Search

SummaryThis study aimed to understand how germ cell development occurs in females of Devario aequipinnatus, by morphologically describing oogenesis and the reproductive phases. Sexually mature females of D. aequipinnatus (n = 70) were obtained from commercial fisheries and delivered to the Laboratório de Ictiologia Neotropical, UNESP, Ilha Solteira, SP, Brazil. The ovaries were removed, fragmented and fixed following the usual techniques for light microscopy. The stages of ovarian development in D. aequipinnatus begin with the oogonia, which proliferate into new cells or differentiate into prophasic oocytes that, at the end of this process, form the ovarian follicle and end folliculogenesis. In the previtellogenic stage, the oocytes were characterized mainly by the gradual loss of basophilia and an increase in oocyte diameter. Vitellogenesis was marked mainly by the incorporation of yolk granules. Mature oocytes were defined by their migration from the nucleus to the micropyle. Postovulatory follicles and atresic oocytes were also observed. The reproductive phases were classified as: immature, early and final developing, spawning capable, regressing and regenerating. Therefore, the development of an understanding of cell modifications that occurs up to oogenesis is a basic step that is essential for the description of the reproductive biology of D. aequipinnatus, given the lack of information about the reproductive aspects of this species.

The aim of this study was to describe, for the first time, the embryogenesis and larval growth of the Paraitinga Brycon nattereri Günther, 1864 reared in captivity. After artificial fertilization, eggs were incubated at constant temperature (~19°C) and collected every 15 min during the first 3 h and then every 3 h until hatching. Five larvae were collected daily over 15 days for evaluation of the length, yolk sac volume and specific growth rate. The following stages of embryonic development were identified: zygote, cleavage, gastrula, segmentation and larval. The hatching occurred after 50-54 h, with larvae poorly developed and fully depigmented, devoid of mouth and swimming capacity, presenting 6.32 mm total length and 3.64 mm3 yolk sac volume. The mouth opening was observed between days 3-4 after hatching. The yolk sac absorption was slow during the first 3 days, increasing sharply after this period, being completed on the day 11. During this period there was a decrease in the larval growth rate. After yolk sac absorption, an increase in the growth rate was observed that coincided with the start of exogenous feeding. Cannibalism was not observed during the 15 days of evaluation. The initial development of B. nattereri was slow and poorly developed larvae in relation to other Brycon species, certainly due to the lower temperature required for egg incubation and larval rearing. Other studies are needed in order to develop techniques to improve the methods of incubating eggs and feeding larvae.

We aimed to analyze the oogenesis of adult females of the cichlid fish Laetacara araguaiae. The specimens' gonads were removed and processed for light and transmission electron microscopy. Oogenesis in L. araguaiae showed the following characteristics: a germinal epithelium with three types of oogonia (A-undifferentiated, A-differentiated and B-oogonia), oocytes at meiotic prophase stage and ovarian follicle formation. Oocytes showing primary growth with pre-vitellogenic and cortical alveolus were observed. Similar to data for other cichlids, oocytes in secondary growth or vitellogenesis were characterized by the initial deposition of yolk microgranules. The event that characterizes the maturation stage is nucleolus migration, also called the germinal vesicle, to the oocyte periphery in the direction of the micropyle. The follicular complex undergoes several changes throughout the oocyte stages. To the best of our knowledge this study is the first to describe L. araguaiae oogenesis. Moreover, this study is the first step to better understand the reproductive biology of this species, which shows great potential for use as an ornamental fish.

