locality = 3) based on material examined.