Research Article |
Corresponding author: Vanessa Meza-Vargas ( meza.sv@gmail.com ) Academic editor: Nicolas Hubert
© 2024 Vanessa Meza-Vargas, Jorge L. Ramirez, Nathan K. Lujan.
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.
Citation:
Meza-Vargas V, Ramirez JL, Lujan NK (2024) The ornate rubbernose pleco (Siluriformes, Loricariidae, Chaetostoma), a new species from the Ucayali River Basin, Peru. Zoosystematics and Evolution 100(4): 1387-1400. https://doi.org/10.3897/zse.100.118522
|
A new species in the rubbernose catfish genus Chaetostoma is described from the Aguaytia, Pisqui and Palcazu Rivers, which drain the Pampa de Sacramento Region in the Ucayali River drainage of central Peru. The new species is distinguished from congeners, except C. anomalum, C. branickii, C. dorsale, C. leucomelas, C. microps, C. nudirostre, C. palmeri and C. thomsoni by having distinct, white, variably-shaped spots or vermiculations ½–2× nostril diameter on dark grey to black background on the head (vs. spots absent or black on light-coloured background). The new species is distinguished from C. anomalum, C. branickii, C. dorsale, C. microps, C. nudirostre and C. thomsoni by having highly variable, distinct white spots, vermiculations or bands ½–10× nostril diameter on the body, from C. leucomelas by having dorsal and caudal fin indistinctly and variably-patterned with zero to four bands (vs. dorsal and caudal fin consistently having five or more uniform bands) and from C. palmeri by having two predorsal plates (vs. three), supraoccipital excrescence present (vs. absent) and pelvic-fin insertion slightly posterior to dorsal-fin insertion (vs. pelvic-fin insertion at middle of dorsal-fin base). Species delimitation analyses of the COI and Cytb genes further support the recognition of this new species.
Amazon, Andes, Chaetostoma clade, freshwater, molecular, Neotropical, taxonomy
With over 1060 currently valid species, 19% of which (200) were described in the last decade, the suckermouth armoured catfish family Loricariidae is the fifth largest vertebrate family and one of the fastest growing (
All but one species of Chaetostoma (C. platyrhynchus) are externally distinguished from most other loricariid genera by having the anterior and anterolateral snout margins free of plates, with this region instead being covered by a broad band of naked (i.e. unplated) skin, lacking tentacles. Five other loricariid genera also have unplated snout margins (Ancistrus Kner, 1854, Corumbataia (Britski, 1997), Paulasquama Armbruster & Taphorn, 2011, Soromonichthys Lujan & Armbruster, 2011 and Transancistrus Lujan, Meza-Vargas & Barriga-Salazar, 2015), but only Ancistrus and Transancistrus are sympatric with Chaetostoma. Chaetostoma can be easily distinguished from Ancistrus by lacking snout tentacles (vs. tentacles present), having at least five longitudinal series of plates at the shallowest part of the caudal peduncle (vs. three) and having eight or more branched dorsal-fin rays (vs. seven). The only Chaetostoma with a fully-plated snout (C. platyrhynchus) is restricted to the upper Caqueta and Napo drainages of Colombia and Ecuador, respectively; it shares all other traits above with congeners.
Chaetostoma has never undergone a comprehensive species-level taxonomic revision, though
In scientific literature, the species was first recognised as new by
This study is based mostly on 12 formalin-fixed, 70% ethanol-preserved, museum-catalogued specimens of the undescribed species collected from the Aguaytia River and the Raya and Omaiz Rivers in the Palcazu River drainage (Fig.
Genetic samples of fin or muscle tissue were dissected prior to specimen fixation and individually linked to source specimens using unique, matching alphanumeric tags on voucher specimens and cryosafe tubes, then preserved in 95% ethanol. Whole genomic DNA was extracted from tissue subsamples using a salt precipitation protocol (Alijanabi and Martinez 1997). DNA sequence data were obtained for two mitochondrial markers: Cytochrome C oxidase I (COI) and Cytochrome b (CytB). A 658-base region of COI was amplified using the primers ANOSCOIF and ANOSCOIR (Ramirez and Galetti 2015) and a 1150-base region of the mitochondrial CytB gene was amplified using the primers and protocol of
Sequences for each gene were automatically aligned using Clustal W (
Tissue samples used in the molecular species delimitation analyses, including GenBank accession number (coI = Cytochrome oxidase subunit I, cytb = cytochrome b), voucher specimen catalogue number, country and drainages of origin. Bold accession numbers = new sequences for this study.
