Ichthyological Exploration of Freshwaters

Online ISSN: 0936-9902
Publications
Article
#Ossubtus xinguense$, genre et espèce nouveaux, se différencie des autres #Serrasalmidae$ par la position strictement ventrale de la bouche et par seulement quatre dents au dentaire. #Ossubtus xinguense$ se caractérise aussi par l'absence de serrae préventrale, les deux séries de dents du prémaxillaire accolées, des dents incisiformes fragiles aux mâchoires, et une tâche humérale triangulaire chez les jeunes. Les deux dernières dents de la série externe du prémaxillaire, incisiformes, tricuspidées et planes, et la fosse olfactive élargie sont des synapomorphies partagées par #Mylesinus$ et #Ossubtus$. (Résumé d'auteur)
 
Article
Une révision taxinomique des espèces de poissons récoltées dans le Sahara a permis de dresser une liste actualisée prenant en compte les connaissances récentes. Il apparaît que la plupart des espèces collectées dans les petites collections d'eau sont des populations reliques d'espèces largement répandues dans les bassins hydrographiques voisins, à l'exception de #Barbus apleurogramma$ qui pourrait être un vestige d'une faune plus ancienne. La distribution actuelle est discutée, à la lumière des données sur l'extension supposée des bassins hydrographiques durant l'Holocène. (Résumé d'auteur)
 
Article
Since its description, the cyprinid genus Parasini-labeo Wu, 1939, has usually been treated as valid (Eschmeyer, 1990, 1998; Zhang, 2000; Zhang et al., 2000). The type species of the genus is usually listed as P. assimilis Wu & Yao, in Wu et al., 1977, by subsequent designation by Wu et al. (1977: 366). Su et al. (2001), however, following Banares-cu (1997), argued that Parasinilabeo is invalid as its type species was inappropriately designated by Wu et al. (1977), and as such, they established a new genus Pararectoris, and noted that it be-comes the replacement name for Parasinilabeo. Parasinilabeo assimilis was retained as the type species. ICZN in force then required that cases of misidentified type species should be submitted to the Commission, and authors did not have the option of solving the case by them-selves. This was maintained in the 1985 edition of ICZN but has now changed with the 1999 edi-tion. Under article 70.3 of this latest code, an author now has the option to select which species is best suited as type species, either the species originally cited, or the species actually involved. This article, however, cannot be applied retroac-tively as article 70.3.2 of the 1999 ICZN has to be specifically cited in the paper where the type species fixation is discussed.
 
Article
A species of Garra without proboscis and transverse groove on the snout and with a smoothly rounded snout tip, prominent triangular- shaped rostral lobe with 10-11 strong, conical tubercles; scales in the predorsal region, chest and abdomen; two pairs of barbels, 31 lateral line scales, 14 circumpeduncular scales; 3.5/1/3.5 transverse-scale rows; 9 gill rakers on first branchial arch; 32 vertebrae; a broad black band near the posterior margin of the dorsal fin and a distinct W-shaped broad black band in the caudal fin.
 
Article
Acanthobrama thisbeae, new species, is described from the lower Ceyhan and Orontes Rivers in Turkey. It is distinguished from other species of the genus by having 73-86/3-4 scales along the lateral line, a thin and short last unbranched dorsal-fin ray, flank scales with a crenulated posterior margin, and 14-16% branched anal-fin rays. Acanthobrarna orontis is a valid species distributed in the Orontes, Ceyhan and Seyhan rivers. Eleven species are recognised as valid in the genus Acanthobrania (A. centisquarna, A. hadiyahensis, A. lissneri, A. inarmid, A. microlepis, A. orontis, A. persidis, A. telavivensis, A. thisbae, A. tricolor, A. urmianus). Acanthalburnus is treated as a synonym of Acanthobrarna.
 
Article
The species of the Macrognathus aculeatus group from Myanmar are reviewed and three new species are described. Macrognathus dorsiocellatus, new species, previously identified as M. aral, is distinguished by rostral tooth plates 19-23, dorsal fin spines 14-22, 7-11 small ocelli along soft dorsal fin, with ventrally open, incomplete white rim; M. obscurus, new species, is distinguished by rostral tooth plates 8-10, dorsal fin spines 20-22, ocelli along dorsal fin developed as small irregularly arranged dark spots or absent, M. pavo, new species, is distinguished by the presence of only 4-6 dorsal-fin spines, only 6-8 rostral tooth plates and details of the colour pattern. In addition, M. lineatomaculatus, new species, is described from India and Nepal and it is distinguished by rostral tooth plates 15-17, dorsal fin spines 19-22, and large black blotches along dorsal fin. The systematic position of M. caudiocel-latus is reviewed and the species is retransferred to Mastacembelus.
 
