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https://doi.org/10.11646/zootaxa.4948.2.2
http://zoobank.org/urn:lsid:zoobank.org:pub:E36ADD5D-B461-4082-8B53-F21AD3D3750C
184 Accepted by J. Armbruster: 18 Feb. 2021; published: 19 Mar. 2021
Article ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Zootaxa 4948 (2): 184–200
https://www.mapress.com/j/zt/
Copyright © 2021 Magnolia Press
A new arc-striped species of Corydoras Lacépède, 1803 (Teleostei: Callichthyidae)
from the Peruvian Amazon
REBECCA FRANCES BENTLEY1, STEVEN GRANT2 & LUIZ FERNANDO CASERTA TENCATT3,4
17 Sweet Briar, Crowthorne, Berkshire, England, RG45 6TJ.
2C/o 4 Milton Street, Castleford, England, WF10 1LW.
3Universidade Federal de Mato Grosso do Sul, Instituto de Biociências, Setor de Zoologia, Laboratório de Ictiologia, Avenida Costa e
Silva, s/nº, Cidade Universitária, 79070-900 Campo Grande, Mato Grosso do Sul, Brazil.
4Universidade Estadual de Mato Grosso do Sul, Unidade Universitária de Coxim, Rua General Mendes de Moraes, 370, Jardim Aero-
porto, 79400-000 Coxim, Mato Grosso do Sul, Brazil.
Abstract
A new Corydoras is described from the Blanco and Ucayali river basins in Peru. The new species can be distinguished
from its congeners by having the following features: (I) posterior margin of dorsal-fin spine with laminar serrations
directed towards the origin of the spine; (II) a long, wide, arched, and continuous black stripe, which runs parallel to
the dorsal profile of the body, extending at least from the region below anterior origin of dorsal fin to the anterior half
of the ventral caudal-fin lobe; (III) a black stripe transversally crossing the eye, forming the typical mask-like blotch;
mask clearly not fused to arched stripe in most specimens; some specimens with mask separated from arched stripe by
a thin line around the suture between neurocranium (in the region composed by the posteroventral margin of parieto-
supraoccipital plus the posterodorsal margin of the compound pterotic) and first dorsolateral body plate; (IV) posterior
margin of pectoral-fin spine with laminar serrations directed towards the origin of the spine; (V) pointed snout, presenting
a long mesethmoid, with anterior tip larger than 50% of the entire length of the bone; and (V) ventral surface of trunk
covered by small, non-coalescent platelets. A discussion on the possible positive adaptive value of the arc-striped color
pattern is also provided.
Key words: Aposematism, Corydoradinae, mimicry, río Blanco, taxonomy
Resumo
Uma nova Corydoras é descrita das bacias dos rios Blanco e Ucayali, no Peru. A espécie nova pode ser distinguida de suas
congêneres por apresentar as seguintes características: (I) margem posterior do espinho da nadadeira dorsal com serrilhas
laminares direcionadas para a origem do espinho; (II) uma faixa preta longa, larga, arqueada e contínua, que corre paralela
ao perfil dorsal do corpo, estendendo-se pelo menos da região abaixo da origem anterior da nadadeira dorsal até a porção
mediana do raio não ramificado ventral da nadadeira caudal; (III) uma faixa preta cruzando transversalmente o olho,
formando a típica mancha semelhante a uma máscara; máscara claramente não fundida a faixa arqueada na maioria dos
espécimes; alguns espécimes com máscara separada da faixa arqueada por uma linha fina ao redor da sutura entre o
neurocrânio (na região composta pela margem póstero-ventral do parieto-supraoccipital mais a margem póstero-dorsal
do pterótico composto) e a primeira placa dorsolateral do corpo; (IV) margem posterior do espinho da nadadeira peitoral
com serrilhas laminares direcionadas para a origem do espinho; (V) focinho pontudo, apresentando um mesetmóide
longo, com a ponta anterior maior que 50% de todo o comprimento do osso; e (V) superfície ventral do tronco coberta por
pequenas placas não coalescentes. Uma discussão sobre a possível valor adaptativo positivo do padrão de cor com faixa
arqueada também é fornecida.
Palavras chave: Aposematismo, Corydoradinae, mimetismo, río Blanco, taxonomia
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 185
Introduction
Corydoras Lacépède, 1803, is currently the most species-rich genus within Siluriformes, with over 170 valid spe-
cies (Tencatt et al., 2019; Lima & Britto, 2020), and at least another 225 phenotypes and morphotypes recognized by
aquarists by way of code numbers (see Tencatt & Evers, 2016 for further discussion on coding system for Corydo-
radinae species). The phylogenetic relationships within the genus and Corydoradinae were hypothesized by Britto
(2003) using morphological data, and by Alexandrou et al. (2011), using molecular data. However, questions still
remain about the monophyly of the genus, and the validity and usage of several available generic names currently
considered as junior synonyms of Corydoras. Despite that, the phylogenetic hypothesis provided by Alexandrou
et al. (2011) allowed the recognition of nine lineages of Corydoradinae, with seven of them (lineages 1, 4, 5, 6,7,
8 and 9) harbouring the species within Corydoras, which have been continuously used to assist the delimitation of
Corydoras species in recent works (Tencatt & Pavanelli, 2015; Tencatt & Ohara, 2016a,b; Bono et al., 2019; Tencatt
et al., 2019; Lima & Britto, 2020)
Fuller & Evers (2011) designated the code number CW006 for a species imported from Peru, under the trade
name ‘narciso’ and ‘narcissus II’. Recently, Tencatt et al. (2019) performed a taxonomic revision of C. arcuatus
Elwin, 1938, an arc-striped species from the lineage 8 sensu Alexandrou et al. (2011), reporting the presence of a
potential new species coded as CW006, which was considered different from C. arcuatus by color pattern details.
