Krzysztof Formicki

REACTIONS OF FISH EMBRYOS AND LARVAE TO CONSTANT MAGNETIC FIELDS

Abstract Constant magnetic field of low value slows down the embryonic development of trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss). Hatchlings were longer and heavier, and also more motile than those in the control experiment. Magnetic field induces a change in the circulation motion in embryos and larvae of pike (Esox lucius) and carp (Cyprinus carpio), and in the embryos of trout (5. tnitta). Exposure to magnetic field in embryos causes an increase in a heart rhythm, particularly during the early pulsation period of the forming heart. Magnetic fields cause a change in the gas exchange in embryos of a rainbow trout (O. mykiss). Intensity of breathing processes increase in a magnetic field, however, is dependent on stage of embryonic development, and it is especially manifested in the period of an advanced organogenesis. Embryos of rainbow trout (O. mykiss) and trout (S. tnttta) exhibit a sense of direction both in natural and artificially created magnetic field.

The effect of a magnetic field on the gas exchange in rainbow trout Oncorhynchus mykiss embryos (Salmonidae)

Abstract Rainbow trout embryos (Oncorhynchus mykiss) in different development stages were exposed to the influence of a constant magnetic field (5 and 10 mT). An increased oxygen uptake was observed in embryos influenced by the field activity as compared to those which develop in a geomagnetic field. The effect of a magnetic field on the breathing processes of embryos was more pronounced in the periods of an advanced morphogenesis.

Early ontogenesis of the angelfish, Pterophyllum scalare Schultze, 1823 (Cichlidae)

This study describes the egg membrane structures of angelfish (Pterophyllum scalare), morpho-physiological changes during angelfish embryogenesis from activation to hatching under optimal conditions (28°C; pH 6.8), the developing larvae and fry, the effect of alkaline pH on the early developmental stages of the species, the relationship between food item size and fry survival. Egg membranes (thin, transparent, 1.67-2.18 µm thick) are covered by a sticky substance. The amber-coloured angelfish eggs were oval in shape, with average diameters of 1.436 and 1.171 mm, i.e., a mean volume of 1.033 ± 0.095 mm3. The survival rate of embryos and larvae kept in water with an elevated, slightly alkaline pH was very low: as few as 2% of the embryos survived, while in the batch kept in optimal water conditions very few eggs died. The first larvae hatched after 1288 h of embryonic development. The newly hatched larvae measured on average 2.60 ± 0.093 mm and had large (0.64 ± 0.077 mm3) yolk sacs. They attached themselves to the substrate with a secretion of thin, viscous threads, which was released from glands situated on the top of the head. The glands vanished on day 5. The 1-day-old larvae showed the first pigment cells on the body and the eyes of the 2-day-olds were already fully pigmented. Between day 4 and 5 of larval life, the larvae began feeding on live food. The 23-day-old fry looked like a miniature versions of the adults. Mortality of the angelfish larvae during their first days after hatching was higher in those fed brine shrimp (Artemia salina) nauplii than those fed protozoans and rotifers.

The effect of magnetic field on permeability of egg shells of salmonid fishes

The embryos of fishes during their development, between the egg activation and their hatching, are exposed to action of various factors of the external environment. Those factors, while acting simultaneously, may exert higher pressure, than when acting individually. Despite the common assumption about alleged stability of the aquatic environment, its biotic and abiotic factors, affecting aquatic organisms, may be highly diversified. An individual organism is not only affected by selected, uniform environmental factors. Usually the maintenance of homeostasis is dependant on a complex system of a number of external and internal stimuli (Haas et al. 1997) The magnetic field, and the associated magnetic phenomena are so ubiquitous that they have hitherto been neglected. They attracted some more attention in recent decades and it become evident that living organisms are not indifferent for the action of the magnetic field (Wiltschko and Wiltschko 1995, Kirschvink 1997). The natural magnetic field of the earth is an integral component of the environment, in the same extent as temperature or gravitation, and it also constitutes the background for life processes on the Earth. The common nature of the magnetic field has prompted many researchers to study in detail its action on living organisms. Wadas (1978) distinguished three basic reasons why magnetic fields affect living organisms: 1) action of non-compensated electron spins, 2) action on liquid crystals, 3) effect on positiveand negative charges, being in motion. To answer the question of the action of the magnetic field on animals, many researchers observed effects of such action. Among the aspects studied was the homing ability of insects (honey bee) (Gould 1980), crustaceans (lobster)(Boles and Lohmann 2003), fishes (salmonids)(Quinn and Brannon 1982), amphibians (newt)(Phillips 1986), reptiles (turtles)(Lohmann et al. 1999), or birds (pidgeon)(Keeton 1971). The behavioral experiments focused mainly on species performing long-distance migrations, such as eels and salmonid fishes, as well as elasmobranch fishes (Mayer et al. 2005, Nishi et al. 2005). ACTA ICHTHYOLOGICA ET PISCATORIA (2007) 37 (2): 129–135 DOI: 10.3750/AIP2007.37.2.10

Specifying the relationship between key stages of pike (Esox lucius L.) embryogenesis and coagulants used in lake recultivation

Abstract The study focused on the effect of iron and aluminium coagulants (PIX®113, PAX®18) commonly used for purification of open waters on key stages of embryonic development of pike (Esox lucius L.). Fertilized pike roe was incubated in lake water and in water with the admixture of coagulants, applied in the concentration of 50.0 mg dm-3 at selected stages of embryogenesis: blastopore closure, inoculation, and the hatching of larvae. In the course of the experiment, live embryos were observed and total lengths of the larvae were measured. Simultaneously, selected hydrochemical indicators were gauged. It was discovered that coagulants had the strongest effect at the first stage of embryogenesis (the end of the process of gastrulation). At that stage the survival rate of embryos was the lowest (73.5- 75.0%) and the percentage of deformities in the hatched larvae was the highest (9.7-10.0%).

The structure and the embryogenetic role of eggs and egg membranes of Ancistrus dolichopterus (Actinopterygii: Siluriformes: Loricariidae)

Genus Ancistrus is represented by fish commonly known as bushymouth or bristlenose plecos. They occur in the watershed of upper Amazon including Peruvian Ucayali and less frequently in the lower Amazon watershed (Kornobis 1990). The fish of this genus living in the wild can reach up to 15 cm of length, whereas in the captivity (culture) they do not exceed 13 cm (Riehl and Baensch 1996). Adults show sexual dimorphism, the juveniles look the same despite their sex. The reproduction of bushymouth catfish, Ancistrus dolichopterus Kner, 1854, is difficult to observe because it occurs at night in shaded areas—most frequently in hiding spots. The male prepares so called “pseudo-nest” before female would lay the eggs. He carefully cleans the nest and protects it from invasion of any potential predators e.g., snails. This specific care fulfilled only by the male lasts during the entire embryonic development till the larvae leave the nest, move independently, and are able to feed themselves (Rymkiewicz 1988). ACTA ICHTHYOLOGICA ET PISCATORIA (2011) 41 (3): 223–227 DOI: 10.3750/AIP2011.41.3.10