The anatomical arrangement of the digestive tract and the length (cm) of the oesophagus and intestine of the catfish Lophiosilurus alexandri were described, and the intestinal coefficient was determined. L. alexandri oesophagus is short, in median position, and presents longitudinally folded mucosa, whilst its epithelium is stratified and non-keratinised, with mucous, claviform and epithelial cells. Stomach has "C" shape, with folded mucosa along cardiac region, disordered in the fundic region, and directed to the sphincter in the pyloric region. Its epithelium is simple prismatic, and cardiac and fundic portions have gastric glands. Cranial intestine is formed by pyloric flexure and descending loop attached to the right side of stomach. Middle intestine is winding and positioned to the right of caudal portion of stomach. Caudal intestine is linear and with a median position up to the anus. Intestinal coefficient was 1.39 ± 0.30 cm. Epithelium is simple prismatic with brush border and contains epithelial and goblet cells. Caudal region has highest concentration of goblet cells. Were detected neutral glycoproteins, carboxylated and sulphated acid glycoconjugates for mucous cells and goblet cells, and neutral glycoproteins for the apical region of gastric epithelial cells. Morphological features could be related to piscivorous species feeding habit. K E Y W O R D S catfish, intestinal coefficient, mucosa morphometry, mucosubstances

The testicular morphology, spermatogenesis and occurrence of sperm in the ovarian lumen of Trachelyopterus striatulus were studied using anatomical, histological and biometric techniques. A total of 50 catfish (T. striatulus) were captured, measuring 14.9 ± 2.5 cm of standard length, body weight was 81.2 ± 34.5 g and their testes weighed 16.9 ± 6.1 g. The testes of T. striatulus are paired organs, showing two distinct regions: cranial, which shows a compact medial part and with fringes ventrally, and caudal region, which is formed of the seminal vesicle with fringes laterally and two saculiform expansions. The testes presented a length of 35.2 ± 6.9 mm, and the fringes showed a cranial length of 12.1 ± 3.8 mm and caudal length of 6.4 ± 2.6 mm. Histologically, the cranial fringes are spermatogenic and showed cells with significantly different nuclear diameters, ranging from 8.2 ± 1.5 μm (primary spermatogonia) to 1.88 ± 0.3 μm (spermatid). The seminal vesicles and saculiform expansions showed tubules with a simple prismatic secretory epithelium containing spermatozoa and secretion into the lumen. The caudal fringes are exclusively for secretory flow, consisting of tubules with a simple cuboidal epithelium. The common spermatic duct showed a simple cuboidal epithelium and contained spermatozoa with secretion into the lumen. The secretion of the caudal region is acidophilic, with neutral glycoproteins and sialomucin. T. striatulus ovaries showed free spermatozoa or were organized in spermatozeugmata into the ovarian lumen and between the ovuligers lamellae.

The early life story of the curimatas <em>Prochilodus argenteus</em> and <em>Prochilodus costatus</em> was studied from hatching until the complete absorption of the yolk, in order to provide knowledge about its growth and behavior, which can be applied to the development of the larval rearing as well as taxonomic characters. The larvae were obtained from artificial reproduction at Hydrobiology and Aquaculture Station of Três Marias, Minas Gerais. Immediately after the hatching approximately 100 larvae of each species were conditioned in two plastic incubators. Larvae behavior was registered daily and were collected 14 larvae of each species to analyze body morphology. On the first day post-hatching the larvae showed elongated and transparent body. The yolk sac was filled with individualized yolk globules<em>.</em> In both species, the embryonic fin rounded the caudal region of the body, the retina showed depigmented and the gut was obliterated. On the second day, larvae have emerged dendritic chromatophores, the mouth was obliterated and the pectoral fin was recorded<em>. </em>The larvae showed 38-43 myomeres in <em>P. costatus</em> and 42-43 in <em>P. argenteus. </em>The gas bladder was inflated and the lumen of the gut was already open. On the third day, the mouth was already open and in a sub terminal position. Retina was pigmented, the gill arches had lamellar protrusions and were partially covered by the operculum. On the fourth day, the pigmentation pattern was maintained with greater intensity; the mouth occupied terminal position, the yolk sac was almost completely reabsorbed and pectoral and caudal fins showed mesenchymal rays. The gut showed broad lumen with folded mucosa and epithelium with striated border. The larvae of both species showed similar swimming behavior during the trial period.