Map showing major river drainages in Nepal.
Neoeucirrhichthys maydelli , KU 29132, 35.2 mm SL; Nepal: Mechi River at Bhadrapur. 
Neoeucirrhichthys maydelli, KU 29132, 35.2 mm SL; left pectoral fin (anterior rays to right) showing elongate tubercles arranged in striae on thickened skin over fin rays (indicated by arrows) in males. Photograph taken with Nikon D200 DSLR using Nikon LV-TV TV tube on a Nikon SMZ-800 binocular dissecting microscope.
Article
An increase in ichthyological activity in Nepal over the past 25 years has raised the number of fish species re-ported for the country. We provide details of the distribution of new records for 10 additional species captured from 25 sites during recent ichthyological exploration throughout Nepal: Puntius terio, Psilorhynchus gracilis, Lepidocephalichthys menoni, Neoeucirrhichthys maydelli, Glyptothorax alaknandi, G. botius, G. garhwali, Nangra assamen-sis, Sisor rheophilus, and Anabas cobojius. Given that these species are relatively rare in Nepal, and that their ecol-ogy is poorly understood throughout their range, we also provide notes on their microhabitat use. Neoeucirrhich-thys maydelli, an inadequately-studied species, is rediagnosed and redescribed from the Nepalese material.
 
Article
Hypsolebias caeruleus, new species, is described from the semi-arid Caatinga savannah of north-eastern Brazil, middle São Francisco River basin. It is similar to H. adornatus and H. lopesi, differing from all other species of this group by having the dorsal-fin origin in a vertical anterior to the pelvic fin in males, flank blue in males, and two black spots, vertically aligned, immediately anterior to the caudal-fin base in females. The new species mainly differs from H. adornatus by the smaller anal-fin base in males, the consequent relative posterior position of the anal-fin origin and details of the colour pattern in males and females; and from H. lopesi by the pointed dorsal fin, relative posterior position of the anal-fin, relatively larger caudal fin, and distinct colour patterns. The discovery of H. caeruleus significantly amplifies the known distribution of the H. magnificus species group northwards.
 
Oryzias sakaizumii; Japan: Fukui Prefecture: Tsuruga: Nakaikemi wetland: a, KPM-NI 27949, paratype, fresh male, 27.4 mm SL; b, KPM-NI 27953, paratype, fresh female, 25.1 mm SL.  
Oryzias latipes; Japan: Ehime Prefecture: Kitauwa: Kitanadakuninaga: a, KPM-NI 14468, fresh male; b, KPM- NI 14473, fresh female.  
Distribution and collection sites of Oryzias sakaizumii. @, type locality; %, localities of paratypes; (, presumed type locality of O. latipes; , distribution range of O. sakaizumii; , distribution range of O. latipes.  
Article
Oryzias sakaizumii, new species, is described from Japanese freshwaters along the northern coast of the Sea of Japan. It is distinguished from its Japanese congener, O. latipes, by a slightly notched membrane between dorsal-fin rays 5 and 6 in males (greatly notched in O. latipes); dense network of melanophores on the body surface (diffuse melanophores in O. latipes); distinctive irregular black spots on posterior portion of body lateral (absent in O. latipes); and several silvery scales arranged in patches on the posterior portion of the body (few in O. lati pes).
 
Article
Rhabdalestes aeratis, new species, is described from the outlet of Lake Tumba at Irebu. It is assigned to the genus Rhabdalestes, pending the determination of phylogenetic diagnoses for genera of the non-monophyletic tribe Petersiini. It is distinguished from all putative congeners by the combination of a slender body form, a complete lateral line with 27-28 pored scales, 4.5 scale rows above the lateral line, 14-15 branched anal-fin rays, 17-19 gill rakers on the lower limb of the first arch, and by a distinctive coloration pattern consisting of dark pigmentation on the dorsum, head, and posterior scale margins overlying a golden-bronze reflective ground coloration, without a broad dark midlateral stripe. Despite problems with the diagnosis of genera currently assigned to the Petersiini, and difficulty in distinguishing species within genera due to variation and broad overlap of features, recognition of species-level diversity from poorly-known geographic regions is both warranted and useful, pending detailed revisionary study.
 
