Research Article |
Corresponding author: Milton Tan ( miltontan@auburn.edu ) Academic editor: Carole Baldwin
© 2016 Milton Tan, Jonathan Armbruster.
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:
Tan M, Armbruster JW (2016) Two new species of spotted Hypancistrus from the Rio Negro drainage (Loricariidae, Hypostominae). ZooKeys 552: 123-135. https://doi.org/10.3897/zookeys.552.5956
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Two new species, Hypancistrus phantasma and Hypancistrus margaritatus, are described based on material from the Rio Negro drainage. Both species are distinguished from congeners by unique color patterns. Hypancistrus phantasma is described from the Rio Uaupes and differs from congeners by having a tan body with small dark spots (vs. dark with light spots or with saddles or stripes). Hypancistrus margaritatus is described from the Takutu River and differs from congeners by having densely-packed light spots on a dark brown background, with spots about the size of the nasal aperture (vs. sparse light spots either smaller or larger than the nasal aperture, or brown to black spots, saddles, or stripes).
Siluriformes , Guyana, Brazil, taxonomy, suckermouth armored catfish, Neotropics
Hypancistrus is a small genus comprising six species of loricariid catfishes in the tribe Ancistrini of the subfamily Hypostominae: H. zebra
Hypancistrus can be distinguished externally from most other hypostomines by having larger and fewer teeth on the dentary relative to the teeth on the premaxilla. Different numbers of teeth on the dentary and premaxilla are found in many loricariids, so this character is not always diagnostic (
Species of Hypancistrus are best distinguished from each other by their color pattern and cannot be separated by traditional morphometrics used in loricariids (
Measurements and counts follow
Hypancistrus phantasma can be distinguished from congeners by a color pattern consisting of a tan base coloration with black spots vs. a color pattern consisting of a dark base coloration and light spots (as in H. contradens, H. inspector, H. lunaorum and H. margaritatus) or a color pattern consisting of saddles, vermiculations, bands, or stripes (as in H. furunculus, H. debilittera, and H. zebra).
Morphometric data given in Table
Morphometric data of new Hypancistrus species. Morphometric data of Hypancistrus phantasma (n = 5) and Hypancistrus margaritatus (n = 1). Morphometric data except standard length are given as percentages of standard length.
H. phantasma | H. margaritatus | |||||
---|---|---|---|---|---|---|
Holotype | Avg | SD | Min | Max | Holotype | |
SL | 123.3 | 103.3 | 12.4 | 92.5 | 123.3 | 45.6 |
Predorsal Length | 42.3 | 42.8 | 0.4 | 42.3 | 43.4 | 45.5 |
Head Length | 35.0 | 35.8 | 0.5 | 35.0 | 36.5 | 38.4 |
Head-dorsal Length | 7.3 | 7.1 | 0.4 | 6.6 | 7.6 | 7.5 |
Cleithral Width | 30.6 | 31.4 | 0.8 | 30.6 | 32.7 | 31.2 |
Head-pectoral Length | 26.7 | 25.8 | 0.8 | 24.8 | 26.7 | 26.6 |
Thorax Length | 23.4 | 23.0 | 0.5 | 22.4 | 23.6 | 25.6 |
Pectoral-spine Length | 32.8 | 34.3 | 1.6 | 32.8 | 36.8 | 35.7 |
Abdominal Length | 24.6 | 25.0 | 0.2 | 24.6 | 25.2 | 24.2 |
Pelvic-spine Length | 26.5 | 27.3 | 0.9 | 26.3 | 28.5 | 33.3 |
