Oocytes of The Endangered Gray Catfish (Surubim-Do-Paraiba) Submitted to Different Conservation Protocols

BACKGROUND

The gray catfish known as Surubim-do-Paraíba (Steindachneridion parahybae), which is endemic to the Paraíba do Sul river basin, is on the red list of Brazilian fauna threatened with extinction and the cryopreservation of germ cells of this fish is needed in support of conservation.

OBJECTIVE

We aimed to assess the effect of storage temperature on S. parahybae mature and immature oocytes.

METHODS

Two trials were carried out. Trial I (TI.1-3) used 30 mature oocytes (diameter >1.8 mm) placed in cryoprotectant solutions and submitted to three different techniques. Trial II (TII.1-3) used 30 immature oocytes (diameter <1.6 mm) placed in cryoprotectant solutions and submitted to three storage temperatures (i.e., TII.1 at room temperature for 120 min; TII.2 in the freezer for 120 min; TII.3 in liquid nitrogen for 24 hours.

RESULT

The mature oocytes were sensitive to every protocol used, including at room temperature. In contrast, the immature oocytes had increased sensitivity according to the temperature reduction to which they were submitted, with the treatment in liquid nitrogen causing greater damage.

CONCLUSION

The immature stages exhibit more promising results, encouraging further studies using the combination of different CPSs, mainly penetrating ones, in oocyte cryopreservation protocols.

Chilling sensitivity of Steindachneridion parahybae (Siluriformes: Pimelodidae) oocytes in different cryoprotectants

The viability of post-thaw fish oocytes can be affected by different stages of the freezing process, such as cryoprotectant toxicity, cold sensitivity, freezing curves and thawing. Therefore, these steps need to be investigated for the development of a protocol. In the present study, the aim was to investigate chilling sensitivity at different oocyte stages of Steindachneridion parahybae. Immature and mature oocytes were incubated in Hanks' or 90% L15 solutions containing different CPAs (cryoprotectant solutions) per experiment: (1) 0.1-0.4 M sucrose + 1-2 M methanol and (2) 1-4 M methanol X 1-4 M propylene glycol X 1-4 M DMSO for mature oocytes; (3) 0.5 M sucrose or fructose + 2 M methanol or PG or DMSO and (4) 0.25-1 M fructose + 1-4 M DMSO for immature oocytes. All treatments were kept for 120 min at -5.9 ± 2.8°C. For the control treatment, only Hanks' or 90% L15 solutions were carried out. Evaluations were made by viability tests: membrane integrity staining in 0.4% Trypan blue (TB) and fertilization rate (%F) sole for mature oocytes. Results presented that mature oocytes were the most sensitive to lower temperatures, because there was no %F. All cryoprotectants tested in the different concentrations can be used for immature oocytes, however the statistically superior cryoprotectant was CPA with fructose and DMSO, with the low concentration of this CPA being was the best statistically. This may indicate that for this species the immature stages have presented a lower chilling sensitivity than the mature stages.

Inseminating dose and water volume applied to the artificial fertilization of Steindachneridion parahybae (Steindachner, 1877) (Siluriformes: Pimelodidae): Brazilian endangered fish

Abstract The Steindachneridion parahybae is an endangered catfish from Brazil and strategies applied for gametes optimization are necessary. The aim of this study was to assess inseminating doses and water volume upon the fertilization, hatching rates and percentage of normal larvae in S. parahybae . Was used a randomized design in factorial scheme (4×4) with four inseminating doses: 1.0×104, 1.0×105, 1.0×106, 1.0×107spermatozoa oocyte-1 and four volumes of water: 1, 35, 65 and 95mL of water g-1 of oocytes. The combination of doses and volumes were performed in triplicates (n=48). Each incubator (1.5L of useful volume) with 1g of oocytes was considered as an experimental unit. Significant interaction between inseminating doses and volumes of water to the values of the fertilization rates and quadratic effect of doses and volume for the values of hatching rates were observed. The doses and volumes did not influence the percentage of normal larvae (87.70±5.06%). It is recommended the use of 5.5×106 spermatozoa oocyte-1 and 1mL of water g-1 of oocytes during in vitro fertilization procedure. These results allowed us to develop new biotechnological strategies applied to the conservation of S. parahybae .

Processo de maturação das gônadas de pintado (Pseudoplatystoma corruscans) alimentado com dois níveis proteicos e suplementados com óleo de milho

Investigou-se o efeito da adição de C18:2n6, por meio da inclusão de óleo de milho em dietas com dois níveis de proteína bruta, sobre o processo de maturação de gametas de pintado, Pseudoplatystoma corruscans, mantidos em tanques-rede. Foram avaliados: taxa de sobrevivência, relação peso x comprimento, fator de condição (K) e índice gonadossomático (IGS). O experimento foi realizado entre março de 2004 e fevereiro de 2006, em 12 tanques-rede, distribuídos em seis viveiros-escavados de 600m² e densidade de estocagem de 20 peixes/tanque-rede. Utilizaram-se três tratamentos (T) com duas repetições/viveiro: T1 com 28% de PB; T2 com 28% de PB + 5% óleo de milho e T3 com 40% de PB. O crescimento foi ligeiramente mais alto nos peixes do T3. As taxas de sobrevivência foram acima de 77%. Pode-se inferir que as rações ofertadas não causaram alterações histomorfológicas durante o processo de maturação gonadal dessa espécie. O IGS e o K foram ligeiramente mais altos nos animais alimentados com a ração enriquecida com óleo de milho.