This study aimed to establish a hormonal induction protocol for spermiation of Brycon cephalus males, using Ala6, Pro9Net-mGnRH + metoclopramide (Ovopel®). Thus, 20 males were used divided into three inductor treatments [⅓ pellet/kg (T1), ⅔ pellet/kg (T2) and 1⅓ pellet/kg (T3)] and one control group (CO), which only received physiological solution applications (0.9% NaCl). All treatments were applied in a single dose. For evaluation of the availability of the treatment, the following seminal parameters were analyzed: seminal volume, subjective spermatic motility, duration of motility, pH, osmolality and spermatic concentration. T3 showed the highest seminal volume (4.66 ± 1.52 ml), and was significantly different in comparison with T1 (2.0 ± 0.9 ml), T2 (3.5 ± 1.3 ml) and CO (2.3 ± 1.2 ml). In relation to spermatic motility, T2 and T3 showed significantly higher levels [5, (81-100%)]. However, T3 showed significantly lower average sperm motility duration than T1, T2 and CO (30 ± 7 s; 28 ± 6 s; 32 ± 8 s, respectively). With regard to the seminal parameters of spermatic concentration, pH and osmolality, no significant variation was verified among treatments. In conclusion, mGnRH + metoclopramide used for hormonal induction of B. cephalus reproduction does not induce changes related to spermatic concentration, pH and osmolality parameters of the seminal fluid and the most adequate doses among tested treatments were ⅔ pellet/kg live fish.

Embryological studies in fish species are useful to the understanding of their biology and systematics. The available biological data in Leiarius marmoratus are scarce and additional information about its reproductive biology is needed, mainly because this species has been commercially exploited and used in production of hybrid lineages. In order to evaluate the temporal-morphological embryonic modifications in L. marmoratus, samples of nearly 200 embryos were collected at random at different stages of development, starting from fecundation (time zero). Embryos were fixed in modified Karnovsk's solution and 2.5% glutaraldehyde, processed and analysed under optic and electron microscopy. The incubation period of L. marmoratus was equal to 14.42 h at a mean temperature of 28.3 ± 0.07°C. The following stages of embryonic development were established: zygote, cleavage, gastrula, organogenesis and hatching. These stages were divided into phases, as follows: cleavage - phases of 2, 4, 8, 16, 32 and 64 cells and morula; gastrula - phases of 25, 50, 75 and 90% of epiboly and blastopore closure; and organogenesis - neurula, segmentation and pre-larval phases. The embryogenesis of L. marmoratus was typical of neotropical teleosteans, with peculiarities in species development.

The aim of the present study was to characterize biopsied and stripped oocytes from the Brazilian endangered teleost pirapitinga (Brycon nattereri) using histochemical and morphological analyses. Biopsied oocytes had a mean diameter of 2.225 mm (modal diameter: 2.312 mm), complete vitellogenesis and a central or slightly eccentric nucleus. Neutral polysaccharides were detected in the follicular cells, zona radiata and yolk globules, while acidic polysaccharides were detected in the follicular cells and cortical alveoli. Ten out of the 19 females treated with two doses of carp pituitary extract (cPE) released oocytes, which were also analysed. Stripping occurred 292 ± 39 degree-hours after the second dose of cPE and led to a mean spawning weight of 36.2 g, 10% spawning index, 241 oocytes/g of ova, 8222 oocytes/female and 23 oocytes/g of body weight. Stripped oocytes had a mean diameter of 2.33 mm and a mode at 2.375 mm, were weakly adhesive and coloration ranged from wine to brown. Under scanning electron microscopy, stripped oocytes exhibited a single funnel-shaped micropyle located at the animal pole and a zona radiata that measured 7.7 μm in thickness with eight pore canals/μm2. Oocyte morphology in Brycon nattereri is similar to that found in other species of the genus, except for the larger size and weaker adhesiveness. These findings provide essential information for a better understanding of the reproductive biology of B. nattereri and the establishment of conservation measures for this threatened species.

