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Hypancistrus Zebra

a new genus and species of uniquely pigmented ancistrine loricariid fish from the Rio Xingu, Brazil (Pisces: Siluriformes: Loricariidae)

By Isaac J. H. Insbrucker and Han Nijssen

Hypancistrus, a new genus, is distinguished from all other genera of the tribe Ancistrini by the combination of the following characteristics: snout margin completely covered with dermal ossifications; presence of an anal and an adipose fin; absence of filiform teeth; premaxillary teeth considerably smaller than mandibullary teeth; dorsal fin with six branched rays, the last one split to its base; depressed body; absense of a membraneous extension posterior to the last dorsal fin ray, reaching to adipose fin spine; no very wide head; no extremely long evertible interopercular odontodes. Its type and only included species is H. zebra, new species, based on specimans collected in the Rio Xingu, Est. Para, Brazil.

 

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Introduction

In this paper a new genus of the family Loricariidae (subfamily Ancistrinae, tribe Ancistrini) is established for a new species, Hypancistrus zebra. It was collected for commercial (aquarium) purposes by staff of Tropicarium Para (Belem). Specimens were sent to us by Maurice Kottelat for identification. The aim of this note is to provide this conspicuous species (referred to as "zebra pleco" in the aquarium trade, Kottelat, in litt.) with a scientific name and to compare it with its probably closest 'relative' (in traditional rather then in phylogenetic sense), withdrawing it from its present nomenclatural anonymity.

Material and methods

Morphometric and meristic data were taken as in previous papers by the authors on Ancistrinae (e.g. Heitmans et al., 1983: 34-35). The state of preservation of all paratypes is not quite perfect, as they were aquarium fishes which died at different times under different circumstances. Eleven specimens (holotype included) were selected to measure and count, an additional 9 paratypes were used for counting the teeth (see Table 1). Of the 10 paratypes choosen to take morphometric and meristic data from, 4 have the dorsal fin spine damaged, 6 the anal fin spine and the longest branched anal fin ray, 2 the pelvic fin spine, and 6 the upper- and lower caudal fin spine.

Material of the new taxon is deposited in Museu de Zoologia da Universidade de Sao Paulo (MZUSP), Instituto Nacional de Pesquisas da Amazonia, Manus (INPA), Institute of Taxonomic Zoology, Zoologisch Museum Amsterdam (ZMA), Zoologische Staatssammlung Munchen (ZSM) and in Museum d'Histoire naturelle, Geneve (MHNG).


Fig 1. Hypancistrus zebra,MZUSP 41668, 41.4 mmSL., holotype in dorsal, lateral and ventral view.

Hypancistrus, new genus

Type species. Hypancistrus zebra, new species.

Diagnosis. Hypancistrus is distinguished from all other genera of the tribe Ancistrini by the combination of the following characters: (1) snout margin completely covered with dermal ossifications; (2) presence of an anal and an adipose fin; (3) absence of filiform teeth; premaxillary teeth (8-16 in number) considerably smaller than mandibullary teeth (4-7); (4) possession of six branched dorsal fin rays, the last one split to its base; (5) a depressed body; (6) absence of a membraneous extension posterior to the last dorsal fin ray, reaching to adipose fin spine; (7) no very wide head; (8) no extremely long evertible interopercular odontodes.

Comparison. Within the tribe Ancistrini (Isbrucker, 1980: 43-75), most genera exclusively contain species with numerous filiform teeth (comparable to the dentition of several genera within Hypostominae and some within Loricariinae). Only Panaque Eigenmann & Eigenmann, 1889 (with 6 species), Scobinancistrus Isbrucker & Nijssen,1989 (1 species), Oligancistrus Rapp Py-Daniel,1989 (1 species), and Hypancistrus (1 species) are characterized by having a reduced number of teeth, none of which is filiform. In number and size of teeth, Hypancistrus and Oligancistrus are more reminiscent of each other than both are of Panaque and Scobinancistrus. In the absence of any good reason to include H. zebra either in Panaque, Scobinancistrus, Oligancistrus, or in any one of the other available genera, it is assigned to a new genus.

