First record of the black bullhead Ameiurus melas (Teleostei: Ictaluridae) in Poland.

The North American catfish, the black bullhead Ameiurus melas, is recorded for the first time in Poland. The origin of these fish is not clear, but their presence may be associated with unregulated introductions by anglers.

Daily changes in the gonadotropin levels and response of carp oocytes to hypophysial homogenate.

Daily changes in carp gonadotropin levels in adult female carp and daily changes in carp oocyte sensitivity to carp hypophysial homogenate, in vitro and in vivo, were investigated. A total of three series of experiments were carried out. Gonadotropin levels were radioimmunologically determined. The results of series 1 and 2 experiments were subjected to statistical analysis with the use of cosinors circle and ellipse of errors. It has been found that in the mature female carp in the pre-spawning period with the light periods being long (L:D = 16:8) the apogee for gonadotropin occurs 10 hr after the onset of the light period. The sensitivity of the oocytes, in terms of the percentage of mature oocytes (after GVBD) following a 24-hr incubation of ovarian fragments with the hypophysial homogenate, reached the highest value at 1300, i.e. 9 hr after the onset of the light period. It was also found that the injections of carp hypophysial homogenate made at 0900 were much more efficient in inducing ovulation than those at 2100.

Histochemical demonstration of the presence of serotonin in the hen (Gallus domesticus) reproductive tract.

The purpose of the present study was to demonstrate visually and localize the presence of serotonin (5-HT) in the ovary and oviduct of the domestic hen using a histochemical Falck-Hillarp method. Experiments were carried out on White Leghorn laying hens with no egg in the shell gland. The specific yellow fluorescence, indicating the presence of 5-HT, was found both in the ovary and all examined oviductal parts. The strongest fluorescence was present in the ovarian stroma containing small follicles with a diameter under 4 mm. In the wall of the largest preovulatory follicle a very strong fluorescence was located mainly in the theca layer. In the oviductal parts, the intensity of 5-HT fluorescence in the infundibulum and magnum was fairly strong, whereas in the isthmus and shell gland it was weak. Fluorescence seen in the infundibulum, magnum, and isthmus was primarily localized along the luminal borders of the fold surface epithelium. In the shell gland 5-HT fluorescence was found within the uterine folds, especially in the tubular glands. Moreover, the presence of an egg in the definite oviductal segment (infundibulum or isthmus) increased the intensity of yellow fluorescence in this part.

Seasonal variations in circadian rhythm of hypothalamic catecholamine content in the eel (Anguilla anguilla L.).

1. Changes in catecholamine content (CA) in hypothalamus of male and female eel (Anguilla anguilla L.) were defined using the Falck-Hillarp histochemical fluorescence method for a 24-hr period during the summer (L:D = 16:8) and winter (L:D = 8:16). 2. A circadian rhythm in the catecholamine content was found in the hypothalamus. CA content was lower by night than by day. 3. A longer light day (summer period) caused the shifting of rhythm phase in CA content. 4. Sex of eels does not affect CA content in the hypothalamus.

Participation of the pineal gland in sexual maturation of female rainbow trout (Oncorhynchus mykiss Walbaum).

In the study rainbow trout, pinealectomized at two different periods of their sexual cycle, i.e., at either 1 or 5 months before spawning, were studied. It was found that the lack of the pineal gland in the period directly preceding the spawning had no statistical effect on either spawning or the number of females that produced eggs. Pinealectomy performed during vitellogenesis delayed spawning by about 2 weeks and resulted in the absence of ovulation in 20% of the females. The results suggest that the pineal gland may influence the hypothalamo-pituitary-gonadal axis by altering the maturation period and controlling spawning in the rainbow trout.

Neuropeptide Y stimulates in vivo gonadotropin secretion in teleost fish.

The effects of the neuropeptide Y (NPY), alone or in combination with a gonadotropin-releasing hormone analogue, D-Ala6-desGly10-Pro9-Net LHRH (LHRHa), have been studied on the in vivo secretion of the maturational gonadotropin (GtH2) in the rainbow trout Oncorhynchus mykiss and the common carp Cyprinus carpio. Depending on the species, two routes of administration were used: in trout, intraperitoneal injection (20 micrograms/kg body wt); in carp, direct infusion (3 micrograms/kg body wt) into the third ventricle via a temporary brain cannula. In both cases NPY alone induced a twofold increase in GtH2 secretion and peaked 2 to 4 hr administration regardless of the route of injection. The plasma gonadotropin levels returned to basal within 8 hr. The relative increases (peaked secretion/basal secretion) did not differ with the route of injection. When the animals were first treated with NPY and then LHRHa (20 micrograms/kg) 1 hr later, the magnitude of the response to LHRHa was greater in the animals pretreated with NPY, indicating either a potentiation of LHRHa action by NPY or additive effects of the two peptides. The return to basal levels also took longer in fish receiving NPY first. NPY may act directly at the pituitary level or activate central neuromediatory systems.

Effects of N,N-dimethylnitrosamine (DMNA) on in vitro oocyte maturation and embryonic development of fertilized eggs of carp (Cyprinus carpio L.) kept in eutrophied ponds.

Toxic effects of N,N-dimethylnitrosamine (DMNA) at doses of 100 or 500 micrograms l-1 on in vitro carp oocyte maturation (steroidogenesis), embryonic development and hatching of larvae (obtained as a result of artificial spawning of females kept for four seasons in normal and eutrophicated ponds) were investigated. There were no significant effects of DMNA on oocyte maturation and steroidogenesis during 24 h of incubation. The DMNA decreased the hatching of fertilized eggs derived from control females. This decrease reached a level of significance at a dose of 500 micrograms l-1. However, the effect of long-term exposure of female fish to eutrophied water was very much higher. The trend of the in vitro DMNA effect was the same, but it did not reach a statistically significant level. The results suggest that nitrosamines, through their effect on egg hatchability, may reduce fish populations along with increasing aquatic eutrophication.

Effects of pimozide and LHRH-Aa on carp (Cyprinus carpio L.) oocyte maturation and ovulationin vivo.

Effects of pimozide (Pim) and [(D-Ala(6), Pro(9)-NEt) LHRH] (LRH-Aa) on common carp oocytes maturation and ovulationin vivo under laboratory and commercial fisheries farm conditions were investigated.Although injections of Pim and LRH-Aa at the doses of 10 mg and 50 µg/kg body weight respectively, did not increase mGtH levels (66.7-155.8 mg/ml) as much as injections of carp pituitary extract (chh) (382.1 ng/ml), induced GtH levels were high enough to induce ovulation. Changes in the ovary caused by Pim and LRH-Aa were similar to those induced by chh, and Pim injected together with LRH-Aa in a single injection gave the same results concerning ovulation induction as when they were applied separately at 6h interval.