Baryancistrus xanthellus, Py-Daniel & Zuanon & Oliveira, 2011

Py-Daniel, Lúcia Rapp, Zuanon, Jansen & Oliveira, Renildo Ribeiro de, 2011, Two new ornamental loricariid catfishes of Baryancistrus from rio Xingu drainage (Siluriformes: Hypostominae), Neotropical Ichthyology 9 (2), pp. 241-252: 242-247

publication ID

http://doi.org/ 10.1590/S1679-62252011000200001

publication LSID

lsid:zoobank.org:pub:E7FAF466-BD3B-4CAF-9E40-AA86CCD6B3AE

persistent identifier

http://treatment.plazi.org/id/9E1A87D5-FF80-5D45-FF74-F9D92CCDFCC1

treatment provided by

Carolina

scientific name

Baryancistrus xanthellus
status

new species

Baryancistrus xanthellus   , new species

Figs. 1 View Fig and 2 View Fig

Holotype. INPA 33849, 214.2 mm SL, Brazil, Pará, Senador José Porfírio, rio Xingu in the vicinity of the cachoeira Buraco do Inferno , 03º27’07”S 51º41’53”W, 18 Mar 1997, J. Zuanon. GoogleMaps  

Paratypes. Brazil, Pará, rio Xingu : ANSP 191482 View Materials , 3 View Materials , 183.8 View Materials   - 188.7 mm SL, MCP 45752 View Materials , 2 View Materials   , 191.0- 196.3 mm SL, MNRJ 37863 View Materials , 2 View Materials , 186.2 View Materials   - 191.5 mm SL, Arroz Cru , 03º25’16”S 51º55’08”W, 1 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. INPA 3942 View Materials , 7 View Materials GoogleMaps   , 78.3-184.8 mm SL (4 not measured), Furo do Tucum Seco , 1 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. INPA 3955 View Materials , 27 View Materials   , 48.9-126.2 mm SL, 1 c&s, 82.0 mm SL, (19 not measured), INPA 3963 View Materials , 3 View Materials , 110.3 View Materials   - 145.1 mm SL (1 not measured), Cachoeira do Kaituká , 03º33’47”S 51º51’20”W, 9 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. INPA 4057 View Materials GoogleMaps   , 1, 223.3 mm SL, Ilha de Babaquara , 03º12’43”S 52º12’12”W, 4 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. INPA 4058 View Materials , 1 View Materials GoogleMaps   , 224.0 mm SL, Praia do Pedral , 03º15’16.7”S 52º13’12”W, 7 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. INPA 31414 View Materials , 9 View Materials GoogleMaps   , 49.8-210.2 mm SL (4 not measured), Comunidade do Maia , 03º30’44”S 51º44’43”W, 9 Nov 2008, L. Rapp Py-Daniel & R. R GoogleMaps   . Oliveira. INPA 31423 View Materials , 1 View Materials   , 48.3 mm SL, Cachoeira do Landi , 03º35’01”S 51º49’21”W, 8 Nov 2008, L. Rapp Py-Daniel & R. R GoogleMaps   . Oliveira. INPA 31473 View Materials , 6 View Materials   , 51.2- 171.8 mm SL, (2 not measured), Arroz Cru , 03º25’20”S 51º57’22”W, 6 Nov 2008, L. Rapp Py-Daniel & R. R GoogleMaps   . Oliveira. INPA 31772 View Materials , 1 View Materials   , 55.3 mm SL, Ilha do Davi , 03º32’39”S 51º57’29”W, 10 Nov 2008, L. Rapp Py-Daniel & R. R GoogleMaps   . Oliveira. INPA 31799 View Materials , 2 View Materials   , 57.8-189.3 mm SL, Gorgulho da Rita , 03º20’14”S 52º11’18”W, 7 Nov 2008, L. Rapp Py-Daniel & R. R GoogleMaps   . Oliveira. INPA 33848 View Materials   , 1, 212.8 mm SL, Cachoeira Buraco do Inferno , 03º27’07”S 51º41’53”W, 17 Mar 1997, J. Zuanon. INPA 33850 View Materials , 5 View Materials GoogleMaps   , 88.4-162.6 mm SL, 1 c&s, 88.4 mm SL, Corredeiras do Arini , 03º24’15”S 51º41’53”W, 6 Sep 1997, J. Zuanon. INPA 33851 View Materials , 1 View Materials