Zoosyst. Evol. 96 (1) 2020, 67–72 | DOI 10.3897/zse.96.48952 A new psammophilic species of the catfish genus Ammoglanis (Siluriformes, Trichomycteridae) from the Amazon River basin, northern Brazil Elisabeth Henschel1, Pedro H.N. Bragança2, Filipe Rangel-Pereira1, Wilson J.E.M. Costa1 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 21941-971, 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-4EC8-4F8B-94D3-BE153BB03FA5 Corresponding author: Elisabeth Henschel ([email protected]) 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. pulex 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 body), small body size, eyes dorsally placed (sometimes reduced or absent), and a specialized head morphology The Amazon river basin exhibits the greatest diversity of (Zuanon et al. 2006). These characteristics can be found fish species in the world, harbouring more than 2,400 spe- in several sand-dwelling (i.e. psammophilic) lineages of cies (Reis et al. 2016). Among this diversity, 956 species the family Trichomycteridae, such as the subfamily Sar- are representatives of the order Siluriformes (Dagosta and coglanidinae. de Pinna 2019), popularly known as catfishes. Occupying Members of Sarcoglanidinae are exclusively psammo- a wide range of habitats throughout this basin (e.g. lakes, philic, inhabiting loose patches of sand in both clearwa- streams, waterfalls, rapids, and flooded forests; Aedriens ter (Costa 1994; Zuanon and Sazima 2004) and black- et al. 2010), catfishes are known for their adaptability, water streams (de Pinna and Winemiller 2000; Costa et but their presence in sandbanks highlights how special- al. 2019). They are miniaturized catfishes that do not ized these fishes can be. Despite being widespread and exceed 25 mm of standard length (de Pinna 1989) and structurally simple, sand bottom habitats shelter a unique are generally translucent, which allows for camouflage fish fauna that bears some remarkable morphological fea- with the surrounding environment (Myers and Weitzman tures: cryptic colour (usually translucent or light-coloured 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 Elisabeth Henschel et al.: A new Amazonian species of Ammoglanis sandy-bottom habitats is so strong that sarcoglanidines de Janeiro, Rio de Janeiro (UFRJ). Comparative material bury themselves in the sand when disturbed and when is listed by Costa (1994), Mattos et al. (2008), and Costa resting (Zuanon and Sazima 2004; Zuanon et al. 2006), to et al. (2019). Additional comparative material is listed in the extreme that Ammoglanis pulex de Pinna & Winemill- Supplementary file 1. Measurements and counts follow er, 2000 burrows 20 cm deep into the substrate (de Pinna Costa (1992), with the addition of preanal length (meas- and Winemiller 2000). ured from snout tip to origin of anal fin), first pectoral-fin Sarcoglanidinae was erected by Myers and Weitzman ray length (measured from basis of first-pectoral fin to its (1966) to allocate at that time two new distinct genera tip), and opercular patch length (longitudinal length of and species, Sarcoglanis simplex Myers & Weitzman, the opercular patch of odontodes). Measurements are pre- 1966 and Malacoglanis gelatinosus Myers & Weitzman, sented as percentages of standard length (SL), except for 1966. Few morphological characters (Myers and Weitz- those related to head morphology, which are expressed man 1966; de Pinna 1989; de Pinna and Starnes 1990; as percentages of head length. Cleared and stained (CS) Costa 1994; de Pinna and Winemiller 2000) have been specimens for osteological examination were prepared described to diagnose Sarcoglanidinae and its genera. according to Taylor and Van Dyke (1985). Osteological However, a recent molecular analysis directed to estab- nomenclature follows Datovo and Bockmann (2010). Os- lish relationships of interstitial trichomycterids from the teological illustrations were made using a stereomicro- Atlantic Forest indicated that Sarcoglanidinae, in the scope Zeiss Stemi SV 6 with a camera