Ictiology

Gonads of 625 specimens of A. vaillanti, H. marginatus, M. costae and R. xenodon
captured at Três Marias reservoir from March/94 to June/96 were the analyzed by
histological methods. Thes analyses indicated fractionated spawning of four
species and the occurrence of fishes in reproductive activity all the year Females
in advanced maturation and partially spawned with peaks of gonado-somatic index
(GSI) were registred at higher frequency in NovemberlDecemberIJanuary, a period
of high preciptation in the region and when the water level of the reservoir starts to
rise.

El siguiente compendio de resúmenes fue tomado de losresúmenes enviados por los autores. Cualquier error no esresponsabilidad nuestra. El trabajo editorial soló consistió enajustar cada resumen de acuerdo a los lineamientosestablecidos en la Convocatori

Resumen La diafanización es una técnica histológica que tiene como principal finalidad aclarar los tejidos blandos de un organismo, lo que permite observar tejidos óseos y cartilaginosos. Se emplean diversas sustancias químicas así como colorantes específicos para teñir específicamente hueso y cartílago. No existen protocolos estandarizados por especie, ya que se generaliza por grandes grupos, siendo el de grupo de los peces uno de los menos definidos. En este trabajo se desarrolló una modificación de la técnica de diafanización y tinción ósea para el pez monja (Gymnocorymbus ternetzi), con el fin de optimizar el tiempo y los costos del proceso, ya que puede ser aplicado en peces de características similares. Palabras clave: diafanización, rojo de alizarina, Gymnocorymbus ternetzi. 1. Introducción La Real Academia Española define la palabra 'diáfano' como un cuerpo que deja pasar la luz a través del mismo casi en su totalidad. Dicho de un espacio que está despejado, o que carece de obstáculos o separaciones. Igualmente lo define como 'algo que se percibe bien' o 'algo claro'. Un sinónimo de la palabra diáfano es transparente. Por ello la palabra 'diafanización' puede entenderse como transparentación o aclaramiento. Fuera de la semántica y dentro de la biología, la diafanización es una técnica histológica que se realiza mediante la combinación sucesiva de sustancias químicas, de las cuales destaca el hidróxido de potasio (KOH), debido a su actividad corrosiva que permite aclarar a los tejidos blandos. Tejidos duros como hueso y cartílago no se ven afectados, lo cual resulta favorable para el estudio de los mismos sin realizar disecciones anatómicas. Asimismo, la diafanización es empleada para establecer centros de osificación de embriones y fetos de animales y humanos (Rivera-Cardona et al., 2015) y para realizar comparaciones de las características óseas de distintas especies. Existen diferentes tipos de métodos para diafanizar y teñir organismos, sin embargo la mayoría comparten el mismo fundamento, basado en tres etapas: fijación, transparentación (diafanización) y tinción específica (Figura 1). La fijación del ejemplar se realiza para mantener a las células intactas, buscando inactivar las reacciones enzimáticas celulares, impidiendo que se presente una autolisis y, por tanto, una degradación post mortem del organismo (Coronado, 2014). Los reactivos esenciales para este paso son: alcohol y formol. Figura 1. Esquema general de la técnica de diafanización con tinción ósea y cartilaginosa. (Modificado de Dawson, 1926). La transparentación se lleva a cabo para visualizar y analizar la estructura ósea y cartilaginosa, se transparenta todo el tejido blando, en este proceso se igualan los índices de refracción de la luz del interior del órgano con el medio que lo contiene (Concha, 2006). El reactivo fundamental es el hidróxido de potasio (KOH), debido a que es miscible y corrosivo. Por último, la tinción ósea y cartilaginosa se da por colorantes específicos que son rojo de alizarina y azul de alcián

Sagittae otoliths are the most studied because of their morphological variability and size; the sagittae may also have valuable taxonomic use and for D. auratus has not yet been described. In the present study we present a morphological description of the sagitta otolith and an analysis of its correlation with various morphometric parameters. The biological material was captured with a beach seine in the coasts of Alvarado and Port of Veracruz, from November 2009 to June 2010. Sagittae were extracted, cleaned, photographed (SEM and optical), and measured. The analysis included the correlations between sagitta's length and width, versus the fish standard length, height and weight, for a total of 449 fishes. The comparison between left and right sagitta showed no significant difference in both otolith length and width (t-tests, p<0.05) for each sex. The right otolith was used for the correlations for both males and females and the Fisher test (d.f. 161 and 143, p<0.001) showed no significant differences in the slopes and intersections between them. The otolith length vs. fish weight correlation showed a positive allometric growth in males (b=3.9754, p<0.05) and females (b=4.3168, p<0.05). Rev. Biol. Trop. 61 (1): 139-147. Epub 2013 March 01.