Examination of CW006 specimens imported for the aquarium trade from Peru, río Tapiche basin, allowed its recog-
nition as a new species. Therefore, the aim of the present contribution is to formally describe this species and discuss
the possible positive adaptive value of the arc-striped color pattern.
Material and methods
Measurements were obtained using digital caliper to the nearest tenth of millimeter. Morphometric and meristic data
were taken following Reis (1997) with the modifications of Tencatt et al. (2013). The last two dorsal-fin rays were
counted as distinct elements. Morphometrics are reported as proportion of standard length (SL) or as proportions of
head length (HL). Homology of barbels follows Britto & Lima (2003). For the osteological analysis, some speci-
mens were cleared and stained (CS) according to the protocol of Taylor & Van Dyke (1985). Osteological terminol-
ogy was based on Reis (1998), except for parieto-supraoccipital instead of supraoccipital (Arratia & Gayet, 1995),
compound pterotic instead of pterotic-supracleithrum (Aquino & Schaefer, 2002), and scapulocoracoid instead of
coracoid (Lundberg, 1970). Nomenclature of the latero-sensory canals and preopercular pores are according to
Schaefer & Aquino (2000) and Schaefer (1988), respectively. The supra-preopercle sensu Huysentruyt & Adriaens
(2005) was treated here as a part of the hyomandibula according to Vera-Alcaraz (2013). Vertebral counts include
only free centra, with the compound caudal centrum (preural 1+ ural 1) counted as a single element. Pharyngeal
teeth were counted in both sides of the branchial arches. The stripes were recognized as in Tencatt & Ohara (2016a).
In the description, numbers in parentheses represent the frequency of a given count. The mask-like blotch was rec-
ognized herein as an elongated dark bar vertically crossing eye. Asterisks refer to the counts of the holotype. Coor-
dinates used to prepare the map of geographical distribution are approximations established on basis of the available
information on collecting data. Institutional abbreviations follow Sabaj (2016).
Corydoras bethanae, new species
(Figs. 1, 2A, 3A, 4-6, Table 1)
Corydoras sp. CW006:—Alexandrou et al., 2011: 85–86 (“C. sp. CW6”; phylogeny; as member of the lineage 8; mimicry).—
Tencatt et al., 2019: 459–460 (comparison with C. arcuatus; photo in life (fig. 8) of the specimen designated as holotype
herein).
Holotype. MUSM 69403, female, 51.2 mm SL, Peru, Department of Loreto, Requena Province, Soplin District, río
Blanco (close to the confluence with the río Tapiche), aquarium specimen imported in 2017 by Aquarium Glaser
GmbH, Germany.
Paratypes. BMNH 2017.5.25.1-21, 21, 43.7–57.3 mm SL, same data as holotype; BMNH 2018.7.5.4-5, 2,
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56.0–56.0 mm SL; MNRJ 52311, 1, 53.1 mm SL; ZUFMS 6470, 1 of 3, 49.9 mm SL, 2 CS of 3, 55.0–56.9 mm
SL, Peru, Department of Loreto, said to be from the río Ucayali basin, aquarium specimens imported in 2018 by
Maidenhead Aquatics, Wigan, UK.
FIGURE 1. Corydoras bethanae, holotype, MUSM 69403, female, 51.2 mm SL, Peru, Department of Loreto, río Blanco, in
dorsal (upper), lateral (middle), and ventral (lower) views. Photo by Nemo Martin; ©The Trustees of the Natural History Mu-
seum, London.