lucida. Fin-ray sense of previous studies, is a polyphyletic assemblage counts include all elements, and vertebral counts include comprising unrelated lineages with convergent morpho- all vertebrae except those part in the Weberian apparatus; logical adaptations to the psammophilic life-style (Costa the compound caudal centrum was counted as a single et al. 2020). Currently, according to Costa et al. (2020), element. Roman numerals represent unbranched rays and Sarcoglanidinae comprises five genera: Malacoglanis Arabic numerals represent branched rays in each fin-ray Myers & Weitzman, 1966, Sarcoglanis Myers & Weitz- count. In the description, the frequency of each fin-ray man, 1966, Stauroglanis de Pinna, 1989, Stenolicmus de count is given in parentheses after each count. Pinna & Starnes, 1990, and Ammoglanis Costa, 1994. Ammoglanis was considered to be exclusively Amazo- nian, but recently, A. multidentatus Costa, Mattos & San- Results tos, 2019 was described from northeastern Brazil, which expanded the geographical range of Ammoglanis 1000 Ammoglanis obliquus sp. nov. km to the east (Costa et al. 2019). Three other species are http://zoobank.org/64D9D3EB-AB94-4AB8-9672-F5DD235DD017 currently recognized for the genus: Ammoglanis diapha- Fig. 1A, B, 2, Table 1 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- Holotype. UFRJ 12477, 14.1 mm SL; Brazil: Amazonas sin. The recent description of A. multidentatus illustrates state: Rio Preto da Eva municipality: sandbank at small that undocumented species may occur throughout South stream, Preto da Eva River drainage, Amazonas riv- America (Costa et al. 2019). The current paper contrib- er basin, 02°46'27"S, 59°38'58"W, altitude about 20 m utes to elucidating the species diversity of sarcoglani- a.s.l.; collected by E. Henschel, P. Bragança and F. Ran- dines by describing a new species of Ammoglanis from gel-Pereira, 28 August 2019. the Amazon river basin, northern Brazil. 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- Material and methods lected with holotype. Diagnosis. Ammoglanis obliquus differs from all its Collections were made with a permit provided by Insti- congeners except A. pulex by the presence of seven di- tuto Chico Mendes de Conservação da Biodiversidade agonal rows of dark cromatophores forming a banded as approved by Instituto Chico Mendes de Conservação pattern on flank of live specimens (vs trunk with three da Biodiversidade (ICMBio; permit number 54636-3). longitudinal rows of dark chromatophores in A. diapha- Specimens were captured with small dip nets and euth- nus and A. amapaensis, or whitish with few minute dark anized in a buffered solution of ethyl-3-amino-benzo- chromatophores scattered on body in A. multidentatus), at-methanesulfonate (MS-222) at a concentration of 250 the absence of metapterygoid (Fig. 3; vs presence), and mg/l until completely ceasing opercular movements, ac- by the presence of two finger-like projections on chin cording to animal welfare laws and guidelines (Leary et region (de Pinna and Winemiller 2000: fig. 2b; vs ab- al. 2013; Close et al. 1996, 1997). Morphological charac- sence). It is distinguished from A. pulex by the presence ters were obtained from specimens fixed in formalin for of dentary teeth (Fig. 4A; vs absence), the presence of a period of 10 days and then transferred to 70% ethanol. premaxillary teeth (Fig. 4B; vs absence), by having 6+6 Specimens are deposited in the ichthyological collection caudal-fin rays (vs 5+5), and by the absence of the pelvic of the Instituto de Biologia, Universidade Federal do Rio splint (vs presence). It further differs from A. diaphanus, zse.pensoft.net Zoosyst. Evol. 96 (1) 2020, 67–72 69 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 Description. Morphometric data in Table 1. Dorsal the sesamoid supraorbital (Fig. 5, vs presence), by hav- profile of body convex from tip of snout to midline of ing fewer premaxillary teeth (3 vs 9–12 in A. diaphanus, trunk and slightly convex from that point to base of cau- 8–11 in A.