Taxa | Tissues Number | cytb | coI | Catalogue Number | Country | Drainage |
---|---|---|---|---|---|---|
Chaetostoma anale | T24822 | OL303592 | – | ROM 107267 | Colombia | Orteguasa |
Chaetostoma anale | T24946 | OL303593 | OK514631 | ROM 107837 | Colombia | Orteguasa |
Chaetostoma anale | T24906 | OL303604 | OK514628 | ROM 107811 | Colombia | Caqueta |
Chaetostoma anale | T24907 | OL303605 | OK514629 | ROM 107811 | Colombia | Caqueta |
Chaetostoma anomalum | T631 | OL303608 | – | INHS 55455 | Venezuela | Maracaibo |
Chaetostoma bifurcum | T13602 | KP960196 | – | ROM 93687 | Ecuador | Esmeraldas |
Chaetostoma bifurcum | T13603 | OL303609 | – | ROM 93687 | Ecuador | Esmeraldas |
Chaetostoma bifurcum | T13665 | OL303610 | – | ROM 93721 | Ecuador | Guayas |
Chaetostoma bifurcum | T13896 | OL303611 | – | ROM 93787 | Ecuador | Santa Rosa |
Chaetostoma bifurcum | T13897 | OL303612 | – | ROM 93787 | Ecuador | Santa Rosa |
Chaetostoma breve | P6292 | KP960190 | – | AUM 46515 | Peru | Marañon |
Chaetostoma breve | PE08208 | OL303613 | – | MHNG 2712.047 | Peru | Huallaga |
Chaetostoma breve | PE08213 | OL303614 | – | MHNG 2712.048 | Peru | Huallaga |
Chaetostoma breve | PE08648 | OL303615 | – | MHNG 2712.074 | Peru | Huallaga |
Chaetostoma breve | PE08673 | OL303616 | – | MHNG 2712.078 | Peru | Huallaga |
Chaetostoma breve | P6294 | OL303617 | – | AUM 46516 | Peru | Marañon |
Chaetostoma breve | T14360 | OL303618 | – | ROM 93950 | Ecuador | Napo S |
Chaetostoma breve | T19715 | OL303619 | – | ROM 100323 | Ecuador | Napo N |
Chaetostoma breve | T19716 | OL303620 | – | ROM 100320 | Ecuador | Napo N |
Chaetostoma breve | T14224 | OL303621 | – | ROM 93923 | Ecuador | Pastaza |
Chaetostoma breve | T14005 | OL303622 | – | ROM 93848 | Ecuador | Santiago |
Chaetostoma brevilabiatum | 6630 | OL303623 | – | ANSP 189597 | Colombia | Honda |
Chaetostoma brevilabiatum | 6631 | OL303624 | – | ANSP 189597 | Colombia | Honda |
Chaetostoma cf. anale | T19707 | OL303594 | – | ROM 100322 | Ecuador | Napo |
Chaetostoma cf. anale | T19708 | OL303595 | OK514634 | ROM 100322 | Ecuador | Napo |
Chaetostoma cf. anale | T19606 | OL303628 | OK514632 | ROM 100250 | Ecuador | Napo |
Chaetostoma cf. anale | T19647 | OL303629 | – | ROM 100263 | Ecuador | Napo |
Chaetostoma cf. fischeri | T9034 | KP960197 | – | STRI 11581 | Panama | Tuira |
Chaetostoma cf. lineopunctatum | CH153 | OL303630 | – | MUSM 44253 | Peru | Huallaga |
Chaetostoma cf. lineopunctatum | PE08318 | OL303631 | – | MHNG 2712.057 | Peru | Huallaga |
Chaetostoma cf. lineopunctatum | PE08545 | OL303632 | – | MHNG 2712.069 | Peru | Huallaga |
Chaetostoma cf. loborhynchos | CH200 | OL303633 | – | MUSM 44899 | Peru | Huallaga |
Chaetostoma cf. loborhynchos | CH202 | OL303634 | – | MUSM 44899 | Peru | Huallaga |
Chaetostoma cf. loborhynchos | CH2023 | OL303635 | – | MUSM 44899 | Peru | Huallaga |
Chaetostoma cf. loborhynchos | CH204 | OL303636 | – | MUSM 44899 | Peru | Huallaga |
Chaetostoma changae | PE08442 | OL303637 | – | MHNG 2712.064 | Peru | Huallaga |
Chaetostoma changae | PE08543 | OL303638 | – | MHNG 2712.067 | Peru | Huallaga |
Chaetostoma chimu | TICT-FCA-07 | – | FBCH009-21 | – | Colombia | Meta |
Chaetostoma chimu | TICT-FCA-223 | – | FBCH118-21 | – | Colombia | Meta |
Chaetostoma chimu | TICT-FCA-148 | – | FBCH143-21 | – | Colombia | Meta |
Chaetostoma daidalmatos | CH140 | OL303639 | – | MUSM 44845 | Peru | Huallaga |
Chaetostoma daidalmatos | CH141 | OL303640 | – | MUSM 44845 | Peru | Huallaga |
Chaetostoma daidalmatos | PE08191 | OL303641 | – | MHNG 2712.045 | Peru | Huallaga |
Chaetostoma daidalmatos | PE08207 | OL303642 | – | MHNG 2712.051 | Peru | Huallaga |
Chaetostoma daidalmatos | PE08347 | OL303644 | – | MHNG 2712.055 | Peru | Huallaga |
