The large 45S rDNA chromosome sites have often been analyzed in fish. In contrast, little is known about the 5S genes in this animal group. In the genus Leporinus, the NOR chromosomal location has been shown to be very diverse. In the present work, chromosome mapping of 5S rDNA in three anostomids, Leporinus elongatus, L. obtusidens and L. friderici, is investigated using fluorescence in-situ hybridization (FISH) with PCR-obtained 5S probes and primed in-situ labeling (PRINS). Major 5S rDNA chromosomal sites were found to be subterminally located in a small metacentric pair, while minor ones were detected near the centromeric region of a medium-sized submetacentric pair in all studied species. The 5S rDNA genes were not associated with the NORs or sex chromosomes. A highly conserved chromosomal location of these genes appears to characterize the karyotype evolution of this fish group.

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Chromosomal localization of 5S rDNA genes in Leporinus fish (Anostomidae, Characiformes).

In this paper we describe Southern blot hybridization results probed with 5S rRNA genes for several Neotropical fish species representing different taxonomic groups. All the studied species showed a general trend with the 5S rDNA tandem repeats organized in two distinct size-classes. At the same time, data on 5S rDNA organization in fish genome were summarized. Previous information on the organization and evolution of 5S rRNA gene arrays in the genome of this vertebrate group are in agreement with the Southern results here presented. Sequences obtained for several fish species have revealed the occurrence of two distinct 5S rDNA classes characterized by distinct nontranscribed spacer sequences, which are clustered in different chromosomes in some species. Moreover, the 5S rDNA loci are generally distributed in an interstitial position in the chromosomes and they are usually not syntenic to the 45S rDNA. The presence of two classes of 5S rDNA in several non-related fish species suggests that this could be a common condition for the 5S rRNA gene organization in the fish genome.

Two 5S rDNA arrays in neotropical fish species: is it a general rule for fishes?

Cytogenetic studies were carried out in the fish, Hoplias malabaricus, from the Parque Florestal do Rio Doce (Brazil). This population is characterized by 2n = 42 chromosomes for both males and females and an XX/XY sex chromosome system, confirmed through several banding methods. Females show 24 metacentric, 16 submetacentric and 2 subtelocentric chromosomes. Males show 24 metacentric, 17 submetacentric and 1 subtelocentric chromosomes. While the X chromosome is easily recognized (the only subtelocentric element), the Y chromosome is somewhat difficult to identify but appears to correspond to the smallest submetacentric in the male karyotype. In-situ hybridization with an 18S rDNA probe showed 10 well-labeled chromosomes, including the X chromosome. The 5S rDNA is interstitially located in a single metacentric pair independent of the 18S rDNA sites. The NOR on the X chromosome is always active and occurs adjacent to a heterochromatic distal segment on the long arm. Variations in size of the NORs and/or heterochromatic segment correspond to a polymorphic size condition observed in the X chromosome. The present results confirm the XX/XY sex chromosome system in the population analyzed as well as a new cytotype in the Hoplias malabaricus group.

An XX/XY sex chromosome system in a fish species, Hoplias malabaricus, with a polymorphic NOR-bearing X chromosome.

Eukaryotic genomes are colonized by different retroposons, including short interspersed repetitive elements (SINEs). All currently known SINEs are derived from tRNA and 7SL RNA genes and exploit their type 2 internal pol III promoters. We report here a novel class of SINE elements, called SINE3, derived from 5S rRNA. SINE3s are transcribed from the type 1 internal pol III promoter. Approximately 10,000 copies of SINE3 elements are present in the zebrafish genome, they constitute approximately 0.4% of the genomic DNA. Some elements are as little as 1% diverged from each other, indicating that the retrotransposition of SINE3 in zebrafish is an ongoing process. The 3'-tail of SINE3 is significantly similar to that of CR1-like non-LTR retrotransposons, represented by numerous subfamilies in the zebrafish genome. Analogously to CR1-like elements, SINE3 copies are not flanked by target site duplications, and their 3' termini are composed of (ACATT)n and (ATT)n microsatellites, specific for different subfamilies of SINE3. Given the common structural features, it is highly likely that the enzymatic machinery encoded by CR1-like elements powers proliferation of SINE3.

/pdf/a-novel-class-of-sine-elements-derived-from-5s-rrna-3d98ktz0yf.pdf

A Novel Class of SINE Elements Derived from 5S rRNA

To address understanding the organization of the 5S rRNA multigene family in the fish genome, the nucleotide sequence and organization array of 5S rDNA were investigated in the genus Leporinus, a representative freshwater fish group of South American fauna. PCR, subgenomic library screening, genomic blotting, fluorescence in situ hybridization, and DNA sequencing were employed in this study. Two arrays of 5S rDNA were identified for all species investigated, one consisting of monomeric repeat units of around 200 bp and another one with monomers of 900 bp. These 5S rDNA arrays were characterized by distinct NTS sequences (designated NTS-I and NTS-II for the 200- and 900-bp monomers, respectively); however, their coding sequences were nearly identical. The 5S rRNA genes were clustered in two chromosome loci, a major one corresponding to the NTS-I sites and a minor one corresponding to the NTS-II sites. The NTS-I sequence was variable among Leporinus spp., whereas the NTS-II was conserved among them and even in the related genus Schizodon. The distinct 5S rDNA arrays might characterize two 5S rRNA gene subfamilies that have been evolving independently in the genome.

