Reproductive and morphological analysis of the trairão Hoplias intermedius in the São Francisco River, downstream from a large reservoir.

Hoplias intermedius, of the Characiformes order and Erytrinidae family, is widely distributed across South America. This commercially interesting species can reach a length of 100 cm and a weight of 15-20 kg. To evaluate the reproductive biology of H. intermedius in the São Francisco River, Brazil, 154 males and 190 females were captured bi-monthly between September 2018 and August 2019 from the downstream regions of the Três Marias dam. Gillnets with differently sized meshes were deployed at distances of 34-54 km after the confluence with the Abaeté River (18°00'49″ S, 45°10'51″ W). Biometric data, gonadosomatic index (GSI), Fulton condition factor (K) and absolute fecundity (AF) were determined for each specimen. Gonad maturation stages and the spawning season were also established. The biometric data, GSI and K average values were relatively higher in females than in males. The reproductive peak for both sexes was reached around January/February. The mean AF was 4300.5 ± 1451.2 follicles per female. Fully developed vitellogenic follicles had a mean diameter of 1014.8 ± 250.7 µm, which is characteristic of fish with moderate fecundity. Fish of all maturation stages, from mature, spawned and spermed, occurred in all bimesters, indicating that this species reproduced throughout the year. The high frequency of spawning females throughout the year and the histological characteristics of spawned ovaries indicated that trairão H. intermedius' spawning type is partial.

Morphological analysis of the reproductive activity of Curimatella lepidura (Characiformes: Curimatidae).

Curimatella lepidura, commonly known as the manjuba, belongs to the Curimatidae family. To assess the reproductive activity of this species, fish were collected from three sections of the São Francisco River: section 1 = the Três Marias reservoir (TMR), section 2 = the SFR immediately downstream of the TMR, and section 3 = the SFR 54 km downstream from the TMR after the confluence of the SFR with the Abaeté River. Fish were collected bimonthly from January to December 2012. From this, the gonadosomatic index (GSI), Fulton condition factor (K), gonadal maturation stages in females and males, and diameters of vitellogenic follicles were determined. That is, this study employed histological and histometrical techniques to study the ovaries and testes of collected fish. The Fulton condition factor was statistically higher in section 1 than in the other sections, indicating that C. lepidura presents better health conditions in this section. Fish in the maturation/mature gonadal stage were collected in the November/December and January/February bimesters, coinciding with high temperatures, a long photoperiod, and abundant rainfall in this region. The mean vitellogenic follicle diameter was statistically lowest for sections 2 and 3, with a better impact on reproduction than in section 1. Overall, the results show that C. lepidura has reproductive success in lentic environments, such as in section 1, the TMR.

Induced reproduction and early development in dourado, Salminus franciscanus Lima & Britski, 2007 (Pisces: Characiformes).

Our study aimed to establish the response of Salminus franciscanus to hypophysation and describe the main morphological events of its embryonic process. Wild fish were captured in São Francisco River and selected broodstock (females: 66.4 ± 11.1 cm and 4.04 ± 2.32 kg; males: 58.3 ± 10.2 cm and 3.62 ± 1.12 kg) were kept at 26.1 ± 0.6°C for induction of final maturation/gamete release via the hypophysation technique. In females, two doses (0.8 and 5.6 mg/kg body weight) of crude pituitary extract of common carp (Cyprinus carpio) were administered with a 14 h interval. For males, a single dose (2.7 mg/kg body weight) of crude pituitary extract was applied at the same time as the females' second dose. Oocytes and sperm were manually stripped 8 h after a females' second hormonal dose. Fertilization was carried out using the dry method. Eggs were kept in funnel-type 60 L incubators at 24.3 ± 0.3°C and were analyzed and photographed every 10 min. After hormonal induction, 60% of females and 100% of males reacted positively and no broodstock mortality was recorded. The females released an average of 385.2 ± 78.4 g of oocytes and the fertilization rate observed was 50.4 ± 12.3%. The blastopore closure occurred at 7.5 h, somite formation at 12 h and hatching at 20 h post-fertilization. In general, the results of this study improve the understanding of the reproductive biology of dourado and confirm its potential for fish farming in the neotropical region.

Reproductive biology of the Neotropical catfish Iheringichthys labrosus (Siluriformes: Pimelodidae), with anatomical and morphometric analysis of gonadal tissues.