Article
Synodontis punu, new species, is described from the Nyanga, the Niari (Kouilou) (Republic of Congo) and the Ogooué (Gabon) basins. This relatively small species (<45 mm SL) is morphologically similar to S. acanthoperca with which it shares the presence of a single hypertrophied opercular spine in sexually mature males and a colour pattern characterised by the presence of a pair of dark patches on the caudal fin, one on each lobe. These two characters separate both species from all congeners. Synodontis punu is distinguished from S. acanthoperca by a wider premaxilla, 24.9-32.7 % HL (mean: 29.0) [vs. 18.0-23.9 (21.1)], a greater postorbital length, 38.1-42.3 % HL (mean: 40.1) [vs. 33.7-38.2 (35.9)] and the absence of a saddle-like dark brown spot posterior to the dorsal fin (vs. presence).
 
Article
'Barbus' devosi, new species, is described from the Malagarazi River drainage, the main affluent of Lake Tanganyika. It belongs to the group of small African 'Barbus' with a strongly ossified and serrated last unbranched dorsal-fin ray and a blackish mid-lateral band, that extends from the tip of the snout to the caudal-fin base, or onto the mid-central part of the caudal fin. 'Barbus' devosi resembles 'B.' eutaenia and 'B.' niiolepis, to which it has formerly been erroneously attributed. It can be distinguished in having a higher number of gill rakers on the ceratobranchial of the first gill arch (6-9 vs. 2-5), shorter anterior (11-19 vs. 20-35% HL for 'B.' eutaenia and 2037% HL for 'B.' miolepis) and posterior (15-27 vs. 22-44% HL for 'B.' eutaenia and 27-46% HL for 'B/ miolepis) barbels, and the absence of a sheath of enlarged, prominent, scales at the base of the dorsal fin.
 
Article
Based on literature and an overview of the specimen holdings available in various natural history museums, a checklist of the riverine fishes of Burundi was compiled. A total of 15 riverine fish families containing 42 genera and a total of 90 described native species are reported for the country. With 35 species, the family Cyprinidae is by far the largest, followed by the families Cichlidae (14), Clariidae (8), Mormyridae and Mochokidae (7). The remaining families are represented by only five or less species. Ten species have been introduced in the Burundese Nile system and three in the Rusizi River system. Five of them have no known native occurrence in Burundi. Some taxa such as the small-size 'Barbus' (Cyprinidae), the catfish genus Synodontis (Mochokidae) and the haplochromine cichlids require further taxonomic attention; their actual species numbers are certainly under-estimated.
 
Article
Distichodus teugelsi, new species, is described from the middle Congo River basin. The species is distinguished from all other Distichodus species by the following combination of characters: presence of two rows of bicuspid teeth on upper jaw and a single one on lower jaw; unique colour pattern characterised by a light greenish band dividing the flanks into a darker greenish upper and lower part. Distichodus teugelsi is a dwarf species of Distichodus (maximum size: 65.0 mm TL), based on the presence of nearly ripe eggs in several female specimens (50.9-54.3 mm SL). With a single row of bicuspid teeth in the lower jaw, instead of two rows, both dwarf Distichodus species (D. teugelsi, D. decemmaculatus) differ in this respect from the current diagnosis of the genus.
 
Article
Synodontis carineae, new species, is described from the Kouilou-Niari Basin (Republic of Congo). It is distinguished from all other Lower Guinea Synodontis species by the following unique combination of characters: entire ante-rior edge of dorsal spine not serrated; posterior margin of operculum without opercular spine; 18-24 mandibular teeth; maxillary barbels bordered by a broad membrane; and a unique colour pattern characterised by numerous dark brown, irregularly shaped spots on a light brownish background colour with, in live specimens, a vivid yellowish overall sheen. Synodontis carineae, espèce nouvelle, est décrite du bassin de la rivière Kouilou-Niari (République du Congo). Elle se distingue de toutes les autres espèces de Synodontis de la province ichtyologique de Basse Guinée par la com-binaison unique des caractères suivants: face antérieure de l'épine dorsale non denticulée; bord postérieur de l'opercule sans épine; 18-24 dents mandibulaires; barbillons maxillaires bordés d'une large membrane d'une largeur maximum au moins aussi large que le barbillon même et un type de coloration unique caractérisé par de nombreuses taches irrégulières, brun foncé sur fond brunâtre plus clair ainsi que, sur le vivant, un reflet jaune vif généralisé.
 
