Zoosyst. Evol. 96 (1) 2020, 67-72 | DOI 10.3897/zse.96.48952 Aha BERLIN A new psammophilic species of the catfish genus Ammoglanis (Siluriformes, Trichomycteridae) from the Amazon River basin, northern Brazil Elisabeth Henschel’, Pedro H.N. Braganga’, Filipe Rangel-Pereira’, Wilson J.E.M. Costa! 1 Laboratory of Systematics and Evolution of Teleost Fishes, Institute of Biology, Federal University of Rio de Janeiro. Avenida Carlos Chagas Filho 373, Caixa Postal 68049, CEP 21941-9711, Rio de Janeiro, Rio de Janeiro, Brazil 2 South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140 South Africa http://zoobank.org/ABA3C83D-4EC8-4F $8 B-94D3-BE153BB03FA5 Corresponding author: Elisabeth Henschel (elisabeth.henschel@hotmail.com) Academic editor: Nicolas Hubert # Received 30 November 2019 # Accepted 4 February 2020 @ Published 18 February 2020 Abstract Ammoglanis obliquus sp. nov., a minute catfish species reaching a maximum adult size of 15.5 mm, is described from the Rio Preto da Eva drainage in the central Brazilian Amazon. It is distinguished from all of its congeners in possessing an exclusive combination of character states, including the presence and number of premaxillary and dentary teeth, number of interopercular and opercular odontodes, presence of cranial fontanel, number of dorsal-fin rays, number of anal-fin rays, number of caudal-fin rays, number of pelvic-fin rays, number of pectoral-fin rays, absence of pelvic splint, antorbital morphology, and absence of supraorbital and auto- palatine morphology. It is considered to be a member of a clade also including A. pulex and A. amapaensis due to the unique oral, antorbital, and autopalatine morphology. Ammoglanis obliquus is regarded as more closely related to A. pu/ex than to any other congener, as both species exhibit a similar colour pattern, an absence of the metapterygoid, and the presence of two finger-like pro- jections on the chin region. Key Words Taxonomy, tropical rain forest, Sarcoglanidinae, systematics Introduction The Amazon river basin exhibits the greatest diversity of fish species in the world, harbouring more than 2,400 spe- cies (Reis et al. 2016). Among this diversity, 956 species are representatives of the order Siluriformes (Dagosta and de Pinna 2019), popularly known as catfishes. Occupying a wide range of habitats throughout this basin (e.g. lakes, streams, waterfalls, rapids, and flooded forests; Aedriens et al. 2010), catfishes are known for their adaptability, but their presence in sandbanks highlights how special- ized these fishes can be. Despite being widespread and structurally simple, sand bottom habitats shelter a unique fish fauna that bears some remarkable morphological fea- tures: cryptic colour (usually translucent or light-coloured body), small body size, eyes dorsally placed (sometimes reduced or absent), and a specialized head morphology (Zuanon et al. 2006). These characteristics can be found in several sand-dwelling (1.e. psammophilic) lineages of the family Trichomycteridae, such as the subfamily Sar- coglanidinae. Members of Sarcoglanidinae are exclusively psammo- philic, inhabiting loose patches of sand in both clearwa- ter (Costa 1994; Zuanon and Sazima 2004) and black- water streams (de Pinna and Winemiller 2000; Costa et al. 2019). They are miniaturized catfishes that do not exceed 25 mm of standard length (de Pinna 1989) and are generally translucent, which allows for camouflage with the surrounding environment (Myers and Weitzman 1966; de Pinna 1989; Costa 1994). Their association with Copyright Elisabeth Henschel et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 68 sandy-bottom habitats is so strong that sarcoglanidines bury themselves in the sand when disturbed and when resting (Zuanon