Inpaichthys parauapiranga, Ferreira & Ribeiro & Lima & Silva & Ferreira & Mirande, 2024

Ferreira, Katiane M., Ribeiro, Alexandre C., Lima, Flávio C. T., Silva, Hugmar P. da, Ferreira, Daniela C. & Mirande, Juan Marcos, 2024, A new species of Inpaichthys from the rio Canamã, rio Aripuanã basin, Mato Grosso State, Brazil, with a redefinition of the genus (Characidae: Stethaprioninae), Neotropical Ichthyology (e 230113) 22 (1) : -

Inpaichthys parauapiranga , new species

urn:lsid:zoobank.org:act:94422A47-3AAF-47D1-9832-17A364AFE9CB

( Figs. 2–4; Tab. 1)

Holotype. CPUFMT 7908, 25.4 mm SL, Brazil, Mato Grosso State, Aripuanã, tributary of the rio Canamã, rio Aripuanã basin, upper rio Madeira basin, 10º24’40”S 58º54’13”W, 14 Mar 2021, A. C. Ribeiro & H. Pains da Silva.

Paratypes. All from the same locality of the holotype. CI-FML 7946, 4, 14.3–16.0 mm SL; CPUFMT 7891, 51, 10.3–25.4 mm SL (8 c&s, 16.1–24.4 mm SL); ZUEC 17698 , 4 , 13.7–16.1 mm SL; collected with the holotype; CPUFMT 7892, 10, 12.9–23.6 mm SL, 20 Aug 2021, H. Pains da Silva. CPUFMT 7893, 11, 13.1–24.2 mm SL, 20 Aug 2021, H. Pains da Silva. MUBIO 113 , 5 , 19.0– 26.3 mm SL; ZUEC 17920 , 4 , 20.9–22.4 mm SL, 25 Oct 2022, F. C. P. Dagosta, T. J. Seren, B. A. Nagamatsu & J. Damasceno .

Diagnosis. Inpaichthys parauapiranga can be easily distinguished from both I. kerri and I. nambiquara by its life color pattern. Inpaichthys parauapiranga has six red dotted longitudinal stripes on the flanks that are absent in I. kerri and I. nambiquara . Additionally, I. parauapiranga has a narrow dark midlateral stripe along the longitudinal septum of body, extending from second humeral blotch to median caudal-fin rays (vs. a large dark midlateral stripe along longitudinal septum of body extending from snout to caudal peduncle in I. kerri and I. nambiquara ). Inpaichthys parauapiranga can also be distinguished from I. kerri by the following combination of characters: presence of two humeral blotches (vs. absence of humeral blotches); five scale rows between dorsal-fin origin and lateral line (vs. six scale rows between dorsal-fin origin and lateral line); and 12–14 circumpeduncular scales (vs. 16 circumpeduncular scales). Inpaichthys parauapiranga is also distinguished from I. nambiquara by the following combination of characters: adipose fin present (vs. adipose fin absent); 21–25 anal-fin branched rays (vs. 16–18 anal-fin branched rays); two humeral blotches (vs. a single humeral blotch), and largest dentary teeth with three cusps (vs. largest dentary teeth with five cusps). We found three morphological autapomorphies for I. parauapiranga : the absence of a bony rhinosphenoid (34:0), the absence of a conspicuous ethmopalatine cartilage (208:0), and the absence of denticles on gill rakers (300:1).

Description. Morphometric and meristic data for holotype and paratypes in Tab. 1. Largest specimen examined 26.3 mm SL. Body laterally compressed. Greatest body depth slightly anterior to vertical through dorsal-fin origin. Dorsal profile of head convex from tip of upper jaw to vertical through anterior nostril; slightly convex from that point to tip of supraoccipital spine. Dorsal body profile slightly convex from tip of supraoccipital spine to dorsal-fin origin; straight along dorsal-fin base; straight from terminus of dorsal-fin base to adipose-fin insertion, and slightly concave posteriorly from that point to anteriormost procurrent caudal-fin ray. Ventral profile of head and body convex from tip of lower jaw to pelvic-fin insertion, straight from that point to anal-fin origin, straight along anal-fin base and slightly concave along caudal peduncle.

Mouth slightly sub-superior, with dentary protruding slightly over anterior tip of premaxilla. Posterior terminus of maxilla surpassing vertical through anterior margin of eye. Premaxillary teeth in single misaligned row ( Fig. 3), with 7(8), 8*(6) or 9(6) tricuspid teeth, with median cusps slightly more developed and the third tooth usually positioned more externally. Maxilla with 6(3), 7(8), 8(4), 9*(1), or 10(2) teeth, the first tooth tricuspid, remaining teeth conical. Dentary with four tricuspid teeth, followed by eight to twelve smaller conical teeth.