Article
Rhabdalestes yokai, new species, is described from the Léfini basin (Middle Congo River, Republic of Congo) and the Sangha basin (Middle Congo River, Central African Republic). It is distinguished from the other Rhabdalestes species by the following combination of characters: 5-7 outer row premaxillary teeth with 5 (exceptionally 3) cusps; 8 mandibular teeth with 5-7 cusps; a complete lateral line with 25-26 pored scales; 4% scales above the lateral line; 3 unbranched and 18-19 (exceptionally 17) branched anal-fin rays and 13-14 gill rakers on the lower limb of the first gill arch.
 
Meristics of Hepsetus odoe and H. occidentalis.
Scatterplot of principal component I (PCI) against PCII for a PCA on 34 measurements (expressed in percentages) for all examined specimen (n = 98). Hepsetus occidentalis: , holotype; , paratypes; , other specimens ; H. akawo: , holotype; , paratypes; and H. odoe: , holotype; , other specimens.  
Measurements of Hepsetus odoe and H. occidentalis.
Scatterplot of the distance between nostril and lower jaw as % of head length against the number of lateral line scales. Hepsetus occidentalis: , holotype; , paratypes; , other specimens; H. akawo: , holotype; , paratypes; H. odoe: , holotype; , other specimens.  
Article
Re-examination of the holotype of Hepsetus odoe indicates that it falls within the range of H. akawo and consequently H. akawo is a junior synonym of H. odoe. As a result, the specimens from the western part of West Africa (from the Senegal to the Cavally River), formerly attributed to H. odoe, remain unnamed. The species is named as H. occidentalis, new species.
 
Article
Akysis hardmani, new species, is described from the Chao Phraya River drainage in central Thailand. The new species is a member of the A. pseudobagarius species group, and is distinguished from all congeners in this group in having highly elevated supraoccipital spine and nuchal plate. It further differs from congeners in having a unique combination of the following: coloration consisting of highly contrasting light brown patches on a chocolate brown body, lack of filamentous extensions to the first pectoral-fin element, presence of 5-6 serrations on posterior edge of pectoral spine, eye diameter 6-9% of head length, branchiostegal membranes meeting at isthmus ventrally, outer mandibular barbels reaching middle of pectoral-fin base, and rounded tubercles on the tip of the snout and dorsal surface of neurocranium.
 
Article
Akysis vespertinus, new species, is described from the Ann Chaung drainage in western Myanmar. It is distinguished from congeners in having a unique combination of the following characters: narrow snout, causing head to appear acutely triangular; length of pectoral spine 17.1-22.2 % SL; length of adipose-fin base 18.8-21.1 % SL; body depth at anus 13.5-16.0 % SL; depth of caudal peduncle 7.4-9.2 % SL; length of caudal peduncle 19.0-22.8 % SL; head length 27.1-30.2 % SL; interorbital distance 24.5-28.8 % HL; length of nasal barbel 37.8-48.3 % HL; length of max-illary barbel 84.9-96.6 % HL; smooth posterior edge of pectoral spine; forked caudal fin; presence of two light saddle-shaped patches on upper surface of postdorsal region; absence of brown coloration on abdomen.
 
Article
Akysis vespa, new species, is described from the Ataran River drainage in southern Myanmar. It is a member of the A. variegatus species group and can be distinguished from congeners in the group (except for A. pictus, A. prashadi and A. varius) in lacking serration on the posterior edge of the pectoral spine. It is distinguished from A. varius in having an emarginate (vs. truncate) caudal fin, from A. pictus in having a larger eye (12-16 % HL vs. 8-10) and smaller adipose fin (17.6-21.1 % SL vs. 22.0-23.6), and from A. prashadi in having a larger eye (12-16 % HL vs. 8-12) and a longer caudal peduncle (19.4-23.3 % SL vs. 16.5-18.4).
 
Article
Two new species of bagrid catfishes are described from the Alas River drainage in the province of Aceh in the northern tip of Sumatra. Leiocassis aculeatus resembles L. poecilopterus in having the supraoccipital process in contact with the nuchal plate, but differs from it in having a longer adipose fin (15.8-16.6% SL vs. 12.9-15.0), and longer dorsal (20.8% SL vs. 15.5-18.4) and pectoral spines (17.9-18.7% SL vs. 14.5-17.5). Mystus alasensis resembles M. castaneus, M. impluviatus and M. nigriceps in having a moderately long, low adipose-fin, uniform body color, fossa on the midline of cranium not reaching to the base of the supraoccipital process and extremely long maxillary barbels that reach to beyond the base of the caudal fin. However, it differs from them in lacking (vs. presence of) a dark triangular mark at the base of the caudal fin. It is further distinguished from M. nigriceps in having a longer (34.3-36.3% SL vs. 26.3-31.4), deeper (6.7-7.5% SL vs. 4.1-6.0) adipose fin and longer pelvic fins (17.6-20.2% SL vs. 13.4-16.7), and from M. castaneus and M. impluviatus in having a more gently-sloping dorsal profile of the head. Mystus alasensis also differs from M. impluviatus in lacking (vs. presence of) a fontanel on the supraoccipital and having a deeper adipose fin (6.7-7.5% SL vs. 4.7-6.0).
 
Article
The identity of Mastaceinbelus dayi is discussed and a lectotype is designated. Mastaceinbelus alboguttatus is a senior synonym of M. dayi and the valid name for this species. It grows up to at least 700 mm SL and is known from its type locality, the Sittang, large parts of the Chindwin and from the Ayeyarwaddy around Mandalay.
 
Article
Alburnus danubicus from the lower River Danube and A. mento from lakes in the upper Danube drainage are valid species of the A. mento species group. Two new species of this group are described based mostly on gill raker counts: A. leobergi from the Azov Sea basin and A. sarmaticus from Rivers South Bug and Danube. A lectotype is designated for A. mento. Alburnus danubicus is globally extinct.
 
Article
Nannopetersius mutambuei, new species, is described from the Inkisi River basin (Lower Congo, Democratic Re-public of Congo). It is distinguished from its congeners by the following combination of characters: 28-30 lateral-line scales; 5 {-6 { scales between lateral line and dorsal-fin origin; caudal peduncle longer than deep (length 135.7-151.7 % of its depth); 21-23 branched anal-fin rays; 10-13 gill rakers on ceratobranchial of first branchial arch; snout length 26.6-29.2 % HL; eye diameter 31.7-39.6 % HL and a black longitudinal band present in preserved specimens but absent in living specimens. Une nouvelle espèce, Nannopetersius mutambuei, est décrite du bassin de l'Inkisi (Bas-Congo ; République Dé-mocratique du Congo). Cette nouvelle espèce se distingue de ses congénères par : 28-30 écailles sur la ligne latérale ; 5 {-6 { écailles entre la ligne latérale et l'origine de la caudale ; un pédoncule caudal plus long que haut (longueur 135,7-151,7 % de sa hauteur) ; 21-23 rayons branchus à l'anale ; 10-13 branchiospines sur le cerato-branchial du premier arc branchial ; le museau d'une longueur de 26,6-29,2 % de la longueur de la tête, le diamè-tre de l'oeil de 31,7-39,6 % de la longueur de la tête et une ligne longitudinale noire présente chez les spécimens préservés, mais absente chez les spécimens vivants.
 
Article
Gut contents of Sicyopterus stimpsoni were examined in relation to the algal community composition in the feeding areas from Hakalau Stream on the island of Hawai'i. Macroalgal fragments were common in the gut contents, although the taxonomic diversity of these fragments did not necessarily resemble that of the feeding area associated with the fish, and a preference for green algae and diatoms was evident. This was in contrast to the results for the diatom comparisons, where the diatom taxonomic distribution in the gut contents more closely resembled that of the feeding area. Though we demonstrate that macroalgae play a role in the diet of S. stimpsoni, controlled feeding studies will be needed in the future to address the nutritional composition of both the macroalgal and microalgal communities, and to determine whether macroalgal ingestion is an incidental byproduct of consuming epiphytic diatoms or if they are consumed for the nutritional benefit they confer on their own.
 