Hypancistrus is most reminiscent of Oligancistrus Rapp Py-Daniel, 1989, which does not imply that they are most closely related phylogenetically. The main differences between Hypancistrus and Oligancistrus are the numbers of teeth (premaxillary teeth 8-16 vs. 7-11); mandibular teeth 4-7 vs. 14-25); premaxillary teeth are considerably smaller than mandibulary teeth (vs. the reverse in Oligancistrus); dorsal fin free from adipose fin (vs. connected by membrane); snout covered with dermal ossifications not showing sutures (vs. sutures distinctly visible); position of scute odontodes on ventral part of caudal peduncle dorsad (vs. axial); Hypancistrus has a more depressed body (body depth at dorsal fin origin 5.4-5.9 in SL, vs. 4.4-5.1); caudal fin forked (vs. weakly concave).

 


Fig. 2. Hypancistrus zebra, a living specimen, about 50 mm SL., collected with the type series.

 

  Holotype range mean SD
SL (mm)        
         
ratios        
SL / head length 2.8 2.8 - 3.0 2.9 0.06
SL / predorsal length 2.3 2.3 - 2.5 2.5 0.07
SL / postdorsal length 3.2 2.7 - 3.2 2.9 0.13
SL / postanal length 3 3.0 - 3.3 3.1 0.09
SL / dorsal spine length 3.1 3.0 - 3.5 3.2 0.16
SL / anal spine length 8.6 7.9 - 9.2 8.5 0.44
SL / anal fin height 6.4 6.4 - 8.5 7.7 0.80
SL / pectoral spine length 3.1 3.0- 3.3 3.7 0.11
SL / pelvic spine length 3.7 3.5 - 4.l 3.8 0.19
SL / adipose fin length 10.4 10.0 - 12.2 10.8 0.69
SL / upper caudal spine length 7 2.9 - 7.0 4.4 2.26
SL / lower caudal spine length 5.5 2.9 - 5.5 3.9 1.40
HL / snout length 1.9 1.9 - 2.0 2.0 0.04
HL / ower lip length 7.4 5.6 - 8.9 7.4 1.02
HL / barbel length 11.3 7.6 - 18.8 10.7 3.09
HL / barbel + lip 3.8 3.6 - 4.5 4.0 0.26
HL / thoracic length 1.6 1.4 - 1.7 1.5 0.11
HL / abdominal length 1.5 1.4 - 1.7 1.5 0.10
HL / orbital diameter 4.2 3.9 - 4.4 4.2 0.16
HL / interorbital width 3.2 3.0 - 3.6 3.4 0.19
HL / cleithral width 1.1 1.0 - 1.1 1.1 0.02
HL / supradeithral width 1.5 1.3 - 1.5 1.4 0.04
HL / head depth 2 1.8 - 2.0 1.9 0.05
HL / body depth at dorsal fin 2 1.9 - 2.1 2.0 0.07
HL / body width at dorsal fin 1.6 1.4 - 1.6 1.5 0.08
HL / body width at anal fin 2.7 2.4 - 3.0 2.7 0.18
HL / depth caudal peduncles 3.6 3.5 - 3.9 3.7 0.12
HL / width caudal peduncle 7.4 6.9 - 8.2 7.6 0.40
         
counts        
lateral scutes left 24 23 - 26 24.5 0.82
lateral scutes right 24 24 - 25 24.4 0.50
predorsal scutes 3 3    
scutes along dorsal fin 8 7 - 8 7.8 0.40
interdorsal scutes 5 4 - 6 4.8 0.60
scutes along anal fin 1 1    
postanal scutes 12 11 - 13 11.9 0.54
transoccipital scutes left 4 4    
transcxcipital scutes right 4 4    
preadipose scutes 2 1 - 2 1.1 0.30
adipose fin membrane 4 3 - 4 3.2 0.40
premaxillary teeth left 12 8 - 16 12.7 2.25
premaxillary teeth right 15 8 - 15 12.3 2.13
mandibular teeth left 7 4 - 7 5.1 0.85
mandibular teeth right 6 4 - 7 5.0 0.65

Table 1. Morphometric and meristic characters of Hypancistrus zebra. Abbreviations: HL, head length; SD, standard deviation; SL, standard length.

Etymology. A contraction of the Greek hypo (meaning less than) and ancistrus, an allusion to
the number of teeth. Gender: masculine.