Postanal Length | 32.4 | 32.6 | 0.7 | 32.1 | 33.8 | 34.1 |
Anal-fin spine Length | 10.3 | 11.7 | 0.9 | 10.3 | 12.6 | 14.6 |
Dorsal-pectoral Distance | 28.3 | 28.9 | 0.5 | 28.3 | 29.6 | 29.5 |
Dorsal spine Length | 32.3 | 33.8 | 2.1 | 32.1 | 36.7 | 36.6 |
Dorsal-pelvic Distance | 26.1 | 25.2 | 0.8 | 24.3 | 26.1 | 24.1 |
Dorsal-fin base Length | 28.3 | 27.7 | 0.6 | 26.7 | 28.3 | 29.0 |
Dorsal-adipose Distance | 16.9 | 16.5 | 0.7 | 15.2 | 17.1 | 16.1 |
Adipose-spine Length | 7.1 | 8.5 | 0.9 | 7.1 | 9.0 | 8.5 |
Adipose-upper caudal Distance | 13.4 | 14.3 | 1.1 | 13.4 | 15.8 | 11.9 |
Caudal peduncle Depth | 11.2 | 11.0 | 0.8 | 9.6 | 11.7 | 13.0 |
Adipose-lower caudal Distance | 21.2 | 22.4 | 0.8 | 21.2 | 23.1 | 21.0 |
Adipose-anal Distance | 19.4 | 19.2 | 0.5 | 18.3 | 19.6 | 19.5 |
Dorsal-anal Distance | 17.4 | 17.3 | 0.7 | 16.5 | 18.2 | 15.9 |
Pelvic-dorsal Distance | 28.2 | 28.1 | 0.7 | 27.0 | 28.9 | 26.0 |
Head-eye Length | 11.7 | 12.0 | 0.3 | 11.7 | 12.4 | 13.8 |
Orbit Diameter | 8.3 | 8.9 | 0.5 | 8.3 | 9.4 | 10.0 |
Snout Length | 19.7 | 19.7 | 0.3 | 19.3 | 20.0 | 21.0 |
Internares Width | 4.9 | 5.1 | 0.5 | 4.7 | 5.9 | 5.5 |
Interorbital Width | 15.1 | 16.1 | 0.7 | 15.1 | 16.8 | 17.9 |
Head Depth | 24.8 | 25.3 | 0.4 | 24.8 | 25.8 | 26.3 |
Mouth Length | 14.6 | 15.2 | 0.4 | 14.6 | 15.5 | 17.4 |
Mouth Width | 12.2 | 13.3 | 1.8 | 11.2 | 16.1 | 17.7 |
Barbel Length | 4.0 | 4.2 | 0.6 | 3.7 | 5.2 | 3.2 |
Dentary tooth cup Length | 4.0 | 3.9 | 0.4 | 3.4 | 4.5 | 2.3 |
Premaxillary tooth cup Length | 2.0 | 1.8 | 0.2 | 1.4 | 2.0 | 2.8 |
Caudal fin emarginate, lower lobe longer than upper. Ventral surface flat. Head tall. Snout short. Vertical through anterior margin of orbit about half-way between vertical through anterior margin of snout and vertical through posteromedial tip of supraoccipital. Head with steep angle in profile, roughly 45° from tip of snout to anterior margin of eye. Body depth increases gradually from anterior margin of eye to dorsal-fin origin, then decreases gradually from dorsal-fin origin to posterior insertion of adipose fin; caudal-peduncle depth increases slightly from insertion of adipose fin to origin of caudal fin.
Supraorbital crest low. Orbital opening oriented at less than 45°from sagittal plane. Interorbital isthmus between supraorbital crests flat. Supraoccipital crest low. Eye large with iris operculum. Gill opening restricted in L-conformation, with half of opening vertical and opening laterally and half of opening horizontal and opening ventrally.
Dorsal-fin spine short; depressed dorsal fin reaching anterior edge of or slightly beyond preadipose plate. Depressed pectoral-fin spine reaching beyond base of pelvic-fin rays; depressed pelvic-fin spine reaching beyond posterior insertion of anal fin. Dorsal fin II,7; caudal fin I,14,I; dorsal procurrent caudal-fin spines four to five, four in holotype; ventral procurrent caudal-fin spines four to five, four in holotype; anal fin i3–4 (one paratype examined with 3 anal-fin rays); pectoral fin I,6; pelvic fin i,5. Fin spines and rays supporting odontodes. Odontodes more elongate distally on pectoral-fin spine and ventrally on pelvic-fin spine than at base of pectoral- and pelvic-fin spines.
