A. Tański

The effect of static magnetic field on Danube huchen, Hucho hucho (L.) sperm motility parameters

Abstract The distribution range of Danube huchen, Hucho hucho (L.) in Polish waters is decreasing, and is currently only 25 to 30% of its original area. Since few data are available concerning Danube huchen, it is necessary to develop a better understanding of its reproduction to improve artificial spawning in hatcheries. Eight sperm motility parameters were assessed using CASA after short-term storage in a static magnetic field. The effect of magnetic field exposure on spermatozoa at fertilization and on sperm morphology (SEM) was also examined. Static magnetic fields had a positive effect on sperm motility parameters, including VCL, which determines fertilization effectiveness; values for this parameter after a 24 h exposure period to fields of different intensity were as follows: 1 mT - 110.09 μm s-1; 5 mT - 111.65 μm s-1; 10 mT - 152.10 μm s-1; control - 102.09 μm s-1. Egg fertilization rates of spermatozoa held for 24 hours in fields of 1mT was 71.32%, 5mT - 58.23%, and 10mT - 59.99%, and in the control - 32.60%. The mean length of spermatozoa was 27.14 ±0.22 μm; the head was elongate; length without the neck was 2.80 ±0.19 μm; the width was 2.0 ±0.08 μm. This study suggests that the method of exposing sperm to magnetic fields might, after more extensive studies, could be used for short-term sperm storage.

Effect of the coagulants PAX and PIX on the embryonic development of pike (Esox lucius L.)

Abstract The study examined the development of pike (Esox lucius L.) roe in water containing variously concentrated coagulants PIX®113 and PAX®18, which are increasingly being used in Poland as a method of lake reclamation. The genital products came from spawners caught from a natural water body (Lake Przybiernów). The eggs were incubated in water taken from the same lake, and subjected to the process of phosphorus and iron precipitation with coagulants. Based on the results, it was found that the coagulants used in the experiment inhibit the embryogenesis of pike by the formation of aggregates falling to the bottom, reducing the percentage of live embryos and affecting the size and malformation of the hatching larvae.

Peculiarities of embryonic development of round goby Neogobius melanostomus (Gobiidae) in fresh water

The results obtained indicate the potential of the round goby to reproduce in fresh water, which may result in further expansion of the species to upper reaches of rivers and to other water bodies (lakes, dam reservoirs). Embryonic development of the round goby in fresh water proceeded in a regular manner. However, embryonic development in fresh water took a shorter time than in saline water. Although the newly hatched larvae were somewhat smaller than those hatching from eggs kept in saline water, the hatching rate was high (90%). If the species finds conditions suitable for reproduction in Polish freshwater bodies, it may pose a threat to numerous native freshwater fish species by taking over both their feeding and reproductive niches.

Water salinity effects on embryogenesis of the lesser sandeel, Ammodytes tobianus (Linnaeus, 1758)

Effects of water salinity (3.0–9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel (Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5–9.0 PSU), higher than that prevailing in the species’s spawning grounds in the Baltic Sea, resulted — similarly to the low-end salinity — in disturbed development and growth of the embryos.

Magnetic field effect on melanophores of the European whitefish Coregonus lavaretus (Linnaeus, 1758) and vendace Coregonus albula (Linnaeus, 1758) (Salmonidae) during early embryogenesis

Abstract The effects of a magnetic field (1, 3 and 5 mT), applied during short- (1, 3, 5, 30 and 60 minutes) and long-term (from the beginning of embryogenesis) exposure, on melanophores of the European whitefish, Coregonus lavaretus and vendace, Coregonus albula, were investigated. Short-term magnetic field exposure effects on the behaviour of melanophores at the stage when the eye and body pigment on whitefish and vendace were distinctly visible in the embryos. The short-term embryo exposure to the magnetic fields induced the pigment of the body cells to move to the central parts of the cells. In the control, we did not observe displacement of the pigment within the melanophores. The long-term exposure to the magnetic field was found to delay the pigment appearance in the eyeballs and on the body of embryos of both investigated species. The number of melanophores in the body of embryos exposed to the magnetic fields was lower than that in the control. The pigment showed an increasing tendency to concentrate in individual embryonic and larval cells with increasing magnetic field strength. Melanophore index in embryos and larvae of whitefish and vendace was found to differ significantly between the control and all the magnetic field treatments. Our results can be extrapolated to other organisms and will allow us to broaden the knowledge on pigment cell magnetoreception in vertebrates.