Scales cycloid. Three to five radii, and inconspicuous circuli anteriorly. Lateral line incomplete, with 6(7) or 7*(14) perforated scales. Longitudinal scale series including lateral-line scales 31*(9), 32(1), 33(7), 34(2), or 35(1). Five* (20) scale rows between dorsal-fin origin and lateral line. Four* (20) scale rows between lateral line and pelvic fin insertion. Predorsal scales 11(6), 12(9), 13(4), or 14*(1). Circumpeduncular scales 12(3), 13(12), or 14*(2). Single row of 11–16 scales covering base of anal-fin rays. Presence of two rows of scales extending over caudal-fin lobes; squamation covering evenly both caudal lobes.

Supraneurals 7(7) or 8(1). Dorsal-fin rays iii, 9*(20), first unbranched dorsal-fin ray visible only in c&s specimens. Dorsal-fin origin at midpoint of standard length. First dorsal-fin pterygiophore located after neural spine of 11 th vertebra (8). First unbranched ray about half the length of second ray. Adipose fin present. Pectoral-fin rays i,10(20), its tip typically falling short before reaching vertical through pelvic-fin insertion, reaching that point in few (5) specimens. Pelvic-fin rays i,6(3) or i,7*(17). Tip of adpressed pelvic fin not reaching origin of anal fin. Anal-fin rays iv(6), 21(1), 22(5), 23(5), 24*(9), or 25(1). First anal-fin pterygiophore inserted behind haemal spine of 15 th vertebra (8). Caudal fin forked, lobes similar in size; principal caudal-fin rays i,9/8,i (20). First gill arch with 10(15) gill rakers on hypobranchial and ceratobranchial, 6(2) or 7(9) on epibranchial, and one on cartilage between ceratobranchial and epibranchial. Four (1) branchiostegals, 3(1) on anterior ceratohyal, and 1(1) on posterior ceratohyal. Vertebrae 31(1), 32(3), or 33(4).

Coloration in alcohol. Overall basic color pale yellow ( Fig. 2A). Dark chromatophores concentrated on the dorsal surface of the head, from tip of the snout to end of supraoccipital spine, and extend posteriorly over the predorsal scales. Small, scattered, dark chromatophores at infraorbitals, preopercle and opercle bones. Two diffuse humeral spots separated by a clearer area. Anterior humeral blotch located at level of second and third perforated scales of lateral line and extends to about one or two scales rows above lateral line. Second humeral blotch located at sixth and/or seventh perforated scales of lateral line and extending to approximately one row of scales above lateral line. Four brown diffuse lateral stripes present in the flanks, from dorsal profile to midline region. Body sides above midline with chromatophores in middle part of scales, chromatophores absent on posterior edges of scales. Scattered chromatophores below median stripe, with chromatophores concentrated at the edges of myosepta of posterior half of lower body above anal fin. All fins without pigmentation. Immediately after preservation ( Fig. 2B), two conspicuous rectangular-shaped humeral blotches present, being the anteriormost blotch more diffuse when compared to the second humeral blotch, and still retaining five to six red dotted longitudinal stripes along body sides. Dorsal, adipose, pectoral, pelvic and anal fins yellow-orange at distal region. Caudal yellowish at the proximal region. Dorsal, caudal, and anal fins with scattered dark chromatophores along interradial membranes.

Coloration in life. Description based on photographs taken in the field of two specimens ( Fig. 4), and of a specimen photographed by Fernando C. P. Dagosta ( MUBIO 113, SL undetermined). Overall body coloration silvery, grayish dorsally, with a reddish tint in the upper third of the facial bones, occupying the upper half of the operculum and infraorbital 3 to infraorbital 5 (apparently imparted by the transparency of these bones, exposing red pigmentation of the gills), upper margin of eye also red. Blue iridescence present on the flanks, longitudinally to opercle to caudal peduncle. Five red dotted longitudinal stripes along the body sides and a narrow iridescent midlateral stripe along longitudinal septum of body, extending from first humeral blotch to median caudal-fin rays. Dorsal, anal, adipose, pectoral, and pelvic fins yellow-orange (being orange specially concentrated at posterior half of pectoral and anal-fin rays in some specimens) ( Fig. 4B), caudal fin yellowish. Tip of anal fin white, forming a stripe along anal-fin margin.

