Helminths of European smelt Osmerus eperlanus (Linnaeus, 1758) in Lake Hańcza and the Vistula Lagoon, with special regard to their zoonotic threats

Reports published in recent years on the increased risk in the Baltic Sea of fish infection with larvae of nematodes potentially pathogenic to humans have prompted a study of European smelt Osmerus eperlanus with respect to the presence of these parasites in the Vistula Lagoon. Additionally, samples of this fish from Lake Hańcza were comparatively considered. The body cavity, the surface of internal organs, the alimentary tract and the swimbladder of fish from two environmentally different water bodies were taken into account in the analysis. Only the tapeworm Proteocephalus longicollis was found in the alimentary tract of the fish from Lake Hańcza. Depending on the period of study, the prevalence ranged from 60% to 100%, and the mean intensity from 11.5 to 42.0. The helminth fauna of smelt from the Vistula Lagoon was more diverse: Cystidicola farionis occurred with a prevalence from 25.9 to 75.0% and a mean intensity of infection from 2.7 to 66.0%, Proteocephalus longicollis and cystacanths of Corynosoma with a prevalence ranging in different years from 12.0 to 44.0% and from 14.8 to 50.0%, respectively. Zoonotic parasites, such as nematode larvae of the Anisakidae family (Contracaecum sp., Anisakis simplex), occurred in the intestine with a prevalence of 31%, 72% and 22% in consecutive years of the study

Cytogenetic and histological studies of the brook trout, Salvelinus fontinalis (Mitchill), and the Arctic char, S-alpinus (L.) hybrids

Although brook trout and the Arctic char hybrids are able to reproduce, individuals with decreased fertility or even fish that are unable to produce any gametes have been also described. Abnormal gonadal development and disturbances in the gamete production in the char hybrid offspring may be triggered by the odd chromosome number and disturbances in their pairing during meiosis. To verify this hypothesis, cytogenetic examination and the gonadal histology analysis of the brook trout x Arctic char hybrids were carried out. Diploid chromosome number in the studied char (F-1) hybrids varied from 82 to 84 (FN = 99-102). Among 28 hybrids, 12 males, three females, nine intersex individuals and two sterile specimens were described. In the case of two individuals, gonads were not found. Diploid chromosome numbers in the males and intersex individuals varied from 82 to 84. Chromosome numbers in the females were 82 and 83 chromosomes. Two sterile fish exhibited karyotypes composed of 82 and 84 chromosomes. Predominance of the ovarian component in the intersex gonads and gonadal sex ratio distortion towards the males suggested hybrid females had problems with gonadal differentiation. However, the lack of the clear relationship between chromosome number and gonadal development in the studied hybrids did not support our hypothesis that odd chromosome number may be responsible for such reproductive disturbances in the hybrid individuals. We have presumed that sterility and intersexual development of the gonads may be caused by interactions between brook trout and Arctic char genes on the sex chromosomes and autosomes rather than unpairing of the parental chromosomes.Polish National Science Center (NCN) [N N311 525240]info:eu-repo/semantics/publishedVersio

Marking of burbot Lota lota (L.) juveniles using commercial feed as a vector of fluorochrome application

The effectiveness of restocking is an important element of sustainable fishery. In restocking programmes, where larvae and juveniles are used mass marking is carried out with non-toxic dyes such as fluorochromes transferred into the fish body by immersion or with feed. The experiment was carried out to assess the possibility of using commercial feed supplemented Alizarin Red S (ARS) as an alternative non-invasive method for the mass marking of burbot fry. Fish of an average body weight of 1.8 (± 0.2) g were reared in separated 10 dm3 tanks and fed for 10 days with extruded feed supplemented ARS in six concentrations, i.e. 0 (control), 20, 40, 60, 80 and 100 g fluorochrome per kg of feed at a daily dose of 5% of biomass. During the next 15 days fish were fed commercial feed without ARS. After 25 days of rearing 30 individuals were sampled from each group, euthanized and total length and wet body weight of each fish were determined. Next, the sampled fish were preserved in 70% ethyl alcohol. Then otoliths were excised from the fish and analysed under a fluorescence microscope to identify fluorescent tags. Marked individuals were identified in each analysed group provided with feed supplemented ARS. The highest rate of marked fish (100%) was found in the group that received 40 g ARS per kg of feed, and the lowest (73.3%) in the group that received 60 g ARS per kg of feed. Supplementation of feed with ARS had no negative effect on the survival rate and growth parameters (mean body weight and total body length) of burbot. The results suggest that ARS applied in commercial feed (40 g/kg for about 7-10 days) is an effective method for marking burbot fry and can be recommended in fishery practice

Characteristics and Cryopreservation of Semen of Sex-Reversed Females of Salmonid Fish

Sex reversal has been used as a breeding strategy by salmonid fish to produce genetically and phenotypically single sex populations. Production of all-female fish has great importance for the creation of monosex female triploids of salmonid fish, which are valued for their sterility, lack of female maturation, and larger commercial size. Among salmonids, the majority of rainbow trout (Oncorhynchus mykiss) production is based on all-female production with a high proportion of all-female triploid production in Europe. The main aim of this review is to present the recent knowledge regarding sex-reversed females (SRFs) of salmonid fish. We discuss the methods of sex reversal as well as their effects on the morphology and histology of the reproductive tract. We focus on the characteristics of SRF semen as well as the factors determining semen quality. The lower quality of SRF sperm compared to that of normal males has resulted in the need for the artificial maturation of semen. Most importantly, methods of semen storage—both short-term and long-term (cryopreservation)—that can improve hatchery operations are presented with the special emphasis on recent progress in development of efficient cryopreservation procedures and use of cryopreserved semen in hatchery practice. Moreover, we also address the emerging knowledge concerning the proteomic investigations of salmonid sperm, focusing primarily on the proteomic comparison of normal male and SRF testicular semen and presenting changes in SRF rainbow trout sperm proteome after in vitro incubation in artificial seminal plasma