Lips papillose, forming oral disk less than half width of head. Maxillary barbels long (reaching past posterior edge of lower lip when extended posteriorly), thin, and pointed; barbel rugose proximally, almost smooth distally.
Median plates 24; mid-dorsal plates 22–24 (24 in holotype, mode 23); mid-ventral plates 24; rows of plates on caudal peduncle five. Dentary teeth two to three (two in holotype), teeth long and wide; premaxillary teeth four to seven (six in holotype), thinner and shorter than dentary teeth. In new teeth, medial cusps longer and wider than lateral cusps; in worn teeth, medial and lateral cusps of approximately the same length and width. Central buccal papilla absent.
Color. Specimens preserved in 70% alcohol with tan base color and small brown spots. Tan base coloration largely uniform, with paler region between orbits, posterior to orbit, and extending posterior to cleithrum. Naked areas white, including ventral surface and areas surrounding origins of pectoral- and pelvic-fin spines. Small brown spots evenly spaced on head. Brown spots on body larger than spots on head, increasing slightly and gradually in size posteriorly. Brown spots on body more closely spaced anteriorly and more distantly spaced posteriorly; on imaginary vertical-oblique lines through the spots, four to five spots occurring per line anteriorly diminishing to two spots per line posteriorly. No spots ventral to an imaginary line between origin of pelvic-fin spine and origin of dorsal caudal-fin spine. Fin rays tan, fin membranes of paired fins and anal fins hyaline. Dorsal-fin rays tan; dorsal-fin membrane tan at base, gradually fading to dark brown band at the distal edge. Caudal-fin membrane on lower lobe transitioning to brown posteriorly. Dark spots present on pectoral-fin rays, pelvic-fin rays, and dorsal-fin rays. Faint white, round spots on dorsal and caudal fins; on dorsal fin, white color more apparent on brown fin membranes than on rays. Odontodes on cheek and fin spines straw-colored with dark brown tips.
The specific epithet phantasma is Latin for “phantom,” and refers to its elusiveness (the described specimens represent the only known specimens, despite nearly a century passing since their collection) and its pale body coloration. It is treated as a noun in apposition.
CSBD F1701/
Hypancistrus margaritatus is distinguished from all congeners by its color pattern of dense, small, light-colored spots on a dark base color. Three other described species have a color pattern of light spots on a dark base color: H. inspector, H. lunaorum, and H. contradens. Hypancistrus margaritatus has consistently-sized spots on head and trunk about the size of the nasal aperture (vs. smaller spots on head than trunk in H. inspector, spots usually smaller than half the nasal diameter in H. lunaorum, and spots ranging in size from equal to or larger in diameter of nasal aperture in H. contradens). Hypancistrus margaritatus also has more spots, 23 in a lateral, horizontal series from snout tip to base of caudal peduncle 23 in holotype (vs. 8–20 spots in H. contradens; 8–16 in H. lunaorum). Hypancistrus margaritatus has more densely-packed spots relative to H. lunaorum, with spots on lateral surface of the body having a minimum interspot to spot diameter ratio ranging from 1.0–1.6 (vs. 1.9–4.4 in H. lunaorum).
Morphometric data given in Table
Caudal fin emarginate, lower lobe longer than upper. Ventral surface flat. Head tall. Snout short. Distance between verticals through tip of snout and anterior margin of orbit greater than distance between verticals through anterior margin of orbit and posteromedial tip of supraoccipital. Head with steep angle in profile, roughly 45º, from tip of snout to anterior margin of eye. Body depth increases gradually from anterior margin of the eye to dorsal-fin origin, then decreases gradually from dorsal-fin origin to insertion of adipose fin, then caudal peduncle depth increases slightly from insertion of adipose fin to caudal-fin origin.