Article
Rivulus amanan, new species, from the Amanã lake drainage, Amazonas river basin, Brazil, is described. It was found in shallow places of lentic aquatic biotopes at igarapé do Bare floodplains, within the Amazon forest. The new species is a member of the subgenus Anablepsoides, which also includes R. atratus and R. ornatus. It differs from both by the unique color pattern of the caudal fin in males, in which the dorsal portion of the fin is orangish red, the middle black with light blue to greenish blue stripe, and the ventral dark red to black posteriorly, and by having frontal squamation F-patterned. It also differs from the other species of Anablepsoides by a combination of pelvic fin reaching between urogenital papilla and base of second anal-fin ray in males, 10-12 anal-fin rays, venter light gray with dark gray dots, and mandibular series of neuromasts not interrupted, with six neuromasts. It is considered to be more closely related to R. ornatus by both having the caudal fin with three zones distinctively colored in males.
 
Article
Anablepsoides urubuiensis, new species, is described from the upper Urubu river drainage, northern Brazil. It constitutes the first record of a species of the A. limoncochae group for the central Amazon region. The new species is distinguished from all other rivulines by a unique colour pattern of flank, including the presence of two red stripes distinctively widened in their posterior portion; it also differs from the other congeners of the A. limoncochae group by a combination of caudal fin oval, absence of light yellow or light orange stripe on the distal margin of the anal fin in males, and dorsal fin placed in a vertical through the base between the last two anal-fin rays or posterior to it.
 
The Pongo de Manseriche, a narrow canyon in Northern Peru through which flows the Rio Marafion; type locality of Hemiancistrus pankimpuju.
Hemiancistrus pankimpuju, MUSM 32337, holotype, 130.1 mm SL; Peru: Departamento Amazonas: Rio Marafton, Pongo de Manseriche.
Type localities of Hemiancistrus pankimpuju (0} and Panaque bathyphilus <*>·
Panaque bathyphilus, MZUSP 56970, holotype, 73.5 mm SL; Brazil: Amazonas: Solimoes River, upstream of confluence with Purus River. Both unbranched principal caudal-fin rays originally elongate as long filaments, dorsal filament broken but retained with specimen.
; from H. cerrado, H. chlorostictus, H. fulginosus, H. guahiborum, H. landoni, H. medi­ ans, H. megalopteryx, H. meizospilos, H. punctulatus, H. subviridis, and H. votouro by having a forked caudal fin (vs. caudal fin emarginate); from H. cer­ rado, H. chlorostictus, H. fulginosus, H. medians, H. megalopteryx, H. meizospilos, H. micrommatos, H. punctulatus, H. snethlageae, H. spilomma, H. spi­ nosissimus, and H. votouro by having a greaterSelected morphometries of Hemiancistrus pankimpuju and Panaque bathyphilus. Interlandmarks represent the two landmarks the measurement is between (see Armbruster, 2003).
Article
Hemiancistrus pankimpuju, new species, and Panaque bathyphilus, new species, are described from the main channel of the upper (Maranon) and middle (Solimões) Amazon River, respectively. Both species are diagnosed by having a nearly white body, long filamentous extensions of both simple caudal-fin rays, small eyes, absence of an iris operculum and unique combinations of morphometrics. The coloration and morphology of these species, unique within Loricariidae, are hypothesized to be apomorphies associated with life in the dark, turbid depths of the Amazon mainstem. Extreme elongation of the caudal filaments in these and a variety of other main channel catfishes is hypothesized to have a mechanosensory function associated with predator detection.
 
Article
Ammoglanis amapaensis, new species, is described from three drainages of the Brazilian Amazon: Jari, Amapari and Araguari. It is distinguished from other congeners by having nostril barbel long, reaching the posterior margin of the eye, cranial fontanel absent, and the anterior portion of the palatine with a small ossification. It seems to be more closely related to A. pulex, with which it shares a scythe-shaped lachrymal with an anterior facet and a short ventro-laterally directed process in the palatine.
 
