Loricaria pumila, 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 : 386-389

Loricaria pumila , new species

Figs. 7 a-b, 3c-d, and 4a

Holotype. INPA 28852 [ex. ANSP 178685 ] (1, 74.6 mm SL), Brazil, Pará , rio Pará (Amazonas dr.), 15.5 km downstream of Curralinho, 9.4 km upstream from Paquetá (01º48’03.0”S, 49º39’53.0”W), 18 Nov 1994, A. M. Zanata et al.

Paratypes (10). Brazil: Pará : ANSP 178684 (2 + 1 c&s, 123.0 mm SL), rio Amazonas, 9.7 km downstream of Vila Canaã, 10.2 km upstream from Porto S. José (01º33’22.0”S, 50º44’05.0”W), 16 Nov 1994, A. M. Zanata et al .; ANSP 178689 (1, 81.0 mm SL), rio Tocantins (Amazonas dr.), 11.3 km downsteam of Curucambaba , 24.8 km upstream from Naiuata (02º02’22.0”S, 49º17’26.0”W), 20 Nov 1994, A. M. Zanata et al .; INPA 28853 [ex. ANSP 178686 ] (3, 59.6-78.3 mm SL) rio Pará (Amazonas dr.), above rio Tocantins, 83.3 km upstream from Abaetetuba, 9.1 km downstream from Boa Vista (01º45’22.0”S, 49º28’48.0”W), 18 Nov 1994, A.M. Zanata, et al .; MZUSP 100310 [ex. ANSP 178686 ] (2, 56.9-68.8 mm SL), same data as INPA 28853; MZUSP 100311 [ex. ANSP 178693 ] (1, 56.1 mm SL), rio Amazonas, 34.3 km downstream of Cabeça de Onça, 2.8 km upstream of Santarem (02º23’59.9”S, 54º41’56.7”W), 1 Nov 1994, O. Oyakawa et al .

Diagnosis. Loricaria pumila is distinguished from all species of Loricaria except L. nickeriensis by attaining a small adult size, reaching sexual maturity at less than 80 mm SL. Loricaria pumila can be distinguished from Loricaria nickeriensis and Amazon basin Loricaria by the following combination of characters: prominent crests on surfaces of head and predorsal plates with numerous well developed odontodes arranged in conspicuous linear rows ( Fig. 3c ), vs. weakly developed crests on head and predorsal plates with odontodes not arranged in conspicuous linear rows; anterior abdominal area covering pectoral girdle naked, with occasional small isolated plates at bases of pectoral fins, pre-anal shield and space between lateral abdominal plates with large polygonal plates ( Fig. 4a ), vs. anterior abdominal area and pre-anal shield covered with tightly arranged plates ( Fig. 4d ); 31-32 (modally 31) vs. 32-36 (modally 33-34, rarely 32) total lateral plates; and 18-19 (modally 18) vs. 19-22 (modally 20-21) post-anal plates ( Table 2 ).

Description. A diminutive species, standard length of specimens examined 56.1-81.0 mm SL. Other morphometric data presented in Table 1 . Meristic data for selected dermal plate characters in Table 2 .

Body moderately elongate and slender, dorsoventrally depressed, widest at posterolateral corner of head ventral to opercle. Head in transverse profile slightly concave between lateral margins and ventral rim of orbit, straight on top of head between orbits; bluntly triangular in frontal profile, lateral margins from snout tip to operculum slightly convex, snout slightly rounded. 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 posterior tip of parieto-supraoccipital, 8.2-10.7% SL. Eye generally small, but variable (see Variation, below), maximum orbital diameter 15.4-20.4% HL; iris operculum slightly developed or absent. Postorbital notch inconspicuous, rounded.

Entire body covered with dermal plates except for ventral surface of head anterior to branchiostegals, anterior median abdominal area between pectoral fins, around bases of pelvic fins, and V-shaped area surrounding anus. Dermal plates on dorsum of body from snout tip to dorsal-fin origin with prominent odontode crests and numerous well developed, sharply pointed odontodes arranged in conspicuous rows. Odontodes strongly developed on lateral margins of head from snout tip to opercle and along anterodorsal margin of orbit. Two prominent odontode crests originating at snout tip converging between nares, becoming divergent on frontals, continuing in parallel to posterior parieto-supraoccipital tip. Dorsal and dorsolateral plates between pterotic-supracleithrum and dorsal-fin origin each with a single prominent median crest and several smaller odontode rows. Lateral surface of exposed cleithrum with inconspicuous median keel of odontodes. Dorsal and lateral plates from dorsal-fin origin to caudal peduncle bearing well developed odontodes forming conspicuous linear rows.