and Sazima 2004; Zuanon et al. 2006), to the extreme that Ammoglanis pulex de Pinna & Winemill- er, 2000 burrows 20 cm deep into the substrate (de Pinna and Winemiller 2000). Sarcoglanidinae was erected by Myers and Weitzman (1966) to allocate at that time two new distinct genera and species, Sarcoglanis simplex Myers & Weitzman, 1966 and Malacoglanis gelatinosus Myers & Weitzman, 1966. Few morphological characters (Myers and Weitz- man 1966; de Pinna 1989; de Pinna and Starnes 1990; Costa 1994; de Pinna and Winemiller 2000) have been described to diagnose Sarcoglanidinae and its genera. However, a recent molecular analysis directed to estab- lish relationships of interstitial trichomycterids from the Atlantic Forest indicated that Sarcoglanidinae, in the sense of previous studies, is a polyphyletic assemblage comprising unrelated lineages with convergent morpho- logical adaptations to the psammophilic life-style (Costa et al. 2020). Currently, according to Costa et al. (2020), Sarcoglanidinae comprises five genera: Malacoglanis Myers & Weitzman, 1966, Sarcoglanis Myers & Weitz- man, 1966, Stauroglanis de Pinna, 1989, Stenolicmus de Pinna & Starnes, 1990, and Ammoglanis Costa, 1994. Ammoglanis was considered to be exclusively Amazo- nian, but recently, A. multidentatus Costa, Mattos & San- tos, 2019 was described from northeastern Brazil, which expanded the geographical range of Ammoglanis 1000 km to the east (Costa et al. 2019). Three other species are currently recognized for the genus: Ammoglanis diapha- nus Costa, 1994, from the Araguaia river basin; A. pulex from the Orinoco river basin; and Ammoglanis amapaen- sis Mattos, Costa & Gama, 2008 from the Jari river ba- sin. The recent description of A. multidentatus illustrates that undocumented species may occur throughout South America (Costa et al. 2019). The current paper contrib- utes to elucidating the species diversity of sarcoglani- dines by describing a new species of Ammoglanis from the Amazon river basin, northern Brazil. Material and methods Collections were made with a permit provided by Insti- tuto Chico Mendes de Conservacéo da Biodiversidade as approved by Instituto Chico Mendes de Conservacao da Biodiversidade (ICMBio; permit number 54636-3). Specimens were captured with small dip nets and euth- anized in a buffered solution of ethyl-3-amino-benzo- at-methanesulfonate (MS-222) at a concentration of 250 mg/l until completely ceasing opercular movements, ac- cording to animal welfare laws and guidelines (Leary et al. 2013; Close et al. 1996, 1997). Morphological charac- ters were obtained from specimens fixed in formalin for a period of 10 days and then transferred to 70% ethanol. Specimens are deposited in the ichthyological collection of the Instituto de Biologia, Universidade Federal do Rio zse.pensoft.net Elisabeth Henschel et al.: A new Amazonian species of Ammoglanis de Janeiro, Rio de Janeiro (UFRJ). Comparative material is listed by Costa (1994), Mattos et al. (2008), and Costa et al. (2019). Additional comparative material is listed in Supplementary file 1. Measurements and counts follow Costa (1992), with the addition of preanal length (meas- ured from snout tip to origin of anal fin), first pectoral-fin ray length (measured from basis of first-pectoral fin to its tip), and opercular patch length (longitudinal length of the opercular patch of odontodes). Measurements are pre- sented as percentages of standard length (SL), except for those related to head morphology, which are expressed as percentages of head length. Cleared and stained (CS) specimens for osteological examination were prepared according to Taylor and Van Dyke (1985). Osteological nomenclature follows Datovo and Bockmann (2010). Os- teological illustrations