Patterns of oocyte development in natural habitat and captive Salminus hilarii Valenciennes, 1850 (Teleostei: Characidae)

Fecundity and oocyte development in Salminus hilarii female brood stock were analyzed with the aim of investigating the impact of migration impediment on oogenesis. Histological analyses of the ovaries were performed in adult females caught in two different environments--the Tietê River (natural) and captivity--and the gonadossomatic index, oocyte diameter and fecundity determined. Five germ cell development stages (oogonium, perinucleolar, cortical alveoli, vitellogenic, ripe) and two other structures (postovulatory follicles and atretic oocytes) were observed in females caught in the river. Captive animals lacked the ripe oocytes and postovulatory follicles and had a relatively higher number of atretic oocytes. Females in captivity are known to produce larger oocytes, and they release fewer eggs in each spawn (absolute fecundity) when compared with animals that are able to migrate. Our results suggest that the Tietê River is undergoing alterations which are being reflected in the reproductive performance of S. hilarii, mainly due to the presence of atretic oocytes in females caught in the river. The lack of postovulatory follicles and ripe oocytes in captive animals reveals that migratory impediment negatively impacts final oocyte maturation. However, the stage of maturation reached is adequate for ovulation induction with hormone manipulation.

The reproductive cycle of male catfish Pseudoplatystoma fasciatum (Teleostei, Pimelodidae) revealed by changes of the germinal epithelium

The aims of the present study were to analyze the gonadal structure of Pseudoplatystoma fasciatum males during their annual cycle to enhance understanding of their reproductive biology and to improve the hormonally induced reproduction and culture of this species in hatcheries. We adopted the recently proposed method that establishes reproductive classes that are based on variations of the germinal epithelium within the year. Five reproductive classes were established: maturation (early, middle, and late), regression and recrudescence. Our observations revealed that in the spawning season P. fasciatum testes display two main functions: sperm production and sperm storage. We also concluded that the analysis of the variation of germinal epithelium was satisfactory when applied to this freshwater catfish and should be adopted for other fish species.

Occurrence and significance of ovarian and follicular regression in cachara Pseudoplatystoma fasciatum (Linnaeus, 1766): a histology approach

The processes of ovarian regression and follicular atresia which reproduction was not induced by hormone in confined cachara, Pseudoplatystoma fasciatum, were investigated. The macro and microscopic characteristics (oocytes diameter and histology) of the ovaries were described every 20 days, in four stages: initial regression (Rg I = first 20 days), intermediate regression (Rg II = from 21st to 40th day), final regression (Rg III = from 41st to 80th day) and the recovering stage, called resting II (R II = from 81st to 150th day). The experiment was conducted from late January (summer - longer days) to May (autumn - shorter days). In the beginning, A0 samples showed oocyte diameters ranging from 437.5 to 1,187.5mm, suggesting that oocytes were in perinucleolar, at final maturation and atretic phases. After 150 days, the diameters reached the lowest values and a ruptured zona radiata, as well as the nearly complete reabsorption of the yolk could be visualized. At the same time, a sharp decrease in the mean values of the gonadosomatic index (GSI), water temperature, photophase and rainfall was observed. The gradual involution of this long process was dynamic and complex, affecting the spawning success (fertilization, eclosion and larvae survival rates) and, consequently, the whole productive system.

Cell junctions in the germinal epithelium may play an important role in spermatogenesis of the catfish P. fasciatum (Pisces, Siluriformes)

We identified adhesive junctions and gap junctions between Sertoli cells, between Sertoli and germ cells and between germ cells in the testis of P. fasciatum, a catfish of commercial relevance. To investigate the role of these junctions in spermatogenesis, as well as the molecular composition of the junctions, we performed an immunohistochemistry light microscopy as well as an immunogold labelling electron microscopy study with antibodies to adhesive and gap junctions proteins. Testes that were at different stages of spermatogenesis were used. Based on our morphological studies we speculate that Sertoli-germ and germ-germ cell adhesive junctions are important for maintaining the three-dimensional structure of the germinal cysts and an organized arrangement of the germ cells inside the cysts. Connexin 32 was identified in the germ cells and in the cysts walls. Our observations also suggest that Sertoli-germ and germ-germ cells gap junctions may be involved in the mechanism of synchronous development of germ cells.

Light and electron microscopy oogenesis in matrinxã, Brycon cephalus

Oocyte development has been divided into 5 distinct stages in the reared matrinxã, Brycon cephalus, based on morphological criteria by light and transmission electron microscopy: I) chromatin-nucleolus; II) perinucleolar; III) cortical alveoli; IV) vitellogenesis; V) final maturation. In stages I and II (primary growth), oocytes reside in nests close to other oocytes (chromatin-nucleolus phase) and then within a definitive follicle (perinucleolar phase) where they greatly increase in size (the Balbiani vitelline body is the main cytoplasmic component in these latter oocytes), respectively. In stage III (cortical alveolus phase) oocytes are distinguished by the appearance of variably sized cortical alveoli and the number of these structures increases steadily towards hydration. The vitelline envelope becomes prominent. In the process of vitellogenesis (stage IV) one major accumulation of yolk proteins occurs in oocytes. In stage V (final maturation), oocyte increase slightly in size. Follicle cells go through a primordial stage and later change to a squamous and to a cubical shape. The chorion grows to a tripartite structure: an outer thin porous layer, an intermediate homogenous layer and an inner thick helicoidal layer. The ovulation of females matrinxã, required hormonal stimulation and this occurred 6 and 8 h after the second application.