Induced spawning and reproductive variables of the catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

Lophiosilurus alexandri is an endemic fish from the São Francisco River basin, Brazil. The aim of this study was to induce L. alexandri to spawn and to obtain data on several reproductive variables for this species. For induced spawning, adults were submitted to Cyprinus carpio pituitary homogenate (CPH). Nine of the 12 females (75%) responded positively to the treatment. The stripping of oocytes was performed 8.4 h after the second dose of CPH with the water temperature maintained at 26ºC. The number of stripped oocytes per gram of ova was 74 ± 5 oocytes g-1, and the mean oocyte diameter was 3.1 ± 0.2 and 3.6 ± 0.2 mm, before and after hydration, respectively. The oocytes were opaque, yellowish, demersal, highly adhesive, and covered by a gelatinous coat. The total fecundity was 4,534 ± 671 oocytes, and the fertilization rate was 59%. The initial and final fertilities were 2,631 ± 740 and 1,542 ± 416 embryos, respectively. Larval hatching occurred up to 56 h after fertilization, and the larvae had a total length of 8.4 ± 0.1 mm. This work provides important biological information for L. alexandri that can be used for management and conservation of this species.

The application of [D-Tle6,ProNHEt9]mGnRH (Lecirelin) with the dopaminergic inhibitor metoclopramide to stimulate ovulation in African catfish (Clarias gariepinus)

The results of reproduction were tested in females of the African catfish (Clarias gariepinus Burchell 1822) after stimulation of ovulation with carp pituitary (4 mg/kg body weight) or with Lecirelin (15 μg/kg) and metoclopramide (10 mg/kg). After administering the synthetic substance eggs were obtained from all females while in the group treated with pituitary homogenate 7 out of 8 hypophysed females spawned. The applied spawning agent did not significantly influence the weight of eggs expressed in grams, but in the case of females treated with carp pituitary homogenate a significantly higher weight of eggs expressed as the percentage of body weight of fish was recorded. The applied stimulators of ovulation did not affect any trait reflecting the quality of eggs. Females used as an experimental material belonged to two categories in respect of body weight: lighter females with average body weight of 2.63 ± 0.36 kg and heavier females with average body weight of 3.91 ± 0.48 kg. It was proved that the weight of eggs expressed either in grams or as a percentage of a female’s weight was significantly related to the body weight of a female (P ≤ 0.01 and P ≤ 0.05, respectively), as well as the percentage of fertilised eggs and the percentage of living embryos after 28 hours of incubation (P ≤ 0.05 and P ≤ 0.05, respectively). The interaction between the stimulator of ovulation and the female body weight was significant only for traits reflecting the weight of obtained eggs (P ≤ 0.05 and P ≤ 0.01).  

Artificial propagation of African catfish (Clarias gariepinus): the application of a single dose of pellets containing D-Ala6,Pro9NEt-mGnRH and dopamine inhibitor metoclopramide

The effects on reproduction of African catfish (Clarias gariepinus Burchell 1822) were investigated in three experiments conducted under controlled conditions, carp pituitary (at the dose of 4 mg/kg body weight) or Ovopel – a preparation that contains a mammalian GnRH analogue D-Ala6,Pro9NEt-mGnRH (1 pellet/kg body weight) and dopamine receptor antagonist metoclopramide (10 mg/kg) being used as ovulation stimulators. The application of Ovopel induced the statistically significantly (P ≤ 0.01) higher weight of eggs per kg female body weight and the statistically significantly (P ≤ 0.05) higher quality of eggs after 24 h incubation in comparison with the effects of hypophysation. No effect of the experiment on the weight or quality of obtained eggs was determined while the interaction between the experiment and the ovulation stimulator was statistically significant (P ≤ 0.05) with respect to the percentage of egg fertilization. Statistically significant (P ≤ 0.05) correlation was found between the percentage of egg fertilization and that of living embryos, the determined correlation coefficient being higher after the application of Ovopel than after the carp pituitary homogenate.  