Hypancistrus zebra, new species
(Figs. 1-2)

Holotype. MZUSP 41668 (ex-ZSM 27328), 41.4 mm SL; Brazil, Est Para, anastomoses of Rio Xingu, about one hour upstream of Altamira by speedboat (Altamira: 03°13'S 52°15'W); don. A. Werner, 1989.

Paratypes. 223 specimens, largest 64.1 mm SL. ZSM 27328,1 ex., 24.0 mm SL; ZSM 27438, 22 ex., 26.9-57.5 mm SL; ZSM 27769, 27 ex., 29.7-46.4 mm SL; ZSM 27770, 48 ex., 21.2-64.1 mm SL; ZMA 120.655, 8 ex., 34.3-51.7 mm SL; ZSM 27962, 16 ex., 27.8-58.9 mm SL; ZMA 120.457, 10 ex., 31.8-55.0 mm SL; MHNG 2513.24, 8 ex., 34.1-54.8 mm SL; same data as holotype. - ZSM 27963, 43 ex., 22.2-50.3 mm SL; MZUSP uncat., 20 ex., 32.2-48.2 mm SL; INPA 4338, 20 ex., 27.2-43.2 mm SL; same data, X 1990.

Description. Morphometric data of holotype in mm: standard length 41.4; axial length 46.5; total length >49.8 (tips of both upper and lower caudal fin lobes damaged); head length 14.7; predorsal length 17.8; postdorsal length 13.1; postanal length 13.6; dorsal spine length 13.3; anal spine length 4.8; anal fin height 6.5; pectoral spine length 13.5; pelvic spine length 11.3; adipose spine length 4.0; upper caudal spine length >5.9 (damaged); lower caudal spine length >7.5 (damaged); snout length 7.6; lower lip length 2.0; maxillary barbel length 1.3 (left barbel, the right one is shorter); maxillary barbel plus lip length 3.9; thoracic length 9.3; abdominal length 9.9; maximum orbital diameter 3.5; interorbital width 4.6; cleithral width 74.0; supradeithral width about 10 (left cleithrum damaged, adjacent temporal plate is missing); head depth 7.5; body depth at dorsal fin origin 7.5; body width at dorsal fin origin 9.0; body width at anal fin origin 5.4; depth caudal peduncle 4.1; width caudal peduncle 2.0.
Counts (including 10 paratypes): dorsal fin rays I,6,i (last one split to its base); anal fin rays I,3,i (last one split to its base); pectoral tin rays I,6; pelvic fin rays 1,5; caudal fin rays 1,14,1 one paratype with 12, another one with 13 branched caudal fin rays.
Evertible interopercttlar odontodes of the holotype 15/15.

Tip of snout with a feeble depression on both sides, best seen in dorsal view. Supraoccipital process acute.
Caudal fin forked, lower lobe longest (caudal fin heavily damaged in most of the specimens).
Abdomen naked, except for some small, irregular dermal ossifications covered with minute odontodes, along posterior margin of underlying pelvic girdle in some specimens.
Lateral line hardly visible.
Outer surface of upper lip is narrow and naked. The tip of snout has a small, roundish naked area. Inner surface of narrow upper lip and of broader lower lip covered with numerous low papillae, except along anterior and posterior margins. Posterior margin of lower lip with numerous irregular minute flat flaps. Protruding part of the maxillary barbel connected to lower lip by a small triangular membrane.
Buccal cavity smooth.
Premaxilla with 8-16 small, bilobed teeth, the inner lobe somewhat longer than the outer. Tip of inner lobe roundish, of outer lobe more acute. Dentary with 4-7 teeth, in shape resembling the premaxillary teeth, at least twice the size of the latter.
Dermal ossifications (including tin spines and most of the fin rays) with odontodes, those on posterior half of body with their tips in a progressively more oblique upward direction. Pectoral fin spine with conspicuous odontodes, especially distally. Interopercular area with a bunch of prominent, slender, evertible odontodes, which posteriorly are considerably longer than anteriorly, where they progressively merge with non-evertible odontodes.
Orbital rim hardly raised. Eye partly covered with a large median flap, originating dorsally.

Secondary sexual dimorphism. Nuptial males with more conspicuous odontodes on pectoral fin spine and with longer evertible odontodes in interopercular area than present in females.

