Parasite inhibitors of cysteine peptidases are known to influence a vast range of processes linked to a degradation of either the parasites' own proteins or proteins native to their hosts. We characterise a novel type I cystatin (stefin) found in a sanguinivorous fish parasite Eudiplozoon nipponicum (Platyhelminthes: Monogenea). We have identified a transcript of its coding gene in the transcriptome of adult worms. Its amino acid sequence is similar to other stefins except for containing a legumain-binding domain, which is in this type of cystatins rather unusual. As expected, the recombinant form of E. nipponicum stefin (rEnStef) produced in Escherichia coli inhibits clan CA peptidases - cathepsins L and B of the worm - via the standard papain-binding domain. It also blocks haemoglobinolysis by cysteine peptidases in the worm's excretory-secretory products and soluble extracts. Furthermore, we had confirmed its ability to inhibit clan CD asparaginyl endopeptidase (legumain). The presence of a native EnStef in the excretory-secretory products of adult worms, detected by mass spectrometry, suggests that this protein has an important biological function at the host-parasite interface. We discuss the inhibitor's possible role in the regulation of blood digestion, modulation of antigen presentation, and in the regeneration of host tissues.

• MeSH
• Cystatins metabolism   MeSH
• Cysteine Endopeptidases metabolism   MeSH
• Escherichia coli MeSH
• Phylogeny MeSH
• Carps parasitology   MeSH
• Cloning, Molecular MeSH
• Protein Conformation MeSH
• Platyhelminths metabolism   MeSH
• Computer Simulation MeSH
• Protein Domains MeSH
• Helminth Proteins genetics   metabolism   MeSH
• Recombinant Proteins genetics   metabolism   MeSH
• Sequence Analysis, Protein MeSH
• Sequence Alignment MeSH
• Protein Binding MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• asparaginylendopeptidase MeSH Browser
• Cystatins MeSH
• Cysteine Endopeptidases MeSH
• Helminth Proteins MeSH
• Recombinant Proteins MeSH

BACKGROUND: The host specificity of fish parasites is considered a useful parasite characteristic with respect to understanding the biogeography of their fish hosts. Dactylogyrus Diesing, 1850 (Monogenea) includes common parasites of cyprinids exhibiting different degrees of host specificity, i.e. from strict specialism to generalism. The phylogenetic relationships and historical dispersions of several cyprinid lineages, including Aulopyge huegelii Heckel, 1843, are still unclear. Therefore, the aims of our study were to investigate (i) the Dactylogyrus spp. parasites of A. huegelii, and (ii) the phylogenetic relationships of Dactylogyrus spp. parasitizing A. huegelii as a possible tool for understanding the phylogenetic position of this fish species within the Cyprininae lineage. RESULTS: Two species of Dactylogyrus, D. vastator Nybelin, 1924 and D. omenti n. sp., were collected from 14 specimens of A. huegelii from the Šujica River (Bosnia and Herzegovina). While D. vastator is a typical species parasitizing Carassius spp. and Cyprinus carpio L, D. omenti n. sp. is, according to phylogenetic reconstruction, closely related to Dactylogyrus species infecting European species of Barbus and Luciobarbus. The genetic distance revealed that the sequence for D. vastator from A. huegelii is identical with that for D. vastator from Barbus plebejus Bonaparte, 1839 (Italy) and Carassius gibelio (Bloch, 1782) (Croatia). Dactylogyrus omenti n. sp. was described as a species new to science. CONCLUSIONS: Our findings support the phylogenetic position of A. huegelii within the Cyprininae lineage and suggest that A. huegelii is phylogenetically closely related to Barbus and Luciobarbus species. The morphological similarity between D. omenti n. sp. and Dactylogyrus species of Middle Eastern Barbus suggests historical contact between cyprinid species recently living in allopatry and the possible diversification of A. huegelii from a common ancestor in this area. On other hand, the genetic similarity between D. vastator ex A. huegelii and D. vastator ex C. gibelio collected in Balkan Peninsula suggests that A. huegelii was secondarily parasitized by D. vastator, originating from C. gibelio after introduction of this fish species from Asia to Europe.

• Keywords
• Aulopyge, Coevolution, Cyprininae, Dactylogyrus, Host specificity, Phylogeography,
• MeSH
• Cyprinidae classification   parasitology   MeSH
• Species Specificity MeSH
• Phylogeny MeSH
• Phylogeography MeSH
• Host Specificity * MeSH
• Trematode Infections parasitology   veterinary   MeSH
• Fish Diseases parasitology   MeSH
• Trematoda classification   genetics   isolation & purification   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Asia MeSH
• Bosnia and Herzegovina MeSH
• Croatia MeSH
• Italy MeSH

Each organism has the limited resources of energy that is distributed among important life traits. A trade-off between immune response and other physiological demands of organism especially costly reproduction is expected. Leuciscus cephalus, the cyprinid fish, was investigated during three periods varying in reproductive investment, that is, before-breeding, breeding, and after-breeding periods. We tested whether a potentially limited investment in immunity during the breeding is associated with higher susceptibility to the metazoan parasites. Following the immunocompetence handicap and sperm protection hypotheses, males expressing more elaborated sexual ornamentation should produce better quality sperm and be more parasitized. We found that reproductive investments in fish play an important role for energy allocation into somatic condition, immunity, and reproduction. The immune parameters including respiratory burst and leukocyte count were higher in breeding; however, parasite species richness and abundance appeared low. Males investing more in spawning tubercles reached high spermatocrite and were more parasitized by digeneans.

• MeSH
• Principal Component Analysis MeSH
• Analysis of Variance MeSH
• Cyprinidae immunology   parasitology   physiology   MeSH
• Host-Parasite Interactions MeSH
• Fish Diseases blood   immunology   parasitology   MeSH
• Parasitic Diseases, Animal blood   immunology   parasitology   MeSH
• Leukocyte Count MeSH
• Reproduction immunology   physiology   MeSH
• Body Weights and Measures MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH