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1275
Accepted by C. Gilbert: 28 Jun 2006; published: 31 Jul. 2006 21
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN 1175-5334 (online edition)
Copyright © 2006 Magnolia Press
Zootaxa 1275: 21–29 (2006)
www.mapress.com/zootaxa/
Rivulus sape, a new species of killifish (Cyprinodontiformes:
Rivulidae) from the Paragua River system, Caroní River drainage,
Guyana Shield, Venezuela
OSCAR M. LASSO-ALCALÁ¹*, DONALD C. TAPHORN B.², CARLOS A. LASSO¹ &
OSCAR LEÓN-MATA²
¹Museo de Historia Natural La Salle, Fundación La Salle de Ciencias Naturales. Apartado Postal 1930,
Caracas 1010-A, Venezuela. E-mail: oscar.lasso@fundacionlasalle.org.ve; carlos.lasso@funcacionla-
salle.org.ve
²Museo de Ciencias Naturales de la UNELLEZ-Guanare, Guanare, Estado Portuguesa, Venezuela.
E-mail: taphorn@gmail.com; oscar_leon64@hotmail.com
*Corresponding author.
Abstract
A new species, Rivulus sape, is described from two tributaries of the upper Paragua River, Caroní
River drainage, of the Guyana Shield in Venezuela. It is a small (all specimens examined less than
50 mm SL), apparently non-annual species that is distinguished from congeners in having the
dorsal, anal, and pelvic fins short; adult males with a truncate caudal fin with the upper and lower
borders black; and an iridescent blue, ovate spot on sides of the body above the pectoral fins.
Neither adults nor juveniles have an ocellus at the dorsal junction of the caudal peduncle and caudal
fin. Only one contact organ per scale on some scales along the sides of the body was observed.
Key words: Fish, Killifish, Rivulus, Rivulidae, Caroní River drainage, Orinoco River basin,
Guyana Shield, Venezuela
Resumen
Se describe una nueva especie, Rivulus sape, proveniente de dos afluentes del alto río Paragua
(cuenca del río Caroní), en la Guayana Venezolana. Es una especie de pequeño tamaño, (todos
ejemplares examinados fueron menores de 50 mm LE) aparentemente no anual, que se diferencia
de otras especies del género por tener las aletas dorsal, anal y pélvicas cortas; la aleta caudal
truncada con los bordes superiores e inferiores negros, y por tener una mancha ovalada azul oscura
en la región superior de la aleta pectoral en los machos adultos. Ni en adultos ni juveniles hay una
mancha negra ocelada en la base de la aleta caudal. Se observó la presencia de un solo órgano “de
contacto” por escama en algunas de las escamas de los costados del cuerpo.
LASSO-ALCALÁ ET AL.
22 © 2006 Magnolia Press
1275
ZOOTAXA Introduction
The killifish genus Rivulus Poey, 1860 (Cyprinodontiformes: Rivulidae) is widely
distributed in both Middle and South America, where it ranges from Mexico to Argentina,
and on many Caribbean islands from Cuba to Trinidad. There are more than 100
recognized species in the genus, making it the most speciose genus in the family. Although
additional species continue to be found and described, only Huber (1992) has cataloged
their diversity, ecology, and distribution patterns, along with their taxonomy. Phylogenetic
studies of rivulids, including the genus Rivulus, reveal that it is polyphyletic, based on
molecular sequence data (Hrbek and Larson, 1999; Murphy et al., 1999), but
monophyletic if only morphological data are considered (Costa, 1998; Hrbek et al., 2004).
Based on maximum body size, adult color pattern and habitat preference Rivulus sape
would belong to the Guyana Shield species group, as proposed by Hrbek and Larson
(1999), but confirmation of this awaits DNA analyses. Generally speaking, species of this
clade are small (i.e., usually less than 50 mm SL, although some, such as Rivulus
tecminae, attain larger sizes) brightly colored fishes that typically exhibit less sexual
dimorphism than most Rivulus species and usually inhabit very small, clear-water streams
or temporary isolated pools that are often devoid of other fish species (Hrbek et al., 2004).
Exceptions exist for each of these conditions, however.
The upper Caroní River, including its principle tributary the Paragua River, represents
one of the most remote and ichthyologically unknown regions remaining in Venezuela.
This drainage interdigitates, to the east, with the upper Cuyuní River, a tributary of the E
ssequibo River that flows into neighboring Guyana; to the south with the upper Branco
River, an Amazon River tributary; and to the west with the Caura River, another Orinoco
tributary.
We collected fishes as part of an AquaRAP (Aquatic Rapid Assessment Program,
December 2005) survey of the region. During our survey we discovered the new Rivulus
described in this paper, as well as another, more robust species of killifish that may also be
new. A report on the complete findings of the survey is in press. A preliminary count
suggests that as many as one hundred species of fishes were obtained.
Methods
Measurements were taken with digital calipers, and follow Hoedeman (1959), with the
exception of head width, which was measured from the tip of the snout to the posterior
margin of the preopercle; and greatest body depth (GBD), which was measured at the
origin of the anal fin. We also included the length of the caudal peduncle (CPL), measured
from the posterior edge of the anal fin base to the midbase of the caudal fin. Measurements
are expressed as thousandths of standard length. The color descriptions are based on
photographs, live specimens maintained in aquaria, and freshly preserved material.
© 2006 Magnolia Press 23
A NEW RIVULUS
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ZOOTAXA
Abbreviations for institutions follow Leviton et al. (1985), with the addition of Museo de
Historia Natural La Salle, Caracas, Venezuela (MHNLS).
Rivulus sape, new species
Figures 1, 2 and 3; table 1.
Holotype. MHNLS 18934, adult male, 47.7 mm SL; Venezuela: Orinoco River basin,
Caroní River system, small stream, a tributary entering the right side of the Ichún River,
downstream from Ichún, or Espuma Falls, tributary of the Paragua River, Bolívar state,
approximately 04°46’04”N, 63°27’57”W, 340 m a. s. l.; C. Lasso, O. León-Mata, and J.
Mora; 4 December 2005.
Paratypes. All from Venezuela, Orinoco River basin, Caroní River system, Bolívar
state. All collected with the holotype unless otherwise indicated. MHNLS 18935, four
males, 15.7–31.3 mm SL; MHNLS 18936, six females, 18.4–27.1 mm SL. MCNG 54730,
two males, 20–26.2 mm SL, and two females, 23.6–25.7 mm SL. MBUCV-V-32971, one
male,18.5 mm SL, and two females, 21–24.8 mm SL. ANSP 182913 two males 16.6–21.6
mm SL and two females, 20.9–24.3 mm SL. MCNG 54731 three males 21.0–24.1 mm SL
and four females 19.3–31.6 mm SL, collected with holotype and kept alive; later preserved
in 95% ethyl alcohol. MHNLS-18937, one female, 15.1 mm SL; Waimesapakén Creek,
right bank tributary of the Paragua River, downstream from CVG-EDELCA camp in
Karún, approximately 05°19’42”N, 63°24’57”W; 320 m a. s. l.; C. Lasso, O. León-Mata
and J. Mora; 2 December 2005.
Diagnosis. Differs from other species of Rivulus by the following combination of
characters: dorsal, anal, and pelvic fins short in males; caudal fin truncate, with upper and
lower edges black in adult males; a large iridescent blue horizontally ovate spot present on
sides of body above and behind pectoral fin in males; ocellated caudal spot absent in all
individuals examined only one contact organ per scale, present on some scales of flanks.
Description. Meristic and morphometric data for holotype and 20 paratypes are given
in Table 1.
A small species of Rivulus (mean [including holotype]: 23.5 mm SL). Figures 1 and 2
show the sexual dimorphism apparent in this species, which includes differences in color
of body and fins, and shape of the caudal fin. Fins short, the pectorals not reaching origin
of pelvics, and pelvics not reaching origin of anal fin. Dorsal and anal fins not reaching
base of caudal fin. Only in two males, 33.8 and 34 mm SL, did pelvic fins reach anal-fin
origin, and folded dorsal just barely touching base of caudal fin. Caudal fin truncate in
adult males over 25 mm SL (figure 1), rounded in smaller males and in all females (figures
2 and 3). All fins without filaments or extensions. Caudal peduncle relatively deep (mean
= 0.13 SL). Head squamation pattern similar to F-scale pattern of Hoedeman (1958) and
Thomerson et al. (1992) and further described by Huber (1992) as S-pattern. Two or three
scales extending into caudal fin after termination of lateral scale series. One contact organ
per scale present on some scales of the lateral series on sides.
LASSO-ALCALÁ ET AL.
24 © 2006 Magnolia Press
1275
ZOOTAXA TABLE 1. Counts and Measurements of Rivulus sape.
Life colors (adult males). See Figure 2. Body light brown, darker brown on dorsum,
tan, pink to white on belly. The outstanding feature of adult males is a bright, shiny,
horizontally ovate sky-blue spot, just above and behind pectoral fin base and posterior to
opercle. Apparently depending on lighting, mood and maturity of the individual fish, the
males, n = 7 females, n = 13
Holotype low high mode /
mean low high mode /
mean
Standard length 40.7 15.7 31.3 22.7 18.4 27.0 22.6
Meristic
Dorsal rays 8 7 8 8 7 8 7
Anal rays 12 10 12 12 9 12 11
Pectoral rays 14 13 14 13 13 14 13
Pelvic rays 6 6 6 6 6 6 6
Lateral scales 36 32 36 35 32 35 33
Transverse scales 11 9 11 10 9 11 9
Caudal peduncule scales 16 13 16 14 13 16 15
Breast scales 11 7 10 8 8 9 9
Thousandths of standard length
Total length 1.200 1.164 1.295 1.257 1.196 1.303 1.260
Greatest body depth 0.096 0.172 0.255 0.214 0.187 0.214 0.198
Caudal peduncule depth 0.129 0.121 0.141 0.131 0.115 0.134 0.127
Caudal peduncule length 0.110 0.161 0.214 0.189 0.156 0.214 0.182
Head width 0.167 0.170 0.199 0.179 0.178 0.199 0.186
Head depth 0.144 0.133 0.154 0.142 0.131 0.151 0.143
Head length 0.237 0.250 0.309 0.273 0.258 0.285 0.270
Snout length 0.050 0.037 0.072 0.057 0.046 0.072 0.057
Eye diameter 0.078 0.082 0.103 0.091 0.084 0.103 0.094
Predorsal length 0.735 0.709 0.768 0.736 0.695 0.767 0.734
Preanal length 0.615 0.594 0.839 0.611 0.602 0.839 0.638
Dorsal fin base length 0.091 0.080 0.105 0.091 0.075 0.105 0.093
Anal fin base length 0.147 0.138 0.171 0.151 0.113 0.171 0.142
Dorsal fin length 0.152 0.134 0.253 0.173 0.114 0.193 0.152
Anal fin length 0.179 0.140 0.301 0.192 0.140 0.265 0.177
Pectoral fin length 0.151 0.158 0.209 0.188 0.162 0.202 0.183
Pelvic fin length 0.082 0.084 0.116 0.099 0.066 0.111 0.090
© 2006 Magnolia Press 25
A NEW RIVULUS
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ZOOTAXA
scales on remainder of lateral sides show bright, shiny blue pigment, which in intensely
colored fish can cause the sides to become an almost solid shiny blue, or in pale
individuals can be reduced to the center of just a few shiny scales on posterior portion of
body, sometimes aligned into chevron patterns that open posteriorly. Dorsum shiny golden
in brightly colored fish, yellow or tan in less intensively colored individuals; in the latter, a
series of brown spots may be present from above eye and along dorsum to caudal
peduncle. In some males there is a patch of shiny golden to yellow pigment just anterior to
the blue patch on upper part of opercle and anterior part of flank. Head golden or tan
above, cheek tan or pale white, sometimes with shiny blue streaks. Eye yellow, golden or
whitish, with a darker brown arc on upper edge. Dorsal fin with three or four alternately
angled horizontal rows of light and dark spots; the dark spots often wine-red or reddish
brown, the light spots yellow or shiny blue. Caudal fin with alternating semi-circular rows
of reddish and shiny blue spots, and edged dorsally and ventrally with a jet-black band. In
some individuals the rear margin of this fin is yellowish, and in other reddish. In less
intensively colored fish, caudal fin with pink fin rays, interspersed with clear membranes.
Anal fin white or pink along base, anterior portion bright yellow or golden, rear portion
blue-green or blue; many individuals with one or more rows of reddish spots parallel to fin
base. Anal fin edged in black in some individuals. Ventral fins blue or green, with yellow
or shiny blue spots. Pectorals fin clear.
FIGURE 1. Photo of Rivulus sape MHNLS 18934 (male holotype, 47.7 mm SL).
Life colors (adult females). See Figure 2. Females have a color pattern similar to
adult males, but with colors much more subdued. Body basically colored tan or brown,
darker dorsally, fading to pink or white on belly. Some scales on dorsum with dark brown
centers that form an irregular row from eye to caudal peduncle along dorsum. Flanks with
three to six rows of light scales, whitish or light blue. Intense spot of centrally located
pigment posterior to opercle either greenish, bluish or golden, and sometimes absent in
frightened individuals or in fish kept in intense light. Eye golden or white, darker dorsally.
Dorsal fin with rows of light yellow, blue or green spots, alternating with darker rows of
brown or reddish spots. Caudal fin lacking the black stripes seen in males, yellowish or
LASSO-ALCALÁ ET AL.
26 © 2006 Magnolia Press
1275
ZOOTAXA clear with flecks of shiny yellow, blue or green. Anal fin yellowish, in some individuals
green anteriorly and blue posteriorly, with faint rows or brown spots on membranes
between rays. Ventral fins yellowish, green or blue. No ‘rivulus’ spot present at any life
stage.
Distribution. Known only from the type locality and surrounding area within the
Paragua River system of the upper Caroni River drainage, Orinoco River basin, within
Bolívar State, Venezuela. Documented localities include two small tributaries of the Ichún
River, which flows into the Paragua River, and Waimesapakén Creek, also a tributary of
the upper Paragua.
Habitat. Rivulus sape was collected from isolated pools (about 5 cm depth) of the
flooded margins of small clear-water creeks situated over a sandy to muddy substrate with
abundant leaf litter. The water temperature was 24°C; the pH was acidic (between 4.5 and
5.2) and saturated with oxygen (7.3 to 7.4 mg/l); with very low conductivity (between 9.8
and 16.3 microsiemens/cm).
Etymology. This species is named to honor the local indigenous people of the Sapé
tribe, inhabitants of the upper Paragua River system, Caroní River drainage, where the fish
was collected.
FIGURE 2. Rivulus sape, adult female (approximately 30 mm SL). Not included in type material.
FIGURE 3. Rivulus sape, juvenile male (approximately 25 mm SL). Not included in type material.
© 2006 Magnolia Press 27
A NEW RIVULUS
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ZOOTAXA
Discussion
Rivulus sape is the fourth species of Rivulus described from the Caroní River drainage.
The other members of the genus known from the Caroní drainage are Rivulus lyricauda
Thomerson, Berkenkamp and Taphorn, 1991, described from the Carrao River in the
vicinity of Canaima; and Rivulus gransabanae Lasso, Taphorn and Thomerson, 1992,
described from the elevated plains of the Gran Sabana. The remaining species, Rivulus
deltaphilus Seegers, 1983, in contrast to the other three Rivulus species mentioned, is
found in lowland regions of the lower Orinoco River floodplains, including the lower
Caroní River (Lasso et al., 2005). The relatively deep caudal peduncle of Rivulus sape
(mean in males 0.131, females: 0.127, given as thousandths of SL) is shared with R.
lyricauda (mean 0.146 in males, and 0.134 in females) and R. gransabanae (mean 0.150 in
males, and 0.140 in females), as are the truncate caudal fin in males, and their relatively
small body size. It differs from these two species, however, in lacking the filamentous
extensions of the fin rays of the ventral, dorsal and caudal fins; in having more lateral
scales (32–36) than all other species except R. lyricauda (29–32), as well as shorter dorsal
and anal fins, (mean = 0.173 in males, and 0.152 in females of R. sape, males 0.231 and
females 0.210 in R. lyricauda, and males 0.282 and females 0.240 in R. gransabanae). No
other killifish has the distinctive blue spot observed on the body of R. sape or the color
pattern in the caudal fin of adult males, which consists of black stripes along the upper and
lower margins, with the center filled with red and blue mottling. These features
distinguishes it from R. gransabanae, which has a dusky caudal fin with a metallic blue
stripe; as well as R. lyricauda, in which the distinctively lyre shaped caudal fin has yellow
or blue filaments extended above and below that are narrowly edged with black, but in
which the distal margin is edged with black and shows an orange crescent along its base.
In marked contrast to R. sape, Rivulus deltaphilus has white stripes along the dorsal and
ventral margins of the caudal fin and reaches a much larger size as adults (more than 50
mm SL). Male R. deltaphilus also have about six series of red dots along the sides, and
females have an ocellus on the dorsal portion of the caudal peduncle.
The contact organs observed on some scales of the lateral series in Rivulus sape have
also been observed in Rivulus immaculatus Thomerson, Nico and Taphorn, 1991, a species
described from the Venamo River, a tributary of the Cuyuní River of the Essequibo River
basin. In that species, however, there are two or three contact organs per scale instead of
just one per scale, as seen in R. sape. Rivulus immaculatus also shares the short dorsal,
anal, and pelvic fins, and black borders of the caudal fin observed in R. sape, but differs in
having seven pelvic-fin rays instead of six as seen in R. sape, in having a rounded caudal
fin in males, and females with a heavily spotted body and fins.
The truncate caudal fin shape of males, an important character in this group, is also
seen in other Guyana Shield Rivulus species, including Rivulus tecminae Thomerson, Nico
and Taphorn, 1992, which was described from the Sipapo River of the upper Orinoco
basin, and Rivulus torrenticola Vermeulen and Isbrücker, 2000, described from the
LASSO-ALCALÁ ET AL.
28 © 2006 Magnolia Press
1275
ZOOTAXA Kamarang River system of the Mazaruni-Essequibo drainage in Guyana. Rivulus sape can
be differentiated from those species by: the absence of an imbricate head scale pattern
(which is characteristic of R. tecminae); presence of short pelvic fins, in which the tips of
the rays do not reach the anal-fin insertion; and by the presence of six pelvic-fin rays
(seven in R. torrenticola). There are also notable differences in color pattern. R. tecminae
has green stripes of varying thickness (thickness of stripes depending upon gender) over a
reddish background along the sides of the body; the caudal fin of males with a yellow
ventral border; and a large, ocellated black spot at the base of the caudal fin of females. In
R. torrenticola the caudal fin is translucent, with a reddish dorsum and ventrum.
Acknowledgments
The fish samples were obtained as part of an AquaRAP mission carried out in the upper
Paragua River of Bolívar state, Venezuela, a mission financed by Conservation
International, and which received generous logistical support from the Corporación
Venezolana de Guayana, Compañía Electrificación del Caroní (CVG-EDELCA). The
work was coordinated by the Fundación La Salle de Ciencias Naturales. INAPESCA
provided scientific collecting permits and the local people of the Karún and Boca Ichún
community helped with all aspects of the field work. Abrahan Mora shared physical and
chemical data that he obtained in the habitat of this species. We would like to thank Tomas
Hrbek and anonymous reviewers for useful comments on the text.
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