A new species of Ituglanis (Siluriformes: Trichomycteridae) from the Uruguai River basin closely related to congeners from Atlantic coastal drainages

Nathana Bressan¹ , Laura M. Donin² and Juliano Ferrer¹

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Associate Editor: Marcelo Melo

Section Editor: Bruno Melo

Editor-in-chief: José Birindelli

Abstract​

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Introduction​

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Trichomycteridae is the second most species-rich family of Siluriformes, comprising 456 Neotropical species, of which 177 have been described in the past decade (Fricke et al., 2025a). The most remarkable feature of trichomycterids is the highly modified opercular apparatus, with the opercular and interopercular bones compact, provided with odontodes, and connected by a strong ligament (de Pinna, 1988). Two main functions are attributed to this structure: the locomotion of individuals through elbowing movements and anchoring in the substrate, bodies, or branchial arches of host fishes (de Pinna, 1988; de Pinna, Wosiacki, 2003).

Trichomycterinae includes over 300 non-parasitic species distributed across nine genera (Fricke et al., 2025a). One of these genera, Ituglanis Costa & Bockmann, 1993, was described to encompass a monophyletic group of nine species that were previously placed in the genus Trichomycterus Valenciennes, 1832(Costa, Bockmann, 1993). By that time, the authors defined three synapomorphies for the genus: (1) posterior cranial fontanel present as a small circular orifice on the posterior region of the parietosupraoccipital; (2) autopalatine with a deep concavity in the medial margin; and (3) anterior portion of sphenotic directed anteriorly. Later, four additional characters shared by a small set of Ituglanis species were proposed: (1) parapophysis of the first four free vertebrae directed medially; (2) presence of five or more abdominal vertebrae (i.e., the post-Weberian vertebrae lacking both a complete haemal spine and an associated rib); (3) presence of two or fewer vertebrae between the first dorsal-fin pterygiophore and the first anal-fin pterygiophore; and (4) presence of 23 or more post-Weberian anterior to the first dorsal-fin pterygiophore (Wosiacki, 2002; Wosiacki et al., 2012). Datovo, de Pinna (2014) discussed these characters in a broader context within the genus and confirmed as a putatively derived character only the presence of five or more abdominal vertebrae.

Costa et al. (2021b) revised those characters proposed by Costa, Bockmann (1993) used to diagnose Ituglanis based on taxonomic works available to the genus. As a result, the character state of the posterior cranial fontanel on the posterior region of the parietosupraoccipital, defined as a “small circular orifice”, was redefined as “rudimentary or absent” and found reversed in I. payaya (Sarmento–Soares, Zanata & Martins-Pinheiro, 2011). The “autopalatine with a deep concavity in the medial margin” was found ambiguous to diagnose Ituglanis due to its presence in other closely related trichomycterine taxa. The anteriorly directed antero-lateral extremity of the sphenotic-prootic-pterosphenoid complex and the lateral process of the parurohyal long were confirmed as synapomorphic to the genus. Lastly, two derived characters were suggested for the genus: the metapterygoid semi-circular with an antero-dorsal convex margin and two to eight pairs of ribs (Costa et al., 2021b).

Currently, Ituglanis comprises 31 species (Fricke et al., 2025b), but the mention of new species within the genus awaiting description is frequent in the literature (e.g., Rizzato, Bichuette, 2014; Bertaco et al., 2016; Datovo et al., 2016; Castro, Wosiacki, 2017; Mendonça, 2017; Gimênes-Junior, Rech, 2022; Bressan, 2024). Two species of Ituglanis are known to the lower Uruguai River basin with records in Brazil, Uruguay, and Argentina: Ituglanis australis Datovo & de Pinna, 2014 and I. inusitatus Ferrer & Donin, 2017 (Datovo, de Pinna, 2014; Ferrer, Donin, 2017). In addition, a putative new species of the genus has been cited in fish inventories in both lower and upper sections of the Uruguai basin in southern Brazil (Bertaco et al., 2016; Cavalheiro, Fialho, 2020), which the scarcity of samples precluded its description. Here, we describe the new species by applying an iterative taxonomic approach to these rare specimens and recent samples.

Material and methods

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Sampling. Fish samplings were carried out using electrofishing gear with a d.c. generator (750 V and 1.5 A, model EFKO FEG 1500, Germany) and hand nets. Tissue samples from muscle or fin clips were preserved in 96% ethanol for molecular analysis, and the respective vouchers were fixed in 10% formaldehyde for morphological analysis (preserved in 70% ethanol). The comparative material was obtained from the following collections and their respective acronyms: Academy of Natural Sciences of Drexel University, Philadelphia (ANSP); Laboratório de Ictiologia de Ribeirão Preto, Ribeirão Preto (LIRP); Museu de Ciências e Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre (MCP); Museu de Zoologia da Universidade Estadual de Londrina, Londrina (MZUEL); Museu de Zoologia da Universidade de São Paulo, São Paulo (MZUSP); Coleção Ictiológica do Núcleo de Pesquisas em Limnologia, Ictiologia e Aqüicultura, Universidade Estadual de Maringá, Maringá (NUP); Coleção de Peixes do Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre (UFRGS); National Museum of Natural History, Smithsonian Institution, Washington D.C. (UNSM).

Morphological procedure. Morphometric data were taken point to point with a digital caliper on the left side of specimens whenever possible and recorded to the nearest 0.1 mm. Nomenclature of measurements followed Tchernavin (1944) for length of barbels; Wosiacki, de Pinna (2008) for length and depth of caudal peduncle, distance between pelvic-fin base and anus, and supraorbital pore s6 distance; Ferrer et al. (2015) for length of interopercular odontodophore, and Costa (1992) for the remaining measurements. Osteological data were obtained from three specimens cleared and counterstained (c&s) prepared according to Taylor, Van Dyke (1985); two of these were dissected on the head. Nomenclature of bones and cartilages followed Bockmann et al. (2004), except for the use of parurohyal following (Arratia, Schultze, 1990) and barbular, which followed de Pinna et al. (2020). Nomenclature of the laterosensory canal system and associated pores followed Rizzato, Bichuette (2016).

Number of branchiostegal rays, odontodes, procurrent rays, pterygiophores, ribs, teeth, vertebrae, and unsegmented rays were counted in four c&s specimens. Vertebral counts excluded those in the Weberian complex, and the compound caudal centrum was counted as a single element. Odontode and procurrent ray counts followed de Pinna et al. (2020). The number of specimens with each count is given in parentheses, and an asterisk indicates the count for the holotype. Osteological photographs were prepared based on c&s specimens in a Nikon AZ100M and stacked with Nikon NIS-Elements Ar Microscope Image software. The distribution map was generated using Google Earth Pro v. 7.3.3.7786 and Quantum GIS v. 3.28.5 Firenze (Geographic Information System – Open Source Geospatial Foundation Project) (Sherman et al., 2005), with geographic layers of the water resources of South America extracted from the project AQUASTAF/FAO (Food and Agriculture Organization of the United Nations), available in electronic format (<data.apps.fao.org/catalog/>).