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 187
Diagnosis. Corydoras bethanae can be distinguished from its congeners, except for those belonging to the
lineage 8 sensu Alexandrou et al. (2011), by having the posterior margin of dorsal-fin spine with laminar serrations
directed towards the origin of the spine (vs. absence of such serration pattern); from the species within lineage 8,
except for C. arcuatus, it differs by the presence of a long, wide, arched, and continuous black stripe, which runs
parallel to the dorsal profile of the body, extending at least from the region below anterior origin of dorsal fin to the
anterior half of the ventral caudal-fin lobe (Fig. 2A) (vs. absence of a similar stripe in remaining lineage 8 conge-
ners); from C. arcuatus (Fig. 2B) differs by the color pattern of the head (presence of a black stripe transversally
crossing the eye, forming the typical mask-like blotch; mask clearly not fused to arched stripe in most specimens;
some specimens with mask separated from arched stripe by a thin line around the suture between neurocranium (on
the region composed by the posteroventral margin of parieto-supraoccipital plus the posterodorsal margin of the
compound pterotic) and first dorsolateral body plate in C. bethanae (Figs. 3A and 6) vs. mask-like blotch absent;
continuous black stripe extending from area at corner of mouth to anteroventral margin of orbit and starting again
from posterodorsal margin of orbit; running close and in parallel to dorsum from this point to anterior margin of first
dorsolateral body plate, merging with trunk section of the arched stripe in C. arcuatus (Fig. 3B), by having a longer
snout (53.4–67.4% of HL vs. 42.1–51.5), a smaller HL (30.4–34.7% of SL vs. 41.1–51.4), and a larger least inter-
orbital distance (42.6–49.2% of HL vs. 28.7–36.0). Additionally, the new species differs from C. gracilis Nijssen &
Isbrücker, 1976 and C. narcissus Nijssen & Isbrücker, 1980a by having laminar serrations on posterior margin of
pectoral-fin spine (vs. conical); from C. gracilis and C. urucu Britto, Wosiacki & Montag, 2009 by having pointed
snout, presenting a long mesethmoid, with anterior tip larger than 50% of the entire length of the bone (vs. rounded
snout, presenting a short mesethmoid, with anterior tip smaller than 50% of the entire bone length); from C. granti
Tencatt, Lima & Britto, 2019 (Fig. 2C) by having ventral surface of trunk covered by small, non-coalescent platelets
(vs. ventral surface of trunk entirely or partially covered by relatively large and coalescent platelets).
Description. Morphometric data are presented in Table 1. Head laterally compressed with convex dorsal pro-
file, roughly triangular in dorsal view. Snout conical in dorsal view, ranging from pointed to conspicuously pointed.
Head profile in lateral view slightly concave from tip of snout to anterior nares, ascending slightly concave from this
point to anterior portion of parieto-supraoccipital process; slightly convex or nearly straight from this point to dor-
sal-fin origin. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile slightly concave to adipose-
fin spine, concave from this point to caudal-fin base. Ventral profile of body nearly straight or slightly convex from
isthmus to pectoral girdle, and slightly convex from this point until pelvic girdle. Profile nearly straight or slightly
convex from pelvic girdle to base of first anal-fin ray, ascending abruptly concave until caudal-fin base. Body
roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.
Eye rounded, located dorsolaterally on head. Orbit delimited anteriorly by lateral ethmoid, anterodorsally by
frontal, posterodorsally by sphenotic, posteriorly by infraorbital 2, and ventrally by infraorbital 1. Anterior and
posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to
anterodorsal margin of orbit, separated from it by distance slightly larger than naris diameter. Mouth small, subter-
minal, width slightly smaller than bony orbit diameter. Maxillary barbel long in size, reaching anteroventral limit
of gill opening. Outer mental barbel slightly longer than maxillary barbel. Inner mental barbel fleshy, base of each
counterpart slightly separated from each other. Small rounded papillae covering entire surface of all barbels, upper
and lower lips, snout and isthmus.
Mesethmoid long with anterior tip well developed, larger than 50% of bone length (see Britto, 2003: 123, char-
acter 1, state 0; fig. 1A); posterior portion relatively narrow, entirely covered by thin layer of skin. Middle portion
of mesethmoid with strongly well-developed lateroventral process; region of process with width clearly larger than
width of posterior portion of mesethmoid. Nasal capsule delimited anteriorly and ventrally by lateral ethmoid, and
posteriorly and dorsally by frontal. Nasal slender, laterally curved, inner margin laminar; mesial border contacting
only frontal. Lateral ethmoid conspicuously expanded anteriorly, with anterodorsal expansion contacting frontal
and mesethmoid, and anteroventral expansion connected to lateroventral process of mesethmoid. Frontal elongated,
ranging from narrow, width less than half of entire length, to relatively wide, with width equal to half of entire
length; anterior projection long, size equal to or slightly larger than nasal length. Frontal fontanel large, slender, and
somewhat ellipsoid; posterior tip extension entering anterior margin of parieto-supraoccipital. Sphenotic somewhat
trapezoid, contacting parieto-supraoccipital dorsally, compound pterotic posteriorly, second infraorbital ventrally
and frontal anteriorly (Fig. 4). Compound pterotic roughly pipe-shaped, with posteriormost portion contacting first
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lateral-line ossicle, posteroventral margin contacting cleithrum, and anteroventral margin contacting opercle and
infraorbital 2, and posterior expansion almost entirely covering lateral opening of swimbladder capsule, leaving
slender area on its dorsal margin covered only by thick layer of skin (Fig. 4). Parieto-supraoccipital wide, posterior
process long and contacting nuchal plate; region of contact between posterior process and nuchal plate covered by
thick layer of skin.
TABLE 1. Morphometric data of the holotype and 24 paratypes of Corydoras bethanae. Values of the holotype included
in range and median. SD = standard deviation.