The reproduction of Iheringichthys labrosus (Lütken, 1874) from the Turvo River, Brazil, was studied using anatomical, biometric, histological, and ultrastructural techniques. Between April 2014 and March 2015, a total of 278 males and 512 females were captured bimonthly. The testes of Iheringichthys labrosus are fringed and possess a cranial spermatogenic region and an exclusively secretory caudal region. Histologically, the cranial region is composed of seminiferous tubules with spermatogenesis being completed in cysts. The spermatozoa are of the primitive type with a spherical head and have a rudimentary intermediate piece and a long tail with an axonemic arrangement of 9 + 2. The caudal region does not form an individualized gland, and cells in this testis area have characteristics of protein secretion. A variable density electron-dense secretion accumulates in the cisternae of the rough endoplasmic reticulum in the lumen of the seminiferous tubules and in the testicular ducts during maturation. The cortical alveoli are discontinuous, and the zona pellucida consists of three layers crossed by pore canals, and the follicular cells are squamous in the early stages of oogenesis and cuboidal in advanced stages. The gonadosomatic index was associated with the maturation of the gonads while the condition factor indicated that the fish feed less and utilize adipose reserves during the reproductive period. Males and females reproductively functional throughout the year with spawning being partial or multiple, similar to that reported in studies of the species in lentic environments.

Comparative morphology of gonads from six species of fish belonging to the family Anostomidae (Characiformes: Anostomidae) / Morfología comparativa de las gónadas de seis especies de peces de la familia Anostomidae (Characiformes: Anostomidae)

AbstractIn fishes, gonad morphology is an important parameter to understand the reproductive biology, phylogenetic relationships and systematic studies. The main objective of this study was to make a comparative analysis of the morphology of mature ovary and testis in six fish species of the family Anostomidae. A total of 212 specimens, presenting maturing gonads, were captured from the São Francisco River, Três Marias Reservoir area, in Southeastern Brazil, between August 2008 and December 2010. The six analyzed species had mature ovaries and showed a grayish color. In vitellogenic oocytes (VO), cortical alveoli (CA) were composed by small vesicles in all Leporinus species, but in Leporellus vittatus and Schizodon knerii the CA were large vesicles. However, the CA of all species showed similar histochemical content. The pellucid zone consists of two layers to all species, but it was thicker in S. knerii (11.5 ± 1.8 µm) than in L. vittatus (9.0 ± 0.8 µm) and Leporinus species (3.5 ± 0.6 - 8.7 ± 0.9 µm). Follicular cells of the VO were respectively cubic and prismatic in animal and vegetative poles of S. knerii (22.3 ± 3.2 and 61.1 ± 9.6 µm), and squamous in the other species (1.3 ± 0.3 - 1.6 ± 0.3 µm). Females of S. knerii and males of L. vittatus showed lower values of gonadosomatic index (GSI) than the other assessed species. All evaluated species presented testicular morphology similar to most neotropical Characiformes, with unrestricted spermatogonial testis and anastomosing tubular organization of seminiferous tubules. Phenotypical differences in the vitellogenic oocyte of Anostomidae fishes, confirmed the taxonomic position of S. knerii as different genus in relation to Leporinus and L. vittatus. Despite being placed in different genera, the characteristics of the vitellogenic oocytes of L. vittatus were similar to those found in the studied Leporinus.

ResumenTeniendo en cuenta que la morfología de las gónadas es un parámetro importante para la comprensión de la biología de la reproducción, las relaciones filogenéticas y estudios sistemáticos, el objetivo principal de este estudio fue realizar un análisis comparativo de la morfología de ovarios maduros y testículos en seis especies de peces de la familia Anostomidae. Un total de 212 especímenes, con las gónadas en maduración, fueron capturados en el río São Francisco, área de embalse de Três Marias, en el sureste de Brasil, entre agosto 2008 y diciembre 2010. Las seis especies analizadas mostraron ovarios maduros de un color grisáceo. En los ovocitos vitelogénicos (VO), los alvéolos corticales (CA) están compuestos por pequeñas vesículas en todas las especies de Leporinus, pero en Leporellus vittatus y Schizodon knerii los CA son grandes vesículas. Los CA de todas las especies mostraron, no obstante, un contenido histoquímico similar. La zona pelucida se compone de dos capas en todas las especies, pero es más gruesa en S. knerii (11.5 ± 1.8 µm) que en L. vittatus (9.0 ± 0.8 µm) y las especies de Leporinus (3.5 ± 0.6 - 8.7 ± 0.9 µm). Las células foliculares de los VO son, cúbico y prismática en polos animales y vegetativos de S. knerii (22.3 ± 3.2 y 61.1 ± 9.6 µm), respectivamente, y escamosas en las otras especies (1.3 ± 0.3 - 1.6 ± 0.3 µm). Las hembras de S. knerii y los machos de L. vittatus mostraron menor GSI que las otras especies evaluadas. Todas las especies presentan una morfología testicular similar a la mayoría de los Characiformes neotropicales, los cuales poseen testículos espermatogonias sin restricciones y organización tubular anastomosis de los túbulos seminíferos. Las diferencias fenotípicas en los VO entre las especies de Anostomidae confirman la posición taxonómica de S. knerii como género diferente en relación a Leporinus y L. vittatus. A pesar de ser colocados en diferentes géneros, las características de los ovocitos vitelogénicos de L. vittatus son similares a los encontrados en los Leporinus estudiados.

