Hypostomus froehlichi, Zawadzki & Nardi & Tencatt, 2021

Zawadzki, Cláudio H., Nardi, Gabriela & Tencatt, Luiz Fernando Caserta, 2021, The crystalline waters of the Bodoquena Plateau revealed Hypostomus froehlichi (Siluriformes: Loricariidae), a new armored catfish from the rio Paraguay basin in Brazil, Zootaxa 4933 (1), pp. 98-112 : 99-108

Hypostomus froehlichi , new species

( Figs. 1–4 and 6 , Table 1 and 2)

Holotype. NUP 22689, 226.2 mm SL, Bodoquena , Mato Grosso do Sul State, Brazil, córrego Salobrinha, tributary of rio Miranda, rio Paraguay basin, -20.68273, -56.78600, Mar 2007, O. Froehlich et al.

Paratypes. All from Brazil, Mato Grosso do Sul State, Bodoquena, rio Paraguay basin, córrego Salobrinha , except when indicated: LIRP 5226 , 5 , 115.8 – 128.6 mm SL, Bonito , rio Formoso , -21.07916, -56.33916, 29 Aug 2004, H. F. dos Santos, O. Froehlich & R. Castro. LIRP 5228 , 3 , 163.1 – 222.2 mm SL, rio Salobra , -20.53860, -56.71500, 2 Sep 2004, H. F. dos Santos, O. Froehlich & R. Castro. LIRP 5240 , 39 , 25.6 –209.0 mm SL, rio Salobra , -20.53860, -56.71500, 22 Aug 2004, H. F. dos Santos, O. Froehlich & R. Castro. LIRP 5242 , 2 , 231.2 – 232.5 mm SL, rio Salobra -20.73805, -56.73472, 22 Aug 2004, H. F. dos Santos, O. Froehlich & R. Castro. NUP 5077 , 5 , 52.2–201.1 mm SL, rio Salobra , -20.49555, -56.86333, 27 Dec 2006, A. G. Bifi. NUP 12138, 2 , 235.3 – 239.1 mm SL, rio Salobra , -20.78027, -56.74194, Dec 2005, O. Froehlich et al. NUP 12139, 2 , 223.0– 227.8 mm SL, rio Salobra , -20.78027, -56.74194, Dec 2005, O. Froehlich et al. NUP 12140, 2 , 235.3 – 241.8 mm SL, rio Salobra , -20.78027, -56.74194, Dec 2005, O. Froehlich et al. NUP 12141, 1 , 225.0 mm SL, rio Salobra , -20.78027, -56.74194, Dec 2005, O. Froehlich et al. ZUFMS 904 , 18 , 20.5–78.2 mm SL, rio Salobra , -20.67527, -56.75694, 13 May 2001, O. Froehlich, M. R. Cavallaro & J. Sedenho. ZUFMS 1024 , 14 , 25.5 –74.0 mm SL, rio Salobra , -20.67527, -56.75694, 28 Jun 2001, O. Froehlich. ZUFMS 1085 , 2 , 51.6–66.5 mm SL, rio Salobra , -20.67527, -56.75694, 10 Oct 2001, O. Froehlich, E. Amorim, M. V. Costa & L. P. C. Lopes. ZUFMS 1126 , 127 , 21.2 –122.0 mm SL, rio Salobra , -20.67527, -56.75694, 13 Oct 2001, O. Froehlich, M. V. Costa & L. P. C. Lopes. ZUFMS 1171 , 6 , 11.5–61.7 mm SL, rio Salobra , -20.67527, -56.75694, 10 Sep 2001, O. Froehlich, M. R. Cavallaro, F. M. Fernandes, L. N. Carvalho & L. S. Inocêncio. ZUFMS 1175 , 89 , 18.7–56.4 mm SL, rio Salobra , -20.67527, -56.75694, 21 May 2000, O. Froehlich, M. R. Cavallaro, R. S. Arruda, D. Silva & L. S. Inocêncio. ZUFMS 1179 , 83 , 16.1–65.2 mm SL, rio Salobra , -20.67527, -56.75694, 14 May 2001, L.S. Inocêncio, M. R. Cavallaro, O. Froehlich & J. Sedenho. ZUFMS 1183 , 1 , 40.4 mm SL, rio Salobra , -20.67527, -56.75694, 21 May 2000, O. Froehlich. ZUFMS 1186 , 3 , 10.6–15.1 mm SL, rio Salobra , -20.67527, -56.75694, 8 Jun 2000, O. Froehlich. ZUFMS 1190 , 1 , 35.3 mm SL, rio Salobra , -20.67527, -56.75694, 20 May 2000, O. Froehlich. ZUFMS 1545 , 34 , 28.5–65.8 mm SL, rio Salobra , -20.67527, -56.75694, 10 Sep 2000, O. Froehlich. ZUFMS 2525 , 41 , 12.8–50.6 mm SL, rio Salobra , -20.78166, -56.74194, 3 Sep 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 2590 , 9 , 33.3–46.5 mm SL, rio Salobra , -20.67, -56.76055, 30 Aug 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 4470 , 38.9–68.6 mm SL, rio Salobra , -20.78027, -56.74194, 3 Sep 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 4748 , 4 , 91.4 –219.0 mm SL, rio Salobra , -20.78166, -56.74194, 3 Sep 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. LIRP 5241 , 6 , 212.0– 256.7 mm SL, Bonito, córrego Mutum, -21.30083, -56.43583, 19 Aug 2004, H. F. dos Santos, O. Froehlich & R. Castro. ZUFMS 895 , 6 , 18.2–81.4 mm SL, córrego Azul e rio Salobra , 9 Apr 2000, O. Froehlich. ZUFMS 1191 , 1 , 16.6 mm SL, córrego Azul, -20.7588, -56.75183, 9 Apr 2000, L. S. Inocêncio, M. R. Cavallaro, F. M. Carvalho, F. M. Fernandes & F. Silva. ZUFMS 1631 , 2 , 27.0– 31.9 mm SL, córrego Azul, -20.75883, -56.75183, 9 Apr 2000, O. Froehlich. ZUFMS 2554 , 2 , 60.0– 60.5 mm SL, stream tributary of the rio Salobra , -20.77439, -56.73683, 5 Sep 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 3606 , 8 , 121.0–188.0 mm SL, Bonito, córrego Taquaral, -21.10833, -56.63277, 4 Feb 2013, Severo-Neto, F. ZUFMS 4747 , 11 , 67.7–121.4 mm SL, mouth of the córrego Paulista, -20.68555, -56.77805, 13 Aug 2001, O. Froehlich, M. R. Cavallaro & D. Silva. ZUFMS 786 , 2 , 51.6–93.2 mm SL, “Bodoquena”, 8 Apr 1998, P. R. Souza. NUP 13392, 4 , 177.0– 200.7 mm SL, -20.683055, -56.78666, 27 Jul 2006, O. Froehlich et al. NUP 13387, 1, 187.3 mm SL, - 20.68305, -56.78666, Mar 2007, O. Froehlich et al. NUP 12142, 4 , 127.8 –233.0 mm SL, -20.67, -56.77, Mar 2007, O. Froehlich et al. NUP 4247 , 3 , 106.1 – 132.9 mm SL, -20.68333, -56.78611, 31 Dec 2005, O. Froehlich et al. ZUFMS 896 , 24 , 24.6–73.9 mm SL, -20.68333, -56.78611, 20 May 2000, O. Froehlich. ZUFMS 1064 , 4 , 66.4–95.9 mm SL, -20.68333, -56.78611, 16 Jun 2001, O. Froehlich & M. R. Cavallaro. ZUFMS 1172 , 13 , 39.2–65.5 mm SL, -20.68333, -56.78611, 20 May 2000, O. Froehlich, M. R. Cavallaro, F. M. Fernandes, L. N. Carvalho & L. S. Inocêncio. ZUFMS 1173 , 2 , 72.8 –77.0 mm SL, -20.68333, -56.78611, 27 Feb 2000, O. Froehlich, M. R. Cavallaro, R. S. Arruda, L. S. Inocêncio, L. P. C. Lopes & R. Diniz. ZUFMS 1178 , 