Article
Laimosemion ubim, new species, is described from a small stream tributary of Lago Amanã system, Central Amazon, northern Brazil, based on external and internal anatomical morphological characters. It is considered closely related to other species of Laimosemion, subgenus Owiyeye, from the same region. It is distinguished from all other rivulids by having double-branched epipleural ribs, a condition never found among cyprinodontiforms, and from all its congeners by having hypertrophied teeth on the anterior portion of the outer row of the premax- illa and dentary in males. It reaches a maximum adult size of about 18 mm SL and exhibits several reductive characters, as expected for a miniature species, including a notable reductive character state - four branchiostegal rays.
 
Article
Rivulus kayabi, new species, from the Arinos and Teles Pires drainages of the Tapajós river basin, central Brazil, is described. It is similar to other species of Melanorivulus from southern Amazonian tributaries of central Brazil by having a unique color pattern of flank, consisting of red marks arranged in a chevron-like pattern with vertex on the ventral portion of the flank. It differs from all other species of this region by a combination of 31-33 scales in the longitudinal series, a horizontal series of white spots on the dorsal portion of the caudal fin in females, 13 pectoral-fin rays, and 28-31 caudal-fin rays.
 
Article
Rivulus schuncki, new species, is described from the Anauerapucu River drainage, lower Amazonas River basin, northern Brazil. It is distinguished from all other species of the subgenus Melanorivulus by its pointed snout in lateral view, 12 rows of scales around the caudal peduncle, bright green bars on the flank and caudal fin in males, flank dark brown with small light gray spots on ventral part in females, pelvic fin without dark gray or black anterior margin in females and by the absence of red bars or dots arranged in chevron-like pattern on flank. Rivulus schuncki constitutes the first record of the subgenus Melanorivulus north of the Amazonas River.
 
Article
Laimosemion jauaperi, new species, from the Jauaperi river drainage, central Brazilian Amazon, is described. It was found in a shallow, black-water pool adjacent to a stream within dense forest. Laimosemion jauaperi differs from all other rivulines by possessing four pelvic-fin rays in the female (vs. 5-9), four branchiostegal rays (vs. 5-6) and the presence of a distinctive anterior white zone on the anal fin (vs. absence). Laimosemion jauaperi is hypothesized to be closely related to Laimosemion uatuman from the Uatuma river drainage by both, uniquely among rivulines, sharing the presence of caudal fin dark coloured with a contrasting distal white band in males.
 
Article
Rivulus megaroni, new species, is described from the Xingu River drainage, southern Amazonas River basin, central Brazil. It is similar to other species of Melanorivulus endemic to the southern Amazonian tributaries of central Brazil by having a unique color pattern of flank in males, consisting of red marks arranged in a chevronlike pattern, in which the chevron vertex is placed on the ventral portion of the flank. The new species is distinguished from all other species sharing that color pattern by a combination of 34-36 scales in the longitudinal series, seven well-developed pelvic-fin rays, chevron marks of flank arranged as oblique bars, absence of red pigmentation on the tip of the lower jaw, a horizontal series of white spots on the dorsal portion of the caudal fin in females, and caudal fin pink in males.
 
Article
Melanorivulus schuncki is first recorded for a vast geographic area of the eastern Brazilian Amazon between Rego Grande River, Amapá state, and the lower Amazonas River basin, Pará state. It was found in shallow parts of clear and black water streams, as well as in broad flooded areas, both in the edge of the forest and in open savannah. Some variability in colour patterns of unpaired fins in males is first recorded. Rivulus albae is formally recognized as a junior synonym of Melanorivulus schuncki.
 
Article
Rivulus tocantinensis, new species, from the middle section of the Tocantins River drainage, and R. xinguensis, new species, from the lower Xingu River drainage, eastern Amazonas River basin, northern Brazil, are described. Both species are missing the well-defined marginal yellow stripes on the caudal fin present in adult males of all other species of the R. urophthalmus group. Rivulus tocantinensis is distinguished from all other species of the R. urophthalmus group in having wide dark orange stripes on the flank and large dark orangish brown blotches on the middle of the caudal fin in males, and the absence of dermosphenotic bone or sometimes represented by a rudimentary ossification; R. xinguensis differs from other species of that group in having fewer scales in the longitudinal series.
 
