Lukáš Kalous

Risk assessment of the crayfish pet trade based on data from the Czech Republic

The pet trade in freshwater crustaceans, including crayfish, has grown rapidly in recent decades and become an important pathway for introducing new non-indigenous species into Europe. This paper provides the first overview of non-indigenous crayfish species (NICS) traded as ornamental and their potential impact in the Czech Republic, which is the second leading importer into Europe. The paper presents a full list of traded crayfish species, their market availability, and trade names or misnomers used in the country. In total, 27 crayfish species from all three families are advertised and marketed, of which Astacus astacus is the only indigenous species. Only three NICS were recognized as very common on the market. The invasiveness and risk associated with ornamental crayfish trade were assessed using the Freshwater Invertebrate Invasiveness Scoring Kit. Five NICS were classified into the high-risk category, the highest score being for Procambarus fallax f. virginalis. The invasiveness of crayfish indigenous to North America is significantly greater than that of crayfish from the rest of the world, and therefore regulation in this regard is recommended.

Massive mortality of Prussian carp Carassius gibelio in the upper Elbe basin associated with herpesviral hematopoietic necrosis (CyHV-2)

From 22 May to 10 June 2011 massive mortality of Prussian carp Carassius gibelio was observed in alluvial Lake Řehacˇka close to the Elbe River in the Czech Republic. More than 1400 kg of dead fish were collected and no other fish species were affected. Further molecular and cytogenetic investigation of fish (n = 232) revealed that the Rˇehacˇka population of Prussian carp consisted exclusively of gynogenetic triploid females. The causative agent was identified by means of molecular and electron microscopy as a herpesviral hematopoietic necrosis virus (Cyprinid herpesvirus 2, CyHV-2). This is the first report of CyHV-2 from the Czech Republic and the second finding worldwide of CyHV-2 causing mass mortality of C. gibelio. Some other localities in the upper Elbe River basin where C. gibelio was affected are also noted. We assume that the massive wave of deaths of all female gynogenetic Prussian carp can be attributed to limited genetic variation and the favourable conditions for development of viral disease.

Aquarium hitchhikers: attached commensals imported with freshwater shrimps via the pet trade.

The keeping of home aquaria is one of the most popular hobbies globally. In contrast to the ornamental fish trade, decapod crustaceans such as shrimps, crayfish and crabs are relatively new to the pet trade. Nevertheless, the popularity of ornamental shrimp in freshwater aquaria has rapidly increased in recent years. Indonesia is one of the leading producers and exporters of ornamental aquatic animals globally and the Czech Republic is a gateway for these animals into the European Union territory. The pathway for introductions of organisms unintentionally moved in association with ornamental shrimps via the international trade has to date not been evaluated. We examined a small number of shrimps imported from Indonesia into the Czech Republic in May 2015 and found large numbers of the protozoan Vorticella sp., one species of scutariellid temnocephalidan (Caridinicola sp.), and one species of bdelloid rotifer, associated with two species of atyid shrimps, indicating an invasion risk from fauna carried unintentionally by this vector. Although our observations were limited in scale, we estimate the total number of commensal fauna imported into the Czech Republic with ornamental shrimps via the pet trade to be in the order of hundreds of thousands per month. As attached organisms can directly or indirectly cause diseases in certain species of decapod crustaceans, we recommend five steps to reduce risks of introduction of “hitchhikers” to aquaria and wildlife.

Chromosome studies of European cyprinid fishes: cross-species painting reveals natural allotetraploid origin of a Carassius female with 206 chromosomes.

A single female with 206 chromosomes and another 26 females with 156 chromosomes identified as Prussian carp, Carassius gibelio, and 5 individuals with 100 chromosomes identified as crucian carp, C. carassius, were sampled during field survey in one locality in the upper Elbe River. To identify the origin of females with high chromosome numbers, comparative karyotype analysis, GISH, with whole C. carassius DNA as probe and phylogenetic positions of sampled individuals revealed by cytochrome b mitochondrial marker were performed. GISH showed consistently bright labeling of 50 chromosomal elements out of 206, corresponding to the haploid chromosome number of C. carassius. The position of these females with high chromosome numbers in a reconstructed phylogenetic tree was within the clade of C. gibelio, documenting its affiliation to C. gibelio mitochondrial, i.e. maternal lineage. Our findings indicated that the mother of the female with high chromosome numbers was a gynogenetically reproducing 156-chromosome C. gibelio female and the father a bisexually reproducing C. carassius male. We, therefore, hypothesized that the C. gibelio × C. carassius allopolyploid female with 206 chromosomes arose by a mechanism of sperm genome addition to an unreduced egg of the mother.

Intestinal Parasite Acanthocephalus lucii (Acanthocephala) from European Perch (Perca fluviatilis) as a Bioindicator for Lead Pollution in the Stream “Jevanský potok” Near Prague, Czech Republic

Lead concentrations in the tissues of perch and its parasites were determined as mg/kg dw. Lead was found at higher concentrations in the acanthocephalans (11.56) than in different tissues (liver, gonads and muscle with skin and bone) of perch. With respect to fish tissues, the highest concentrations of lead were present in the liver (1.24), followed by the gonads (0.57) whereas the lowest concentrations were in the muscle with skin and bone (0.21). The bioconcentration factors for lead indicated that parasites accumulate metals to a higher degree than fish tissues—lead concentrations in acanthocephalans were 9.32, 19.27 and 55.05 higher than in liver, gonads and muscles of host, respectively.