1 , 65.4 mm SL, -20.68333, -56.78611, 11 Jul 2001, F. Silva, M. R. Cavallaro & L. S. Inocêncio. ZUFMS 1180 , 90 , 27.1–67.8 mm SL, -20.683333, -56.78611, 9 Sep 2000, O. Froehlich, M. R. Cavallaro, D. Silva, A. Fecchio, J. Sedenho & L. S. Inocêncio. ZUFMS 1182 , 15 , 30.0– 108.6 mm SL, -20.68333, -56.786111, 26 Feb 2001, O. Froehlich, L. S. Inocêncio, L. P. C. Lopes & R. Diniz. ZUFMS 1185 , 1 , 24.5 mm SL, -20.68333, -56.78611, 27 Feb 2001, O. Froehlich, D. Silva, L. S. Inocêncio, L. P. C. Lopes & R. D. R. Diniz. ZUFMS 1187 , 3 , 67.2–74.4 mm SL, -20.68333, -56.786111, 13 Aug 2001, O. Froehlich, M. R. Cavallaro & L. S. Inocêncio. ZUFMS 1203 , 1 , 34.4 mm SL, -20.68333, -56.78611, 20 May 2001, O. Froehlich, M. R. Cavallaro, R. Arruda, L. A. Espíndola, D. M. Alves & F. M. Fernandes. ZUFMS 1461 , 40 , 25.5–53.3 mm SL, -20.68333, -56.78611, 9 Sep 2001, M. R. Cavallaro, J. Sedenho, E. Amorim & L. P. C. Lopes. ZUFMS 1474 , 27 , 25.6 –66.0 mm SL, -20.68333, -56.78611, 9 Sep 2001, M. R. Cavallaro, J. Sedenho, E. Amorim & L. P. C. Lopes. ZUFMS 1619 , 13 , 26.2–50.5 mm SL, -20.68333, -56.786111, 20 May 2000, O. Froehlich. ZUFMS 2539 , 1 , 50.7 mm SL, -20.68555, -56.77888, 2 Sep 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 2544 , 2 , 11.1 –45.0 mm SL, -- 20.68583, -56.78333, 2005, M. R. Cavallaro, M. J. A. Vilela, N. V. A. Almeida, O. Froehlich & R. D. Vargas. ZUFMS 2579 , 7 , 22.8–64.3 mm SL, -20.68333, -56.78583, 2005, M. R. Cavallaro, M. J. A. Vilela, N. V. A. Almeida, O. Froehlich & R. D. Vargas. ZUFMS 2594 , 7 , 16.8–53.6 mm SL, -20.68583, -56.78333, 2005, M. R. Cavallaro, M. J. A. Vilela, N. V. A. Almeida, O. Froehlich & R. D. Vargas. ZUFMS 2636 , 20 , 21.2 –195.0 mm SL, -20.68583, -56.78333, 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas. ZUFMS 3276 , 2 , 71.3 –75.0 mm SL, -20.682778, -56.7775, 27 Feb 2001, O. Froehlich. ZUFMS 4664 , 4 , 29.3–78.9 mm SL, -20.68305, -56.78638, 26 Jul 2006, O. Froehlich, F. Severo-Neto, M. C. Teixeira, M. O. Tanaka, M. R. Cavallaro, M. Beccari & T. T. M. Taveira. ZUFMS 4693 , 1 , 208.0 mm SL, -20.68361, -56.78527, 27 Jul 2006, O. Froehlich, F. Severo-Neto, M. C. Teixeira, M. O. Tanaka, M. R. Cavallaro, M. Beccari & T. T. M. Taveira. ZUFMS 4730 , 12 , 73.2 –181.0 mm SL, -20.68305, -56.78638, 26 Jul 2006, O. Froehlich, F. Severo-Neto, M. C. Teixeira, M. O. Tanaka, M. R. Cavallaro, M. Beccari & T. T. M. Taveira. ZUFMS 4750 , 1 , 171.0 mm SL, -20.68361, -56.78527, 27 Jul 2006, O. Froehlich, F. Severo-Neto, M. C. Teixeira, M. O. Tanaka, M. R. Cavallaro, M. Beccari & T. T. M. Taveira. ZUFMS 5230 , 30 , 24.0– 91.3 mm SL, -20.68333, -56.78611, 31 Aug 2005, M. J. A. Vilela, O. Froehlich, O. C. Forster & R. D. Vargas .

