José Enemir dos Santos

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.

Aparelho reprodutor e gametogênese de Lophiosilurus alexandri Steindachner (Pisces, Teleostei, Siluriformes)

The gonad morphology and gametogenesis of Lophiosilurus alexandri Steindachner, 1877 from Santo Antonio 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 characteristics of the cell layers that surround them.

Ontogenic events and swimming behavior of larvae of the characid fish Salminus brasiliensis (Cuvier) (Characiformes, Characidae) under laboratory conditions

The larval ontogeny and swimming behavior of the characid fish Salminus brasiliensis (Cuvier, 1816) were studied under experimental laboratory conditions, from hatching to yolk absorption. At day 1, the larvae were transparent, with sparse dendrite chromatophores and a well-developed adhesive organ on the head. The retinal epithelial cells were initiating pigmentation. The branchial arches were at the initial phase of differentiation. The larvae were able to perform only vertical displacements and, when resting on the tank bottom, remained in lateral decumbency, in groups of 3 to 15 larvae. On day 2, the mouth was open, with conical teeth, and the digestive tube presented lumen and folded mucosa. The gaseous bladder and pectoral fins also were in differentiation. The larvae performed vertical and horizontal movements, adhered to the water surface by means of the adhesive organ or formed groups of three to six on the tank bottom. On day 3, the adhesive organ turned dorsal, the retina was pigmented, the digestive tube mucosa showed goblet cells, and the yolk sac exhausted. The larvae were now scattering in the water column forming no groups on the bottom.

Testicular structure of three species of neotropical freshwater pimelodids (Pisces, Pimelodidae)

Estudou-se a estrutura testicular dos seguintes peixes Siluriformes: Pimelodus maculatus (Lacepede, 1803), Iheringichtys labrosus (Lutken, 1874) e Conorhynchos conirostris (Valenciennes, 1840). Os testiculos foram dissecados e divididos anatomicamente em regioes cranial e caudal. As franjas dos testiculos em maturacao foram contadas e mediu-se o comprimento das mesmas. O teste t de Student foi utilizado para verificar diferencas significativas entre o comprimento das franjas das duas regioes. Para estudo histologico, testiculos inteiros de cada especie, em repouso e em maturacao, foram fixados em liquido de Bouin por 6-8 horas e submetidos as tecnicas histologicas de rotina. Utilizaram-se tecnicas histoquimicas classicas para detectar carboidratos e proteinas. Os testiculos das especies estudadas sao orgaos pares e franjados. Histologicamente, as franjas da regiao cranial de todas as especies sao espermatogenicas, com celulas da linhagem em mesma fase de desenvolvimento contidas em cistos. As franjas da regiao caudal de C. conirostris sao tambem espermatogenicas, enquanto P. maculatus e I. labrosus apresentam franjas caudais exclusivamente secretoras. Histoquimicamente detectou-se na secrecao das franjas caudais de P. maculatus glicoproteinas neutras, glicoconjugados acidos carboxilados, incluindo sialomucinas e glicoconjugados acidos e sulfatados e em I. labrosus glicoproteinas neutras. Houve diferencas significativas entre o comprimento das franjas das regioes cranial e caudal para todas as especies estudadas.

Gonadal structure and gametogenesis of Loricaria lentiginosa Isbrücker (Pisces, Teleostei, Siluriformes)

The gonadal structure and gametogenesis of Loricaria lentiginosa Isbrucker, 1979 were studied through anatomical and histological techniques. Forty two males and ten females in maturation/mature stage were captured in the reservoir of Porto Colombia, Parana river basin, Minas Gerais, using gill nets, from November 2001 to October 2002 (tri-monthly captures). Examination of the testes revealed that they were paired, elongated and not fringed organs. Histologically, the testes presented three distinct regions: cranial espermatogenic; transistion espermatogenic and secretory; and caudal exclusively secretory. Standard histochemical techniques detected neutral glycoproteins from the secretion of the tubules of the caudal region. Espermatogenesis occurred in cysts throughout the whole extension of the wall of the seminiferous tubules, which anastomosis themselves and liberated the spermatozoa into the lumen of the espermatic ducts. The ovaries were paired, saculiformes and, histologically, they presented ovigerous lamellae that contained the cells of ovogenic ancestry. The oocytes were classified into four stages, based on their cytological characteristics and the cell layers that surrounded them. Post-ovulatory follicles and vitelogenic oocytes in the follicular atresia process also were observed.