Predictions of marbled crayfish establishment in conurbations fulfilled: Evidences from the Czech Republic

Abstract The marbled craynsn (Procambarus fallax f. virginalis) has become one of the potentially most dangerous nonindigenous crayfish species spreading in European countries and elsewhere. This taxon reproduces parthenogenetically and recently has been verified as a vector of the crayfish plague pathogen. Here, we report on two established populations of marbled crayfish in the Czech Republic. The marbled crayfish was observed during autumn 2015 in an urban pond connected by sewer piping with the Rokytka brook near its mouth to the Vltava River in Prague. Subsequently, three adult females, two of them having well-developed glair glands and oocytes, were captured in this pond during spring 2016, suggesting successful overwintering of the local population. Furthermore, four adult females were captured in an artificial pond at the Radovesická lignite spoil heap in the vicinity to the industrial conurbation of Bílina in summer 2016; one of them carried eggs. We tested these for the presence of the crayfish plague pathogen Aphanomyces astaci, with negative results. The introduction pathway for both populations is most likely a release from private aquaria, as these sites are popular for recreation activities. Our findings substantiate previous predictions that conurbations are likely to be the primary areas for marbled crayfish introductions.

EUROPEAN HUB FOR INVADERS: RISK ASSESSMENT OF FRESHWATER AQUARIUM FISHES EXPORTED FROM THE CZECH REPUBLIC

Background. The aquarium fi sh trade is characterized by an enormous number of species. Aquarium fi sh may have an impact on native biota by means of their invasiveness as well as through pathogen transfer. The Czech Republic has become a gateway for aquatic pets into the European Union. The aims of this study were to identify the most common aquarium fi sh species on the wholesale market, to estimate temperature suitability for seasonal (winter and summer) survival in the EU, and also to assess the invasiveness risk of the most common aquarium fi shes with the strongest temperature matching. Materials and methods. Data on aquarium fi sh species, their origin, and availability from producers and traders based in the Czech Republic were collected based on all available sources. The target area was defi ned as all member states of the EU. Estimation of the temperature suitability for each species was done using Climatch 1.0 software. The Freshwater Fish Invasiveness Screening Kit (FISK) was employed for species with temperature suitability within the target area exceeding 10% in the coldest quarter of the year. Results. In total, 1118 fi sh species representing 51 families were identifi ed. Thirty-three species belonging to 13 families were classifi ed as “very common”. Three sources of origin were identifi ed: domestic production within the EU, farm production outside the EU, and wild harvests in the region of origin. The major suppliers outside the EU are in south-east Asia. Only one common species originated from wild harvests. FISK scoring divided the 11 species evaluated as having the strongest temperature suitability in the EU (TSEU) into seven species bearing medium risk and four species representing high risk. The family Cyprinidae was the most frequently represented among all evaluated taxa (seven species), but the majority of high-risk fi shes belonged to the family Poeciliidae (three species). The highest score was earned by Carassius auratus (Linnaeus, 1758). Conclusion. The risk potential of aquarium fi shes most traded in the EU seems to be not alarming. Attention should be focused on the possibility of novel pathogen transfer to native aquatic biota as an important aspect of regulating the aquarium fi sh trade.

Concentrations of Zn, Mn, Cu and Cd in different tissues of perch (Perca fluviatilis) and in perch intestinal parasite (Acanthocephalus lucii) from the stream near Prague (Czech Republic)

We monitored concentrations of Cd, Cu, Mn and Zn in acantocephalan parasites (Acanthocephalus lucii) and its final host (Perca fluviatilis). The concentrations in parasites were found to be significantly higher than those found in the muscle, gonads and liver of fish host. The bioaccumulation factor values (BF=C(parasite)/C(host muscle)) were 194, 24.4, 2.2 and 4.7 for Cd, Cu, Mn and Zn, respectively. This suggests a benefit for the host due to the high accumulation of toxic cadmium.

Occurrence of bifidobacteria and lactobacilli in digestive tract of some freshwater fishes

Distal parts of the fish intestine were analyzed for presence of bifidobacteria and lactobacilli using selective agars. Seventy seven samples from Cyprinus carpio, Oncorhynchus mykiss, Carassius auratus, Tinca tinca, Perca fluviatilis, Rutilus rutilus, Scardinius erythrophthalmus, Oreochromis niloticus, and Squalius cephalus were collected randomly throughout years 2008 and 2009. Bifidobacteria were detected in 5 samples from 4 fish species at counts 2.18–4.29 log CFU/g, lactobacilli were present in 6 fish species at counts 1.21–3.65 log CFU/g. Seven bifidobacterial isolates were identified to the species level using biochemical tests and by sequencing of 16S rRNA gene. Three strains belonged to species B. longum, two isolates were identified as B. dentium, one strain as B. asteroides and one isolate was not determined to the species level by employed methods. As identified bifidobacterial species are considered to be of human, animal or honeybee origin, they probably derived as contamination from sewage or other sources. After further more detail testing, the possible use of isolated bifidobacteria as probiotics is promising since they were able to pass through the digestive tract successfully.

Karyotype diversity of the offspring resulting from reproduction experiment between diploid male and triploid female of silver Prussian carp, Carassius gibelio (Cyprinidae, Actinopterygii)

Abstract. Populations of silver Prussian carp (Carassius gibelio) are known to exhibit different ploidy levels among their individuals. No consistent information is available regarding chromosome number of triploid biotype. Generally diploids have 100 chromosomes while triploids have 150–160 chromosomes. The karyotype of the C. gibelio triploid biotype is characterized by a variable number of small chromosomal elements called supernumerary chromosomes. Here we report the results of a reproduction experiment between a diploid male and triploid female with respect to chromosome numbers of the parents and their offspring. Thirty metaphases of both parents and fifteen individuals of the offspring were investigated. We found variability in chromosome numbers among analysed offspring with a fluctuation from 150 to 159. In comparison, the chromosome numbers of male and female individuals were found to be 100 and 159 respectively. Our results show a high chromosomal plasticity of the Carassius gibelio triploid biotype.