Artificial propagation of female Hungarian strain 7 carp (Cyprinus carpio) after treatment with carp pituitary homogenate, Ovopel or Dagin

The effects of reproduction were investigated in carp females of the Hungarian strain 7 whose ovulation was stimulated with carp pituitary homogenate (0.3 + 2.7 mg/kg; group I), Ovopel (1/5 + 1 pellet/kg; group II) or Dagin (1 dose/kg; group III). The least-squares means calculated for the weight of eggs expressed in grams show that eggs of the highest weight were given by females treated with Ovopel and those of the lowest weight by females treated with carp pituitary homogenate (1 047.65 g and 769.28 g, respectively). For this parameter a statistically significant (P ≤ 0.05) difference was found between the means of group I and II and between the means of group II and III. In the percentage of egg fertilization a statistically significant (P ≤ 0.05) difference was also determined between the means of group I and II and between the means of group II and III. The applied spawning inducing agent did not affect the percentage of living embryos after 48 h incubation. Within group I and II the latency time did not affect any of the investigated parameters significantly, however, after Ovopel stimulation eggs obtained 7 h after the second injection showed higher weight and better quality in comparison with eggs yielded two hours later. Within the latency time of 7 h and 9 h statistically significantly (P ≤ 0.05) higher weight of eggs and statistically significantly (P ≤ 0.05) better quality after 12-h incubation were found in the ovulation stimulation with Ovopel. In the group of fish treated with Dagin the latency time affected the weight of eggs. In this group statistically significantly (P ≤ 0.05) higher weight of eggs was noted for females whose ovulation occurred after 17 h from the application of Dagin while in the latency time of 15 h and 17 h the quality of eggs was similar after the incubation of 12 h and also after 48 h.  

Effects of reproductive stage, GH, and 11-ketotestosterone on expression of growth differentiation factor-9 in the ovary of the eel, Anguilla australis

In order to study the regulation of the growth differentiation factor-9 (gdf9) gene in a primitive teleost with semelparous life history, we cloned a cDNA encoding shortfinned eel Gdf9, expressed a partial peptide inEscherichia coli, and raised an antiserum to evaluate changes in Gdf9 expression during its pituitary homogenate-induced reproductive cycle. The effects ofin vivoandin vitroexposure to the androgen 11-ketotestosterone (11-KT), known to affect previtellogenic (PV) oocyte growth, were also determined. Furthermore, we investigated whether Gdf9 expression was metabolically gated by treating PV fish with recombinant GHin vivo. Immunoreactive proteins ofca. 52 and 55 kDa were identified by western blot analysis. Gdf9 message and protein were most abundant in PV oocytes, and peaked slightly earlier for mRNA than for protein. Captivity resulted in reducedgdf9mRNA levels, which were restored following pituitary homogenate treatment. As oocytes progressed through induced oogenesis, Gdf9 expression decreased. Neither 11-KT nor GH treatment affectedgdf9mRNA levels in PV fish, although GH could partially restore handling- or captivity-induced decreases ingdf9mRNA levels. Semelparous eels thus show an expression pattern of Gdf9 during oogenesis that is similar to that seen in other vertebrates, that appears responsive to handling or captivity stress, and whose control remains to be elucidated.

Modulators of Bufo arenarum ovulation

SummaryIn this study we investigated ovulation in vitro using ovary samples from Bufo arenarum with respect to their response to stimulation with homologous pituitary homogenate (HPH) or with progesterone and prostaglandins (PGF2α and PGE1) as intermediates of pituitary action. Ovary samples were obtained from animals captured during the breeding period. Our results demonstrate that the ovulatory response to all different inducers was dose dependent, the highest percentage of ovulated oocytes being obtained with HPH treatment. An important increase in the ovulatory response was obtained by the association of PGF2α with either HPH or progesterone at suboptimal doses, indicating that this prostaglandin induced a synergistic potentiating effect. Incubation with cyclooxygenase inhibitors (indomethacin or diclofenac sodium) produced a significant decrease in the ovulation induced by HPH, demonstrating that prostaglandins are involved in the action of the pituitary gland in this process. According to our results, PGE1 not only had no participation in the ovulatory process, but also produced an inhibitory effect on ovulation induced by HPH treatment.