Chaetostoma dermorhynchus | T14258 | KP960191 | – | ROM 93656 | Ecuador | Pastaza |
Chaetostoma dermorhynchus | T14287 | OL303647 | – | ROM 93656 | Ecuador | Pastaza |
Chaetostoma dermorhynchus | T14293 | OL303648 | – | ROM 93946 | Ecuador | Bobonaza |
Chaetostoma dermorhynchus | T14296 | OL303649 | – | ROM 93946 | Ecuador | Bobonaza |
Chaetostoma dermorhynchus | T14308 | OL303650 | – | ROM 93946 | Ecuador | Bobonaza |
Chaetostoma dorsale | TICT-FCA-08 | – | FBCH008-21 | – | Colombia | Meta |
Chaetostoma dorsale | TICT-FCA-168 | – | FBCH078-21 | – | Colombia | Meta |
Chaetostoma dorsale | TICT-FCA-185 | – | FBCH086-21 | – | Colombia | Meta |
Chaetostoma dorsale | TICT-FCA-244 | – | FBCH091-21 | – | Colombia | Meta |
Chaetostoma fischeri | T9026 | KP960195 | – | STRI 7604 | Panama | Chagres |
Chaetostoma fischeri | T9027 | OL303651 | – | STRI 905 | Panama | Bayano |
Chaetostoma fischeri | T9036 | OL303652 | – | STRI 12274 | Panama | Bayano |
Chaetostoma fischeri | T9037 | OL303653 | – | STRI | Panama | Chagres |
Chaetostoma fischeri | STRI-01740 | – | BSFFA489-07 | – | Panama | Tuira |
Chaetostoma fischeri | STRI-01732 | – | BSFFA490-07 | – | Panama | Acla |
Chaetostoma fischeri | STRI-01735 | – | BSFFA491-07 | – | Panama | Bayano |
Chaetostoma fischeri | STRI-01754 | – | BSFFA492-07 | – | Panama | Tuira |
Chaetostoma fischeri | STRI-01760 | – | BSFFA493-07 | – | Panama | Bayano |
Chaetostoma fischeri | STRI-07104 | – | BSFFA735-07 | – | Panama | Chagres |
Chaetostoma formosae | T17431 | OL303654 | – | ROM 95260 | Colombia | Meta |
Chaetostoma formosae | TICT-FCA-64 | – | FBCH052-21 | – | Colombia | Meta |
Chaetostoma guairense | VZ122 | OL303655 | – | INHS 34786 | Venezuela | Limon |
Chaetostoma jegui | Tec63785 | OL303596 | OK514635 | LBP 15478 | Brazil | Branco |
Chaetostoma jegui | Tec63786 | OL303597 | OK514636 | LBP 15478 | Brazil | Branco |
Chaetostoma joropo | T17428 | OL303656 | – | ROM 95259 | Colombia | Meta |
Chaetostoma joropo | T17429 | OL303657 | – | ROM 95259 | Colombia | Meta |
Chaetostoma joropo | TICT-FCA-208 | – | FBCH134-21 | – | Colombia | Meta |
Chaetostoma joropo | TICT-FCA-224 | – | FBCH136-21 | – | Colombia | Meta |
Chaetostoma joropo | TICT-FCA-245 | – | FBCH137-21 | – | Colombia | Meta |
Chaetostoma leucomelas | – | – | CIUA550-20 | – | Colombia | Cauca |
Chaetostoma leucomelas | – | – | CIUA557-20 | – | Colombia | Cauca |
Chaetostoma leucomelas | CIUA-7439 | – | UDEA074-18 | – | Colombia | Cauca |
Chaetostoma leucomelas | CIUA-7441 | – | UDEA075-18 | – | Colombia | Cauca |
Chaetostoma leucomelas | CIUA-7482 | – | UDEA076-18 | – | Colombia | Magdalena |
Chaetostoma leucomelas | CIUA-7491 | – | UDEA077-18 | – | Colombia | Magdalena |
Chaetostoma lineopunctatum | P4772 | GU569899 | EU359409 | ANSP 180446 | Peru | Urubamba |
Chaetostoma lineopunctatum | P4814 | GU569913 | EU359410 | ANSP 180448 | Peru | Madre de Dios |
Chaetostoma lineopunctatum | PE08047 | KP960199 | – | MHNG 2712.041 | Peru | Ucayali |
Chaetostoma lineopunctatum | T10088 | OL303658 | – | AUM 51166 | Peru | Madre de Dios |
Chaetostoma lineopunctatum | T10089 | OL303659 | – | AUM 51166 | Peru | Madre de Dios |
Chaetostoma loborhynchos | TK70561 | KJ947862 | – | MUSM 20291 | Peru | Tulumayo |
Chaetostoma loborhynchos | TK70563 | KJ947864 | – | MUSM 20291 | Peru | Tulumayo |
Chaetostoma loborhynchos | TK70579 | KJ947865 | – | MUSM 20307 | Peru | Paucartambo |
Chaetostoma loborhynchos | TK70580 | KJ947866 | – | MUSM 20307 | Peru | Paucartambo |
Chaetostoma loborhynchos | TK70581 | KJ947867 | – | MUSM 20307 | Peru | Paucartambo |
Chaetostoma marmorescens | CH198 | KP960194 | – | MUSM 44898 | Peru | Huallaga |
Chaetostoma marmorescens | CH197 | OL303660 | – | MUSM 44898 | Peru | Huallaga |
Chaetostoma marmorescens | CH199 | OL303661 | – | MUSM 44898 | Peru | Huallaga |