Morphological data for all species of Ituglanis were obtained directly from specimens (see comparative material), the following references: Canto (2009), Rizzato, Bichuette (2016), Mendonça (2017), and Costa et al. (2021b): Ituglanis agreste Lima, Neves & Campos-Paiva, 2013; I. amazonicus (Steindachner, 1882); I. amphipotamus Mendonça, Oyakawa & Wosiacki, 2018; I. apteryx Datovo, 2014; I. australis; I. bambui Bichuette & Trajano, 2004; I. boitata Ferrer, Donin & Malabarba, 2015; I. boticario Rizzato & Bichuette, 2015; I. cahyensis Sarmento-Soares, Martins-Pinheiro, Aranda & Chamon, 2006; I. compactus Castro & Wosiacki, 2017; I. crispim Donin, de Pinna, Severi & Ramos, 2023; I. eichhorniarum (Miranda Ribeiro, 1912); I. epikarsticus Bichuette & Trajano, 2004; I. goya Datovo, Aquino & Langeani, 2016; I. gracilior (Eigenmann, 1912); I. guayaberensis (Dahl, 1960); I. herberti (Miranda Ribeiro, 1940); I. ina Wosiacki, Dutra & Mendonça, 2012; I. inusitatus; I. laticeps (Kner, 1863); I. macunaima Datovo & Landim, 2005; I. mambai Bichuette & Trajano, 2008; I. metae (Eigenmann, 1917); I. nebulosus de Pinna & Keith, 2003; I. paraguassuensis Campos-Paiva & Costa, 2007; I. parahybae (Eigenmann, 1918); I. parkoi (Miranda Ribeiro, 1944); I. passensis Fernández & Bichuette, 2002; I. payaya; I. proops (Miranda Ribeiro, 1908); I. ramiroi (Bichuette & Trajano, 2004), and original descriptions (i.e., Steindachner (1882), Eigenmann (1912, 1917, 1918), Miranda Ribeiro (1908, 1912), Miranda Ribeiro (1940, 1944), Dahl (1960), Fernández, Bichuette (2002), de Pinna, Keith (2003), Bichuette, Trajano (2004, 2008), Datovo, Landim (2005), Campos-Paiva, Costa (2007), Sarmento-Soares et al. (2006, 2011), Wosiacki et al. (2012), Lima et al. (2013), Datovo (2014), Datovo, de Pinna (2014), Ferrer et al. (2015), Rizzato, Bichuette (2015), Datovo et al. (2016), Ferrer, Donin (2017), Castro, Wosiacki (2017), Mendonça et al. (2018), Donin et al. (2023)).

Molecular procedure. DNA extractions from 14 samples were performed using the cetyltrimethylammonium bromide protocol (Doyle, Doyle, 1990) (CTAB). Partial sequences of the mitochondrial gene cytochrome c oxidase subunit I were amplified by Polymerase Chain Reaction (PCR) in a total volume of 20 µL, with component volumes varying as follows: 9.7–11.9 µL of ultra-pure water, 2.0 µL of 10x PCR buffer, 1.0–1.5 µL of each primer, 0.1–0.3 µL of Taq DNA Polymerase (Quatro G Biotecnologia), 2 µL of dNTPs, and 2–3 µL of DNA template (10–50 ng). The primers used were Fish F1, Fish R1, Fish F2, and Fish R2 (Ward et al., 2005), and L6252, Asn and H7271, COXI (Melo et al., 2011), all at a concentration of 10 µM. The amplification reaction was carried out in a thermocycler with the following program: initial denaturation at 95°C for 2 min, 35 cycles of 94°C for 0.5 min, primer hybridization at 52°C – 56°C for 0.5 min, and final extension at 10 min. PCR products were analyzed using electrophoresis in agarose gel. Purification, quantification, and sequencing in both directions were performed by ACTGene Análises Moleculares, Ludwig Biotecnologia LTDA, UFRGS. Sequences were edited using BioEdit v. 7.7.1 (Hall, 1999), with obvious inconsistencies corrected manually. Additionally, 24 sequences available in Genbank (Tab. S1) were used in our analyses. Alignment was performed using the MUSCLE algorithm (Edgar, 2004), within MEGA v. 11.0.13 (Molecular Evolutionary Genetic Analysis) (Tamura et al., 2021) under default parameters. The pair-wise genetic distance for the COI matrix was also estimated in MEGA program, calculated by Kimura 2-parameter model, K2P (Kimura, 1980). DNA sequences from samples used in the molecular analysis were deposited in GenBank (Tab. S1). Phylogenetic relationships were inferred by Bayesian Inference (BI) using an uncorrelated relaxed molecular clock model (lognormal) in BEAST v. 1.10.14 (Drummond et al., 2012) programmed to run for 10 million generations of Markov Chain Monte Carlo (MCMC), with tree sampling every 1,000 generations, under a Yule process tree prior (Gernhard, 2008) and HKY as nucleotide substitution model. The remaining parameters were set as default. The first 1 million generations (10%) were discarded as bur-in, and the remaining trees were used to summarize the results of the BI analysis using the maximum clade credibility tree in TreeAnnotator, on BEAST v. 1.10.14 (Drummond et al., 2012). Cambeva zonata (Eigenmann, 1918) and Scleronema minutum (Boulenger, 1891) were included as outgroup taxa in the BI analysis.

Results​

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Ituglanis jaguarete,new species

urn:lsid:zoobank.org:act:520BCB76-76BD-401C-BDD3-E31ED3384F0A

(Figs. 1–9; Tabs. 1–2)

Ituglanis sp. 3. —Bertaco et al., 2016:421 (tab. 1; checklist from Rio Grande do Sul State).—Ferrer, Donin, 2017:6, 8 (comparative material examined).

Ituglanis sp. —Cavalheiro, Fialho, 2020:7 (tab. 1; fish composition in the streams of the Ijuí River basin).

Ituglanis sp. uruguai. —Bressan, 2024 (tab. 3, figs. 4–11; diagnosis, description, distribution).

Holotype. UFRGS 28000, 74.7 mm SL, Lajeado Taipa stream, tributary of the right bank of the Uruguai River, upper Uruguai River basin, 27°07’44”S 53°28’22”W, Mondaí, Santa Catarina State, Brazil, 2 Jan 2023, N. Bressan, J. Ferrer, D. Kroth & J. C. C. Pires.

Paratypes. All from Brazil. Santa Catarina State, upper Uruguai River basin: MCP 20882, 1, 42.3 mm SL, Lajeado Mondaí stream, tributary of the right bank of the Uruguai River, 27°08’44”S 53°27’38”W, Mondaí, 27 Jan 1998, C. A. S. Lucena, Z. M. S. Lucena, E. H. L. Pereira & J. F. P. Silva. MCP 40011, 3, 45.5–49.5 mm SL, Lajeado Taipa stream, tributary of the right bank of the Uruguai River, 27°07’42”S 53°28’53”W, Mondaí, 26 Jan 2006, V. A. Bertaco, C. A. S. Lucena, J. F. P. Silva & E. H. L. Pereira. UFRGS 19179, 2 (two tissue samples: TEC 4882A and TEC 4882B), 59.0–59.1 mm SL, Jaboticaba stream, tributary of the right bank of the Uruguai River, 27°10’14”S 53°38’45”W, Itapiranga, 27 Dec 2013, J. Ferrer & J. M. Wingert. UFRGS 29219, 11 (2 c&s, two tissue samples: TEC 9987D and 9987E), 48.6–69.9 mm SL, collected with holotype. Rio Grande do Sul State, upper Uruguai River basin: MZUEL 17033, 2, 46.0–56.4 mm SL, Lajeado União stream, tributary of Pardo River, 27°12’48.4”S 53°34’51.90”W, Pinheirinho do Vale, 4 Oct 2016, O. A. E. Santana, L. S. Shibatta, O. A. Shibatta & V. P. Abrahão. MZUEL 17048, 1, 73.5 mm SL, Parizinho River, 27°11’52”S 53°47’38”W, Derrubadas, 4 Oct 2016, E. Santana, L. S. Shibatta, O. A. Shibatta & V. P. Abrahão. UFRGS 20134, 1 c&s, 50.1 mm SL, Lajeado do Tigre stream, tributary of Guarita River, 27°11’50”S 53°42’29”W, Barra do Guarita, 6 Jun 2015, J. Ferrer & J. M. Wingert. UFRGS 29220, 1, 59.6 mm SL, Parizinho River upstream to “Cotovelo do Parizinho”, 27°11’52”S 53°47’40”W, Derrubadas, 3 Jan 2023, N. Bressan, J. Ferrer, D. Kroth & J. C. C. Pires. Rio Grande do Sul State, lower Uruguai River basin: UFRGS 21920, 1 c&s, 79.3 mm SL, Noque stream, tributary of Ijuí River, 28°18’58”S 53°54’17”W, Ijuí, 17 Jan 2016, L. W. Cavalheiro, G. N. Cavalheiro, L. M. Donin & L. B. Medeiros. UFRGS 21921, one tissue sample TEC 7923, 86.0 mm SL, Noque stream, tributary of Ijuí River, 28°18’58”S 53°54’17”W, Ijuí, 20 Mar 2016, L. W. Cavalheiro, G. N. Cavalheiro, L. M. Donin & L. B. Medeiros.