Early larvae ontogeny of the Neotropical fishes: Prochilodus costatus and P. argenteus (Characiformes: Prochilodontidae).

Early development of fish larvae is a highly dynamic process and its study may provide important information about ontogenetic development, bioenergetic growth, behaviour, taxonomic characteristics for identification in natural environments, identification of spawning areas, and population monitoring. With the aim to provide knowledge about their growth and behaviour, to support larval rearing, and also taxonomic purposes, we studied the life history of the Prochilodus argenteus and P. costatus from hatching until the complete absorption of the yolk. Larvae were obtained through artificial reproduction at the Hydrobiology and Aquaculture Station of Três Marias, Minas Gerais, Brazil. Immediately after hatching, 100 larvae of each species were put in two plastic incubators for conditioning. On a daily basis, larvae behavior was recorded and 14 larvae of each species were collected to analyse body morphology. On the first day after hatching, larvae of P. costatus and P. argenteus showed an elongated and transparent body; the yolk sac was filled with individualized yolk globules. In both species, the embryonic fin rounded the caudal region of the body, the retina was non-pigmented and the gut was obliterated. At the second day post-hatching, larvae of both species dendritic chromatophores had emerged, the mouth was obliterated and the pectoral fin was observed. The larvae showed 38-43 myomeres in P. costatus and 42-43 in P. argenteus. For both species, the gas bladder was inflated and the lumen of the gut was already open. On the third day post-hatching, the mouth of P. costatus and P. argenteus was already open in a sub-terminal position; the retina was pigmented; the gill arches had lamellar protrusions and were partially covered by the operculum. On the fourth day post-hatching, the pigmentation pattern was maintained with greater intensity; the mouth occupied a terminal position, the yolk sac was almost completely reabsorbed, and the pectoral and caudal fins showed mesenchymal rays in both species. The gut showed a broad lumen with folded mucosa and epithelium with striated border. The larvae of both species showed similar swimming behaviour. Our study provided understanding about the morphophysiological aspects, species identification, larval development and growth, and the ontogenic characteristics of two Neotropical fishes with importance for commercial and sports fishing.

Comparative morphology of the gonadal structure related to reproductive strategies in six species of neotropical catfishes (Teleostei: Siluriformes).

We studied the relationship between the morphology of the reproductive system and the reproductive strategies of six neotropical catfishes using macroscopic and microscopic analyses. The reproductive system of the examined Siluriformes showed diversified characteristics, but permitted their being grouped according to three reproductive strategies: pelagic spawning, demersal spawning, and internally fertilizing. The pelagic spawners Pseudoplatystoma corruscans and Conorhynchos conirostris have testes that are characterized by filiform lobes, absence of testicular secretion, full-grown oocytes of small diameter, thin zona radiata, and cuboidal follicular cells. Pimelodus maculatus is morphologically distinct from the other two pelagic spawners catfishes due to the presence of testicular secretion. The demersal spawners Lophiosilurus alexandri and Rhinelepis aspera possess homogeneous testicular secretion, large mature oocytes, and columnar follicular cells. The most specialized reproductive system was observed in the internally fertilizing Trachelyopterus galeatus, which possesses a seminal vesicle accessory to the testes, spermatozoa with elongated nuclei that form spermatozeugmata, and a secretory ovarian lamellar epithelium that is associated with sperm storage. The reproductive system observed in Neotropical catfishes showed a relationship associated with the type of fertilization and the reproductive strategies of the six species studied.

Genetic characterization of native and introduced populations of the neotropical cichlid genus Cichla in Brazil.

A molecular phylogenetic analysis based on mitochondrial 16S ribosomal DNA and Control Region sequences from native and introduced populations was undertaken, in order to characterize the introduction of Cichla (peacock bass or tucunaré) species in Brazil. Mitochondrial DNA haplotypes found in introduced fish from Minas Gerais state (southeastern Brazil) clustered only with those from native species of the Tocantins River (Cichla piquiti and C. kelberi), thereby suggesting a single or, at most, few translocation acts in this area, even though with fish from the same source-population. Our study contributes to an understanding of the introduction of Cichla in regions of Brazil outside the Amazon basin, and adds phylogenetic data to the recently describe Cichla species, endemic from the Tocantins-Araguaia basin.