Chaetostoma microps | T14125 | KP960189 | – | ROM 93895 | Ecuador | Santiago |
Chaetostoma microps | CH121 | OL303662 | – | MUSM 44313 | Peru | Huallaga |
Chaetostoma microps | CH149 | OL303665 | – | MUSM 44869 | Peru | Huallaga |
Chaetostoma microps | CH150 | OL303666 | – | MUSM 44869 | Peru | Huallaga |
Chaetostoma microps | PE08190 | OL303667 | – | MHNG 2712.046 | Peru | Huallaga |
Chaetostoma microps | PE08580 | OL303668 | – | MHNG 2712.07 | Peru | Huallaga |
Chaetostoma microps | P6034 | OL303669 | – | AUM 45518 | Peru | Marañon |
Chaetostoma microps | T14364 | OL303670 | – | ROM 93949 | Ecuador | Napo S |
Chaetostoma microps | MEPN1255 | OL303671 | – | MEPN 1255 | Ecuador | Napo S cave |
Chaetostoma microps | MEPN1259 | OL303672 | – | MEPN 19165 | Ecuador | Napo S cave |
Chaetostoma microps | ROM 93902 | OL303673 | – | ROM 93902 | Ecuador | Santiago |
Chaetostoma microps | T14096 | OL303674 | – | ROM 93877 | Ecuador | Yungantza |
Chaetostoma microps | T14097 | OL303675 | – | ROM 93877 | Ecuador | Yungantza |
Chaetostoma milesi | JAM1984 | OL303677 | – | MPUJ | Colombia | Suaza |
Chaetostoma milesi | CIUA-8907 | – | UDEA079-18 | – | Colombia | Magdalena |
Chaetostoma milesi | T24605 | OL303676 | – | ROM 106963 | Colombia | Suaza |
Chaetostoma milesi | – | – | CIUA680-20 | – | Colombia | Magdalena |
Chaetostoma nudirostre | T2084 | OL303682 | – | ANSP 191471 | Venezuela | Valencia |
Chaetostoma orientale | B1464 | OL303679 | OK514638 | ANSP 199686 | Brazil | Xingu |
Chaetostoma orientale | B1472 | OL303680 | OK514639 | ANSP 199686 | Brazil | Xingu |
Chaetostoma orientale | B1487 | OL303681 | OK514640 | ANSP 199686 | Brazil | Xingu |
Chaetostoma orientale | 2606 | – | OK514647 | INPA-ICT 58146 | Brazil | Xingu |
Chaetostoma sacramento sp. nov. | PE08121 | OL303678 | – | MHNG 2712.042 | Peru | Ucayali |
Chaetostoma sacramento sp. nov. | LGBBF358 | OR875871 | OR859576 | MUSM 72046 | Peru | Ucayali |
Chaetostoma sacramento sp. nov. | LGBBF359 | OR875872 | OR859577 | MUSM 72046 | Peru | Ucayali |
Chaetostoma sacramento sp. nov. | MUSMT1564 | – | OR859578 | MUSM 71392 | Peru | Ucayali |
Chaetostoma sacramento sp. nov. | MUSMT1566 | – | OR859579 | MUSM 71392 | Peru | Ucayali |
Chaetostoma sp. Apure | T08954 | OL303683 | – | AUM 54034 | Venezuela | Apure |
Chaetostoma sp. Apure | T08955 | OL303684 | – | AUM 54034 | Venezuela | Apure |
Chaetostoma sp. Apure | T491 | OL303685 | – | AUM 41073 | Venezuela | Apure |
Chaetostoma sp. Apure | T621 | OL303686 | – | INHS 56147 | Venezuela | Apure |
Chaetostoma sp. CuruaUna | 525 | OL303599 | OK514641 | MCP 53005 | Brazil | Curua-Una |
Chaetostoma sp. L445 | T12930 | KP960193 | – | ROM 94925 | Colombia | Meta |
Chaetostoma sp. L445 | T17424 | OL303687 | – | ROM 95257 | Colombia | Meta |
Chaetostoma sp. L445 | T17425 | OL303688 | – | ROM 95257 | Colombia | Meta |
Chaetostoma sp. Meta | – | – | CIUA698-20 | – | Colombia | Cauca |
Chaetostoma sp. Meta | – | – | CIUA707-20 | – | Colombia | Cauca |
Chaetostoma stroumpoulos | CH120 | OL303689 | – | MUSM 44303 | Peru | Huallaga |
Chaetostoma stroumpoulos | CH142 | OL303691 | – | MUSM 44847 | Peru | Huallaga |
Chaetostoma stroumpoulos | PE08210 | OL303693 | – | MHNG 2712.049 | Peru | Huallaga |
Chaetostoma thomsoni | JAM1966 | OL303695 | – | ICNMHN 17768 | Colombia | Chucuri |
Chaetostoma thomsoni | – | – | CIUA541-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA542-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA543-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA544-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA545-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA546-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA547-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA553-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA554-20 | – | Colombia | Magdalena |