TABLE 1 | Morphological data of Ituglanis species. Data in parentheses indicate personal observations, question marks (?) indicate missing data, and dashes (–) indicate characters “not applicable”. Unbranched fin-rays are represented by Roman numerals and branched fin-rays by Arabic numerals. Abbreviations: Antorbital segment of the infraorbital canal (ASI), Nasal canal (N), Nasal and frontal canals fused (N+F), Frontal canal (F), Sphenotic canal (S), Optic canal (O), Post-optic canal (Po), Scapular canal (Sc), Trunk canal (T), Present (P), Absent (A), Variable (V).

Species

Osteology

Laterosensory system

Opercular odontodes

Interopercular odontodes

Pelvic fin rays

Pectoral fin rays

Vertebrae

Rib counts

Anterior fontanel

Posterior fontanel

ASI

N

N+F

F

S

O

Po

Sc

T

Ituglanis agreste

16–17

26–30

i,4

i,6

36

5–6

P

P

P

P

P

P

P

P

P

P

P

Ituglanis amazonicus

16–20

17–24

i,3–i,4

i,5–i,6

41–43

1–3

P

P

A

P

P

P

P

P

P

P

P

Ituglanis amphipotamus

18–20

18–28

i,4

i,4–i,5

39

4–6

P

P

A

A

–

P

P

P

P

P

P

Ituglanis apteryx

13–16

20–25

A

i,4

43–45

2

P

A

A

P

P

P

P

P

P

P

P

Ituglanis australis

9–16

18–21

i,4

i,5

39–41

4–6

P

P

V

A

–

P

P

P

P

P

P

Ituglanis bambui

11

26

i,4

i,7

36–37

5–9

A

P

A

V

A

V

P

P

P

P

P

Ituglanis boitata

13–18

16–22

i,4

i,6

41–42

5–6

P

P

P

P

A

P

P

P

P

P

P

Ituglanis boticario

(7–9)

(29)

i,4

i,7–i,8

<40

7–8

A

P

P

P

V

P

P

P

P

P

P

Ituglanis cahyensis

9–12

16

i,3

i,4

40

4

P

P

A

A

–

P

P

P

P

P

P

Ituglanis compactus

8–10

12–15

i,4

i,5–i,6

36–37

2

P

P

P

P

P

P

P

P

P

P

P

Ituglanis crispim

13–19

14–19

i,4

i,5

36–38

2–3

P

P

A

P

P

P

P

P

P

P

P

Ituglanis eichhorniarum

?

?

i,4

i,5

38–39

2–3

?

?

A

P

V

P

P

P

P

P

P

Ituglanis epikarsticus

9

20–21

i,4

i,7

36

5

A

V

A

A

–

A

A

V

P

P

A

Ituglanis goya

15–23

39–52

i,4

i,5–i,6

40–42

4–8

A

P

P

P

P

P

P

P

P

P

P

Ituglanis gracilior

?

?

?

?

41–43

2–3

P

?

A

P

P

P

P

P

P

P

P

Ituglanis guayaberensis

?

?

?

i,6–i,7

?

?

?

?

?

?

?

?

?

?

?

?

?

Ituglanis herberti

?

?

i,4

i,6

42–43

1–3

?

?

A

P

P

P

P

P

P

P

P

Ituglanis ina

10–16

19–25

i,3–i,4

i,5–i,6

38–40

2–3

?

P

A

P

V

P

P

P

P

P

P

Ituglanis inusitatus

17–19

18–20

i,4

i,6

42

2–3

A

P

A

P

P

P

P

P

P

P

P

Ituglanis jaguarete

19–23

21–26

i,4

i,6

39–40

4–5

P

P

P

P

A

P

P

P

P

P

P

Ituglanis laticeps

?

?

i,4

i,6

≤39

4

?

P

?

?

?

?

?

?

?

?

?

Ituglanis macunaima

10–15

10–15

i,4

i,4

35–38

2–3

A

A

A

A

–

P

P

P

P

P

P

Ituglanis mambai

14–16

24–26

i,4

i,7

37–38

6–10

?

A

V

P

V

P

P

P

P

P

P

Ituglanis metae

?

?

i,4

i,5–i,6

42

2–3

?

P

A

P

P

P

P

P

P

P

P

Ituglanis nebulosus

12

17

i,4

i,5

35–36

2–3

P

P

A

P

?

P

P

P

P

P

P

Ituglanis paraguassuensis

14–17

15

i,4

i,6

34–36

6

P

P

P

P

V

P

P

P

P

P

P

Ituglanis parahybae

13–15

17–25

i,3

i,4

38–40

6

P

P

A

A

–

A

P

P

P

P

P

Ituglanis parkoi

?

?

i,4

i,6

43

3

P

P

A

P

P

P

P

P

P

P

P

Ituglanis passensis

8–19

21–45

i,3–i,4

i,6–i,8

36–42

5–8

A

V

A

A

–

A

A

P

P

P

V

Ituglanis payaya

16–19

21–26

i,4

i,6

36

5–6

P

P

P

P

P

P

P

P

P

P

P

Ituglanis proops

17–23

26–39

i,3–i,4

i,5–i,6

39–41

5–6

P

P

P

P

A

P

P

P

P

P

P

Ituglanis ramiroi

12–13

24–25

i,4

i,8

36

5–8

A

P

A

V

A

V

V

P

P

P

V

Diagnosis. Ituglanis jaguarete is distinguished from all congeners, except I. boitata Ferrer, Donin & Malabarba, 2015, I. amphipotamus Mendonça, Oyakawa & Wosiacki, 2018, and I. proops (Miranda Ribeiro, 1908), by the body color pattern consisting of two spotted layers of pigmentation over a yellowish background: inner layer with rounded dark brown spots, somewhat coalescent, equivalent in size to the eye circumference, covered by the outer layer composed of several smaller rounded brown spots. (Fig. 2; vs. body with a non-spotted coloration; body with a single spotted layer of pigmentation; body with the inner layer of pigmentation composed of one or more longitudinal stripes). Ituglanis jaguarete is distinguished from I. boitata by the interopercular odontophore length (35.1–39.3 vs. 22.7–31.4% of head length) and number of opercular odontodes (19–23 vs. 13–18). Ituglanis jaguarete is distinguished from I. proops by the interopercular odontophore distal margin not reaching the transverse line through the anterior margin of the opercular odontophore (vs. surpassing the transverse line through the mid-length of the opercular odontophore) and number of interopercular odontodes (21–26 vs. 26–39). Ituglanis jaguarete is distinguished from I. amphipotamus by the pectoral fin with seven rays with a short filament (vs. six rays with the first one with a distinct filament), and the cephalic laterosensory system morphology with the antorbital segment of the infraorbital canal and the nasal canal of the supraorbital segment present on at least one side of the head (vs. antorbital segment of the infraorbital canal and nasal canal of the supraorbital segment completely absent).