Los peces de acuario Danio rerio (Pez cebra) y Poecilia reticulata (Guppy) son organismos recomendados para realizar diferentes tipos de estudios debido a sus características como su poco periodo de gestación, fácil manipulación y cuidado sencillo. Ambos organismos pertenecen a la infraclase Teleosti y se caracterizan por ser peces pequeños de aguas dulces. Ambos organismos son utilizados en diferentes tipos de estudio como la carcinogénesis, desarrollo embrionario y biología del desarrollo (Crespo, S. 2002). Sin embargo, el uso del pez cebra ha aumentado debido a que existe una similitud entre el genoma de este y el del hombre (Pez cebra ~1.7 x 10 9 pb, humano ~ 3 x 10 9 pb)( Rocha A, Ruiz S, Estepa A, Coll JM. 2001). Gracias a la microscopía óptica, fue posible observar y caracterizar la composición celular de Poecilia reticulata y de esta forma, realizar una comparación entre los tejidos hepáticos de Poecilia reticulata y Danio rerio.

El estado de Hidalgo contiene numerosos cuerpos de agua que alojan una variada ictiofauna. Con el fin de conocer las especies de peces que habitan el estado, se realizaron colectas en distintos cuerpos de agua de 42 municipios durante los años 2008 a 2011, utilizando diferentes métodos de pesca. El resultado de los muestreos permitió formar una lista de especies de peces de agua dulce que se encuentra alojada en el Centro de Investigaciones Biológicas de La Universidad Autónoma del Estado de Hidalgo. La colección cuenta con 518 registros que pertenecen a 14 familias y a 47 especies, de las que 14 son endémicas a México, 18 nativas de Hidalgo y 12 son introducidas. Las familias más diversas son: Poeciliidae, con 14 especies, de ésta, Poeciliopsis gracilis es la especie nativa más abundante; Cyprinidae, con 11 especies y Cichlidae con siete. Los ríos con mayor número de especies se encuentran en la región de la huasteca hidalguense y el río Huazalingo, en el municipio de Yahualica, es el que presenta más. Esto sugiere continuar con la revisión de los cuerpos de agua en el estado de Hidalgo para conocer a mayor profundidad la diversidad de peces, y así contar con un mejor conocimiento de la conservación de las especies nativas y endémicas, sobre todo por el deterioro de algunos cuerpos de agua, debido a la contaminación y a la presencia de especies introducidas en el estado.

El género Sicydium en la costa ecuatoriana, llamado localmente “chautiza”, es un tipo de pez con comportamiento migratorio anfídromo, cuyo estadio post-larvario constituye un recurso pesquero de interés local. La presencia de este pez tiene registros en fuentes bibliográficas muy antiguas y en relatos populares que no solo describen su dinámica pesquera sino que narran su presencia en ríos donde hoy en día su existencia es muy baja o tal vez la especie se encuentra extinta. Sin embargo, amplían considerablemente su área de distribución geográfica

Através de análise microscópica de gônadas de B. cf. affinis capturados na lagoa do Pantaninho, município de Lagoa da Prata, MG, constatou-se que fêmeas e machos em atividade reprodutiva ocorrem durante todo o ano e a espécie apresenta desova do tipo parcelado. De outubro a janeiro registraram-se picos do índice gonadossomático (IGS) coincidindo com os períodos de elevação da temperatura e precipitação pluviométrica na região. Os valores do índice hepatossomático (IHS) de machos e fêmeas apresentaram-se mais altos no período reprodutivo. O índice de repleção estomacal (IRE) apresentou seu pico no subestádio 4a (parcialmente desovado/esgotado).