GoogleMaps   , 65.1 mm SL, Furo do Ramiro , 03º15’21”S 52º05’06”W, 15 Sep 1997, J. Zuanon. INPA 33852 View Materials GoogleMaps   , 1, 175.2 mm SL, Ponta da Ilha da Bela Vista , 03º24’22”S 51º43’03”W, 29 Sep 1996, J. Zuanon. INPA 33941 View Materials GoogleMaps   , 1, 110.9 mm SL, Costa Junior , 03º29’28”S 52º19’07”W, 12 Oct 1996, J. Zuanon. MPEG 19132 View Materials , 2 View Materials , 171.3 View Materials GoogleMaps   -183.0 mm SL, Ilha de Babaquara , 5 Oct 1990, J. Zuanon. MZUSP 106738 View Materials , 3 View Materials , 173.3 View Materials   - 194.7 mm SL, Ilha de Kaituká , 03º33’47”S 51º51’20”W, 8 Oct 1990, L. Rapp Py-Daniel & J. Zuanon. ZUEC 4485 View Materials , 2 View Materials GoogleMaps   , 46.6-52.5 mm SL, just above Senador José Porfirio , 02º41’7.7”S 52º00’30.9”W, 13 Sep 1997, J. Zuanon. Rio Iriri: INPA 30767 View Materials GoogleMaps   , 1, 146.4 mm SL, ROM 88756 View Materials , 2 View Materials , 137.2 View Materials   - 191.2 mm SL, Ilha do Curapé , 04º06’53”S 53º22’28”W, 17 Aug 2008, H. López- Fernández et al. INPA 31081 View Materials , 2 View Materials , 184.4 View Materials GoogleMaps   - 207.0 mm SL, ROM 88757 View Materials   , 1, 172.5 mm SL, Cachoeira Grande do Iriri , 03º51’34”S 52º41’25”W, 23 Aug 2008, H. López-Fernández et al. INPA 31095 View Materials , 2 View Materials , 176.6 View Materials GoogleMaps   - 188.6 mm SL, ROM 88755 View Materials , 2 View Materials , 103.8 View Materials   - 187.5 mm SL, above mouth of rio Novo , 04º28’11”S 53º41’38”W, 21 Aug 2008, H. López- Fernández et al. INPA 31169 View Materials GoogleMaps   , 1, 140.8 mm SL, ROM 88754 View Materials   , 1, 131.1 mm SL, Cachoeira Grande do Iriri , 03º50’35”S 52º44’03”W, 24 Aug 2008, H. López-Fernández et al. INPA 32452 View Materials , 1 View Materials GoogleMaps   , 46.3 mm SL, Barinha , 04º09’05”S 53º23’28”W, 19 Aug 2008, H. López- Fernández et al GoogleMaps   .

Diagnosis. Baryancistrus xanthellus   differs from all its congeners by having a broad light band on dorsal and caudal fin distal borders in juveniles, becoming a small dot on dorsal and caudal-fin tips in adults (vs. conspicuous band at all ages in B. chrysolomus   and light bands absent in B. demantoides   , B. beggini   , B. longipinnis   , and B. niveatus   ). It can also be distinguished from all congeners except B. niveatus   and B. longipinnis   by the presence of light spots on the whole body (vs. the presence of uniform dark coloration in Baryancistrus beggini   and B. chrysolomus   ; presence of round spots only on the anterior part of the body until the end of dorsal-fin base in B. demantoides   ; presence of inconspicuous dots on the fins and rest of the body dark colored in B. longipinnis   ). Baryancistrus xanthellus   can be further distinguished from B. demantoides   , B. longipinnis   , and B. niveatus   by having a naked abdomen (vs. partially or completely plated in these three species). Baryancistrus xanthellus   differs from B. beggini   by a larger number of mandibulary teeth (around 60) on both maxillae versus 34-36 teeth in the premaxillary and 34 teeth in the dentary in B. beggini   ). The presence of bold yellow markings in young B. xanthellus   is the reason for its popular name in the aquarium trade: “amarelinho” in Portuguese (meaning little yellow).