Description. Morphometric data in Tab. 2. Elongated body, approximately cylindrical in anterior trunk, gradually compressed toward caudal peduncle. Dorsal profile slightly convex up to dorsal-fin insertion. Ventral profile straight up to dorsal-fin insertion. Dorsal and ventral profiles of caudal peduncle straight. Some largest specimens with dorsal region of trunk and head covered with minute papillae (Fig. 1).

TABLE 2 | Morphometric data of Ituglanis jaguarete based on 25 specimens. Range represents the smallest and largest measurements for each character. SD = Standard deviation.

	Holotype	Range	Mean	SD
Standard length (mm)	74.7	41.5–87.6	58.5	–
Percentage of standard length
Pre-anal length	71.5	71.4–78.0	73.5	1.50
Pre-dorsal length	67.3	64.9–71.4	68.6	1.68
Pre-pelvic length	58.7	57.4–62.9	60.0	1.45
Trunk length	41.9	40.4–46.8	43.7	1.60
Pectoral fin length	11.9	8.4–12.0	10.7	0.86
Pelvic fin length	8.0	7.3–9.3	8.0	0.47
Distance between pelvic-fin base and anus	5.8	5.1–8.8	6.8	0.88
Length of dorsal-fin base	10.6	8.7–12.3	10.6	0.98
Length of anal-fin base	8.5	7.4–10.6	8.8	0.70
Caudal peduncle length	17.8	16.4–21.0	18.6	1.37
Caudal peduncle depth	12.8	9.5–13.3	11.9	0.96
Body width	7.3	5.8–8.2	7.1	0.74
Body depth	15.1	12.1–15.9	14.4	0.98
Scapular girdle width	11.3	10.7–13.8	12.3	0.91
Head length	16.8	15.5–19.4	17.2	1.05
Percentage of head length
Head depth	48.8	44.2–57.6	50.2	3.32
Head width	85.7	84.8–93.4	88.2	2.36
Mouth width	37.2	32.2–40.5	36.2	2.65
Eye diameter	10.4	8.8–13.7	10.8	1.16
Interorbital	39.5	30.4–39.6	34.9	2.45
Pre-orbital	35.1	31.8–42.6	37.1	2.66
Interopercular odontophore length	35.5	35.1–39.3	36.8	1.33
Nasal barbel length	61.2	50.5–81.3	65.6	8.82
Maxillary barbel length	85.6	66.5–105.8	83.5	8.18
Rictal barbel length	69.1	54.2–82.0	66.9	7.04

FIGURE 1| Ituglanis jaguarete, holotype, UFRGS 28000, 74.7 mm SL, in lateral, dorsal and ventral view, Lajeado Taipa stream, tributary of the right bank of the Uruguai River, upper Uruguai River basin, 27°07’44”S 53°28’22”W, Mondaí, Santa Catarina State, Brazil.

FIGURE 2| Detail of body coloration in species of Ituglanis. Two layers of spotted pigmentation: A. I. jaguarete, holotype, UFRGS 28000, 74.7 mm SL; B. I. boitata, UFRGS 8833, paratype, 82.3 mm SL (photo from Malabarba et al., 2013). Inner layer of pigmentation composed of one or more longitudinal stripes: C. I. australis, not measured; D. I. nebulosus, holotype, MNHN 2001–1128, 36.6 mm SL (photo from Donin et al., 2023). A single spotted layer of pigmentation: E. I. crispim, MZUSP 126762, holotype, 28.8 mm SL (photo from original description in Donin et al., 2023, fig. 1). Body with a non-spotted coloration: F. I. ina, MPEG 19613, holotype, 62.0 mm SL (photo from Wosiacki et al., 2012).

Head depressed and trapezoidal from dorsal view, wider posteriorly. Dorsal and ventral profiles straight or slightly convex. Snout straight or slightly rounded from dorsal view. Eyes positioned dorsally, approximately anterior to mid-length of head, near posterior nostrils. Eyes visible in lateral view, covered by thin and transparent skin, with non-free orbital rim. Nostrils smaller than eye diameter. Posterior nostrils surrounded by thin membrane. Anterior nostrils surrounded by membrane continuous with nasal barbels. Mouth sub-terminal, slightly convex in ventral view. Lower lips with fleshy lobes at corners, continuous with rictal barbels. Opercular and interopercular odontophores well-developed surrounded by thin skin flap. Distal margin of interopercular odontophore aligned with anterior margin of opercular odontophore.

Barbels gradually narrowing toward tips. Nasal barbel originating from postero-lateral edge of anterior nostril, reaching or extending beyond head. Maxillary barbel originating from mouth corner, always extending beyond interopercular odontophore. Rictal barbel reaching posterior margin of interopercular odontophore, slightly shorter than maxillary barbels.

Pectoral fin with slightly convex distal margin. First unbranched ray extended as short filament, followed by six branched rays (24). Pelvic fin origin at mid-length of body with distal margin vertically aligned with dorsal-fin origin. Pelvic fin covering urogenital papilla, with one unbranched ray and four branched rays, with distal margin usually rounded (pointed in two specimens). Pelvic fin insertions very close to each other (in medial contact). Anterior arms of basipterygium with similar size, joined each other in mid-length (Fig. 3). Medial process usually absent, present on left side of one specimen. Pelvic splint present. Cartilage between basipterygium and fin rays well-developed.

FIGURE 3| Pelvic girdle of Ituglanis jaguarete, UFRGS 29219, 65.4 mm SL, dorsal view. Abbreviations: basipterygium (BP); external process (EP); internal process (IP); medial process (MP); pelvic splint (PS).

Dorsal fin with posterior margin slightly convex, with three (3 c&s) or four (1 c&s) procurrent rays, two (23) or three (2) unbranched rays, and five (1), six (6), or seven (18) branched rays. Dorsal-fin origin aligned with pelvic-fin extremity. Dorsal fin with eight pterygiophores, first one or first three inserted posterior to neural spine of 23^rd or 24^th vertebra. Dorsal and anal fins with approximately equal size. Anal fin with posterior margin slightly convex, with three (1 c&s) or four (3 c&s) procurrent rays, one (6) or two (19) unbranched rays, and four (2), five (17), or six (6) branched rays. Anal-fin origin slightly posterior to dorsal-fin origin. Anal fin with six (3 c&s) or seven (1 c&s) pterygiophores, first one or first two inserted posterior to hemal spine of the 25^th or 26^th vertebra. Caudal fin with distal margin rounded. Upper caudal plate with one unbranched ray and five branched rays (4 c&s). Lower caudal plate with one unbranched ray and six branched rays (4 c&s). Dorsal procurrent rays 12 (1 c&s), 13 (2 c&s), or 15 (1 c&s) and ventral procurrent rays 11 (1 c&s), 12 (2 c&s), or 13 (1 c&s). Epural absent (2 c&s) or present (2 c&s); epural rounded or comma-shaped. Upper caudal plate with uroneural, hypural 3 autogenous, and fused hypurals 4 and 5. Lower caudal plate with parhypural and hypurals 1 and 2 co-ossified, fused to compound caudal centrum.

Post-Weberian vertebrae 39 (2 c&s) or 40 (2 c&s). Four or five pairs of ribs (variable individually); first pair thicker and shorter, last pair usually vestigial. First complete hemal arch on 6^th (2 c&s) or 7^th (2 c&s) free vertebra; first complete hemal spine on 13^th (1 c&s) or 14^th (3 c&s) free vertebra.