Gônadas de 625 exemplares de A. vaillanti, H. marginatus, M. costae e R. xenodon capturados no reservatório de Três Marias, no período de março/94 a junho/96, foram analisadas histologicamente. A desova das quatro espécies é do tipo parcelado e peixes em atividade reprodutiva ocorreram durante todo o ano. Registrouse maior freqüência de fêmeas em maturação avançada e parcialmente desovadas, com picos de índice gônado-somático (IGS) no período de novembroldezembroljaneiro, quando a precipitação pluviométrica na região é alta e o nível de água da represa começa a subir. ABSTRACT Gonads of 625 specimens of A. vaillanti, H. marginatus, M. costae and R. xenodon captured at Três Marias reservoir from March/94 to June/96 were the analyzed by histological methods. Thes analyses indicated fractionated spawning of four species and the occurrence of fishes in reproductive activity all the year Females in advanced maturation and partially spawned with peaks of gonado-somatic index (GSI) were registred at higher frequency in NovemberlDecemberIJanuary, a period of high preciptation in the region and when the water level of the reservoir starts to rise.

The microscopic analysis of gonads of B. cf. affinis captured in Pantaninho lake,
Lagoa da Prata County, MG, showed that males and females engage in reproductive
activity throughout the year and the species presents fractionated spawning.
Peaks of the gonadosomatic index (GSI) were registered from October to January,
coinciding with the periods of high temperature and precipitation, in the studied
area. The values of the hepatosomatic index of males and females got higher in
the reproductive period. The stomach repletion index presented its peak in substage
4a (partially spawnedIspent).

Background: Artisanal fishery is one of the most important economic activities for human populations living in coastal areas. The traditional knowledge that fishermen have of fishes is of utmost importance for the establishment of conservation strategies for many species. This study aimed to analyse the knowledge of and utilization of fishes by the artisanal fishermen in a fishing community on the coast of Ceará State (Northeast Brazil).

Lophiosilurus alexandri reproduces in captivity, has a high
commercial value in Brazil and carries great potential for
aquaculture. Research was carried out on L. alexandri larvae
from days 1 to 30 post-hatch (DPH). Based on descriptions in
the literature four developmental stages were observed using
anatomic, histological and statistical techniques to provide
useful data for the taxonomy, aquaculture and conservation of
this species. In the yolk sac stage (1–2 DPH) the larvae
presented myomeres (pre 17–23 and post anal 25–32) evident
along the body, open mouth, the beginning of eye pigmentation
and intestine with simple prismatic epithelium. The
preflexion stage (3–4 DPH) was characterized by onset of
body pigmentation and appearance of the pectoral fin bud.
The oesophagus, stomach and intestine presented a folded
mucosa. The flexion stage (5–7 DPH) was characterized by a
flexion of the notochord, the chondrogenesis of the neural
arches, formation of the dorsal and anal fins (11 rays) and
appearance of the pelvic fin bud. In the postflexion stage (8–30
DPH) the formation of pelvic fin rays (6 rays) occurred along
with the development of three different stomach regions.
Except for the variables related to the yolk sac, all other
studied variables presented significant differences between
developmental stages.

Martins, Y.S., Arantes, F.P., Sato, Y., dos Santos, J.E., Rizzo, E. and Bazzoli, N. 2012. Comparative analysis of gonadal morphology in six fish species of the Incertae Sedis genera in Characidae of occurrence in the São Francisco River Basin, Brazil. -Acta Zoologica (Stockholm) 93: 48-56.

The digestive tract of Trachelyopterus striatulus (Steindachner, 1877) was studied using morphological, histological, and histochemical techniques. The barbels, lips and tongue had stratified squamous epithelium with mucous, claviform cells, and taste buds. Trachelyopterus striatulus had a dental plaque with villiform teeth. The bucopharyngeal
cavity was formed by the gill apparatus and pharyngeal teeth with vilifform denticles. The oesophagus presented
stratified squamous epithelium with mucous cells and taste buds. The stomach included cardiac, fundic, and pyloric
regions and a simple prismatic epithelium with prismatic cells that reacted positively to periodic acid-Schiff (PAS) and
amylase+PAS. Only the cardiac and pyloric regions responded positively to alcian blue pH 2.5 (Ab pH 2.5) and alcian
blue pH 0.5 (Ab pH 0.5). The cardiac and fundic regions exhibited tubular gastric glands. The intestine was 118.90 ±
22.49 mm long with an intestinal coefficient (CO) of 0.83 ± 0.13. The epithelium was simple prismatic with a brush
border and goblet cells, and a greater number of goblet cells were found in the caudal region of the intestine. The
mucous cells and goblet cells reacted positively to PAS, amylase+PAS, Ab pH 2.5, and Ab pH 0.5. We analysed if the
function of the mucosubstances and morphological characteristics of the digestive tract of T. striatulus are compatible with omnivorous feeding habit.