Description. Morphometrics and meristics in Table 1. Mediumsize loricariids, bigger specimen examined reached 224.1 mm SL. Body short and robust, deep. Profile from snout to eye strongly sloped, gently convex from eye to insertion of dorsal fin due to prominence of supraoccipital process. Profile strongly inclined from dorsal-fin insertion to caudal fin. Body deepest at region between supraoccipital and dorsal-fin insertion. Ventral surface flat and straight from snout tip to caudal-fin base. Head and eyes without crest. Anterior lateral plates gently bent; rest of body not keeled. Anterior portion of body half oval in cross section, triangular at caudal peduncle.

Head large and wide; snout round in dorsal view. Eye large and round, iris operculum not visible. Orbit slightly elevated; interorbital area almost completely flat. No ridge between eyes and nares. Supraoccipital process conspicuous, elevated and rounded posteriorly. Supraoccipital limited posteriorly by pair of large quadrangular plates, almost fused. Predorsal area reduced, with only one pair of small, separated diamond-shaped plates anterior to nuchal plate.

Baryancistrus xanthellus   Baryancistrus chrysolo mus   Measurement Holotype N Mean Range SD Holotype N Mean Range SD Standard length (mm) 214.2 62 - 46.3-224.1 - 219.0 20 - 4 7.4-219.0 - Percents of st andard length Predorsal length 43.4 62 44.7 40.2-47.8 1.4 41.3 20 42.2 39.6 -45.1 1.2 Head length 35.8 62 37.7 35.3-41.0 1.4 33.7 20 36.6 33.6 -39.5 1.6 Cleithral width 33.7 62 34.4 31.0-37.5 1.5 34.3 20 34.4 32.9 -36.5 0.8 Thorax length 25.0 62 24.3 20.9-27.3 1.3 21.7 20 24.1 21.0 -26.2 1.4 Pectoral-spine len gth 33.7 62 33.0 25.7-38.7 3.3 34.9 20 32.0 28.5 -36.1 2.2 Abdominal length 24.3 62 24.6 21.5-27.7 1.4 25.1 20 24.3 20.9 -26.7 1.6 Pelvic-spine length 24.2 62 25.9 23.1-29.3 1.4 25.1 20 25.0 23.5 -27.0 0.8 Postanal length 21.3 62 27.8 21.3-30.7 1.7 31.1 20 29.5 26.6 -31.5 1.1 Anal-fin spine length 10.8 62 10.1 7.6-13.3 0.9 10.6 19 10.6 9.1-12.0 0.7 Dorsal spine length 25.6 62 26.6 22.8-32.1 1.9 26.0 20 27.0 24.0 -29.7 1.6 Dorsal-fin base length 40.6 62 40.5 35.4-48.0 2.7 41.2 20 39.3 36.5 -43.3 2.0 Dorsal-ad ipose distance 1.3 62 1.1 0-2.7 0.9 1.6 20 1.7 0.5 -4.0 1.1 Caudal penduncle d epth 10.6 62 10.7 9.0-12.3 0.8 11.3 20 10.6 9.4-11.9 0.6 Adipose-spine length 7.8 62 7.9 6.4-9.1 0.6 8.3 20 8.2 7.1 -9.2 0.6 Adipose-caudal length 21.1 62 22.4 19.5-24.8 0.9 25.2 20 23.5 21.2 -26.1 1.1 Body depth at dorsal-fin origin 22.2 62 22.1 17.1-26.8 1.9 21.2 20 20.4 16.6 -22.9 1.8 Body width at dorsal-fin origin 31.9 62 31.9 27.7-37.1 2.0 32.4 20 30.6 27.9 -34.0 1.7 Body width at anal-fin origin 17.6 62 16.9 12.6-20.5 1.7 18.7 20 15.7 12.4 -19.3 2.1 Postdorsal length 22.8 62 23.3 19.1-25.7 1.4 26.0 20 25.5 23.4 -27.7 1.2 Anus-anal fin len gth 3.6 62 4.1 2.9-5.6 0.6 4.5 20 4.1 3.3 -5.7 0.6 Body width 36.5 62 36.1 33.3-39.3 1.3 36.3 20 36.3 35.2 -37.8 0.8 Percents of head length Orb ital diameter 15.4 62 18.4 15.1-23.4 2.3 17.3 20 21.6 17.1 -24.9 2.9 Sn out length 74.8 62 67.2 60.6-74.8 3.1 64.0 20 61.9 58.5 -66.5 2.8 Internares width 13.8 62 13.0 9.4-15.6 1.6 14.5 20 12.3 9.6-15.7 1.6 Interorbital width 37.5 62 36.0 28.0-41.4 3.9 41.8 20 36.7 31.4 -45.2 4.1 Head depth 57.6 62 56.3 46.5-66.8 4.3 63.7 20 54.0 47.1 -63.7 5.3 Dentary len gth 21.2 62 19.5 16.7-24.4 1.6 23.2 20 20.6 17.3 -24.9 2.3 Premaxillary length 21.3 62 19.3 15.9-22.6 1.4 23.7 20 19.9 16.1 -23.7 2.1 Head width 103.9 62 90.5 77.2-103.9 7.2 100.4 20 89.3 7 9.1-100.4 6.6 Eye-nostril length 16.3 62 14.7 9.1-17.8 2.2 15.5 20 13.2 10.2 -17.9 2.3 Interbranchial distance 59.6 62 56.5 51.8-60.9 2.4 58.8 20 57.7 53.6 -61.2 2.2 Teeth on premaxilla 60 62 28-72 74 20 14 -91 Teeth on dentary 64 62 25-76 81 20 22 -96 Lateral plates in middle series 24 62 23-24 24 20 24 -25 Plates between anal and caudal 10 62 9-11 10 20 10 -11 Plates between dorsal and adipose 0 62 0-2 0.5 20 0 -2 Plates predorsal 3 62 3 3 20 3