Head osteology. Mesethmoid elongated, expanded at mid-length, with anterior margin straight to slightly concave; lateral cornuas extending to two-thirds of premaxilla, narrowing toward tips (Fig. 4). Anterior cranial fontanel small and drop-shaped. Posterior cranial fontanel restricted to small rounded orifice. Posterior fontanel slightly smaller than anterior one (2 c&s) or equal in size (2 c&s). Lacrimal-antorbital short, extending over autopalatine. Lacrimal-antorbital and barbular fused in left side of one specimen. Barbular elongated, approximately three times larger than lacrimal-antorbital, with dorsolateral process elongated and pointed backward (1 c&s), inconspicuous or absent (2 c&s).

FIGURE 4| Neurocranium of Ituglanis jaguarete, UFRGS 29219, 53.5 mm SL, dorsal view on the left and ventral view on the right. Abbreviations: antorbital (AN); anterior fontanel (AF); autopalatine (AP); barbular (BA); basioccipital (BO); frontal (FR); mesethmoid (ME); maxilla (MX); orbitosphenoid (OS); sphenotic-prootic-pterosphenoid (SP+PO+PN); parieto-supraoccipital (SU); parasphenoid (PA); posterior fontanel (PF); premaxilla (PMX); vomer (VO); Weberian capsule (WC). Scale bar: 1 mm.

Sphenotic, prootic, and pterosphenoid fused. Sphenotic with antero-lateral extremity pointed, with medial margin diverging from lateral margin of frontal. Vomer arrow-shaped with anterior tip extending near mesethmoid cornua; lateral arms well-defined directed postero-laterally; posterior process elongated and pointed, overlapping anterior margin of parasphenoid. Parasphenoid with long, narrow and pointed posterior process, overlapping anterior portion of basioccipital. Weberian capsule rounded, with medial margins fused to basioccipital and lateral tube-shaped projections.

Premaxilla rectangular with 16–24 pointed teeth arranged in two well-defined rows; teeth of outer row longer than inner one. Maxilla boomerang-shaped, shorter than premaxilla. Dentary with 13–29 pointed teeth arranged in three irregular rows, not reaching coronoid process; teeth of outer row longer than inner ones. Autopalatine with anterior margin straight, medial margin notched, lateral margin slightly concave; and pointed posterior process overlapping metapterygoid. Metapterygoid laminar and semi-circular in general aspect; anterior margin rounded and posterior margin straight with cartilage connecting to quadrate (Fig. 5). Quadrate L-shaped with small process on anterior margin, articulated dorsally with metapterygoid. Hyomandibula well-developed with dorsal margin notched. Preopercle elongated and narrow, connected to posterior ventral margin of quadrate and anterior ventral margin of hyomandibula.

FIGURE 5| Suspensorium of Ituglanis jaguarete: A. UFRGS 20134, 50.1 mm SL, right side; B. UFRGS 21921, 86.0 mm SL, left side; C. UFRGS 29219, 53.5 mm SL, right side and D. left side, lateral view. Abbreviations: metapterygoid (MT); hyomandibula (HY); preopercle (PO); quadrate (QU). Images B and D changed to the standard position. Scale bars: 1 mm.

Opercle robust articulated with hyomandibula and preopercle. Opercle with straight, pointed process ascending upwards and 19–23 backwards odontodes circularly arranged. Interopercular elongated, robust with small anterior dorsal process and 21–26 downward-facing odontodes arranged in three rows. Both opercular and interopercular odontophores pointed, curved at tips, gradually increasing in size posteriorly (Fig. 6).

FIGURE 6| Opercular series of Ituglanis jaguarete, UFRGS 21921, 86.0 mm SL, lateral view. Abbreviations: interopercle (IO); opercle (OP). Right side, inverted image.

Ventral hypohyal triangular. Anterior ceratohyal elongated, slightly concave at mid-length. Posterior ceratohyal short, L-shaped (Fig. 7B). Seven branchiostegal rays, first five rays narrow and last three rays wide. Parurohyal expanded anterior with drop-shaped foramen; two long and wide lateral projections tapering distally and extending to 2^nd branchiostegal ray; and posterior process thin and pointed (Fig. 7A).

FIGURE 7| A. Hyoid arch of Ituglanis jaguarete, UFRGS 21921, 86.0 mm SL, lateral view. Abbreviations: anterior ceratohyal (AC); branchiostegal ray 1 (BR1); branchiostegal ray 8 (BR8); posterior ceratohyal (PC); ventral hypohyal (VH). Right side, inverted image. B. Parurohyal of I. jaguarete, UFRGS 21921, 86.0 mm SL, dorsal view.

Basibranchials 2 and 3 connected by cartilage, with basibranchial 2 larger than basibranchial 3, both with small longitudinal foramen anteriorly (Fig. 8). Basibranchial 4 entirely cartilaginous, pentagonal-shaped with slightly concave edges. Elongated hypobranchial 1 with cartilaginous tips. Hypobranchials 2 and 3 with anterior narrow ossified portion and posterior broad cartilage. Ossified portion of hypobranchial 2 distinct elongate. Five elongated ceratobranchials with cartilaginous tips, with ceratobranchials 1–3 with distinct concavity in medial posterior margin. Ceratobranchial 5 with approximately 12 pointed conical teeth in medial margin. Conspicuous gill rakers in ceratobranchials 4 and 5 and vestigial in ceratobranchials 2 and 3. Four epibranchials with cartilaginous tips. Epibranchials 1–3 narrow and elongated. Epibranchials 1 and 2 with process in anterior margin, epibranchial 1 process longer and distinctly curved. Epibranchial 3 with small process in posterior margin. Epibranchial 4 rectangular articulating with upper pharyngeal plate. Pharyngobranchial 3 narrow and curved with cartilaginous tips. Pharyngobranchial 4 connected to dorso-lateral surface of upper pharyngeal plate. Upper pharyngeal plate curved and large, with approximately 11 conical teeth, similar in size to those of ceratobranchial 5 and increasing in size posteriorly.

FIGURE 8| Branchial arches of Ituglanis jaguarete, UFRGS 20134, 50.1 mm SL, dorsal view. Abbreviations: basibranchials 2 to 4 (BB2–4); ceratobranchials 1 to 5 (CB1–5); epibranchials 1 to 4 (EB1–4); hypobranchials 1 to 3 (HB1–3); pharyngeal tooth plate (TP); pharyngobranchial 3 (PB3). Epibranchials from the right side removed for better visualization. Scale bar: 1 mm.

Laterosensory system. Laterosensory canals with simple (non-dendritic) branches ending in single pores. Nasal and frontal canals of supraorbital line not fused. Nasal canal with two pores (s1 and s2). Pore s1 bilaterally symmetric in 19 specimens (present in 18 specimens and absent in one specimen) and bilaterally asymmetric (absent in one side) in three specimens. Pore s2 bilaterally symmetric in 19 specimens (present) and bilaterally asymmetric (absent in one side) in three specimens. Frontal canal with two pores (s3 and s6). Pores s3 bilaterally symmetric in 22 specimens (present). Pores s6 bilaterally symmetric in 16 specimens (present in 13 specimens and absent in three specimens) and bilaterally asymmetric (absent in one side). Antorbital segment of infraorbital line with two pores (i1 and i3) bilaterally symmetric in 21 specimens (present) and bilaterally asymmetric (absent in one side) in one specimen. Sphenotic canal present with two pores (i10 and i11) bilaterally symmetric in 22 specimens (present). Optic, post-optic, and scapular canals present with two pores (Po1 and Po2) bilaterally symmetric in 22 specimens (present). Trunk canal short with two pores bilaterally symmetric in 22 specimens (present).