Diagnosis. Hypostomus froehlichi is distinguished from the species of the H. cochliodon group (sensu Zawadzki & Hollanda Carvalho, 2014) by having villiform teeth and angle between dentaries usually larger than 80° (vs. spoon-or shovel-shaped teeth and angle between dentaries about 80°); from H. affinis , H. ancistroides , H. arecuta , H. argus , H. aspilogaster , H. borellii , H. boulengeri , H. carinatus , H. careopinnatus , H. carvalhoi , H. commersoni , H. crassicauda , H. delimai , H. derbyi , H. dlouhyi , H. faveolus , H. formosae , H. hemiurus , H. interruptus ,

H. itacua , H. laplatae , H. niceforoi , H. nigrolineatus , H. nigropunctatus , H. nudiventris , H. paucimaculatus , H. piratatu , H. plecostomus , H. pantherinus , H. punctatus , H. pusarum , H. scabryceps , H. seminudus , H. spiniger , H. subcarinatus , H. tapijara , H. variostictus , H. velhochico and H. watwata by lacking keels on lateral series of plates (vs. having moderate or strong keels along lateral series of plates); from H. alatus , H. albopunctatus , H. francisci , H. luteomaculatus , H. luteus , H. margaritifer , H. meleagris , H. microstomus , H. multidens , H. myersi , H. regani , H. roseopunctatus , H. sertanejo , H. strigaticeps , H. tietensis and H. variipictus by having dark blotches on a clearer background (vs. pale spots or vermiculations on a darker background); from H. isbrueckeri by having caudal fin with dark blotches (vs caudal fin homogeneously dark or often with yellow distal band in mature males); from H. laplatae by having from 24 to 27 plates on lateral series (vs. 31); from H. latifrons by having juveniles with dark blotches on flanks (vs. juveniles with dark saddles); from H. uruguayensis by having shorter unbranched caudalfin rays—ventral unbranched caudal-fin ray similar in length to head length (vs. similar to predorsal length); it is additionally diagnosed from H. isbrueckeri , H. laplatae , H. latifrons , and H. uruguayensis by usually having one plate bordering supraoccipital (vs. three to seven). Hypostomus froehlichi is distinguished from H. denticulatus by having lower number of teeth, 10–61 (vs. more than 100 teeth); from H. brevis , H. paulinus , H. mutucae , and H. nigromacutlatus by having anterior portion of abdomen totally covered by platelets (vs. abdomen mostly naked); from H. heraldoi by having pectoral-fin spine clearly longer than pelvic-fin spine (vs. pectoral-fin spine equal to or shorter than pelvic-fin spine); from H. iheringii , H. latirostris and H. ternetzi by having short ventral unbranched caudal-fin ray, its length usually similar to head length (vs. long, usually similar in length to predorsal distance); from H. hermanni and H. topavae by lacking dark stripe margining dorsal-fin branched rays anteriorly (vs. dorsal fin with longitudinal inconspicuous dark stripe anteriorly margining branched rays); from H. renestoi and H. yaku by lacking hypertrophied odontodes along dorsal and mid-dorsal series of plates (vs. having moderately developed odontodes in H. renestoi —see Zawadzki et al. 2018, Fig. 9b to highly developed hypertrophied odontodes on caudal portions of lateral series of plates in H. yaku , see Martins et al. 2014, Fig. 2 ).

Description. Morphometric data in Tables 1 . Overall view of body in Fig. 1 . Head broad and stout. Snout and anterior profile of head rounded in dorsal view. Eye of moderate size, dorsolaterally positioned. Dorsal margin of orbit not or very slightly raised. Body width at cleithral region much larger than head depth and approximately equal to head length. Greatest body width at cleithrum, narrowing from dorsal-fin region to caudal-fin origin. Dorsal profile of head straight from snout tip to vertical through interorbital region angling about 35° with ventral region of head; slightly convex from that point to dorsal-fin origin; straight to first procurrent rays of dorsal fin; raising again to caudal fin. Ventral profile almost straight from snout tip to insertion of pelvic-fin unbranched ray; straight and slightly narrowing from pelvic-fin insertion to ventral caudal-fin procurrent rays. Caudal peduncle slightly compressed anteriorly; moderate to strongly compressed posteriorly. Plates along mesethmoid forming longitudinal bulge from snout tip to nares, more conspicuous in specimens up to 100 mm SL (NUP 4247); in larger specimens depending on fixation. Supraoccipital with very slight median bulge; its short posterior process bordered by single plate. Moderate bulge originating lateral to nares, passing through supraorbital, and weakly extending along dorsal portion of pterotic-supracleithrum. Opercle large; horizontal length similar to or slightly larger than orbital diameter. Oral disk round, moderate in size; margins smooth. Lower lip not reaching transverse line through gill openings. Odontodes on anterior portion of upper lip. Upper lip ventrally covered with transverse papilla. Lower lip ventral surface covered with numerous small round papillae, larger proximally. Maxillary barbel usually small, from half to slightly smaller than eye diameter; usually mostly coadnate to lower lip by membrane. Median buccal papilla large, its tip rough. Smaller buccal papillae along internal margins of each dentary and mandibullary ramus. Dentaries moderate to strongly angled, averaging from 108° to 137° between left and right dentary rami. Teeth viliform, bicuspid; crowns bent ventrally. Crowns with main cusp lanceolate and smaller pointed lateral cusp. Some specimens with 14–17 shorter and robust teeth bearing a proportionally smaller lateral cusp (NUP 12139, 223.0 mm SL), while some other specimens with 55–61 slightly longer, thinner and viliform teeth (NUP 12140, 241.8 mm SL). Holotype and several other specimens with about 32–37 moderate viliform teeth.