Upper lip narrow with numerous marginal fringe barbels, each simple, bifid, or trifid. Maxillary barbel short, not extending beyond marginal fringe barbels on lower lip, bearing simple or bifid secondary barbels. Lower lip well developed with shallow median notch; surface covered with numerous elongate filaments; and marginal fringe barbels simple. 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 short, not longer than premaxillary teeth, arranged in cluster of approximately 16. Dentary teeth 5-8 on each side; less than half length of premaxillary teeth; structure similar to that of premaxillary teeth except lobes usually shorter, more rounded.

Total plates in lateral series 31-32 (modally 31). Anterior 16-18 lateral plates with two parallel odontode keels widely separated, converging at midline on caudal peduncle; posterior (coalesced) lateral plates 13-16 (modally 14). Post-anal plates 18-19 (modally 18). Lateral abdominal plates 5-7 (modally 7), rectangular and elongate. Median abdominal area with large triangular to diamond shaped plates between lateral abdominal plates; area covering pectoral girdle naked, with occasional small isolated plates at bases of pectoral fins; preanal shield well developed ( Fig. 4a ).

Dorsal fin when depressed reaching seventh or eighth plate posterior to its origin; distal margin straight to slightly concave when erected. Pectoral fin when depressed reaching seventh lateral plate posterior to cleithrum; distal margin straight to slightly concave when erected. Unbranched pelvic-fin ray (spine) longest, reaching to anterior half of analfin length. Anal fin when depressed reaching seventh 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. Diffuse brown blotches irregularly distributed on dorsal surface of head and trunk; faint brown transverse bands on dorsal surface from middle of dorsal fin to caudal peduncle present on most specimens. Dorsal surfaces of upper lip lightly sprinkled with melanophores. Ventral surfaces pale yellow or cream. Pectoral and dorsal fins with elongate brown spots on rays with spaced concentrations of melanophores on interradial membranes. Pelvic fin opaque, hyaline or with faint melanophores arranged in elongate brown spots or irregularly distributed on rays and interradial membranes. Anal fin hyaline or opaque. Caudal fin with elongate brown spots forming vertical bands throughout, faint or inconspicuous on most specimens; light brown melanophores concentrated around edges of basicaudal plate.

Variation. A single specimen (ANSP 178689) collected from the lower rio Tocantins ( Fig. 7a ) has a larger eye and maximum orbital diameter (20.4% HL) than remaining specimens (n = 10, maximum orbital diameter 15.4-17.7% HL) from the lowerAmazon. This same specimen also has a slightly developed iris operculum (absent in Amazon specimens) and conspicuous pigment pattern consisting of brown blotches on the head and fins with five dark saddles on the dorsum of the body (patterns in Amazon specimens similar, but diffuse). This individual is identified as Loricaria pumila on the basis of odontode development on head and predorsal plates, abdominal plate pattern and plate counts, all of which are consistent with L. pumila from the deeperAmazon River habitats. Futhermore, this specimen is an adult male exhibiting external sexually dimorphic characters (see Sexual Dimorphism, below). Eye size was observed to be variable among specimens collected at different depths in the lower Amazon, from small and deeply recessed in to the orbit and not visible from above ( Figs. 7b and 3c ) to distinctly larger and clearly visible from above (see Discussion, below). Bivariate regression analyses revealed a significant relationship between minimum orbital diameter and capture depth based on these specimens (R 2 = 0.692, F 1,8 = 17.96, P <0.05; Fig. 5 ).

Sexual dimorphism. Two specimens (INPA 28853, 78.3 mm SL and ANSP 178689, 81.0 mm SL) possess sexually dimorphic traits similar to those observed in nuptial male Loricaria spinulifera .

Distribution and ecology. Loricaria pumila is known from the rio Amazonas near the mouth of rio Tapajós and rio Pará adjacent to and including lower rio Tocantins ( Fig. 6). All specimens were collected in bottom trawls at depths ranging from 3 to 29 m and at distances of 15 to 1500 m from the shoreline (J. G. Lundberg et al., unpubl. data). Some specimens were reportedly collected over silt and organic detritus. Ten specimens examined were collected in white waters of the Amazon system; a single specimen (ANSP 178689, 81.0 mm SL) was collected in clear waters of the lower rio Tocantins, at relatively shallow (3 to 8 m) depths over a substrate composed of organic detritus. Stomach contents of a single dissected specimen (ANSP 178684, 73.1 mm SL) collected at a depth between 13 to 17 m contained an entire aquatic insect larva (order Coleoptera), sclerotized body parts of unidentified insects, organic detritus and sand.

Etymology. From the Latin word pumilus meaning “dwarf”, in reference to the small adult size of this species, particularly among Loricaria .

Figures

Fig. 7. Loricaria pumila. a. paratype, ANSP 178689 (81.0 mm SL), rio Tocantins (Amazonas dr.), 11.3 km downsteam of Curucambaba, 24.8 km upstream from Naiuata, Pará, Brazil; b. holotype, INPA 28852 [ex.ANSP 178685] (74.6 mm SL), rio Pará (Amazonas dr.), 15.5 km downstream of Curralinho, 9.4 km upstream from Paquetá, Pará, 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.