Chaetostoma thomsoni | – | – | CIUA559-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA560-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA563-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA565-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA566-20 | – | Colombia | Magdalena |
Chaetostoma thomsoni | – | – | CIUA570-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA572-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA574-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA576-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA579-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | CIUA580-20 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | UDEA080-18 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | UDEA083-18 | – | Colombia | Cauca |
Chaetostoma thomsoni | – | – | UDEA085-18 | – | Colombia | Cauca |
Chaetostoma trimaculineum | P6047 | OL303696 | – | AUM 45524 | Peru | Marañon |
Chaetostoma trimaculineum | T14136 | OL303697 | – | ROM 93894 | Ecuador | Santiago |
Chaetostoma vasquezi | T09945 | KP960192 | – | AUM 53812 | Venezuela | Caura |
Chaetostoma vasquezi | V27 | OL303698 | OK514643 | AUM 36555 | Venezuela | Caroni |
Chaetostoma vasquezi | V28 | OL303699 | OK514644 | AUM 36555 | Venezuela | Caroni |
Morphometric landmarks follow
Chaetostoma
sp. nov. Ucayali:
Holotype • Adult MUSM 72045; 65.1 mm SL; Peru, Ucayali Department, Padre Abad Province, Boqueron District, Shambillo, Amazon Basin, Ucayali River, unnamed left-bank tributary of Aguaytia River; 09°0'29.88"S, 75°37'1.92"W; alt. 365 m; 07 Aug 2022; D. Faustino, J. Chuctaya, C. Nolasco, O. Quispe.
Paratype : All Peru, Amazon – Ucayali River Basin • MHNG 2712.042, 1; 32.2 mm SL; tissues PE08-122, 123, 124; Padre Abad Province, Aguaytia River at mouth of the Boca Yurac River; 11 September 2008; S. Fisch- Muller, R. Covain, P. de Rham, H. Ortega, J. Figuerosa Minaya, J. Sanchez Ramirez • MUSM 71392, 4; 50.5–79.4 mm SL; Pasco Department, Oxapampa Province, Palcazu District, Raya River; 10°22'13.61"S, 75°7'52.90"W; 7 September 2022; R. Olivera, R. Quispe, J. Arana, M. Paniagua • MUSM 72046, 34; 44.2–12.5 mm SL; Ucayali Department, Padre Abad Province, Padre Abad District, Aguaytia River; 9°4'8.58"S, 75°30'51.48"W; 8 August 2022; D. Faustino, J. Chuctaya, C. Nolasco, R. Quispe • ANSP 182805, 3; 57.8–70.5 mm SL; same data as MUSM 71392 • ROM 114668, 4; 54.3–76.7 mm SL; same data as MUSM 71392.
Chaetostoma sacramento can be diagnosed from all congeners, except C. anomalum, C. branickii, C. dorsale, C. leucomelas, C. microps, C. nudirostre, C. palmeri and C. thomsoni by having distinct, white, variably-shaped spots or vermiculations ½–2× nostril diameter on grey to brown background on the head (vs. spots absent or black on light-coloured background). Chaetostoma sacramento is distinguished from C. anomalum, C. branickii, C. dorsale, C. nudirostre and C. thomsonii by having highly variable, small to large distinct white spots, vermiculations or bands on the body (vs. spots, vermiculations or bands absent or black on light-coloured background), from C. anomalum by having adipose fin fully formed (vs. rudimentary), from C. dorsale by having uniformly brown adipose fin (vs. adipose fin with black spot), from C. leucomelas by having golden spots across the dorsal fin rays (vs. light bands), from C. microps by having eight branched dorsal-fin rays (vs. nine), from C. nudirostre by having curved cheek odontodes (vs. strait), from C. palmeri by having two predorsal plates (vs. three), excrescence present (vs. absent) and pelvic-fin insertion slightly posterior of dorsal-fin insertion (vs. pelvic-fin insertion at middle of dorsal-fin base).