Colour in alcohol (Figs. 1-2). Ground colour (also of naked belly) whitish. On dorsum of snout, just anterior to orbital rim, solid black pigment forms a pattern reminiscent of a transversely arranged capital letter E (i.e., a narrow transverse stripe with anteriorly three rather broad parallel stripes). Posterior half of interorbital area with a broad, transverse, solid black stripe at either side just behind and below orbital, connected with a stripe obliquely running forward and down. Body with a broad, solid black, transverse stripe from about or slightly posterior to base of pectoral fin spine; this stripe extends on the first few pectoral fin rays almost to their distal tips forming a stripe along the inner side of the spine; frequently a second stripe parallel to the anterior one is visible.
From this anterior transverse body stripe two oblique stripes reach posterior half of dorsal fin base. This pigmentation is variable: posterior to occipital process a third (median) stripe may be present; it can entirely or partly stretch between occipital process and anterior half of dorsal fin base. Body with two or three solid black stripes, anteriorly lower than posteriorly, the pairs of left and right sides meeting dorsally.

Dorsal fin with two or three narrow, solid black, horizontal lines, of which the lower one is frequently connected to body pigment.
Caudal fin with up to seven oblique or horizontal solid black markings.
Dorsum of pelvic fins with one or two stripes running posterior to inner edge of first (unbranched) ray.
Pigment on anal fin negligable.
Colour in life (from colour transparencies). Black and white

Etymology. The Abyssinian name for the striped equine of Africa. A noun in apposition.

A note on the type locality
of
Oligancistrus punctatissimus

Steindachner (1882) described Chaetostomus punctatissimus (type species of Oligancistrus, with which Hypancistrus was compared in detail) from a single specimen, stating (1882:120):

"Das beschriebene Exemplar [= holotype] ist 13 1/2 cm lang und stammt aus dem Amazonen- Strome ohne nahere Angabe des Fundortes".

During a visit to Naturhistorisches Museum Wien, we encountered a single specimen of Chaetostomus punctatissimus. It agrees in all details of Steindachner's description and the accompanying figure by Konopicky (in Steindachner, 1882, pl. 3 figs. 3, 3a). This specimen, NMW 47206, 105.8 mm SL, is beyond doubt the holotype. The locality on its label reads: "Porto Moz", hence, the type locality of Oligancistrus punctatissimus is: Brazil, Est. Para, Porto de Mos, on eastern shore of Rio Xingu, Ol°45'8, 52°10'W. It is plausible to assume that while Steindachner wrote the manuscript of this paper, the only specimen of this species - including its locality label - was with its artist.

Acknowledgments

Dr. Maurice Kottelat (ZSM) and Mr. Arthur Werner (Munich) kindly provided us with the type series, Mr. Louis A. van der Laan (ZMA) made the photographs of the holotype and Mr. Rainer Stawikowski (Gelsenkirchen) provided Figure 2. (Ichthyological Exploration of Freshwaters, Volume 1, Number 4, March 1991).

Literature cited

Heitmans, W. R. B., H. Nijssen & I. J. H. Isbriicker.1983. The mailed catfish genus Lasiancistrus Regan, 1904, from French Guiana and Surinam, with descriptions of two new species (Pisces, Siluriformes, Loricariidae). Bijdr. Dierk., 53: 33-48.
Isbriicker, I. ]. H. 1980. Classification and catalogue of the mailed Loricariidae (Pisces, Siluriformes). Verslagen en technische Gegevens, Inst. Taxon. Zool. (Zool. Mus.), Univ. Amsterdam, 22: I-188.
Isbriicker, I. J. H. & H. Nijssen. 1989. Diagnose dreier neuer Harnischwelsgattungen mit funf neuen Arten aus Brasilien (Pisces, Siluriformes, Loricariidae). Die Aquarien- and Terrarien-Zeitschrift, 42: 541-547.
Rapp Py-Daniel, L. H. 1989. Redescription of parancistrus aurantiacus (Castelnau,1855) and preliminary establishment of two new genera: Baryancistrus and Oligancistrus (Siluriformes, Loricariidae). Cybium, 13:235-246.
Steindachner, F.1882. Beitrage zur Kenntniss der Flussfische Sudamerika's. II. Denkschr. Akad. Wiss. Wien, Math.-Naturwiss. Cl., 43: 103-146, 7 pls.