Holotype Range Mean±SD
Standard length (mm) 51.2 43.7–57.5 49.3±3.7
Percents of standard length
Depth of body 35.7 35.1–38.6 36.7±1.0
Predorsal distance 43.8 41.7–50.4 47.2±2.5
Prepelvic distance 46.3 44.2–48.0 46.5±0.9
Preanal distance 78.0 72.8–80.7 77.8±1.5
Preadipose distance 76.9 76.9–83.6 80.2±1.7
Length of dorsal-fin spine 25.2 21.9–26.8 24.7±1.3
Length of pectoral-fin spine 22.3 21.5–26.1 23.4±1.3
Length of adipose-fin spine 10.2 8.6–10.6 9.5±0.6
Depth of caudal peduncle 15.8 8.0–16.0 14.7±1.6
Length of dorsal-fin base 21.1 19.1–25.8 21.5±1.5
Dorsal to adipose distance 14.5 13.4–21.8 16.2±1.8
Maximum cleithral width 23.0 21.6–24.8 23.1±0.9
Head length 31.2 30.4–34.7 32.4±1.0
Length of maxillary barbel 21.0 14.6–22.9 19.1±2.3
Percents of head length
Head depth 70.4 58.6–81.7 72.1±5.6
Least interorbital distance 48.8 42.6–49.2 45.7±1.8
Horizontal orbit diameter 28.9 20.7–30.2 26.8±2.1
Snout length 59.0 53.4–67.4 58.9±2.9
Least internarial distance 27.3 15.0–29.0 21.3±4.2
Two laminar infraorbitals with minute odontodes. Infraorbital 1 large, ventral laminar expansion moderately
developed, anterior portion with well-developed laminar expansion, reaching to or slightly surpassing anterior mar-
gin of nasal capsule; inner laminar expansion strongly reduced (Fig. 4). Infraorbital 2 small, widened, with pos-
terior laminar expansion well developed; posteroventral margin contacting posterodorsal ridge of hyomandibula,
posterodorsal edge contacting sphenotic and compound pterotic; inner laminar expansion strongly reduced (Fig. 4).
Posterodorsal ridge of hyomandibula close to its articulation with opercle relatively slender, exposed, and bearing
small odontodes. Dorsal ridge of hyomandibula between compound pterotic and opercle covered by thick layer of
skin; covered by posterodorsal edge of infraorbital 2 in some specimens. Interopercle partially exposed, with an-
terior portion covered by thick skin layer; subtriangular, anterior projection well-developed. Preopercle elongated,
ranging from relatively slender to widened; minute odontodes sparse on external surface. Opercle dorsoventrally
elongated, width smaller than half of entire length; free margin slightly convex, without serrations and covered by
small odontodes.
Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and
directed towards anterior portion, posterior margin cartilaginous; ossified portion conspicuously well developed,
its size about three times cartilaginous portion. Five ceratobranchials with expansions increasing posteriorly; cera-
tobranchial 1 with small process on anterior margin of mesial portion; ceratobranchial 3 with continuous laminar
expansion on postero-lateral margin; ceratobranchial 5 toothed on posterodorsal surface, with 34 to 42 (2) teeth
aligned in one row. Four epibranchials with similar size; epibranchial 2 slightly larger than others, with small
pointed process on laminar expansion of posterior margin; epibranchial 3 with roughly triangular or somewhat
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 189
FIGURE 2. A. Corydoras bethanae, holotype alive, MUSM 69403, female, 51.2 mm SL, Peru, Department of Loreto, río
Blanco. B. Corydoras arcuatus unpreserved aquarium specimen. C. Corydoras granti unpreserved aquarium specimen from
Peru, río Tapiche. Photos A and C by Steven Grant, B by Hans-Georg Evers.
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trapezoid uncinate process on laminar expansion of posterior margin; uncinate process curved mesially in left side
of paratype ZUFMS 6470, 56.9 mm SL. Two wide pharyngobranchials (3 and 4); pharyngobranchial 3 with roughly
triangular laminar expansion on posterior margin; variably notched expansion in some specimens. Upper tooth plate
oval, 34 to 47 (2) teeth aligned in two rows on posteroventral surface.
Lateral-line canal reaching cephalic laterosensory system through compound pterotic, branching twice before
reaching sphenotic: pterotic branch, with single pore, preoperculomandibular branch conspicuously reduced, with
single pore opening at postotic main canal; postotic main canal becoming widened just posterior to pterotic branch.
Sensory canal continuing through compound pterotic, reaching sphenotic as temporal canal, which splits into two
branches: one branch giving rise to infraorbital canal, other branch connecting to frontal through supraorbital canal,
both with single pore. Supraorbital canal branched, running through nasal bone. Epiphyseal branch conspicuously
reduced; pore opening close to supraorbital main canal, directed towards frontal fontanel. Nasal canal with two or
three openings, first on posterior edge, second, when present, on posterolateral portion and generally fused with first
pore, and third on anterior edge. Infraorbital canal running through entire infraorbital 2, extending to infraorbital 1
and opening into two pores. Preoperculomandibular branch giving rise to preoperculo-mandibular canal, which runs
through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively.
FIGURE 3. Dorsal view of the head of A. the holotype of Corydoras bethanae, MUSM 69403, female, 51.2 mm SL., show-
ing the gap (yellow arrow) between body stripe and mask-like blotch, and B. Corydoras arcuatus, MNRJ 51069, 47.8 mm SL,
showing the continuous stripe on region posterior to eye. Photo A. by Nemo Martin, and B. by Bruno Ferreira. Scale bar: 1
mm.