were made using a stereomicro- scope Zeiss Stemi SV 6 with a camera lucida. Fin-ray counts include all elements, and vertebral counts include all vertebrae except those part in the Weberian apparatus; the compound caudal centrum was counted as a single element. Roman numerals represent unbranched rays and Arabic numerals represent branched rays in each fin-ray count. In the description, the frequency of each fin-ray count is given in parentheses after each count. Results Ammoglanis obliquus sp. nov. http://zoobank.org/64D9D3EB-A B94-4A B8-9672-F5DD235DD017 Fig. 1A, B, 2, Table 1 Holotype. UFRJ 12477, 14.1 mm SL; Brazil: Amazonas state: Rio Preto da Eva municipality: sandbank at small stream, Preto da Eva River drainage, Amazonas riv- er basin, 02°46'27"S, 59°38'58"W, altitude about 20 m a.s.1.; collected by E. Henschel, P. Bragang¢a and F. Ran- gel-Pereira, 28 August 2019. Paratypes. UFRJ 12448, 25, 12.0-15.5 mm SL; UFRJ 12479, 4, 12.8-13.2 mm SL; UFRJ 12478, 4 (CS), 13.0- 14.1 mm SL; INPA 59277, 2, 12.8-12.9 mm SL; all col- lected with holotype. Diagnosis. Ammoglanis obliquus differs from all its congeners except A. pulex by the presence of seven di- agonal rows of dark cromatophores forming a banded pattern on flank of live specimens (vs trunk with three longitudinal rows of dark chromatophores in A. diapha- nus and A. amapaensis, or whitish with few minute dark chromatophores scattered on body in A. multidentatus), the absence of metapterygoid (Fig. 3; vs presence), and by the presence of two finger-like projections on chin region (de Pinna and Winemiller 2000: fig. 2b; vs ab- sence). It is distinguished from A. pulex by the presence of dentary teeth (Fig. 4A; vs absence), the presence of premaxillary teeth (Fig. 4B; vs absence), by having 6+6 caudal-fin rays (vs 5+5), and by the absence of the pelvic splint (vs presence). It further differs from A. diaphanus, Zoosyst. Evol. 96 (1) 2020, 67-72 +. —_ < Ly 4 ’ nee . 4 sor x a * aan! bed x, oe, ee ae ee ee 69 . . om by ; , gies, i * .* - Figure 1. Ammoglanis obliquus: UFRJ 12477, 14.1 mm SL (holotype): Amazonas river basin. A. Lateral left view; B. Dorsal view. Figure 2. Live specimen of Ammoglanis obliquus: UFRJ 12448; 13.0 mm SL. A. amapaensis, and A. multidentatus by the absence of the sesamoid supraorbital (Fig. 5, vs presence), by hav- ing fewer premaxillary teeth (3 vs 9-12 in A. diaphanus, 8—11 in A. amapaensis, and 10 or 11 in A. multidentatus), fewer dentary teeth (4 vs 8 in A. diaphanus, 7 or 8 in A. amapaensis, and 11-13 in A. multidentatus), and few- er dorsal-fin rays (total of 8 vs 10 in A. diaphanus, 9 in A. amapaensis, and A. multidentatus). It is distinguished from A. diaphanus and A. multidentatus by the presence of 6 pectoral-fin rays (vs 7 in A. diaphanus and 7 or 8 in A. multidentatus), and the presence of a scythe-shaped antorbital (vs antorbital straight, with its tip not curved mesially); from A. amapaensis, by the presence of a wide cranial fontanel (vs dorsal surface of the neurocranium totally ossified, without a fontanel; Mattos et al. 2008: fig. 4), absence of separate ossification of the anterior carti- lage of autopalatine (vs presence); from A. multidentatus, by possessing fewer opercular odontodes (8-11 vs 15 or 16), fewer interopercular odontodes (5—8 vs 10 or 11), fewer anal-fin rays (total of 8 vs 9), and fewer pelvic-fin rays (total of 4 or 5 vs 6). Description. Morphometric data in Table 1. Dorsal profile of body convex from tip of snout to midline of trunk and slightly convex from that point to base of cau- dal fin. Ventral body profile convex from mouth to point at vertical through pectoral-fin origin; slightly convex from that point to origin of caudal peduncle; slightly convex from origin of caudal peduncle to