Counts

Mouth wide; lips large, covered with small round papillae except on area around maxillae. Maxillary barbel thick and short. Branchial opening moderate, wider in larger specimens. Interbranchial distance approx. 56.5% in head length.

Head and body completely covered by large plates dorsally, except dorsal-fin base. Ventral surface largely unplated from snout to anal fin; in larger specimens, presence of two or three minute round plates close to insertion of pectoral spine or urogenital opening. Twenty-two perforated median plates, 23 lateral plates; four oblong plates on caudalfin base. All plates marked with lines of odontodes. Numerous hypertrophied odontodes only on evertible cheek plates, well developed in larger specimens with largest odontode reaching posterior end of first lateral plate. Ventral border of opercle with series of strong but short odontodes on probably mature males.

Dorsal fin II,7; spinelet present and dorsal-fin locking mechanism functional. Dorsal fin long and low, reaching adipose spine on small specimens when adpressed. Dorsalfin posterior membrane covering four plates immediately behind last dorsal-fin ray, but not reaching preadipose plate. Adipose fin large and with posterior membrane slightly developed. One single plate separating dorsal from preadipose plate. Caudal fin i,14,i, emarginated. Pectoral fin I,6, large, reaching well beyond posterior end of pelvic-fin base when adpressed. Pectoral fin covered by large odontodes on (possibly mature) males. Pelvic fin i,5 reaching posterior end of anal fin base when adpressed. Anal fin i,4, very reduced. All simple first rays covered by numerous short odontodes on their free surface.

Teeth long and deeply cuspidate. Cusps round and similar in larger specimens with vertical divide between cusps; in smaller specimens cusps are largely asymmetrical, with internal cups larger. Premaxilla and dentary of similar size and disposed in parallel to anterior border of snout. Modal number of premaxillary teeth 32; dentary teeth mode 46 (range of number of mandibulary teeth in Table 1). Buccal papilla long and digitiform.