Dorsal fin subtriangular, located just posterior to second or third dorsolateral body plate. Dorsal-fin rays II,7 (1),
II,8* (19), I,9 (4), posterior margin of dorsal-fin spine with 18 to 19 poorly to moderately-developed laminar serra-
tions; most serrations directed towards origin of spine; some serrations variably perpendicularly directed; serrations
absent close to origin of spine; small odontodes on anterior and lateral surfaces of spine (Fig. 5A). Nuchal plate well
developed, almost entirely exposed, with minute odontodes. Spinelet short, spine moderately developed, adpressed
distal tip slightly surpassing posterior origin of dorsal-fin base, and anterior margin with small odontodes. Pectoral
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 191
fin roughly triangular, its origin just posterior to gill opening. Pectoral-fin rays I,6*(1), I,7 (2), I,8 (4), I,9 (15), I,9,i
(1), posterior margin of pectoral spine with 24 to 28 poorly- to moderately-developed laminar serrations along
almost its entire length, absent close to origin of spine; most serrations directed towards pectoral-fin origin; some
serrations perpendicularly directed or directed towards tip of spine; small odontodes on anterior, dorsal and ventral
surfaces of spine (Fig. 5B). Anteroventral portion of cleithrum exposed; posterolateral portion of scapulocoracoid
moderately developed, exposed, with anterior portion strongly expanded anteriorly, almost reaching to or contacting
anteroventral portion of cleithrum; exposed areas bearing small odontodes; Opening of axillary gland sensu Kiehl
et al. (2006) located just posterior to pectoral-fin spine base. Pelvic fin oblong, located just below first ventrolateral
body plate, and at vertical through region between first and second branched dorsal-fin ray. Pelvic-fin rays i,5* (24).
Adipose fin roughly triangular, separated from base of last dorsal-fin ray by generally six dorsolateral body plates.
Anal fin subtriangular, located just posterior to 12th or 13th ventrolateral body plates, and at vertical through adipose-
fin spine base. Anal-fin rays ii,6* (22). Caudal fin bilobed, with dorsal lobe slightly larger than ventral lobe; lobes
with similar size in some specimens. Caudal-fin rays i,10,i (1), i,11,i (2), i,12,i* (20), i,13,i (1), generally five or six
dorsal and ventral procurrent rays.
FIGURE 4. Lateral view of the right side of the head in a CS paratype of Corydoras bethanae, ZUFMS 6470, 56.9 SL. cpt,
compound pterotic; f, frontal; io1, infraorbital 1; io2, infraorbital 2; iop, interopercle; op, opercle; pop, preopercle; prh, postero-
dorsal ridge of hyomandibula; sph, sphenotic. Scale bar: 1 mm.
Three laterosensory canals on trunk. First ossicle tubular, second ossicle laminar, and third lateral-line canal
encased in third dorsolateral body plate. Body plates with minute odontodes scattered over exposed area, conspicu-
ous line of odontodes confined on posterior margins. Dorsolateral body plates 24* (22), 25 (2). Ventrolateral body
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plates 21 (10), 22* (13), 23 (1). Dorsolateral body plates along dorsal-fin base 6 (2), 7* (22). Dorsolateral body
plates between adipose- and caudal-fin 7 (3), 8* (18), 9 (1). Preadipose platelets 4* (3). Small platelets covering
base of caudal-fin rays. Small platelets disposed dorsally and ventrally between junctions of lateral plates on poste-
rior portion of caudal peduncle. Anterior margin of orbit, above posterior portion of lateral ethmoid, variably with
small, irregular platelets bearing odontodes. Ventral surface of trunk densely covered by small irregular platelets
bearing odontodes.
Vertebral count 22 (2). Ribs 7 (1), 8 (1); first pair conspicuously large, its middle portion closely connected
to first ventrolateral body plate; its tip connected to anterior external process of basipterygium. Complex vertebra
moderately developed.
FIGURE 5. Lateral view of the dorsal-fin spine (A) and dorsal view of the left pectoral-fin spine (B) (mirrored) in a CS para-
type of Corydoras bethanae, ZUFMS 6470, 56.9 mm SL. Black arrows indicate serrations that are perpendicularly directed or
directed towards tip of spine. Scale bar: 1 mm.
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 193
FIGURE 6. Live coloration of paratypes of Corydoras bethanae, BMNH 2017.5.25.1-21, showing A. female, and B. male. Fin
coloration affected by background colors. Arrows indicate gap in arc-stripe around the suture between neurocranium. Photos
by Steven Grant.
Color in alcohol. Overall color light whitish, grey, light beige, or tan, with area above dark arched line and
mask being slightly darker, sometimes orange-brown; melanophores along, above and below the midline of the
lateral scutes, being darker and larger in some specimens; snout area anterior to dark eye mask and opercular region
dark grey or diffuse black. Eye mask and body stripe (as set out in diagnosis) black; basal portion of six outermost
segmented rays of ventral lobe of caudal fin black, and innermost procurrent ray of same lobe black or dark grey,
forming extension of body stripe; some specimens with one dark or black pigmented transverse, diffuse, vertical
band in caudal fin. Pale area on middle portion of dorsolateral surface of cleithrum corresponds with axillary gland
sensu Kiehl et al. (2006) underneath; holotype similarly colored area on the ventral margin of the base of the adi-
pose-fin spine.