Body covered with five rows of dermal plates with weakly-developed odontodes, except one small naked area on snout tip and on base of dorsal fin. Predorsal region with very slight median keel. Dorsal series of plates with moderate keels. Dorsal series strongly bent on interdorsal region resulting in anterodorsal surface of caudal peduncle strongly flat. Mid-dorsal and median series without keels. Median series bearing continuous lateral line. Mid-ventral series strongly angled from first to third or fourth plates. Ventral series bent ventrally resulting in flat caudal peduncle floor. Ventral surface of head and abdomen naked in specimens up to 80 mm SL (NUP 5077). In larger specimens, abdomen completely covered with platelets on anterior portion and with naked areas around ventral-fin origins.

Dorsal fin II,7; origin at vertical through posterior two third between pectoral- and pelvic-fin insertions. First spine as functional spinelet. Second spine bearing dorsal fin; flexible. Distal margin of dorsal fin slightly convex; tip of last dorsal-fin branched rays from almost to just reaching adipose-fin spine. Adipose-fin spine compressed and slightly curved inward. Adipose-fin spine tip reaching forth to fifth plate after origin. Pectoral fin I,6; distal bor-der straight. Pectoral-fin spine slightly curved inward, slightly depressed proximally, round distally; covered with developed odontodes, more developed on distal portion, particularly in larger specimens. Odontodes from pectoral spine curved proximally. Distal region of pectoral fin with swollen skin usually forming tissue sheath around emerging odontodes. Tip of adpressed pectoral fin reaching about one-third of adpressed pelvic-fin spine. Pelvic fin i,5; distal border straight to slightly convex; when adpressed unbranched ray surpassing anal-fin origin. Anal fin i,4; tip reaching fifth plate after origin. All anal-fin rays similar in length. Caudal fin i,14,i; posterior margin falcate, with ventral lobe slightly longer than dorsal.

Color in alcohol. Dorsolateral ground color of head, trunk and fins brown to grayish-brown and covered with many large faded dark blotches ( Fig. 1 ). Dark blotches numerous, close to each other and varying in size from slightly smaller to slightly larger than eye pupil diameter in head. Blotches larger on trunk and fins, varying from slightly larger than eye pupil diameter to similar to eye diameter. Blotch diameters and distances to each other relatively constant along anteroposterior axis of trunk. Space between each blotch usually smaller than diameter of blotches. Dorsal, pectoral and ventral fins usually with one row of blotches on each interadial membrane in specimens up to 100 mm SL; usually with two rows of blotches along each interadial membrane in specimens larger than 100 mm SL. Some specimens with blotches fused to each other forming from two or three irregular lines on proximal region of dorsal fin. Anal and caudal fins usually with one row of blotch per interadial membrane; anal and caudal fins blurred in some specimens. Ventral surface beige, usually lacking blotches. Blotches progressively faded along time of preservation of specimens, and almost or totally absent in old preserved specimens. Teeth with pale stalks and orange crowns.

Color in life. Color pattern of living specimens similar to preserved ones, except for clearer and bright background color, with more conspicuous black blotches ( Figs. 2 , 3 , 4 ). According to underwater observations of P. Petersen (pers. comm.), the specimens ranging from 20.0 to 40.0 mm TL displayed a very peculiar color pattern, with slightly yellow to orange fins. At around 50.0 mm TL, the yellow/orange colors fade and the typical rounded dark blotches begin to appear ( Fig. 4 ).

Sexual dimorphism. No external sexual dimorphism was observed among the analyzed specimens.