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.

Morphological, histological and histochemical analysis of the digestive tract of Trachelyopterusstriatulus (Siluriformes: Auchenipteridae)

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.

Morphological characteristics of the digestive tract of Schizodon knerii (Steindachner, 1875), (Characiformes: Anostomidae): An anatomical, histological and histochemical study

The digestive tracts of 44 specimens of Schizodon knerii were studied using anatomical, histological and histochemical techniques. The mouth has terminal position, the lip epithelium is squamous stratified with mucous, claviform cells and taste buds, teeth have an incisive form and the tongue has a stratified squamous epithelium with mucous cells and taste buds. The oropharynx cavity is formed by gill apparatus and pharyngeal teeth. The oesophagus presented pleated mucosa, a stratified squamous epithelium with mucous cells, oesophageal glands and taste buds. The stomach presented cardiac, fundic and pyloric regions, simple prismatic epithelium with tubular glands, with none in the pyloric region. The intestine contains 11-15 pyloric caeca, a simple prismatic epithelium with brush border, goblet cells and lymphocytes. Mucosal cells, oesophageal glands and goblet cells reacted positively to PAS, amylase + PAS, Ab pH 2.5 and Ab pH 0.5. Gastric prismatic cells reacted positively to PAS, amylase + PAS, but only those in the pyloric region reacted positively to Ab pH 2.5 and Ab pH 0.5. The results improve the understanding of the anatomy of S. knerii feeding habits and the presence of mucosubstances in the epithelium, highlights the importance of glycoproteins for passing food through the digestive tract.

Allometric larval growth of the bottom-dwelling catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

We investigated the early life growth pattern of pacama, Lophiosilurus alexandri , a catfish endemic to the rio Sao Francisco basin, Brazil. Pacama larvae were kept in a galvanized trough for 29 days after hatching. We collected approximately 10 larvae daily (total number = 285). We obtained from each specimen the total length (independent variable) and 11 other body measurements (dependent variables). We performed linear regressions on the log-transformed data to determine the growth pattern of the body measurements and the respective inflexion point on the growth curves. Except for trunk length, trunk width and yolk sac volume, the remaining body measurements showed a positive allometric growth coefficient up to the respective IP followed by a decrease in the rate of relative growth afterwards. Although trunk width presented a positive allometric growth, no significant inflexion point was detected. The dorsal-ventral head flattening seen in the adult pacama was quickly expressed in the larvae as indicated by the large allometric growth of head width. Maxillary barbels showed the highest growth rate. The exceptionally high growth rates of eyes and maxillary barbels and the acquired ability to capture prey (as suggested by mouth length growth) strengthened the hypothesis of growth priorities in which the most essential organs develop first.

Allometric growth patterns in hatchery-reared larvae of the catfish Lophiosilurus alexandri (Pisces: Pseudopimelodidae)

The aim of the present study was to characterize the relationships that occur between morphometric variables of larvae of Lophiosilurus alexandri Steindachner, 1876 through their allometric growth analysis. Total length, head length and body height were correlated with standard length, head height and body height, as well as eye diameter and head height with head length. The results revealed allometric positive relation during the initial development, where the b coefficient varied between 1.10 and 2.81. The variable pre-anal distance in relation to the standard length and the snout length in relation to the head length revealed an allometric negative relation, where the b coefficient was 0.85 and 0.94, respectively.