Removal of dead fish eggs by Asellus aquaticus as a potential biological control in aquaculture.

The objective of the present experimental study was to gain a better understanding of the foraging activity of Asellus aquaticus during fish egg incubation. A. aquaticus were introduced into experimental setups of dead eggs, viable eggs and hatched larvae of zebrafish (Danio rerio), a commonly used model organism. The amount of A. aquaticus and the duration of their exposure to the eggs significantly affected the proportion of consumed dead eggs in each experimental cycle. A. aquaticus belongs to the group of aquatic detritivores, and no predatory behavior was observed during the experiments. These crustaceans could distinguish between the dead eggs and those containing living embryos. Furthermore, zebrafish larvae remained unharmed by A. aquaticus, even in the absence of alternative food source. These findings underscore the potential sanitary role of these crustaceans in natural waters and offer new perspectives on their possible use as biological control organisms in aquaculture hatcheries. Additionally, our results suggest a potential application of A. aquaticus in combating pathogens by reducing the growth substrates for bacteria and fungi.

Effects of high ambient temperature on fish sperm plasma membrane integrity and mitochondrial activity - A flow cytometric study.

Local extreme climatic conditions occurring as a result of global climate change may interfere with the reproduction of animals. In the present study fish spermatozoa were incubated at different temperatures (20, 25, 30 and 40 °C) for 10 and 30 minutes, respectively and plasma membrane integrity and mitochondrial membrane potential changes were evaluated with flow cytometry using SYBR-14/PI and Mitotracker Deep Red FM fluorescent dyes. No significant differences were found in plasma membrane integrity at either incubation temperatures or time points. Mitotracker Deep Red FM histogram profiles indicating mitochondrial activity showed significant (p < 0.001) alterations in all cases of higher (25, 30 and 40 °C) temperature treatments as compared to the samples incubated at 20 °C. Our results indicate that fish spermatozoa exposed to high temperatures suffer sublethal damage that cannot be detected with conventional, vital staining techniques.

The complete mitochondrial genome of perch Perca fluviatilis (Perciformes: Percidae).

In this study, we cloned and sequenced the complete mitochondrial genome of Perca fluviatilis. It was a circular double-stranded DNA molecule of 16,537 base pairs (bp) in length and consists of 13 protein-coding genes, 22 tRNA genes, two ribosomal RNA genes and two main non-coding regions (the control region and the origin of the light strand replication). The mitogenome of shared common features with those of other toleosts in terms of gene order and base composition. All protein-coding genes were initiated with ATG except for COX 1, which began with GTG instead. However, the termination codons of 13 protein-coding genes are varied with TAG, TAA or T. This mitogenome sequence data would contribute to better understanding phylogenetic relationships and population genetics of the family Percidae.