Sexual dimorphism. Contrary to what is observed for I. kerri and I. nambiquara (see Remarks of I. nambiquara ), no secondary sexual characters were detected on examined specimens of I. parauapiranga .

Geographical distribution. Inpaichthys parauapiranga is known from a tributary of the rio Canamã, a tributary of rio Aripuanã, itself a tributary of the rio Madeira, Amazon basin, Mato Grosso State, Brazil ( Fig. 5).

Ecological notes. The type-locality is a narrow and shallow stream (approximately 2 m wide and 60 cm deep), with clear water, slow to moderately-flowing current, and a sandy bottom with abundant aquatic vegetation, where specimens were typically captured ( Fig. 6). Stomach contents of four paratypes revealed mainly remnants of insect larvae.

Etymology. The specific epithet parauapiranga derives from Tupi language, paraua, meaning blotch and piranga, meaning red, and it is in allusion to its color pattern in living specimens. A noun in apposition.

Conservation status. Inpaichthys parauapiranga was collected at only one sampling site. Several specimens were collected at the type-locality, indicating that the species is relatively common at this site, which is currently moderately well preserved. However,

the species is already being targeted by fish collectors operating for the aquarium hobby and unsustainable levels of extraction of wild specimens may pose a threat to the species in the future. Thus, we suggest that pending more efforts to establish the distributional range, population, and impacts from capture for the aquarium hobby, Inpaichthys parauapiranga should be classified as Data Deficient (DD), according to the International Union for Conservation of Nature ( IUCN) categories and criteria ( IUCN Standards and Petitions Subcommittee, 2022).

Remarks. The phylogenetic hypothesis herein presented was obtained in SEP64

(i.e., each character weighted according to its own homoplasy and using a K-value

of 64, the mildest explored). In these conditions we found three most parsimonious

trees of 70439 steps (5600 of them morphological) and fit = 508.27677 ( Fig. 7). The

monophyly of Inpaichthys , including I. nambiquara as the sister group a clade composed

of I. kerri and I. parauapiranga , was obtained in all performed analyses. In SEP64 the

monophyly of the genus is moderately well supported ( GC =36), while the relationships

of I. kerri and I. parauapiranga have better support ( GC =71). In the final hypothesis,

Nematobrycon palmeri Eigenmann, 1911 was obtained as the sister group of Inpaichthys ,

but such relationship is weakly supported (negative GC value) and unstable among

the most parsimonious trees of different analytical conditions (Freq = 41 and GC = - 16

in the optimal trees of the explored conditions). Also with low support, we found as successive sister groups of Inpaichthys and Nematobrycon the clade composed of Carlana , Pseudochalceus , and Rhoadsia , and the group composed of Hollandichthys Eigenmann, 1909 and Rachoviscus Myers, 1926 ( Fig. 7). The condition in which the number of morphological steps was lowest (5574) is SEP32. In the most parsimonious trees under SEP32 (70685 steps and fit = 738.45437), the relationships between Inpaichthys and Nematobrycon as the sister group of the clade of Carlana , Pseudochalceus , and Rhoadsia are the same than in SEP64. However, the sister group of this clade is composed of the genus Jupiaba Zanata, 1997 ( J. ajuricaba (Marinho, Lima, 2009) , J. anterior (Eigenmann, 1908) , J. anteroides (Géry, 1965) , J. polylepis (Günther, 1864) , and J. poranga Zanata, 1997 ). In SEP64, we found eight morphological synapomorphies supporting the monophyly of Inpaichthys : nasal septum of mesethmoid formed by two parallel lamellae (9:1), absence of a dorsal expansion of rhinosphenoid projected medial to olfactory nerves (35:0), short supraoccipital spine covering dorsally only anterior axis of neural complex of Weberian apparatus (62:1), articulation between second and third infraorbitals anteroventrally angled (86:1), absence of anguloarticular portion of mandibular laterosensory canal (105:1), frontal and pterotic laterosensory canals forming an angle on pore receiving infraorbital canal (118:1), maxillary teeth extended approximately to half maxillary length (191:0), and presence of 24 or fewer branched anal-fin rays (420:0). The sister-group relationship of I. kerri and I. parauapiranga is supported by three morphological synapomorphies: three cusps on anterior dentary teeth (201:0), metapterygoid foramen as a simple rounded opening (228:0), and first anal-fin pterygiophore located ventral to last dorsal-fin pterygiophores (416:1).