caudal-fin origin. Cau- dal peduncle strongly compressed. Urogenital opening at vertical posterior to dorsal-fin origin. Head triangular in dorsal view, depressed, broader than long. Eye elliptical, laterally positioned on head. Anterior profile of snout rounded. Mouth subterminal and crescent-shaped. Nasal barbel reaching posterior margin of eye. Maxillary barbel extending to posterior border of interopercular patch of odontodes. Rictal barbel reaching middle of interopercu- lar patch of odontodes. Chin region with two finger-like projections. Teeth conical, three on premaxilla, irregular- ly arranged in a single row; four on dentary arranged in a single row. Opercular and interopercular patches of odon- todes elliptical; opercular odontodes 8—11; interopercular odontodes 5—8. Opercular and interopercular odontodes zse.pensoft.net 70 Table 1. Morphometric data of Ammoglanis obliquus sp. nov. Holotype Minimum Maximum Mean SD Standard Length 14.1 12.9 L5.5 14.0 Body Depth 10.6 10.6 13.7 L199" * O27 Caudal-Peduncle Depth 8.5 8.3 9.8 970), 055, Body Width 8.5 7.6 9.8 8.9 0.7 Caudal-Peduncle Width 1.4 0.7 2.6 10 0.6 Predorsal Length 63.8 60.7 65.5 63rlarel*3 Preanal Length 68.8 68.8 74.4 TOBav 187 Prepelvic Length Bil al 50.4 52.6 51.4 0.6 Dorsal-fin base length 57. 3.9 6.5 576. OM) Anal-fin base length 5.0 Sal 5.8 48 08 Pectoral-fin length 8.5 7.0 9.8 8.7 0.7 First pectoral-fin ray length 25.5 18.6 28.7 22.5 3.4 Pelvic-fin length 7.8 7.0 9.8 8.7 0.8 Head Length 12.8 L1t-9 135 12.9 0.4 Head Depth 55.6 55.6 70.6 61.6 4.9 Head Width 100.0 100.0 105.9 102.0 2.8 Snout Length 44.4 3735 50.0 43.8 4.3 Interorbital Width 27.8 25.0 3353 28.3 2.5 Eye Diameter 16.7 16.7 23.5 TOT me 237; Mouth Width 44.4 43.8 55.0 47.4 4.0 Interopercular Patch Length 22.2 18.8 27.8 22,76 233 Opercular Patch Length 22.2 15.0 23.5 20.8 2.7 conical, tips of odontodes curved dorsomedially. Cranial fontanel wide, lozenge-shaped, delimited anteriorly by mesethmoid and frontal and posteriorly by sphenotic and supraoccipital. Dorsal fin subtriangular; dorsal-fin rays 11,6. Dor- sal-fin first pterygiophore posterior to neural spines of 18 vertebra; tip of its last pterygiophore immediately anterior to neural spine of 21‘ vertebra. Seven dorsal-fin pterygiophores. Anal fin subtriangular, its origin at ver- tical posterior to dorsal-fin base; anal-fin rays 11,5 plus one rudimentary ray on fin origin. Anal-fin first pterygi- ophore posterior to neural spines of 20" or 21% vertebra; tip of its last pterygiophore immediately anterior to neural spine of 24" vertebra. Six anal-fin pterygiophores. Origin of anal fin in a vertical through origin of first or second branched dorsal-fin ray. Caudal fin subtruncate; princi- pal caudal-fin rays 11,4+4,11. Dorsal procurrent caudal-fin rays 6 or 7; ventral procurrent caudal-fin rays 7. Both caudal-fin lobes with four branched rays. Middle rays of caudal fin branched once. Parhypural and hypurals 1 and 2 fused and bearing six rays. Hypurals 3, 4, and 5 fused to each other, bearing six rays. Neural arch of compound centrum incomplete. Uroneural thin and elongate. Pelvic fin slightly pointed, its tip reaching vertical through ori- gin of dorsal-fin base, pelvic-fin bases medially separated by interspace nearly equal to pelvic-fin base width; pel- vic-fin rays 1,2,1 (2) or 1,2,11 (2). Pelvic-fin origin in ver- tical through base of hemal spine of 11" or 12" vertebra. Pectoral fin approximately subtriangular in dorsal view, first pectoral-fin ray terminating in long filament reaching about 50% of pectoral-fin length without filament; pecto- ral-fin rays 1,5. Vertebrae 34 or 35; ribs two. Mesethmoidal region and adjacent structures (Fig. 5). Anterior margin of mesethmoid slightly concave. Antorbital scythe-shaped