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Color in life. See Figs 2A, and 6 of the holotype and two paratypes, respectively, whilst alive for color in life.
Overall color same as in alcohol; third dorsolateral body scute usually whitish; green or gold to copper hue on lateral
scutes above and below midline, opercular area, cleithrum, and underneath and behind the eye; snout area anterior
to dark eye mask is usually light grey. Eye mask, body, and caudal fins dark markings as per preserved specimens.
Whitish narrow transversal area from ventral half of fourth dorsolateral body plate, passing through dorsal half of
first ventrolateral body plate, and reaching to posterolateral margin of cleithrum. Other fin membranes and rays
hyaline, with some of the dorsal and adipose fin membranes with whitish chromatophores (colors in Fig. 6 are back-
ground colors). Color of fry can be determined from the spawning in the account by Petersson (2020).
Sexual dimorphism. In addition to a tubular genital papilla (see Spadella et al., 2017), males have more
pointed and elongated pelvic fins; the dark arched body stripe can appear proportionately wider; and tend to have
the lateral scutes with darker and larger markings along, above and below the midline of flank.
Geographical distribution. Corydoras bethanae is so far only known from the río Blanco system (río Ucayali
basin), Soplin District, Requena Province, Department of Loreto, Peru (Fig. 7). Based on the findings of Corahua et
al. (2015) it is likely that it is found in the streams that drain into the main river.
Natural history notes. Corydoras bethanae may be found in blackwater streams that drain into the predomi-
nantly whitewater río Blanco (Fig. 8A), although the UK aquarist Mark Breeze (pers. comm.) states that in the
dry season he found small clearwater tributary streams near the confluence with the río Tapiche (Fig. 8B). Those
streams had a sand substrate with hardly any leaf litter and just overhanging terrestrial plants. Corahua et al. (2015)
found several Corydoras species in shallow, lotic blackwater streams or flooded forests that flowed into the middle
reaches of the río Blanco, that were low in pH (5.4–5.5), electrical conductivity (4.8–8.9 μs/cm), temperature of 25
degrees Centigrade, with abundant organic detritus, and white sand. A site in the lower region, closer to the type
locality of Corydoras bethanae, was the same except it was lentic, the pH ranged from 4.1 – 5.6, and the electrical
conductivity was 29.5–41.0 μs/cm. Corydoras granti was found by Corhua et al. (2015) in this location (misidenti-
fied as Corydoras arcuatus); another species with an arched dark body band. Corahua et al. (2015) list at least eight
species from the río Blanco, and in addition to those, information from fish collectors indicates that the following
Corydoras can also be found in the río Blanco system: Corydoras coriatae Burgess, 1997, C138 (which is superfi-
cially similar to Corydoras bethanae), and CW073.
FIGURE 7. Map of the upper rio Ucayali basin and adjoining areas (red star denotes type-locality).
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 195
FIGURE 8. Photos of the habitat of Corydoras bethanae, new species, showing A. its type-locality, the río Blanco, and B. the
confluence of río Blanco (left) with río Tapiche, both in Peru. Photo A by Mark Breeze, and B by Tom Christoffersen.
Grant (2020) discussed curious behavior exhibited by Corydoras bethanae when in the aquarium. All corydora-
dins appear to be able to maintain their position in the water column, above the substrate, by using a combination of
body movement and fin movement. They usually to do this when maneuvering while performing definite activities
e.g., avoiding another fish or predator, feeding, spawning etc. In the aquarium C. bethanae tend to hover regularly
and for long periods of time, apparently not related to any particular activity; a behavior that has not been reported
for other lineage 8 Corydoras. The pale transversal bar from fourth dorsolateral body plate to posterolateral margin
BENTLEY ET AL.
196 · Zootaxa 4948 (2) © 2021 Magnolia Press
of cleithrum corresponds with a large ligament attached dorsally to the transverse process of dorsal pterygiophore
and ventrally to the posterior laminar expansion of the first rib, which itself is connected to the anterior external pro-
cess of basipterygium. Such condition may have some effect on the ability to hover in the water column, especially
by offering a strong support to pelvic fins, which along with pectoral fins seem to be the main fins responsible for
keeping them lifting above the substrate. Videos of the holotype and some BMNH paratypes hovering can be seen
at: https://www.youtube.com/watch?v=hcg45PlwHjs and https://www.youtube.com/watch?v=v6p1hUdls54
There is a single record of successful spawning of this species, in which the water parameters were pH 6, Total
Dissolved Solids (TDS) 82ppm, and temperature 22.4°C (Petersson, 2020).
Etymology. Named in honor of Bethan Grant, daughter of SG, who, like her brother, has battled health issues
all her life.
Discussion
Alexandrou et al. (2011) proposed nine lineages within Corydoradinae, based on molecular data, which somewhat
matched with the morphology-based clades of Britto (2003). Once Scleromystax Günther and Aspidoras Ihering
are removed from discussion, this leaves within Corydoras seven lineages, some of which have available generic
names. Corydoras bethanae is a lineage 8 species sensu Alexandrou et al. (2011), characterized by Tencatt & Ohara
(2016a) as having the posterior margin of dorsal-fin spine with laminar serrations directed towards the origin of the
spine (vs. absence of such serration pattern). An available generic name for subclade 1 of lineage 8 is Brochis Cope,
1871, whereas Corydoras bethanae is in subclade 4. Further evidence and analyses are needed to resolve the inter-
relationships and generic nomenclature of Corydoras species.