/pdf/organization-of-5s-rdna-in-species-of-the-fish-leporinus-two-1kr13a8u33.pdf

Organization of 5S rDNA in species of the fish Leporinus: two different genomic locations are characterized by distinct nontranscribed spacers.

This study was designed to characterize further the nontranscribed intergenic spacers (NTSs) of the 5S rRNA genes of fish and evaluate this marker as a tool for comparative studies. Two members of the closely related North American Great Lakes cisco species complex (Coregonus artedi and C. zenithicus) were chosen for comparison. Fluorescence in situ hybridization found the ciscoes to have a single multicopy 5S locus located in a C band-positive region of the largest submetacentric chromosome. The entire NTS was amplified from the two species by polymerase chain reaction with oligonucleotide primers anchored in the conserved 5S coding region. Complete sequences were determined for 25 clones from four individuals representing two discrete NTS length variants. Sequence analysis found the length variants to result from presence of a 130-bp direct repeat. No two sequences from a single fish were identical. Examination of sequence from the coding region revealed two types of 5S genes in addition to pseudogenes. This suggests the presence of both somatic and germline (oocyte) forms of the 5S gene in the genome of Coregonus. The amount of variation present among NTS sequences indicates that accumulation of variation (mutation) is greater in this multicopy gene than is gene conversion (homogenization). The high level of sequence variation makes the 5S NTS an inappropriate DNA sequence for comparisons of closely related taxa.

Intraindividual and interspecies variation in the 5s rdna of coregonid fish

Vaccinations for pet rabbits using biological preparations registered in Poland provide protection against three clinical entities: myxomatosis, rabbit haemorrhagic disease types 1 and 2 (RHD1 and RHD2). This article presents an analysis of the number of vaccinations performed in rabbits in the years 2011-2020 at the Clinic of Infectious Diseases of the Faculty of Veterinary Medicine, University of Life Sciences in Lublin. Among the total number of 3304 rabbits admitted to the clinic, 574 visits were for vaccinations, which indicates that the owners of these animals are interested in specific prevention of myxomatosis and RHD. Detailed analysis of the clinic’s records makes it possible to identify certain tendencies, e.g. those associated with the choice of biological preparations or the percentage of immunized animals in different years. Vaccination of rabbits is not difficult for the veterinarian from a technical point of view, it provides excellent protection against lethal infectious diseases, and it can be a source of income for veterinary clinics. For this reason it is worth disseminating knowledge on the vaccination programme for rabbits kept as companion animals among owners of these animals.

Use of vaccines in rabbits kept as companion animals based on an analysis of clinical cases at the Clinic of Infectious Diseases, Faculty of Veterinary Medicine, University of Life Sciences in Lublin in 2011-2020

The study objective was to determine reference values of selected biochemical parameters of the haemolymph of Cepaea nemoralis snails (Mollusca, Gastropoda, Helicidae). The study determined the activity of aminotransferases (AST and ALT), which was 11.22 ± 10.92 [u/l] and 6.72 ± 3.18 [u/l], respectively, and alkaline phosphatase (ALP) at a level of 3.92 ± 2.08 [u/l]. The level of amylase (AMY) in the haemolymph was 2.32 ± 0.74 [u/l], while lipase (LIP) was 0.74 ± 0.79 [u/l]. The concentration of urea (UREA) was established at 2.28 ± 0.48 [mg/dl], creatinine (CREA) at 2.28 ± 0.09 [mg/dl], uric acid (UA) at 0.22 ± 0.16 [mg/dl], calcium (Ca) at 21.24 ± 2.4 [mg/dl], and total protein (TP) at 1.38 ± 0.34 [g/l]. The specific gravity of the haemolymph was 1.0 ± 0.002. The haemolymph was obtained from 211 individuals in the active phase collected from their natural habitat. The biochemical parameters of the haemolymph were determined with a BS 180 apparatus (Mindray), and the specific gravity with a refractometer. The article also desrcibes an intravital technique of collecting haemolymph from C. nemoralis. The results obtained may constitute an aid and a guideline for scientists dealing with the physiology of land molluscs.

S. Linn Sajdak

Papers

Intraindividual and interspecies variation in the 5s rdna of coregonid fish

Use of vaccines in rabbits kept as companion animals based on an analysis of clinical cases at the Clinic of Infectious Diseases, Faculty of Veterinary Medicine, University of Life Sciences in Lublin in 2011-2020

Determination of selected biochemical parameters of the haemolymph of free-living Cepaea nemoralis (L.) snails. Preliminary study