The impact of electromagnetic fields generated by high-voltage power lines on the spatial arrangement of pike (Esox Lucius Linnaeus 1758) embryos.

Urbanization and technological advancements result in the dispersion of antropogenic electromagnetic fields (EMF) that can affect on ecosystems. Therefore, it is important to understand their impact on the environment. Aquatic ecosystems are subject to EMF as part of various electricity sources, e.g., high-voltage transmission lines (HVTL). We examined the impact of EMF generated by HVTL on the spatial arrangement and survival of pike (Esox lucius) embryos. Fertilized eggs were incubated under two HVTL configurations 110 kV and 220 kV compared with a control group devoid of anthropogenic EMF. Embryo orientation and survival were monitored until blastopore closure. The control group showed dominance in the arrangement of embryos along the N-S, NNW-SSE, and NNE-SSW axes, with a slight prevalence of northern directions. EMF originating from HVTL did not exert a significant influence on the spatial arrangement of pike embryos, although some deviations from the arrangement noticed in the control group were observed. Increased embryo mortality was observed only at 110 kV site, but probably due to factors unrelated to EMF. In conclusion, EMF generated by HVTL did not significantly change pike embryo orientation or chances of survival. However, longer exposure or higher EMF levels could provoke notable reactions, requiring ongoing evaluation as power networks continue to spread more widely.

Histomorphometric evaluation of melanomacrophage centers (MMCs) and CD3+ T cells of two morphs of brown trout (Salmo trutta) fed diets with immunostimulants.

The brown trout (Salmo trutta) is a salmonid residing in riverine and coastal waters throughout the Northern Hemisphere, whose various populations evolved into distinct ecological morphs, differing in their migratory tendencies and preferred habitats. Unfortunately, due to progressing degradation of natural environment, the conservation of these populations is of growing importance and is undoubtedly a challenging task. Therefore, various means to refine the preparatory protocols for restocking using hatchery-reared fish are being pursued, some of which involve the administration of immunity-boosting substances. The current study assessed the effects of two dietary immunostimulants: Bioimmuno (4% inosine pranobex and 96% ß-glucan) and Focus Plus (commercial preparation by Biomar, Denmark) on two morphs of the brown trout - the river trout (S. trutta morpha fario) and the sea trout (S. trutta morpha trutta). Tissue samples were obtained from ∼75 to 100g fish after 0, 2 and 4 weeks of experimental feeding. Multi-factorial analysis of conducted histological measurements of melanomacrophage centers (MMCs) revealed no changes of their parameters within spleens, but showed a decrease of the occupied tissue area and MMC counts in the livers, progressing with time regardless of the applied diet. Immunohistochemical analysis of CD3+ T cells showed their increased recruitment into mucosal folds of pyloric caeca in the 2-week sampling of trouts fed with the diet with 2% Bioimmuno addition, but this effect was not present in the 4-week sampling. When studying all groups jointly within each morph, there was a significant difference in terms of maintained CD3+ T cells levels, as sea trouts showed significantly higher tissue areas occupied by these cells than river trouts, both in the pyloric caeca and hepatic parenchyma. The study revealed that feeding with a diet enriched with Bioimmuno for 2 weeks may be a favorable enhancement of rearing protocols of brown trout stocks prior to their release, but more studies need to be conducted to test the possibility of an even shorter feeding period.

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.

En este trabajo se ha descrito la estructura de las túnicas ovulares del escalar o pez ángel (Pterophyllum scalare), las modificaciones morfo-fisiológicas que transcurren durante la embriogénesis del escalar desde el momento de activización para el desove en condiciones ambientales óptimas (28ºC y pH 6,8) y, se han caracterizado las larvas y los alevines desarrollándose. Adicionalmente, se ha estudiado el efecto del pH básico del agua sobre los primeros estadios de desarrollo y la dependencia entre la cantidad de alimento y la supervivencia de los alevines. Las túnicas ovulares del escalar son finas (1,67-2,18 mm), transparentes, cubiertas de una sustancia viscosa. Los huevos de color ámbar tienen forma ovalada de diámetros medios 1,436 y 1,171 mm y de un volumen medio de 1,033 ± 0,095mm³. El porcentaje de supervivencia de embriones y de larvas en agua con pH aumentado, ligeramente básico, fue muy bajo, ya que sólo el 2% de los embriones sobrevivió, mientras que en agua de parámetros óptimos sólo algunos huevos palidecieron. Las larvas recién salidas del huevo medían 2,60 ± 0,093 mm por término medio y poseían grandes (0,64 ± 0,077 mm³) sacos vitelinos. Se han adherido al substrato mediante una secreción en forma de filamentos finos y viscosos. Esta secreción se ha desprendido de las glándulas ubicadas en la cumbre de la cabeza. Las glándulas desaparecieron al 5º día de vida de las larvas. Las larvas de un día poseían ya las primeras células pigmentarias en el cuerpo, los ojos de las larvas de dos días estaban pigmentadas plenamente. Entre el 4º y 5º día de vida las larvas empezaron a tomar alimento. Las larvas de 23 días se parecían a una versión miniaturizada de los adultos. La mortalidad de las larvas del escalar alimentadas durante los primeros días a partir del desove con larvas de artemia salina (Artemia salina) fue mayor que la de las alimentadas con protozoarios y rotíferos.