Coloration in alcohol. Dorsal and lateral surfaces of body with two layers of pigmentation over yellowish background: inner layer with dark brown, rounded spots, somewhat coalescent, equivalent in size to eye circumference; covered by outer layer of several rounded brown spots (Figs. 1–2A, B). Dorsal surface of body with numerous rounded dark spots. Ventral surface of body yellowish anteriorly with few rounded dark spots posterior to pelvic fin. Head coloration similar to body pattern, with well-defined rounded spots on sides and densely pigmented in parietosupraoccipital. Barbels yellowish with sparse rounded dark brown spots. Pectoral fin with rounded dark brown spots over yellowish background, spots larger and brighter in first unbranched ray gradually decreasing in number. Pelvic fin hyaline. Dorsal and anal with rounded dark brown spots, more numerous and brighter near fins origin and aligned in stripes on distal portion of dorsal fin. Caudal fin with rounded dark brown spots aligned in vertical stripes. Some small specimens with brighter spots arranged homogeneously.

Coloration in life. The coloration of live specimens is similar to those preserved in alcohol, but with a darker reddish-brown background and inconspicuous spot layers, giving a homogeneous color pattern in the first glimpse (Fig. 9).

FIGURE 9| Live specimen of Ituglanis jaguarete collected with the holotype photographed just after sampling, UFRGS 21921, 56.7 mm SL.

Geographical distribution. Ituglanis jaguarete distributes in the upper and lower sections of the Uruguai River basin (Fig. 10), two freshwater ecoregions recognized by Abell et al. (2008), inserted in the Atlantic Forest biome in Brazil (IBGE, 2024). The species in the upper Uruguai ecoregion is mainly known from rivers and streams flowing directly to the Uruguai River (Santa Catarina and Rio Grande do Sul States). In the lower Uruguai ecoregion, the species is so far known from a stream tributary of the Ijuí River (Rio Grande do Sul). Ituglanis jaguarete probably occurs in the tributaries of the right bank of the Uruguai River in Argentina.

FIGURE 10| Geographical distribution of Ituglanis species from southern Brazil, from records of scientific collections and literature. Some symbols represent more than one locality. Abbreviations: Rio Grande do Sul State (RS); Santa Catarina State (SC).

Ecological notes. The type-locality of Ituglanis jaguarete (Lajeado Taipa stream) on the day of collection was characterized by a narrow and shallow stream, approximately 4.0 m wide and depth ranging from few centimeters to 0.5 m, with moderate flow and substrate composed of gravel and rocks, surrounded by well-preserved riparian vegetation, typical of the Deciduous Seasonal Forest physiognomy (Fig. 11A). Twelve specimens were captured in the stream current among rocks with the help of electroshocking. The remaining sampling sites share similar general aspects and bottom microhabitats (Fig. 11B). However, I. jaguarete was additionally recorded in two distinct microhabitats: a lentic stream stretch with litter-covered substrate (UFRGS 19179) and a deep marginal ravine of a fast-flowing river section (UFRGS 21920, 21921; see fig. 2A of Cavalheiro, Fialho, 2020). Elevation at sampling sites ranges from 179 to 304 m.

FIGURE 11| A. Type-locality of Ituglanis jaguarete: Lajeado Taipa stream, a right-bank tributary of the Uruguai River, upper Uruguai basin, Mondaí, Santa Catarina State, Brazil. Photo taken on January 2, 2023. B. Lajeado do Tigre stream, tributary of Guarita River, Barra do Guarita, Rio Grande do Sul State, Brazil. Photo taken on June 6, 2015.

The following species were collected along with Ituglanis jaguarete at the type-locality, not necessarily in the same microhabitat: Crenicichla hadrostigma Lucena, 2007 (UFRGS 29413), Phalloceros caudimaculatus (Hensel, 1868)(UFRGS 29416), Psalidodon aff. fasciatus (Cuvier, 1819) (UFRGS 29421), Hoplias australis Oyakawa & Mattox, 2009 (UFRGS 29425), Diapoma lepiclastum (Malabarba, Weitzman & Casciotta, 2003) (UFRGS 29429), Psalidodon saguazu (Casciotta, Almirón & Azpelicueta, 2003)(UFRGS 29432), Bryconamericus iheringii (Boulenger, 1887) (UFRGS 29447), Oligosarcus oligolepis (Steindachner, 1867)(UFRGS 29457), Heptapterus mustelinus (Valenciennes, 1835)(UFRGS 29565), Heptapterus sp. (UFRGS 29475) Rhamdia aff. quelen (Quoy & Gaimard, 1824)(UFRGS 29467).

Etymology. “Jaguareté” is an Indigenous noun from the language Tupi-Guarani to the feline Panthera onca, called “jaguar” (English) or “onça-pintada” (Portuguese). The specific epithet is given in reference to the similarity of their body coloration. A noun in apposition.

Conservation status. Ituglanis jaguarete is known for a few localities, encompassing an Extent of Occurrence (EOO) of approximately 2,130 km². However, the species probably has a broader distribution occurring in other tributaries of the Uruguai River in Brazil and Argentina. Furthermore, data on abundance or population tendencies are unknown at present. Possible impacts on the species are related to deforestation, pollution, and soil erosion resulting from agricultural activities in Southern Brazil. Consequently, we recommend classifying I. jaguarete as Least Concern (LC) (IUCN, 2024) until we better understand the species distribution and the effects of these impacts.

Phylogenetic inference. According to the BI analysis using the mitochondrial gene Cytochrome c oxidase subunit I (COI), Ituglanis jaguarete was recovered as a sister group of I. boitata (PP = 0.99), a species endemic to the southern Brazilian coastal drainages, which are closely related with I. proops plus I. amphipotamus (PP = 0.99) (Fig. 12). Ituglanis proops is endemic to the southeastern Brazilian coastal drainage of the Ribeira de Iguape, while I. amphipotamus occurs in both Ribeira de Iguape and upper Tietê River basins. The interspecific distances between I. jaguarete and its congeners were 8.99% to I. amazonicus (Steindachner, 1882), 3.20% to I. amphipotamus, 5.03% to I. australis, 1.08% to I. boitata, 9.51% to I. eichhorniarum (Miranda Ribeiro, 1912), 8.23% to I. goya Datovo, Aquino & Langeani, 2016, 11.42% to I. herberti (Miranda Ribeiro, 1940), 12.90% to I. inusitatus, and 2.39% to I. proops (Tab. 3).

FIGURE 12| Bayesian inference including Ituglanis jaguarete, I. amazonicus, I. amphipotamus, I. australis, I. boitata, I. eichhorniarum, I. goya, I. herberti, I. inusitatus, and I. proops, with Cambeva zonata and Scleronema minutum as outgroups. Numbers on the nodes represent posterior probability values (PP).

TABLE 3 | Genetic distance values (%) based on mitochondrial COI gene between species, calculated using the Kimura-2-parameter model.