The presence of a convergent color pattern within Corydoras has been known for at least 40 years and have
been consistently been documented by a series of studies (Nijssen & Isbrücker, 1980a,b; Britto, 2003; Britto et al.,
2009; Tencatt et al., 2013, 2019; Tencatt & Pavanelli, 2015; Tencatt & Britto, 2016; Tencatt & Ohara, 2016a,b; Lima
& Sazima, 2017). Corydoras bethanae shares the same general color pattern of a light body with a black arched
body band (but differs as set out in the Diagnosis) with some congeners, specifically C. arcuatus (lineage 8) (Fig.
2B), C. narcissus (lineage 1), C. granti (lineage 9) (Fig. 2C), and C. urucu (lineage 6 or 9). Additionally, there are
other potentially undescribed coded species that share a similar color pattern to C. bethanae: C138 (lineage 8) which
is said to be sympatric with C. bethanae (L. Enrique and J. Garcia, pers. comm.), C052 (lineage 8), CW072 (lineage
8), CW073 (lineage 1) which is said to be sympatric with C. bethanae (L. Enrique and J. Garcia, pers. comm.),
and CW120 (lineage 1). Interestingly, Alexandrou et al. (2011) recovered Corydoras bethanae, C052, and CW013
as a small monophyletic clade within lineage 8, with only the first two sharing a similar color pattern, which are
conspicuously different from the color pattern displayed by CW013, although the latter presents a sequence of rela-
tively large blotches along the area of the stripe in the other two congeners, which suggests a relation between both
color patterns. The new species can be distinguished from C052 and CW072 by having mask-like blotch not fused
dorsally with its counterpart (vs. counterparts fused dorsally); from C052, CW013, CW072 and C138 by having
the typical arc-striped pattern on flanks (vs. nearly straight dorsal stripe on trunk in C052 and CW072; flanks with
elongated blotches, not forming long, continuous stripe in C138; flanks with small- to medium-sized conspicuous,
irregular dark brown or black blotches, not forming long, continuous stripe in CW013); from CW073 and CW120,
as well as from any other member of the lineage 1, it differs by having posterior margin of dorsal-fin spine with
laminar serrations directed towards origin of the spine; it can be additionally distinguished from CW120 by lacking
small conspicuous blotches on middle portion of flank (vs. presence).
Animal color patterns are complex traits which serve a multitude of functions, including shielding against UV
irradiation from sunlight, defense against predators (such as camouflage and aposematism), improving visual acuity,
social signaling (including schooling) (Cott, 1940; Price et al., 2008; Gur et al., 2018). The way color patterns are
perceived by animals is unique to a given visual system in a specific context, that depends on the visual background
against which or through they are viewed (e.g. water), as well as the visual capabilities of the observer, distance
between signaling and observer, and ambient lighting (van den Berg et al., 2019).
Warning colorations present in aposematism or mimetism cases are generally assumed to be highly conspicuous,
resulting in a high-quality signaling, whereas cryptic coloration is assumed to have evolved to minimize conspicu-
ousness, decreasing the risk of detection. Such assumptions led cryptic and warning color patterns to be often con-
CORYDORAS BETHANAE, NEW SPECIES Zootaxa 4948 (2) © 2021 Magnolia Press · 197
sidered as mutually exclusive and conflicting anti-predator strategies (Tullberg et al., 2005) . However, some prey
coloration has combined the apparently opposing functions of anti-predator signaling and camouflage (Tullberg et
al., 2005; Price et al., 2008; Fabricant & Herberstein, 2015). Eventually, conspicuous signaling may result in higher
encounter rates with naive, specialized or nutritionally stressed predators (Endler & Mappes, 2004; Nokelainen et
al., 2014). In this way, intermediate levels of detectability may be more effective to increase survival, especially for
intermediately defended species (with moderate unpalatability), providing balance between signal effectiveness and
predator encounter rate (Sherratt et al., 2004; Barnett et al., 2007, 2016; Speed & Ruxton, 2007).
In different cases, some fish species (Trachinidae and Uranoscopidae) can display cryptic pattern while forag-
ing, which becomes aposematic when under threat of a predator (Price et al., 2008). Armbruster & Page (1996)
studied North American stream fishes that have a similar color pattern of four dark saddles against a light back-
ground. They hypothesized that these fishes achieve crypsis through disruptive coloration by background matching
and obliterative shading, although one species also had defensive capabilities of spines and venom. In the case of
Corydoradinae, color patterns may present both cryptic and disruptive elements, such as spots, counter-shading and
mask-like blotches, and putatively aposematic elements, like strongly contrasting black and white stripes, orange
and black patches, and conspicuously colored spines (Alexandrou et al,, 2011).