Este estudo teve como objetivo descrever as variações espaço-temporais da ictiofauna em uma laguna costeira aberta. Os peixes foram coletados na Lagoa da Conceição, Florianópolis-SC, totalizando 19 meses de amostragem entre outubro de 1987 e novembro de 1989. Foram realizadas coletas em sete pontos, sendo que em cada um foram empregados lances de tarrafa de diferentes malhas, rede de mão do tipo puçá, rede de arrasto de praia e pesca manual com anzóis. Foram coletados 8.299 indivíduos, classiicados em 61 espécies pertencentes a 28 famílias de peixes, totalizando 52.902,4 g. Em relação à permanência na laguna, 48 espécies (80%) foram classiicadas como visitantes e as outras 12 eram residentes. Foram observadas diferenças signiicativas entre as estações (n, biomassa, riqueza de espécies e H'Loge), entre as áreas (n e riqueza de espécies) e nas interações entre os fatores estação e área (n e biomassa). Os dados sobre a ictiofauna reforçam a importância ecológica do ambiente da laguna costeira como área berçário e de alimentação, já que a maioria das espécies encontra-se em fases de recrutamento dentro da Lagoa da Conceição.

This study presents, for the first time, information on the eggs and early development of Franciscodoras marmoratus, fish of Sa˜o Francisco river, Brazil. To analyse the egg ultrastructure and morphological events of embryogenesis, a total of 36 F. marmoratus specimens (18 males and 18 females) were captured
and subjected to spawning induction. Gametes were collected by manual extrusion, and fertilization was conducted using the dry method. After fertilization, eggs were kept in incubators with water temperature of 24°C. The embryonic development was monitored using a stereomicroscope until hatching. There was a 67% positive response to hypophysation by the females and the fertilization rate was 73.8 ± 6.2%. The oocytes are discoid, yellow, adhesive and covered by a thick jelly coat. Under the electron scanning microscope, the oocytes presented a surface with pore canals and funnel-shaped micropyle with a smooth vestibule. Recently extruded oocytes had a mean diameter of 1.27 ± 0.4 mm and after hydration was 1.91 ± 0.05 mm. The jelly coat was
0.34 ± 0.03 mm thickness, and the perivitelline space was 0.19 ± 0.04 mm. Eight phases of the embryonic development were identified, and embryogenesis was completed at 47 h after fertilization, at 24°C water temperature. The recently hatched larvae had 2.76 ± 0.57 mm of total length. These results provide useful information for the successful breeding and reproductive strategies of fishes.

From March to April 2010, specimens of Acestrorhynchus lacustris were collected in the Peixe
River, Anhembi, São Paulo State, Brazil. This characid, commonly known as peixe-cachorro, has a
preference for lentic habitats and it features carnivorous habits, with an important role in the food chain.
This study aimed to carry out a parasitological analysis of 34 specimens of A. lacustris, and 33 of these were
infected by at least one species of metazoan parasite. Nine species were identified: Ameloblastella sp. and
Diaphorocleidus sp. (Monogenea); Ascocotyle sp., Diplostomidae gen. sp. and Sphincterodiplostomum
musculosum (Digenea); Contracaecum sp., Philometroides caudata, Procamallanus (Spirocamallanus) inopinatus
and P. (S.) saofranciscensis (Nematoda). Except P. caudata and P. (S.) saofranciscensis, all parasites showed
prevalence higher than 10%. There was a positive correlation between host weight and length and the
Ameloblastella sp. Diaphorocleidus sp. was the dominant species. No species was considered central. All
parasites showed an aggregated distribution. The parasite community of A. lacustris was characterized by
high richness (d = 0.85) and uniformity (J’ = 0.85) and low diversity (HB = 0.56). Except Nematoda, all
other parasites were recorded for the first time in this host. Ameloblastella sp., Diaphorocleidus sp. and
Ascocotyle sp. are recorded for the first time in the Peixe River.

Characidium cacah, new species, apparently endemic to the rio das Velhas sub-basin, upper rio São Francisco basin, Brazil, is described. The new species is easily distinguished from congeners, except C. chicoi, C. helmeri, C. mirim, C. nana, C. nupelia, C. stigmosum and C. xavante, by having an incomplete lateral line and for lacking an adipose fin. The new species can be diagnosed from the aforementioned species by a series of characters, including the presence of 12 circumpeduncular scales, the isthmus completely scaled, a thin inconspicuous or dashed midlateral dark stripe, the absence of a conspicuous peduncular blotch, and humeral blotch and basicaudal spot variably marked.