Color in life. Overall body color dark brown at dorsum and sides, paler on abdomen. Numerous bright, similar-sized yellow spots over head, body, dorsal, adipose, and caudal fins, and on dorsal surface of pectoral and pelvic fins. Yellow spots almost size of pupil in juveniles, becoming proportionally smaller, more numerous and somewhat paler in adults. Young specimens with wide yellow band on distal third of caudal and dorsal fin; dorsal-fin band larger anteriorly, becoming gradually slender posteriorly. In adults, bands on fins become reduced to spots on anterior distal ends of dorsal and caudal fins ( Fig. 2 View Fig ). Considerable variation in density and size of spots.

Color in alcohol. Similar to pattern described for living specimens but with ground color brown to dark olive and white to cream markings ( Fig. 1 View Fig ).

Distribution. This species has been recorded from the area called Volta Grande do rio Xingu, an area immediately above Belo Monte falls, and from rio Iriri, the larger tributary of rio Xingu ( Figs. 3 View Fig and 4a View Fig ).

Etymology. From the Greek xanthellus   , yellow, in allusion to the bright color of the specimens. A noun in apposition.

Popular name. Known in the aquarium trade as “amarelinho” (= little yellow) and “cascudo pepita-de-ouro” (in Portuguese), or L018 and L085; and golden nugget pleco or Iriri golden nugget pleco (in English), or L177.

Ecological notes. Baryancistrus xanthellus   is one of the most common species observed in the rapids of rio Xingu in the area known as “Volta Grande do Xingu” near the town of Altamira, Pará State ( Fig. 4a View Fig ). Young specimens of B. xanthellus   occur in groups of several individuals under flat rocks at the bottom of shallow rapid stretches. Other loricariid species found sintopically are Ancistrus   spp., Oligancistrus punctatissimus   , and an undescribed species of Oligancistrus   , young individuals of Baryancistrus aff. niveatus   , Parancistrus nudiventris   , and Pseudancistrus   sp. Adult specimens occupy larger spaces among and under submerged boulders, together with large specimens of Baryancistrus aff. niveatus   , Scobinancistrus aureatus   , and S. cf. pariolispos   , and Hypostomus   spp. The diet of three examined specimens of B. xanthellus   was composed mainly of algae, especially diatoms and loose filaments of clorophyceans such as Spirogyra   , which are commonly found associated with fine sediments and sand grains in the long

Rapp Py-Daniel & R. R. Oliveira. INPA 33844 View Materials , 1, 166.2 mm SL, Viracebo do Arroz Cru , 03º25’16”S 51º55’08”W, 7 Oct 1996, J. Zuanon. INPA 33845 View Materials , 2 View Materials , 207.6 View Materials - 207.8 mm SL, same data as holotype. INPA 33846 View Materials , 1, 191.7 mm SL, MPEG 19133 View Materials , 1, 142.7 mm SL, Furo do Ramiro , 03º15’21”S 52º05’06”W, 12 Sep 1997, J. Zuanon. MZUSP 106739 View Materials , 1, 184.2 mm SL, Furo do Ramiro , 03º15’21”S 52º05’06”W, 6 Oct 1996, J. Zuanon. ZUEC 4484 View Materials , 1 View Materials , 69.5 mm SL, Furo de Ramiro , 03º15’21”S 52º05’06”W, 13 September 1997, J. Zuanon. Rio Curuá: MZUSP 97226 View Materials , 8 View Materials , 45.5-182.4 mm SL, rio Iriri drainage, 08º19’07”S 55º05’23”W, 22 Oct 2007, J. L. Birindelli et al GoogleMaps   .

intestines of loricariids (intestinal length up to 16 times the body length; Zuanon, 1999). Occasional bryozoans and chironomid larvae were also found. Underwater observations indicate that the food is scraped from the surface of submerged rocks by gently combing the periphyton cover with the numerous and tightly spaced teeth (JZ, pers. obs.).

INPA

Instituto Nacional de Pesquisas da Amazonia

SL

University of Sierra Leone, Njala University College

MCP

Pontificia Universidade Catolica do Rio Grande do Sul

R

Departamento de Geologia, Universidad de Chile

ROM

Royal Ontario Museum