Sands (1994) studied the positive adaptive value of the color pattern in two Corydoras species with dark marks
along the dorsal ridge and eye masks. The author concluded that the pattern aided in crypsis, including how the pat-
tern functions when viewed from above, looking down on the substrate. This view is one seen by not only potential
predators above them in the water, but those outside of it, especially birds. Zuanon (2018, pers. comm.) observed
Brachyrhamdia thayeria Slobodian & Bockmann, 2013 and a species attributed to C. arcuatus and noted that the
vertical stalks of the plants were casting shadows on the bottom, which was basically composed by white sand,
creating light and dark contrasting bands on the substrate, possibly making the color pattern of the fishes (clear with
a black stripe) cryptic. Notwithstanding, Tencatt et al. (2019) concluded that the mimicry between the arc-striped
Corydoras and Brachyrhamdia species is Müllerian, due to the shared defensive tripod formed by the pungent
dorsal and pectoral spines, in addition to venom. Considering this, it is possible that the arc-striped color pattern
may present different adaptive values according to the perspective of the observer (dorsal and lateral views) and the
behavior of the signaler.
When viewed from above all of the arc-striped mimetics display two black parallel lines with a pale line in-
between. The Concealment function of the dorsal view of this could be Disruptive Coloration, as well as Counter-
shading and Color Resemblance. As well as providing Concealment in dorsal view it is possible that the arc-striped
pattern also provides this in lateral view by way of the arc or mask going through the eye, and also an overall dis-
rupting effect; which could prevent the predator from detecting or recognizing the fish’s outline, or shape of its eye;
as discussed for six different species of dark and pale banded fishes in Cott (1940). It is known that such striped
patterns can help shoaling fishes co-ordinate with each other and also cause visual confusion for predators when
moving (Price et al., 2008).
As mentioned by Andersson (2015), contrasting black and white or yellow are typical aposematic colourations.
Similarly, conspicuously colored spines observed in both animals and plants were found to be aposematic in numer-
ous cases, including in several families of fishes (Inbar & Lev-Yadun, 2005). The distinct black arc pattern on a pale
or white background could at times provide an aposematic warning of unpalatability due to the sharp, serrated dorsal
(with pale base and black tip in some species) and pectoral fin spines, the latter having associated venom gland.
These secondary defensive abilities help to protect Corydoras and Brachyrhamdia but the profitability of these ca-
pabilities is increased if the individual can warn a predator of their unpalatability by a primary defense of warning
signaling, rather than deploying them when physically attacked and risking a negative outcome. The curious regular
hovering and shimmying behavior by C. bethanae discussed under Natural history notes could be an example of
aposematic conspicuous signaling to potential predators.
Comparative material examined
Same as listed in Tencatt et al. (2019: 468).
BENTLEY ET AL.
198 · Zootaxa 4948 (2) © 2021 Magnolia Press
Acknowledgments
The Laboratório de Zoologia da Universidade Federal de Mato Grosso do Sul and the Universidade Estadual do Mato
Grosso do Sul provided logistical support. The authors are grateful to Carlos Lucena (MCP), Cláudio Oliveira (LBP),
Mário de Pinna, Aléssio Datovo, Michel Gianeti and Osvaldo Oyakawa (MZUSP), Carla Pavanelli (NUP), Flávio
Lima (ZUEC), Otávio Froehlich (in memoriam) (ZUFMS-PIS), James Maclaine and Oliver Crimmen (BMNH),
for hosting museum visits, curatorial assistance and loaning of material. We also thank Hernán López-Fernández,
Don Stacey and Erling Holm (ROM), Jorge Casciotta and Adriana Almirón (AI), Juan Mirande (Fundación Miguel
Lillo) and Sven Kullander (NRM) for the loaning and/or donation of several specimens analyzed in this paper. To
Francisco Severo-Neto and Thomaz Sinani (ZUFMS-PIS), Carlos Lucena and Héctor Vera-Alcaraz (MCP), Cláudio
Oliveira, Ricardo Britzke, Fábio Roxo, Bruno Melo and Gabriel Silva (LBP), Willian Ohara, Vinícius Espíndola and
Túlio Teixeira (MZUSP), Kris Murphy, Sandra Raredon, and Jeffrey Clayton (USNM), Mark Sabaj and Mariange-
les Arce for gently welcoming LFCT during museum visits. To James Maclaine (BMNH) for facilitating and wel-
coming RB to work on specimens, and for arranging the photograph of the holotype (Fig. 1), taken by Nemo Martin.
To Hans Evers and Bruno Ferreira for taking the photographs used in Figs. 2B and 3B, respectively. To Roman
Neunkirchen, Cesar Majin Flores, Luis Enrique, John Chung, Tom Christoffersen, and Jorge Garcia for obtaining
information on the locality details for the new species. To Tom Christoffersen for use of images of the río Tapiche-
Blanco confluence (Fig. 8B). To Rob Johnston, Oliver Frank, and Mike King for obtaining specimens of the new
species. To Mark Breeze for information on the area around the type locality and the photograph of the río Blanco
(Fig. 8A). To Michael Petersson for information and images from breeding the new species. To Fernando Carvalho
(Universidade Federal de Mato Grosso do Sul) for the general support devoted to LFCT. To Aleny Francisco and
Alan Eriksson by permitting the use and by the assistance with the image capture equipment of the Laboratório de
Ecologia da Universidade Federal de Mato Grosso do Sul, used to prepare Figs. 4 and 5. The Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq) provided grants to LFCT (process #160674/2019-0)
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