Article
Rivulus cajariensis, new species, is described from the Cajari River drainage, lower Amazonas River basin, north-ern Brazil. It is hypothesized to be a member of a species assemblage endemic to the Guiana Shield area and adjacent lowlands of Venezuela, diagnosed by the presence of numerous rays in the anal and pectoral fins. The new species is distinguished from all other species of the genus, except R. igneus, by the presence of a dark green-ish blue blotch on the upper portion of the opercle, and lower jaw, distal portion of anal fin and lower portion of caudal fin orange in males. Rivulus cajariensis is distinguished from R. igneus by having fewer scales in the longi-tudinal and transverse series and by the presence of a black round spot on the upper portion of the caudal-fin base in females. Rivulus cajariensis, sp. n., é descrita da drenagem do rio Cajari, bacia do baixo rio Amazonas, norte do Brasil. Ela é hipotetizada ser um membro de um agrupamento de espécies endêmico da área do Escudo da Guiana e terras baixas adjacentes da Venezuela, diagnosticado pela presença de numerosos raios nas nadadeiras anal e peitoral. A nova espécie se distingue de todas as outras espécies do gênero, menos R. igneus, pela presença de uma man-cha azul esverdeada na porção superior do opérculo, e mandíbula inferior, porção distal da nadadeira anal e porção inferior da nadadeira caudal alaranjadas em machos. Rivulus cajariensis se distingue de R. igneus por possuir menos escamas nas séries longitudinal e transversal e pela presença de uma mancha redonda negra na porção superior da base da nadadeira caudal em fêmeas.
 
Article
Studies of fish fauna in the Amazon region have focused mainly on large rivers and commercially exploited species. The vast majority of information for small-sized species inhabiting forest streams comes from aquarium observations, in non-natural conditions. In the present study, we made underwater observations to investigate the use of space and food resources in a fish assemblage at Igarapé Guaraná, tributary of the Igarapé Tarumã of the Rio Negro system. We recorded 29 species belonging to 11 families and 6 orders. The fish species showed different patterns of space use, both in relation to their position in the water column and to their horizontal distribution. We also detected different use of resources through 13 different feeding tactics, some of the species exhibiting more than one tactic. Our results indicate the existence of a general pattern of use of space and feeding tactics in fish assemblages of Amazon streams.
 
Article
The biology of #Colossoma macropomum$ is studied in the Trinidad region (Mamore Basin, Bolivia) and the results are compared with those from other basins. Almost unexploited in Bolivia, #C. macropomum$ stocks are already in regression in central Amazonia. It inhabits flood-plain and is indifferent to the two main water types, white waters originally from the Andes and black waters formed in "pampas". It is oustandingly resistant to hypoxia through the development of lower lip extensions often observed in numerous adults. During high waters, #C. macropomum$ are scattered into the flooded areas ; they gather together in the lakes when the water recedes and finally reach the Mamore river. At low water, they migrate upstream for reproduction which takes place in the last quarter of the year near the Securé riverbanks. In the breeding season, males remain at the spawning places while, after spawning, females move to recently flooded areas. The length at sexual maturity is 62 cm for females and 60 cm for males. There is a clear condition cycle composed of rapid fattening during high waters followed by a long thinning down beginning at fall and lasting till the middle of next flood. These results on feeding agree with those obtained in central Amazonia : intense feeding period on fruits and seeds falling from the trees during high waters followed by a long fast, total for adults, partial for youngs. This cycle is registered on otolith (asteriscus) sections by alternating broad opaque zones and hyaline rings well stained by toluidin blue. These marks were useful to age most fishes with a good accuracy and to study the growth. The growth is fast and similar in both sexes until sexual maturity, which occurs between 7 and 10 years. Adult male growth is slightly slower than that of female ; the difference between the two average maximal lengths is only 2 cm (74 cm for females, 72 cm for males). #Colossoma macropomum$ can live a very long time, at least 40 years (maximum, 65 years). Growth curve shows a pattern characteristic of inexploited stocks. (D'après résumé d'auteur)
 
Top-cited authors
Maurice Kottelat
Jörg Freyhof
  • Museum für Naturkunde - Leibniz Institute for Research on Evolution and Biodiversity
Wilson J e M Costa
  • Federal University of Rio de Janeiro
Sven Kullander
  • Swedish Museum of Natural History
Heok Hee Ng
  • National University of Singapore