in dorsal view; sesamoid su- praorbital absent. Premaxilla without prominent lateral process, but with distal portion pointed. Maxilla slender, twice longer than premaxilla. Autopalatine approximate- zse.pensoft.net Elisabeth Henschel et al.: Anew Amazonian species of Ammoglanis hyomandibula quadrate interopercle Imm Figure 3. Ammoglanis obliquus, UFRJ 12478, 13.2 mm SL; lateral view of the left suspensorium and opercular apparatus. APO - anteroventral process of opercle length; OML — opercu- lar main axis length. anguloarticular A 500um Figure 4. Ammoglanis obliquus, UFRJ 12478, 13.2 mm SL. A. Ventral view of the left premaxilla; B. Medial view of left lower jaw. mesethmoid premaxilla maxilla antorbital autopalatine frontal 500um Figure 5. Ammoglanis obliquus, UFRJ 12478, 13.2mm SL; dorsal view of mesethmoidal region and associated structures. ly rectangular; latero-posterior process of autopalatine short; cartilaginous head of autopalatine long, about one- third of autopalatine; anterior autopalatine ossification absent. Suspensorium and opercular apparatus (Fig. 3). Metapterygoid absent. Quadrate long and slender, its length about 75% length of hyomandibula without ante- rior process, its depth about 30% to quadrate total length; postero-dorsal process of quadrate absent. Hyomandib- Zoosyst. Evol. 96 (1) 2020, 67-72 ula with narrow, pointed anteriorly directed process, its length about 67% hyomandibula longitudinal length excluding process, its tip anteriorly reaching vertical through anterior half of quadrate. Interopercle compact, without anterior projection. Opercle robust, its greatest depth about 40% of its length, excluding processes and odontodes patch; anteroventral process of opercle long, its length about 75% length of opercle main axis exclud- ing odontode patch. Colouration in life. Head integument and muscula- ture transparent, pinkish colouration from blood vessels visible by transparency. Dorsal surface of head and dor- so-lateral surface of body with dark chromatophores scat- tered over snout and distal portion of premaxilla, internal pigmentation from brain case visible mainly by transpar- ency. Head ventral and ventro-lateral surfaces with few dark chromatophores, mostly forming small patches. Eyes black. Barbels transparent with few minute internal chromatophores over support cartilage. Trunk transparent with lipid grains visible along visceral cavity and dorsal midline. Pinkish colouration from blood vessels visible by transparency. Dorsal surface with dark chromatophores grouped in regular intervals, forming seven poorly-de- fined blotches. Trunk lateral surface with scattered dark chromatophores arranged along midline, highly concen- trated near caudal fin base, forming banded pattern. Trunk ventro-lateral surface with grouped inner dark chromato- phores, forming seven diagonal bands. Vertebral column with dark colouration visible by transparency, arranged in regular intervals matching dorsal and ventro-lateral chromatophores and composing lateral portion of banded pattern. Fins hyaline, with few dark chromatophores scat- tered on caudal fin and at base of anal fin. Colour in alcohol. Ground colouration of trunk and head whitish, with few minute dark chromatophores on dorsum, flank, and head. Chromatophores concentrated forming a vertical band on base of caudal fin and in mid- dle of caudal peduncle. Melanophores concentrated at regular intervals along dorsum, forming eight bands in dorsal view. Dark chromatophores in head concentrated in base of opercular patch of odontodes and in brain and snout area. Fins hyaline. Distribution. Known only from its type locality in Rio Preto da Eva drainage, Amazonas river basin, northern Brazil. Etymology. From the Latin ob/iquus, meaning