 Abstract Godinho, H. P., Santos, J. E., Formagio, P. S. and Guimarães-Cruz, R. J. 2005. Gonadal morphology and reproductive traits of the Amazonian fish Arapaima gigas (Schinz, 1822). -Acta Zoologica (Stockholm) 86: 289-294An account of gonadal morphology and reproductive traits of the Amazonian arapaimatid, Arapaima gigas (Schinz 1822), is given. The only functional ovary (left) was foliaceous in shape having the ventral surface without an ovarian capsule. The absence of the ovarian capsule ventral portion, absence of oviduct and funnel-shaped coelomic cavity are features that imply that oocytes are freed in the coelomic cavity before being shed to the aquatic environment through a genital papilla. The only functional testis (left) was cord-like with a maximum diameter of 1-1.5 cm and was connected to the genital papilla through a spermatic duct. Size at sexual maturity was 145-154 cm and 115-124 cm, total length class, for females and males, respectively.

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 characteristics of the cell layers that surround them.

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.

The reproduction of Astyanax scabripinnis captured bimonthly in the Cristais small stream (20 o 00¢03¢S and 43 o 56¢46¢W), in the Das Velhas River basin, was studied using gross anatomical and histological techniques. Standard length of females (56 ± 8 mm) was longer than males (49 ± 6 mm). The diameter of the nucleus of the primary spermatogonia was 7.5 ± 0.9 lm and of the spermatozoon head 1.8 ± 0.4 lm. For the females, the oogonia nuclei measured 10.2 ± 2.2 lm and the vitellogenic oocyte nuclei measured 675.0 ± 66.7 lm. The following stages of the reproductive cycle were established: developing, mature, partially spent ⁄ spawned and completely spent ⁄ spawned. Maximum number of males (61.3%) and females (58.2%) at the mature stage was observed during November ⁄ December. The gonadosomatic index of males and females was highest during the mature stage (2.4 ± 0.6; 7.5 ± 1.3, respectively) and decreased in subsequent stages. In females, the hepatosomatic index was highest during the developing stage (2.8 ± 0.3), and slightly decreased in the following stages. The highest stomach repletion index found for males was observed during the partially spent stage (2.0 ± 1.2), while for the females, this index varied discretely between the reproductive stages. The highest values of FultonÕs condition factor were registered during the mature stage in both sexes (2.9 ± 0.4 for males; 3.0 ± 0.3 for females). The continuous reproductive period and the presence of partially spawned females during the entire sampling period indicated that the species has fractional spawning.

ABSTRACT. The gonadal structure and gametogenesis of Loricaria lentiginosa Isbrücker, 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, Paraná 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.

We investigated the early life growth pattern of pacamã, Lophiosilurus alexandri, a catfish endemic to the rio São Francisco basin, Brazil. Pacamã 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 pacamã 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.Investigamos o padrão de crescimento inicial do pacamã, Lophiosilurus alexandri, um bagre endêmico da bacia do rio São Francisco, Brasil. Larvas de pacamã foram mantidas numa canaleta horizontal de metal galvanizado durante 29 dias após a eclosão. Diariamente, coletamos circa 10 larvas (número total = 285) das quais obtivemos o comprimento total (variável independente) e 11 outras medidas corporais (variáveis dependentes). Fizemos regressões lineares nos dados log transformados para determinar o padrão de crescimento das medidas corporais e respectivo ponto de inflexão das curvas de crescimento. Exceto comprimento do tronco, largura do tronco e volume do saco vitelino, as demais medidas corporais apresentaram crescimento alométrico positivo até o respectivo ponto de inflexão, seguido de redução na taxa relativa de crescimento. Embora a largura do tronco apresentasse crescimento alométrico positivo, não foi detectado um ponto de inflexão significativo. O achatamento dorso-ventral da cabeça, presente nos adultos, mostrou-se evidente nas larvas com o acentuado crescimento alométrico de sua largura. Os barbilhões maxilares exibiram a maior taxa de crescimento. O extraordinário crescimento dos olhos e dos barbilhões maxilares e a habilidade adquirida para a captura de presas (como sugere o crescimento do comprimento bucal) reforçam a hipótese de prioridade de crescimento em que os órgãos essenciais são os primeiros a se desenvolverem.

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.