Morphometric data in Table
Morphometrics of Chaetostoma sacramento. Morphometric values as percentages of standard length (SL) or head length (HL). H = holotype, SD = standard deviation, (n = 11).
H | Min | Max | Mean | SD | |
---|---|---|---|---|---|
Standard length (mm) | 65.13 | 50.49 | 76.74 | 63.7 | – |
Percent of standard length | |||||
Head length | 33.9 | 34.6 | 37.6 | 36.0 | 1.0 |
Predorsal length | 43.4 | 41.9 | 47.3 | 45.1 | 1.5 |
Head-dorsal length | 9.8 | 8.7 | 11.1 | 9.9 | 0.7 |
Cleithral width | 33.6 | 29.3 | 33.4 | 32.0 | 1.2 |
Cleithral widest distance | 37.1 | 34.8 | 36.5 | 35.7 | 0.5 |
Head-pectoral length | 31.2 | 30.1 | 34.3 | 31.8 | 1.3 |
Thorax length | 21.7 | 19.2 | 23.9 | 21.3 | 1.2 |
Pectoral-spine length | 36.3 | 26.2 | 29.1 | 28.1 | 0.9 |
Abdominal length | 25.4 | 23.0 | 25.5 | 24.5 | 0.7 |
Pelvic-spine length | 25.7 | 24.8 | 28.5 | 26.4 | 1.0 |
Postanal length | 30.2 | 29.1 | 34.8 | 32.0 | 1.4 |
Anal-fin spine length | 15.0 | 8.7 | 10.4 | 9.8 | 0.5 |
Dorsal-pectoral distance | 27.9 | 28.5 | 31.0 | 29.8 | 0.7 |
Dorsal spine length | 26.7 | 25.5 | 29.4 | 27.8 | 1.0 |
Dorsal-pelvic distance | 24.0 | 21.5 | 24.1 | 23.1 | 0.7 |
Dorsal-fin base length | 28.7 | 25.0 | 26.4 | 25.5 | 0.4 |
Dorsal-fin base length | 26.2 | 22.8 | 26.3 | 23.8 | 0.9 |
Dorsal-adipose distance | 16.1 | 13.2 | 15.6 | 14.4 | 0.8 |
Adipose-spine length | 8.2 | 7.7 | 9.4 | 8.2 | 0.5 |
Adipose-up. caudal distance | 12.2 | 12.2 | 17.4 | 15.1 | 1.6 |
Caudal peduncle depth | 15.2 | 12.4 | 13.9 | 13.1 | 0.6 |
Adipose-low. caudal distance | 21.3 | 21.2 | 24.8 | 23.3 | 1.2 |
Adipose-anal distance | 20.9 | 18.6 | 22.4 | 20.7 | 1.0 |
Dorsal-anal distance | 17.1 | 15.6 | 17.0 | 16.3 | 0.5 |
Pelvic-dorsal distance | 28.9 | 26.9 | 29.7 | 27.9 | 0.9 |
Percent of head length | |||||
Head-eye length | 29.7 | 10.0 | 11.1 | 10.6 | 0.3 |
Orbit diameter | 14.0 | 5.2 | 6.6 | 5.9 | 0.4 |
Snout length | 71.4 | 22.7 | 24.9 | 23.6 | 0.7 |
Internares width | 14.5 | 4.6 | 5.7 | 5.2 | 0.4 |
Interorbital width | 45.0 | 13.8 | 16.1 | 15.1 | 0.7 |
Head depth | 71.9 | 24.7 | 26.3 | 25.6 | 0.5 |
Head width | 95.6 | 33.3 | 35.6 | 34.5 | 0.9 |
Mouth length | 60.3 | 21.1 | 23.5 | 22.2 | 0.8 |
Mouth width | 81.3 | 29.5 | 33.2 | 30.9 | 1.0 |
Barbel length | 12.3 | 2.5 | 4.4 | 3.6 | 0.6 |
Dentary tooth cup length | 32.0 | 11.5 | 13.4 | 12.3 | 0.7 |
Premaxillary tooth cup length | 27.1 | 10.4 | 11.6 | 11.0 | 0.3 |
Occipital length | 54.1 | 17.9 | 20.0 | 19.1 | 0.8 |
Caudal peduncle length | 24.3 | 24.5 | 28.2 | 26.8 | 1.3 |
Opercle length | 9.7 | 3.3 | 5.0 | 4.0 | 0.5 |
Interbranchial distance | 25.9 | 24.2 | 26.3 | 24.9 | 0.7 |
Meristics of Chaetostoma sacramento. H = holotype, SD = standard deviation, (n = 11).