Characidium cacah, espécie nova, aparentemente endêmica da sub-bacia do rio das Velhas, alto rio São Francisco, Brasil, é descrita. A nova espécie se distingue facilmente das congêneres, exceto C. chicoi, C. helmeri, C. mirim, C. nana, C. nupelia, C. stigmosum e C. xavante, por ter linha lateral incompleta e ausência de nadadeira adiposa. A nova espécie pode ser diagnosticada das espécies citadas por uma série de características, incluindo a presença de 12 escamas circumpedunculares, istmo completamente coberto por escamas, faixa estreita mediana lateral escura inconspícua ou interrompida, ausência de mancha no pedúnculo caudal e manchas umeral e basicaudal variavelmente marcadas.

Seasonal abundance and composition of fish assemblage in two estuarine beaches in Paranaguá's Bay, Paraná. The aim of the present work was the characterization of the ichthyofauna of two estuarine beaches in the Bay of Paranaguá, PR. Highest numbers of species and individuals were sampled in the warmer months, during which the occurrence of sporadical visiting species was greater. Few estuarine species are considered residents of which Atherinella brasiliensis Quoy & Gaimard, 1824 and puffer species, (Sphoeroides testudineus Linnaeus, 1758) seems to use the area as nursery grounds. The aggregates of sardines and anchovies had occurred occasionally at determined seasons depending on the species, which seems to indicate a migration pathway from the areas of spawning in the continental shelf to estuarine areas. These behavioral patterns associated with reproductive and feeding periods suggest the important ecological role of these areas during part of the life cycle of many fish species, mainly when juvenile.

A través de esta nueva serie tratamos de conocer diferentes aspectos personales de los integrantes de la comunidad ictiológica iberoamericana. Esta iniciativa, comparte el espíritu y objetivo de las semblanzas nacionales buscando informalmente otro punto de unión en la "comunidad de ictiólogos iberoamericanos". Quizás esté equivocado en mi apreciación, pero creo que vale la pena este intento, ya que, con la colaboración generosa e insoslayable de los integrantes de este "universo", señalaremos un registro en el tiempo de la Ictiología Neotropical.

Wave action in sandy beach surf zones and its influence on species composition were evaluated at three sites at Pontal do Paraná, Paraná State, between June/2004 and May/2005. At each sampling site, five hauls were performed monthly using a 15 m long, 2.6 m height beach seine with a 5 mm mesh-size. Samplings were carried out at low water spring tides during daylight. A total of 26,866 fishes were collected, amounting to a total weight of 84,838 kg, which were distributed amongst 28 families and 63 taxa. Multi- and univariated methods used indicated that sheltered and moderately exposed beach samples had similar ichthyofaunal composition, being clupeids and engraulids the most abundant at these beaches. Although abiotic factors differed significantly between beaches, depth appears to exert the major influence on ichthyofauna structure by providing less turbulent waters which might have permitted shoals maintenance. Conversely, exposed beach samples differed largely from the other bea...

The morphofunctional organisation of the female reproductive system, the oocyte growth and the follicular envelope ultrastructure were studied by the first time in the catfish Iheringichthys labrosus from Upper Paraná River basin, Southeastern Brazil, in order to contribute to the knowledge of the reproductive behaviour strategies of this species. As in other Neotropical freshwater siluriforms, the ovaries are of the cystovarian type, the oocytes develop in an asynchronous pattern and mature oocytes are released in clusters in the ovarian lumen, being transported through the oviduct to the urogenital papilla. During the primary growth, nuclear material is transported to the ooplasm, forming the yolk nucleus, where proliferate membranous organelles. The onset of the zona radiata formation occurs during the late perionucleolar stage with the deposition of the outer layer. At the vitellogenic stage, this envelope reaches 6.35 ± 0.84 m of thickness, being constituted by three distinct layers crossed by pore-canals containing oocyte and follicular cells processes. Cytochemical analyses evidence neutral glycoproteins in cortical alveoli, yolk globules and zona radiata. Follicular cells with squamous shape during the primary growth acquire synthetic activity at the secondary growth, reaching 37.82 ± 4.72 m in height at the mature vitellogenic follicles. These cells accumulate sulphated polysaccharides in large electron-lucent vesicles during the vitellogenic stage which are possibly secreted to form a mucous coat at the egg surface. These evidences suggest that I. labrosus may have adhesive eggs as also detected in other Neotropical freshwater Siluriformes.