	1	2	3	4	5	6	7	8	9	10	11	12
1. Ituglanis jaguarete
2. Ituglanis amazonicus	8.99
3. Ituglanis amphipotamus	3.20	9.64
4. Ituglanis australis	5.03	9.27	6.26
5. Ituglanis boitata	1.08	9.16	2.94	5.07
6. Ituglanis eichhorniarum	9.51	5.02	10.02	9.94	9.26
7. Ituglanis goya	8.23	11.71	9.45	9.41	8.56	11.77
8. Ituglanis herberti	11.42	12.93	11.72	12.28	12.12	13.52	13.45
9. Ituglanis inusitatus	12.90	15.13	12.35	11.86	13.34	15.15	14.94	8.47
10. Ituglanis proops	2.39	9.70	1.16	6.69	3.03	10,45	8.77	11.60	12.59
11. Cambeva zonata	12.99	15.93	14.49	13.93	13.97	15.68	15.38	15.63	15.73	13.75
12. Scleronema minutum	13.48	15.98	13.71	15.13	13.28	16.18	15.69	16.80	16.83	13.22	10.89

Discussion​

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Phylogenetic relationships within Ituglanis have been investigated mainly through comparative analyses of morphological characters (e.g., de Pinna, Keith, 2003; Canto, 2009; Wosiacki et al., 2012; Rizzato, Bichuette, 2016, Costa et al., 2021b). The most comprehensive phylogenies of the genus to date have utilized mainly osteological characters (Mendonça, 2017) or molecular approaches, including ultra-conserved genomic elements (Ochoa et al., 2020) and multigene analyses (Costa et al., 2021b). Both these previous molecular analyses are congruent in recovering a lineage comprising three species from coastal drainages of southeast and south Brazil: Ituglanis amphipotamus, I. boitata, and I. parahybae (Eigenmann, 1918). Our findings (BI and genetic distance) recovered this clade with the inclusion of I. jaguarete (Uruguai River basin) and I. proops (endemic to the Ribeira de Iguape coastal basin), and the exclusion of I. parahybae, which was not evaluated in our analysis (Fig. 12). Morphologically, I. jaguarete and these three related species are characterized by a distinct body coloration composed of two layers of rounded dark brown blotches over a yellowish background (Figs. 2A, B), that is apparently not shared by I. parahybae. Within this lineage, two sister-group pairs were recovered: Ituglanis amphipotamus plus I. proops, which are sympatric in the Ribeira de Iguape basin, and I. jaguarete plus I. boitata, which are allopatrically distributed in the Uruguai River basin and southern Brazilian coastal drainages, respectively (Fig. 10).

This phylogenetic affinity of I. jaguarete with I. boitata may be explained by a shared biogeographic history between continental and adjacent coastal drainages in South America, potentially resulting from river capture events or drainage rearrangements (Ribeiro, 2006; Lima, Ribeiro, 2011). Interestingly, I. jaguarete is the only known species of the genus inhabiting the upper Uruguai River basin, whose headwaters are geographically adjacent to those of coastal drainages inhabited by I. boitata. Additional examples of sister-group relationships between fish species in the Uruguai River basin and its adjacent coastal drainages were demonstrated by Malabarba et al. (2021): Pseudocorynopoma doriae Perugia, 1891 and Oligosarcus oligolepis (Steindachner, 1867) from the former area, and their respective sister taxa P. stanleyi Malabarba, Chuctaya, Hirschmann, Oliveira & Thomaz, 2020 and O. robustus Menezes, 1969 from the latter.

Ituglanis jaguarete exhibits all morphological synapomorphies proposed by Costa, Bockmann (1993) and revised by Costa et al. (2021b): posterior cranial fontanel on the parietosupraoccipital rudimentary, anterolateral extremity of the sphenotic-prootic-pterosphenoid complex directed anteriorly (Fig. 4), metapterygoid semi-circular with an anterodorsal convex margin (Fig. 5), lateral process of the parurohyal long (Fig. 7), and four to five pairs of ribs (Costa et al., 2021b). Although the intraspecific variability of laterosensory pores is more pronounced in subterranean Ituglanis species, certain epigean congeners exhibit some degree of variability, as seen in I. australis and I. paraguassuensis Campos–Paiva & Costa, 2007 (Rizzato, Bichuette, 2016). Ituglanis jaguarete usually exhibits the pores s1, s2, s3, s6, i1, i3, i10, i11, po1, and po2 of the lateral sensory system bilaterally present, with observed asymmetries or complete absence restricted to the supraorbital and infraorbital canals in few specimens. As emphasized by Ferrer et al. (2015) and Ferrer, Malabarba (2020), reliable morphological comparisons in such cases require large sample sizes.

The La Plata system, comprising the Paraná, Paraguay, and Uruguai River basins, represents the third most diverse drainage in terms of freshwater fish in South America (Reis et al., 2016) and one of the most densely sampled in Brazil (Bertaco et al., 2016; Dagosta et al., 2024). Despite extensive ichthyological research in the region, significant biogeographic gaps persist in Ituglanis distribution across the La Plata system. For example, the genus is absent in the well-known Iguaçu River basin, and the two species of the upper Paraná basin are restricted to the headwaters of Tietê and Paranaíba rivers: Ituglanis amphipotamus and I. goya, respectively (Datovo et al., 2016; Mendonça et al., 2018; Dagosta et al., 2024). In the lower Paraná River basin, only I. eichhorniarum has been recorded, with sparse representation in zoological collections and literature (Azpelicueta, García, 1994).

In contrast, the Paraguay and Uruguay River basins harbor a higher genus diversity within the drainage. The Paraguay River basin contains four Ituglanis species: I. eichhorniarum, I. herberti and two new species recently documented (Gimênes-Junior, Rech, 2022), while the Uruguai River basin has three: Ituglanis australis, I. inusitatus, and I. jaguarete. These pronounced disparities in Ituglanis diversity and distribution present an intriguing case study for understanding Neotropical freshwater fish diversification, particularly regarding the ecological and historical factors.