Supraorbital crest pronounced. Orbital opening oriented at less than 45° from sagittal plane. Interorbital isthmus between supraorbital crests flat. Supraoccipital crest low. Eye large with iris operculum. Gill opening restricted in L-conformation, with half of opening vertical and opening laterally and half of opening horizontal and opening ventrally.
Dorsal-fin spine short; depressed dorsal fin reaching slightly beyond pre-adipose plate to origin of adipose fin. Depressed pectoral-fin spine reaching beyond base of pelvic-fin rays; depressed pelvic-fin spine reaching beyond posterior insertion of anal fin. Dorsal fin II,7; caudal fin I,14,I; four dorsal procurrent caudal-fin spines; four ventral procurrent caudal-fin spines; anal fin i4; pectoral fin I,6; pelvic fin i,5. Fin spines and rays supporting odontodes.
Lips papillose, forming oral disk approximately half the width of the head. Maxillary barbels long, not reaching past the posterior edge of the lower lip when extended posteriorly, thin, and pointed; barbel rugose proximally, almost smooth distally.
Median plates 24; mid-dorsal plates 23; mid-ventral plates 24; rows of plates on caudal peduncle five. Dentary teeth five on one side and six on other, long and wide. Premaxillary teeth eight, smaller than dentary teeth. Medial cusps longer and wider than lateral cusps, with cusps separate and angled away from one another (vs. parallel and adjacent). Central buccal papilla absent.
Color. Light yellow spots on dark brown base color in life (Figure
Hypancistrus margaritatus is described from a single specimen collected in the Takutu River, a tributary of the Rio Branco of the Rio Negro drainage.
The specific epithet is Latin for “adorned with pearls,” referring to the dense white spots on the body.
The holotype and only known specimen of the species was dual-accessioned at
A Hypancistrus from the Takutu River that may represent H. margaritatus has been designated as L404 in the aquarium pet trade (
Hypancistrus margaritatus appears to be rare, as only one specimen was collected during four expeditions that yielded 55,156 fish specimens (
Of the described species, Hypancistrus phantasma appears most similar to H. inspector, as both species have large maximum sizes relative to other Hypancistrus species and share the presence of dark distal edges on the dorsal and caudal fins. Hypancistrus inspector is found in the upper Rio Negro, and H. phantasma is found in the Rio Uaupes, a tributary to the Rio Negro. Because of their morphological similarity and close geographical proximity, H. inspector and H. phantasma may be closely related. They can be separated by the light base color and presence of dark spots in H. phantasma vs. dark base color with light spots in H. inspector. Although H. inspector is distinguished from H. contradens in part by having a dorsal fin that does not reach the adipose fin when depressed (
The specimens of Hypancistrus phantasma were collected in 1924, and it is likely their coloration has been affected by age since preservation. Nevertheless, the distal edge of the dorsal fin is relatively dark. Faded specimens of H. inspector do not have dark spots like those in H. phantasma, and merely show a reduction in intensity of coloration. Thus, even if the preserved color pattern in H. phantasma may not be representative of the live coloration, the presence of small dark spots on the body is diagnostic.
Hypancistrus margaritatus is most similar to the other small-bodied, spotted Hypancistrus: H. contradens and H. lunaorum. It differs from these species in having more body spots. In H. contradens and H. lunaorum, the spots increase in number allometrically (
Hypancistrus margaritatus is also similar to some undescribed forms of Hypancistrus. A specimen of Hypancistrus with small spots from the Rio Madeira was identified as Hypancistrus cf. inspector (
Both new species of Hypancistrus may be extremely rare. Hypancistrus margaritatus was only collected once, as a single specimen, in four collecting trips to the Takutu River region (
Locality data listed in
H. contradens:
H. inspector:
H. lunaorum:
We would like to thank D.C. Werneke for assistance with