O presente trabalho tem por escopo propor um sistema de zonação para espinhos de peixe. A implementação desse sistema visa registrar a presença e a frequência de distintas quebras observadas durante as análises da arqueofauna do sítio PSG02. Ademais, a aplicação deste método tem por objetivo diferenciar os distintos padrões de quebra e o grau de fragmentação dos elementos, buscando assim compreender melhor os processos tafonômicos naturais e culturais envolvidos.

DESCRIPTION Are the fish distribution patterns in an open coastal lagoon in the subtropical west Atlantic inluenced by spatial and seasonal variations? This study aimed to describe the spatial-temporal variations of the ish fauna in an open coastal lagoon. Fish were collected in Lagoa da Conceição, Florianópolis, Santa Catarina, Brazil, totaling 19 sampling months between October 1987 and November 1989. Sampling took place at 7 sites, and in each of them cast net throws of different meshes, “puçá” handheld fishing net, beach seine fishing net, and manual fishing hooks were used. A total of 8,299 individuals were collected, classiied into 61 species belonging to 28 fish families, totaling 52,902.4 g. Regarding stay in the lagoon, 48 species (80%) were classiied as visitors and the other 12 were residents. Signiicant differences were observed between seasons (n, biomass, species richness, and H’Loge), between areas (n and species richness), and in the interactions between the factors ...

Sagittae otoliths are the most studied because of their morphological variability and size; the sagittae may also have valuable taxonomic use and for D. auratus has not yet been described. In the present study we present a morphological description of the sagitta otolith and an analysis of its correlation with various morphometric parameters. The biological material was captured with a beach seine in the coasts of Alvarado and Port of Veracruz, from November 2009 to June 2010. Sagittae were extracted, cleaned, photographed (SEM and optical), and measured. The analysis included the correlations between sagitta's length and width, versus the fish standard length, height and weight, for a total of 449 fishes. The comparison between left and right sagitta showed no significant difference in both otolith length and width (t-tests, p<0.05) for each sex. The right otolith was used for the correlations for both males and females and the Fisher test (d.f. 161 and 143, p<0.001) showed no significant differences in the slopes and intersections between them. The otolith length vs. fish weight correlation showed a positive allometric growth in males (b=3.9754, p<0.05) and females (b=4.3168, p<0.05). Rev.

Este estudo teve como objetivo descrever as variações espaço-temporais da ictiofauna em uma laguna costeira aberta. Os peixes foram coletados na Lagoa da Conceição, Florianópolis-SC, totalizando 19 meses de amostragem entre outubro de 1987 e novembro de 1989. Foram realizadas coletas em sete pontos, sendo que em cada um foram empregados lances de tarrafa de diferentes malhas, rede de mão do tipo puçá, rede de arrasto de praia e pesca manual com anzóis. Foram coletados 8.299 indivíduos, classiicados em 61 espécies pertencentes a 28 famílias de peixes, totalizando 52.902,4 g. Em relação à permanência na laguna, 48 espécies (80%) foram classiicadas como visitantes e as outras 12 eram residentes. Foram observadas diferenças signiicativas entre as estações (n, biomassa, riqueza de espécies e H'Loge), entre as áreas (n e riqueza de espécies) e nas interações entre os fatores estação e área (n e biomassa). Os dados sobre a ictiofauna reforçam a importância ecológica do ambiente da laguna costeira como área berçário e de alimentação, já que a maioria das espécies encontra-se em fases de recrutamento dentro da Lagoa da Conceição.

The gonad morphology and gametogenesis of Lophiosilurus alexandri Steindachner, 1877 from Santo Antônio river (Minas Gerais, Brazil) were studied through anatomical and histological techniques. Examination of the testis revealed that they were paired, fringed organs with two distinct regions: cranial spermatogenic and caudal spermatogenic and secretory. The cranial region represents ca. 60% of the mature/maturing testis, containing 41 to 73 fringes, while the caudal portion represents ca. 40% and contains 44 to 68 fringes. At the cranial portion the length of the fringes was 3.70 ± 1.70 mm and in the caudal portion was 0.20 ± 0.10 mm. The spermatogenesis was cystic, synchronic, and occurred throughout the whole extension of the seminiferous tubules. The ovaries were saculiforms, paired organs, which present ovigerous lamellae containing cells of the oogenic lineage. The oocytes were classified into four developmental stages according to their cytological characteristics and the char...