Comparative material examined. Ituglanis agreste: MZUSP 102535, 6 paratypes, 37.8–43.6 mm SL. Ituglanis amazonicus: MCP 36257, 1 c&s; UNSM 317738, 1 c&s. Ituglanis amphipotamus: MZUSP 69393, holotype, 71.4 mm SL; MZUSP 65750, 6 paratypes (2 c&s), 47.2–62.6 mm SL; MZUSP 84618, 3 paratypes, 41.8–49.4 mm SL. Ituglanis apteryx: MZUSP 115048, holotype, 60.9 mm SL; MZUSP 96876, 1 paratype, 55.3 mm SL; ANSP 200908, 1 paratype, 65.71 mm SL. Ituglanis australis: MZUSP 112505, holotype, 55.3 mm SL; MCP 10420, 1 paratype (c&s); MCP 37695, 2 paratypes (c&s); MZUSP 81016, 1 paratype, 35.5 mm SL; MZUSP 112506, 1 paratype, 28.6 mm SL; MZUSP 112507, 2 paratypes, 40.2–43.5 mm SL; UFRGS 7444, 1 paratype, 62.7 mm SL. Ituglanis bambui: MZUSP 79860, holotype, 41.7 mm SL; MZUSP 79862, 1 paratype (c&s); MZUSP 79863, 3 paratypes (1 c&s), 34.0–40.7 mm SL; MZUSP 79864, 2 paratypes, 38.1–45.9 mm SL. Ituglanis boitata: MZUSP 116532, 1 paratype, 85.0 mm SL; MZUSP 116533, 1 paratype, 65.6 mm SL; MZUSP 116534, 2 paratypes, 37.6–56.4 mm SL; UFRGS 17617, 1 paratype (c&s); UFRGS 17576, 1 to 2, 93.2 mm SL; UFRGS 21347, 2, 61.9–89.2 mm SL; UFRGS 21916, 3, 46.5–69.3 mm SL; UFRGS 22522, 1, 92.2 mm SL; UFRGS 22710, 5, 62.2–91.0 mm SL; UFRGS 22903, 3, 50.1–63.5 mm SL; UFRGS 24547, 3, 60.0–93.5 mm SL; UFRGS 28570, 2, 50.6–55.6 mm SL; UFRGS 28571, 5, 42.4–49.4 mm SL; UFRGS 28578, 12, 51.1–75.2 mm SL; UFRGS 28583, 4, 57.9–67.3 mm SL; UFRGS 28591, 1, 80.27 mm SL. Ituglanis boticario: LIRP 11010, 1 paratype (c&s); LIRP 11012, 1 paratype, 59.7 mm SL. Ituglanis crispim: MZUSP 126762, holotype, 29.3 mm SL; MZUSP 126756, 3 paratypes (1 c&s), 30.8–32.7 mm SL. Ituglanis eichhorniarum: MCP 36243, 1, 26.0 mm SL; MCP 36244, 1, 33.5 mm SL; MZUEL 12190, 6, 21.1–30.6 mm SL; MZUSP 37605, 2 c&s; MZUSP 052511, 4, 28.1–34.6 mm SL. Ituglanis epikarsticus: MZUSP 79869, holotype, 26.0 mm SL; MZUSP 79871, 1 paratype (c&s); MZUSP 79872, 1 paratype (c&s). Ituglanis goya: MZUSP 119759, holotype, 64.6 mm SL; MZUSP 53973, 1 paratype (c&s); MZUSP 114319, 2 paratypes, 53.4–55.8 mm SL; MZUSP 114359, 5 paratypes, 34.4–42.1 mm SL; MZUSP 114397, 1 paratype, 58.3 mm SL; ANSP 200229, 4 paratypes, 55.78–64.36 mm SL. Ituglanis herberti: MZUEL 09074, 5, 34.5–45.9 mm SL; MZUSP 2209, 1, 140.9 mm SL; MZUSP 22186, 1, 141.1 mm SL; NUP 5794, 1, 59.8 mm SL; NUP 11044, 1, 79.0 mm SL; NUP 21489, 1, 85.7 mm SL. Ituglanis ina: MZUSP 24153, 1, 33.0 mm SL; MZUSP 107002, 1, 20.8 mm SL; MZUSP 107066, 1, 22.9 mm SL. Ituglanis inusitatus: UFRGS 21829, holotype, 62.2 mm SL; UFRGS 19311, 1 paratype, 56.6–64.9 mm SL; UFRGS 21242, 1 paratype, 32.8 mm SL; UFRGS 20201, 8 (1 c&s), 43.3–70.2 mm SL; UFRGS 28855, 1, 131.1 mm SL. Ituglanis macunaima: MZUSP 88452, holotype, 29.8 mm SL; MZUSP 86237, 4 paratypes, 23.7–31.7 mm SL; MZUSP 86251, 1 paratype, 22.4 mm SL; MZUSP 86272, 1 paratype, 26.4 mm SL; ANSP 187244, paratypes, 2, 24.5–25.4 mm SL; MZUSP 103799, 2 (c&s). Ituglanis mambai: MZUSP 94719, 4 paratypes, 26.3–65.9 mm SL. Ituglanis nebulosus: MZUSP 69574, 1 paratype (c&s). Ituglanis paraguassuensis: USNM 301016, 5 paratypes, 18.8–36.0 mm SL. Ituglanis parahybae: MCP 18032, 1, 46.2 mm SL; MZUSP 79810, 2 (1 c&s), 41.4 mm SL; MZUSP 115069, 3, 51.2–64.3 mm SL. Ituglanis passensis: MZUSP 80098, 3 (1 c&s), 25.9–49.4 mm SL; MZUSP 80099, 2, 49.5–52.6 mm SL. Ituglanis proops: MZUSP 60226, 1, 71.1 mm SL; MZUSP 60255, 9 (1 c&s), 55.7–76.6 mm SL; MZUSP 61798, 1, 84.0 mm SL; MZUSP 70723, 2, 41.5–59.4 mm SL; MZUSP 83728, 2, 44.8–54.5 mm SL. Ituglanis ramiroi: MZUSP 79865, holotype, 27.3 mm SL; MZUSP 79866, 2 paratypes (c&s); MZUSP 79867, 3 paratypes (2 c&s), 29.2 mm SL; MZUSP 79868, 1 paratype, 28.7 mm SL. Ituglanis sp.: MCP 22144, 1, 55.9 mm SL; MCP 30716, 1, 85.3 mm SL; MCP 41144, 2, 45.0–75.0 mm SL; MCP 50883, 1, 67.9 mm SL; UFRGS 19949, 1, 62.3 mm SL; UFRGS 19950, 1 c&s, 51.7 mm SL; UFRGS 20373, 1, 53.9 mm SL; MCP 9285, 1, 54.3 mm SL; MCP 22725, 1, 34.5 mm SL; UFRGS 20370, 17, 31.5–57.7 mm SL; UFRGS 20371, 20 (3 c&s), 19.3–53.9 mm SL.; UFRGS 27982, 1, 74.4 mm SL; UFRGS 29187, 2 (1 c&s), 56.1–58.5 mm SL; UFRGS 29188, 2, 55.5–82.1 mm SL; UFRGS 8848, 1 c&s; UFRGS 14169, 1, 56.5 mm SL; UFRGS 20372, 4 (1 c&s), 54.7–60.2 mm SL.

Acknowledgments​

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This research is part of the first author’s dissertation within the Programa de Pós-Graduação em Biologia Animal at the UFRGS. We thank the following ichthyological collections and their curators and staff for loan material and assistance during visits: ANSP, LIRP, MZUSP, MZUEL, and MCP. Juliana M. Wingert and Rafael Angrizani for their help in the molecular procedures at UFRGS and Jean C. C. Pires for their help in field trips and figure editing support. Mario de Pinna for sponsoring part of the genetic sequencing, which resulted from molecular laboratory bench work conducted at MZUSP. We thank Marina B. Mendonça (UFPA) for early discussions that aided in distinguishing the new species. The manuscript was improved by the valuable comments and suggestions provided by Maria Elina Bichuette (UFSCar) and Vinícius Reis (MZUSP).

References​

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Authors

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Nathana Bressan¹ , Laura M. Donin² and Juliano Ferrer¹

^[1]    Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9090, 91540-000 Porto Alegre, RS, Brazil. (NB) nathana.pires@gmail.com (corresponding author), (JF) julianoferrer@gmail.com.

^[2]    Seção de Peixes, Museu de Zoologia da Universidade de São Paulo, Av. Nazaré, 481, Ipiranga, 04263-000 São Paulo, SP, Brazil. (LMD) lauramdonin@usp.br.

Authors’ Contribution

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Nathana Bressan: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Resources, Writing-original draft, Writing-review and editing.

Laura M. Donin: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Writing-review and editing.

Juliano Ferrer: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Resources, Supervision, Writing-original draft, Writing-review and editing.

Ethical Statement​

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The fish were collected under permission issued by the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio/SISBIO number 81917–1) and Ethical Committee for Animal Use in Experiments of Universidade Federal do Rio Grande do Sul (CEUA/UFRGS number 24434). All specimens collected were anesthetized and euthanized using a concentrated Eugenol solution (Lucena et al., 2013).

Competing Interests

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The author declares no competing interests.

Data availability statement

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The authors confirm that the data supporting the findings of this study are available within the article.

Funding

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This study was financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES), Finance Code 001 (Process number 88887.712445/2022–00 to NB; 88887.639838/2021–00 to LMD) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (PNPD scholarship process number 88887.463771/2019–00 to JF).

How to cite this article

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Bressan N, Donin LM, Ferrer J. A new species of Ituglanis (Siluriformes: Trichomycteridae) from the Uruguai River basin closely related to congeners from Atlantic coastal drainages. Neotrop Ichthyol. 2025; 23(3):e250071. https://doi.org/10.1590/1982-0224-2025-0071

Copyright​

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Distributed under

Creative Commons CC-BY 4.0

© 2025 The Authors.

Diversity and Distributions Published by SBI

Accepted August 29, 2025

Submitted April 19, 2025

Epub November 11, 2025