Geographical distribution. Hypostomus froehlichi is currently known from the following tributaries of the rio Miranda basin, a tributary of the rio Paraguay basin: córrego Salobrinha, its type-locality, córrego Azul, córrego Mutum, córrego Paulista, córrego Taquaral, rio Formoso, and rio Salobra. Additionally, photographic records by both Marcelo Krause and Peter Petersen confirmed the occurrence of the new species in the Mimoso and da Prata rivers, also tributaries of the rio Miranda basin. All known records are within the Bodoquena Plateau region, Mato Grosso do Sul, Brazil ( Fig. 5 ).

Natural history notes. According to Penatti (2010), young specimens of Hypostomus froehlichi were observed foraging during day and night, whereas larger specimens were more active at night, being generally observed hiding in cavities at the margins of the stream during day. The new species was generally found associated with rocky substrate. Differences in feeding strategy was observed between juvenile and adult specimens of H. froehlichi , through underwater observations at the Bodoquena Plateau region by Peter Petersen (pers. comm.). Regarding juveniles, the smallest specimens (approximately 20 mm TL), were usually found in the fast currents of waterfalls in small rivers and streams, not hiding but foraging on rock formations in open water. Although these young specimens seem to prefer shaded areas, they are clearly diurnal. The nostrils are very large in small specimens similar to those seen in young Pterygoplichthys species. Middle-sized specimens (approximately 100.0 mm TL) were not observed in the waterfalls, inhabiting other parts of the small rivers and streams, usually hiding under rocks and driftwood ( Fig. 3 ).

Although large specimens with approximately 600.0 mm TL were observed in shallow waters, shoals were observed in deeper areas. Adult shoals are formed up to several hundred specimens, usually resting and feeding on the steep rocky shelves from one meter to more than 10 meters deep. According to Froehlich (2010) and Penatti (2010), the new species graze on hard substrates, from which they remove the periphytic matrix by scraping it. In the main rivers they seem to use rocky and clay cave formations as breeding sites. Both soft and hardened clay caves are used, with holes in the areas of soft clay substrate, apparently dig by large specimens. Contrary to the observation by Penatti (2010), larger adults were observed active during day (P. Petersen, pers. comm.) ( Fig. 4 ). A video file by Peter Petersen showing the new species in its natural habitat, the rio da Prata, is available at https://youtu. be/QJ62856SlIo.

Hypostomus froehlichi cooccurs with three congeners, namely H. basilisko , H. cochliodon and an undescribed species referred here as Hypostomus aff. ancistroides .

Etymology. The specific epithet froehlichi honors Otávio Froehlich (1958–2015), beloved friend and ichthyologist who devoted most of his work on the knowledge of the fishes from the Bodoquena Plateau, Mato Grosso do Sul. Treated as a genitive.

Figures

FIGURE 1. Hypostomus froehlichi, NUP 22689, 226.2 mm SL, holotype, Brazil, Mato Grosso do Sul State, municipality of Bodoquena, córrego Salobrinha, tributary of rio Miranda, rio Paraguay basin.

FIGURE 2. Live specimen of Hypostomus froehlichi, ZUFMS 3606, 188.0 mm SL, Brazil, Mato Grosso do Sul State, córrego Taquaral, rio Paraguay basin, showing general color pattern in lateral view. Photo by Francisco Severo Neto.

FIGURE 3. Uncatalogued live specimens of Hypostomus froehlichi in natural habitat, showing juvenile specimens, with (a) 30.0 mm TL and (b) 50.0 mm TL, foraging on rock formations of waterfalls, both in the rio Formoso. Larger specimens, (c) with around 120.0 mm TL, from the rio Formoso, and (d), with around 200.0 mm TL, from the rio da Prata, were often found hiding under rocks and driftwood. Photos (a) and (b) by Peter Petersen, and (c) and (d) by Marcelo Krause.

FIGURE 4. Uncatalogued live specimens of Hypostomus froehlichi in natural habitat, showing (a) a solitary large adult from the rio Mimoso, and (b) part of shoal of large adults from the rio da Prata, both associated with rock formations, where they feed scraping the substrate, leaving feeding scars in the areas in which the periphytic matrix was removed (c). Specimens in (a) and (b) were estimated to have about 400.0 mm TL. Photo (a) by Marcelo Krause, and (b) and (c) by Peter Petersen.

FIGURE 5. Geographic distribution of Hypostomus froehlichi; (red star = type-locality; white circles = additional records).

FIGURE 6. Hypostomus froehlichi (a) LIRP 5228, 163.1 mm SL; (b) NUP 12140, 241.8 mm SL, showing tooth variation in specimens.