oblique, referring to the conspicuous diagonal banded colouration pattern of living specimens. Ecological notes. This species is known only from a small clearwater tributary of Preto da Eva river, which 1s a left margin tributary of the Amazonas river. Individuals were found associated with a sand-bank lying on the cen- tre of an artificial widening of the main course, next to a road. The stream course margins were lined by gallery rainforest, and the water column was about | m deep with a weak current. The sand-bank was composed of coarse, yellow sand and with sparse patches of small banks of macrophytes. Capture was accomplished by scooping of Tal Preto da Eva River ul Solim6es River Figure 6. Geographic distribution of species of Ammoglanis. Red circle — A. pulex; black circle — A. obliquus; orange circle — A. amapaensis, yellow circle — A. diaphanous, blue circle — A. multidentatus. Figure 7. Habitat of Ammoglanis obliquus. the superficial layer of sand with fine hand-nets. Speci- mens of Potamoglanis Henschel, Mattos, Katz & Costa, 2018 and Ammocryptocharax Weitzman & Kanazawa, 1976 were frequently captured together with Ammoglanis obliquus. This area as a whole is under high deforestation pressure due to local human occupation. Discussion Ammoglanis obliquus is allocated to the genus Ammo- glanis by the presence of a long and slender quadrate, its greatest length about 75% of the length of the hyomandib- ula excluding the anterior process and its greatest depth about 30% of the quadrate total length (Fig. 3). This char- acter state was first proposed by Costa (1994) to diagnose the genus and was confirmed to occur in all other species of Ammmoglanis, as stated by de Pinna and Winemiller (2000), Mattos et al. (2008), and Costa et al. (2019). Am- moglanis obliquus is probably more closely related to A. pulex and A. amapaensis than to its other congeners. Am- moglanis pulex and A. amapaensis have been considered closely related taxa due to their unique oral, antorbital, and autopalatine morphology (Mattos et al. 2008; Cos- ta et al. 2019a). As seen in A. pulex and A. amapaensis, zse.pensoft.net 72 A. obliquus also exhibits a subventral mouth, a scythe- shaped antorbital with an anterior facet (Fig. 5; de Pinna and Winemiller 2000: fig. 6; Mattos et al. 2008: fig. 5), and a compact autopalatine with the lateral margin slight- ly concave and the medial margin slightly convex, bearing a small posterolateral process (Fig. 5; de Pinna and Wine- miller 2000: fig. 6; Mattos et al. 2008: fig. 5). According to Costa et al. (2019a), the autopalatine morphology re- corded for A. pulex and A. amapaensis is apomorphic and indicates a close relationship between these two species. Therefore, because A. obliquus has the same autopalatine shape, we consider this character state synapomorphic for A. obliquus, A. pulex, and A. amapaensis. Ammo- glanis obliquus and A. pulex share some unique character states indicating that they are sister taxa: absence of the metapterygoid, a condition unique among sarcoglanidines (Fig. 3; de Pinna and Winemiller: fig. 5), and a similar col- our pattern, with eight poorly-defined bands of chromat- ophores visible in dorsal view and dark chromatophores in the interior of the body forming a banded pattern (Figs 1A, B, 2). Acknowledgements Thanks are due to J.L.O. Mattos for laboratorial assistance and to P. Vilardo for helping to edit images. A. Katz gen- tly helped photographing fixed specimens. E. Henschel was funded by National Geographic Society (Early Car- reer Grant Number EC-316R-18) and CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Ministério de Ciéncia e Tecnologia). This study is part of E. Henschel’s PhD thesis. 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