Count | H | Min | Max | Mode | SD |
---|---|---|---|---|---|
Median plates | 24 | 22 | 24 | 23 | 0.5 |
Supramedian plates | 23 | 22 | 24 | 24 | 0.7 |
Inframedian plates | 24 | 24 | 25 | 24 | 0.5 |
Caudal plates rows | 5 | 5 | 5 | 5 | 0.0 |
Dorsal-fin branched rays | 8 | 8 | 8 | 8 | 0.0 |
Pectoral-fin branched rays | 6 | 6 | 6 | 6 | 0.0 |
Pelvic-fin branched rays | 5 | 5 | 5 | 5 | 0.0 |
Anal-fin branched rays | 4 | 4 | 4 | 4 | 0.0 |
Caudal–fin branched rays | 14 | 13 | 14 | 14 | 0.3 |
Dorsal procurrent caudal–fin rays | 4 | 4 | 4 | 4 | 0.0 |
Ventral procurrent caudal–fin rays | 4 | 2 | 4 | 3 | 0.6 |
Dorsal fin base plates | 7 | 7 | 7 | 7 | 0.0 |
Preadipose plates | 6 | 5 | 5 | 5 | 0.0 |
Adipose-caudal plates | 5 | 6 | 6 | 6 | 0.0 |
Infraorbital plates | 6 | 6 | 6 | 6 | 0.0 |
Left dentary teeth | 186 | 82 | 214 | 104 | 40.3 |
Left premaxillary teeth | 115 | 63 | 137 | 86 | 19.4 |
Cheek odontodes | 4 | 3 | 5 | 5 | 0.6 |
Head wide, anteriorly rounded in dorsal view; snout anterior margin unplated, lacking odontodes and tentacles. Orbit small (5.2–6.6% HL), dorsolaterally positioned, posterior margin aligned with vertical through anterior margin of cleithrum; skull roof flat. Oral disc wide, elliptical, occupying most of head width, lower lip ending just anterior to origin of opercular opening. Oval papillae covering upper lip, roundish papillae covering lower lip; all papillae smaller towards outer lip margins; lower lip margin crenulate. Buccal cavity with digitate papillae present posterior to premaxillary symphysis, one large patch of rugose papillae dorsomedial to each dentary tooth row. Maxillary barbel short (2.5–4.4% HL). Premaxillary tooth row straight, joining contralateral tooth row at 160º angle. Dentary straight, joining contralateral tooth row at 170º angle. Teeth small, villiform, asymmetrically bicuspid. Opercle external border having row of six straight odontodes, odontodes slightly larger than elsewhere on body. Three to five type 3 hypertrophied hook-like evertible cheek odontodes (mode 5), odontodes hooked anteriorly, not reaching cleithrum. Supraoccipital excrescence restricted to vestigial longitudinal unplated patch, keel absent.
Flanks covered by five longitudinal plate series. Plates absent from abdomen and around dorsal-fin base. Body plates flat or gently curved, lacking keel or ridge. Dorsal-fin base bordered laterally by seven dorsal plates. Medial interdorsal plates five. Dorsal plate series with 20 plates, supramedian with 24, median series with 23, mid-ventral series with 24, ventral series with 19.
Dorsal fin II,8; locking mechanism functional, spinelet V-shape, dorsal-fin origin slightly anterior to pelvic-fin origin, last dorsal-fin ray not reaching adipose fin when adpressed. Pectoral-fin rays I,6; pectoral-fin spine reaching first third of pelvic fin when adpressed. Pelvic-fin rays i,5; unbranched rays surpassing anal-fin origin; dorsal skin folds present on proximalmost two-thirds of unbranched pelvic-fin rays. Pectoral-fin spine with thicker odontodes irregularly distributed along entire dorsal, anterior and ventral surface of spine; one aligned row of larger odontodes along posterodorsal margin. Odontodes present on all, but posteriormost branched pectoral- and pelvic-fin rays. Anal-fin rays ii,4, first unbranched ray almost as long as second. Second branched anal-fin ray longest, with remaining rays successively shorter. Caudal fin obliquely forked, lower lobe longer than upper; i,7+7,i. Dorsal procurrent caudal-fin rays four, ventral two to four.
Head and body base colour brown dorsally, yellowish-white ventrally. Head with dense small white dots. In some specimens, scattered white spots on the body may be fused. Supraoccipital excrescence black or grey. Dorsal fin with white scattered spots on brownish base composed of melanophores distributed on rays and membrane. Remaining fins with brownish base composed of scattered melanophores. Tip of unbranched dorsal- and caudal-fin rays whitish in some individuals.
Males with fleshy dorsal fold on the pelvic-fin leading ray. Males have more distinct, intense and contrasting white patterns on darker brown to black base colour. Females with duller colour patterns on lighter brown to black base colour.