The embryogenesis of Brycon cephalus was established in seven stages: zygote, cleavage, blastula, gastrula, segmentation, larval and hatching, in an incubation period of 11 h (26 degrees C). The zygote phase was observed directly after fertilization and egg hydration. Cleavage began at 0.5 h of incubation and extended up to the morula phase (1.5 h; +100 blastomeres). Cleavage was meroblastic and underwent the following division pattern: the first five divisions were vertical and perpendicular to each other, following the model 2 x 2, 4 x 2, 4 x 4 and 4 x 8. The sixth division was horizontal and occurred at 1.25 h after fertilization, giving rise to two cell layers (4 x 8 x 2) with 64 blastomeres. At the blastula stage (1.25-1.5 h), an irregular space between the blastomeres, the blastocoele, could be detected and the periblast structure initiated. The gastrula (1.75-6.0 h) was characterized by the morphogenetic movements of epiboly, convergence and cell involution, and formation of the embryonic axis. The segmentation stage (7-9 h) comprised the development of somites, the notochord, optic, otic and Kupffer's vesicles, neural tube, primitive intestine and ended with the release of the tail. The larval stage (up to 10 h) was characterized by the presence of 30 somites and growth and elongation of the larvae. At the hatching stage, the embryos presented more than 30 somites and exhibited swimming movements and a soft chorion. The blastomeres presented euchromatic nuclei, indicating a high mitotic activity and many yolk globules in the cytoplasm. The periblast was constituted of a layer with several nuclei and many vesicles, which grew during the epiboly movement.

SummaryWhile the freezing techniques of mammal embryos have been providing promising results, the cryopreservation of teleostean eggs and embryos have remained unsuccessful up to now. Therefore, this work aimed to develop a procedure of cryogenic preservation of embryos of Prochilodus lineatus and to observe, at both structural and ultrastructural levels, the morphological alterations that took place after the application of freezing/thawing techniques. The embryos at the morula stage could not tolerate exposure to the cryoprotectants ethylene glycol monomethyl ether, propylene glycol monomethyl ether, methanol, dimethyl sulphoxide and propylene glycol, presenting 100% of mortality. Embryos at the 4- to 6-somites stage tolerated exposure to propylene glycol and dimethyl sulphoxide, and the results revealed no significant differences (alpha = 0.05) regarding survival from both treatments. None of the freezing, thawing and hydration protocols was effective on preserving embryo viability. The ultrastructural analyses of frozen and thawed embryos showed that cells from ectoderm, somites, notochord and endoderm were structurally intact, with well preserved nuclei and mitochondria. The yolk globules were able to tolerate the freezing process, but the yolk syncytial layer was unorganized, displaying an electron-dense and compacted appearance, collapsed reticules, nuclei with modified chromatin and ruptures on the plasmatic membrane at the contact zone with endoderm. It might be concluded that the procedures tested for freezing were unable to avoid the formation of intracellular ice crystals, leading to drastic morphological modifications and making P. lineatus embryos unviable.

This survey was performed to characterize the embryogenesis of Prochilodus lineatus. Seven stages of embryo development were identified--zygote, cleavage, blastula, gastrula, segmentation, larval and hatching--after a period of incubation of 22 h (24 degrees C) or 14 h (28 degrees C). The following cleavage pattern was identified: the first plane was vertical (2 blastomeres); the second was vertical and perpendicular to the first (4 blastomeres); the third was vertical and parallel to the first (4 x 2); the fourth cleavage was vertical and parallel to the second (4 x 4); the fifth was vertical and parallel to the first (4 x 8); and the sixth cleavage was horizontal (64 blastomeres). At the blastula stage (3.0-4.0 h (24 degrees C); 1.66-2.0 h (28 degrees C)) irregular spaces were detected and periblast structuring was initiated. At the gastrula stage (4.0-8.0 h (24 degrees C); 3.0-6.0 h (28 degrees C)) the epiboly, convergence and cell movements, as well as the formation of embryonic layers, had begun. The segmentation stage (10.0-15.0 h (24 degrees C); 7.0-10.0 h (28 degrees C)) was characterized by a rudimentary formation of organs and systems (somites, optic vesicle and intestinal delimitation). The embryo at the larval stage (16.0-21.0 h (24 degrees C); 11.0-13.0 h (28 degrees C)) showed a free tail, more than 25 somites, an optic vesicle and a ready-to-hatch larval shape. The blastomeres at cleavage stage had disorganized nuclei indicating high mitotic activity. At gastrula, the blastomeres and the periblast had euchromatic nuclei and a large number of mitochondria and vesicles. The yolk was organized into globose sacs, which were dispersed into small pieces prior to absorption.