Chaetostoma sacramento is known exclusively from the Pampa de Sacramento valley east of the eastern cordillera of the Andes in Peru, inhabiting the Negro River, a tributary of the Pisqui River in Loreto Department; the Yamino River, a tributary of the Aguaytia River; the Chui River, a tributary of upper San Alejandro River in Ucayali Department; and the Raya River, a left-bank tributary of Iscozacin River in Pasco Department (Fig.
The species epithet sacramento refers to the plain (pampa) in central Peru between the Huallaga and Ucayali Rivers, approximately delimited by the Pisqui River in the north and Palcazu River in the south. Chaetostoma sacramento is currently known exclusively from this region, known as the Pampa de Sacramento, which occupies a valley between Huánuco and Ucayali provinces that is part of the Peruvian subandean belt and surrounds Boqueron del Padre Abad in the Cordillera Azul. The Pampa de Sacramento was first encountered by Europeans on 21 June 1726, by an expedition led by Don Juan Nunez Lobo and was christened Pampa del Sacramento to commemorate the Catholic ceremony of the Corpus Christi. Subsequent Franciscan missionaries highlighted the rich ethnic diversity of this region (IBC 2016). A noun in apposition.
With 626 total bases and 72 sequences from 12 nominal species, the COI dataset yielded 158 parsimony informative sites (25%). The ASAP species delimitation analysis yielded 20 Molecular Operational Taxonomic units (MOTUs) (score = 2.5), whereas GMYC and bPTP yielded 23 and 22 MOTUs, respectively. These results can be summarised with 22 consensus MOTUs (Fig.
With 1048 total bases and 108 sequences from 24 nominal species, the CytB dataset yielded 355 parsimony informative sites (34%). ASAP (score = 8.0), GMYC and bPTP species delimitation analyses yielded 46, 45, 49 MOTUs, respectively, for a total of 46 consensus MOTUs (Fig.
In all species delimitation analyses of both genes, Chaetostoma sacramento was identified as an MOTU distinct from all other examined Chaetostoma species. The minimum genetic distance to the nearest species was 6.15% for CytB, with C. branickii being the closest species. For COI, the closest species was C. leucomelas, with a genetic distance of 4.48%.
Chaetostoma breve
As for Chaetostoma breve in
Chaetostoma branickii was described by
Chaetostoma taczanowskii Steindachner 1882 is another taxonomically ambiguous species from northern Peru, described from the Huallaga River Basin, a southern tributary of the Marañon. Type images of this species suggest that it is also closely related to Chaetostoma branickii, if not another junior synonym, but a robust evaluation of the status of this species must await availability of fresh topotypic specimens and tissues.
Fourteen Chaetostoma species are currently recognised from Peruvian drainages, most of which (12) inhabit the Marañon River Basin, including the Huallaga, Pastaza and Napo Rivers, with only three now described from the Ucayali River Basin: C. lineopunctatum from the Pachitea River, C. loborhynchos from the Tulumayo Rivers and C. sacramento. Until now, the colour pattern described for most species of Chaetostoma in Peru comprises black spots on the body and head (C. daidalmatos, C. lineopunctatum, C. stroumpoulos, C. trimaculineum) or irregular black spots on the body alone (C. loborhynchos, C. spondylus). There are also six species described as having uniform or marbled colouration (C. branickii, C. changae, C. marmorescens, C. lexa and C. taczanowskii). White patterns on a darker base colour are observed in only two species in Peru, C. dermorhynchus and C. microps, from which C. sacramento differs by having distinct and highly variable small to large white spots on the body, head and fins (vs. white spots on only the dorsal fin in C. dermorhynchus) and by having eight dorsal-fin branched rays (vs. nine in C. microps). Our recognition of C. sacramento is further supported by our molecular results, which consistently identify it as a distinct MOTU using the mitochondrial genes COI and CytB. Additionally, our findings demonstrate that C. dermorhynchus and C. microps each represent a separate MOTU and are phylogenetically distant species to C. sacramento, as shown in
One of the fundamental criticisms of DNA-based approaches to species delimitation is that such analyses are incapable of distinguishing between genetic structure due to population-level processes and that due to species boundaries (
Although Chaetostoma sacramento has been known in the aquarium fish trade for almost 30 years, it was originally assigned three L-numbers in 2011 (L455, L456 and L457;
We thank Dario Faustino, Junior Chuctaya, Claudia Nolasco, Omar Quispe, Jerry Arana and Miguel Paniagua for field assistance, Raphael Covain at MHNG for sharing specimens and data and Julian Dignall at PlanetCatfish.com for sharing photos, aquarium literature and his thoughts on L455. This work was financed by CONCYTEC through the PROCIENCIA programme within the framework of the contest “Projects for the incorporation of postdoctoral researchers in Peruvian institutions” according to contract [074-2021] and [PE501084299-2023-PROCIENCIA-BM] within the framework of the call “Interinstitutional Alliances for Doctorate Programs”.