Management of an ornamental pond as a conservation site for a threatened native fish species, crucian carp Carassius carassius

Ornamental ponds are important sites for conserving threatened native fish species (e.g. crucian carp Carassius carassius L.), but pond management plans rarely include considerations of native fishes. We developed and implemented a management plan for a small (0.8 h), ornamental estate pond in Hertfordshire (England) using historical information (aquatic plant and animal surveys) and a 9-year data set on climatic variables and crucian carp body condition. Crucian carp growth was not correlated with climatic variables, but body condition decreased with increasing temperature (in degree-days), which suggests that temperature influences on growth are counter-balanced by environmental factors. Management included the removal of one fish species (to eliminate hybridization with another species) and the introduction of two native species (to re-balance the fish assemblage), a reduction in floating aquatic plants (to reduce shading of the sediments) as well as the use of a chemical agent to compact the pond’s fine sediments and barley straw to enhance invertebrate habitat and thus fish prey production. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli and S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Molecular identification of hybrids of the invasive gibel carp Carassius auratus gibelio and crucian carp Carassius carassius in Swedish waters

Both mitochondrial DNA sequence and two nuclear microsatellite markers were used to confirm the identity of the first record of Carassius auratus gibelio in the western (Swedish) Baltic Sea region. A total of 49 fishes were analysed, where 22 were from three Swedish sites connected to the Baltic Sea. The D-loop mitochondrial DNA sequences showed that 16 of 22 Swedish fishes were related to C. a. gibelio. The phylogenetic analysis of these sequences showed that these fish are probably not native, but represent different lineages of C. a. gibelio from China, Japan and Russia. All except three of these 16 fishes had microsatellite alleles suggesting hybridization with Carassius carassius. These findings suggest that a cryptic invasion of C. a. gibelio might be in progress.     

New cell types of the pancreatic islets in the crucian carp,Carassius carassius

Summary The pancreatic islets ofCarassius carassius have been studied by electron microscopy. 1. Besides A-, B- and D-cells, two new cell types, the fourth and the fifth, have been identified. The fourth cell type is numerous; it occurs interposed among the other types of islet cells or in small clusters. The secretory granules (90–280 mg in diameter) are round or oval and usually with much lower electron density than α- and δ-granules. The secretory granules of the fifth type of cell (approximately 140–240 mμ in diameter) contain finely granular material and an electron dense core that is round or often tetra- or hexagonal. 2. The islet cells with clear cytoplasmic matrix generally contain large numbers of fine, agranular and cored vesicles 400–680 ? in diameter. They appear, in bead-like chains, or randomly scattered throughout the cytoplasm, or often clustered in aggregates close to the secretory granules and show evidence of incorporation into the secretory granules. The two types of vesicles may be formed by constriction or pinching-off of the tubular smooth endoplasmic reticulum.     

Development and application of environmental DNA surveillance for the threatened crucian carp (Carassius carassius)

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Intrinsic contractile properties of the crucian carp (Carassius carassius) heart during anoxic and acidotic stress

The crucian carp (Carassius carassius) seems unique among vertebrates in its ability to maintain cardiac performance during prolonged anoxia. We investigated whether this phenomenon arises in part from a myocardium tolerant to severe acidosis or because the anoxic crucian carp heart may not experience a severe extracellular acidosis due to the fish's ability to convert lactate to ethanol. Spontaneously contracting heart preparations from cold-acclimated (6-8°C) carp were exposed (at 6.5°C) to graded or ungraded levels of acidosis under normoxic or anoxic conditions and intrinsic contractile performance was assessed. Our results clearly show that the carp heart is tolerant of acidosis as long as oxygen is available. However, heart rate and contraction kinetics of anoxic hearts were severely impaired when extracellular pH was decreased below 7.4. Nevertheless, the crucian carp heart was capable of recovering intrinsic contractile performance upon reoxygenation regardless of the severity of the anoxic + acidotic insult. Finally, we show that increased adrenergic stimulation can ameliorate, to a degree, the negative effects of severe acidosis on the intrinsic contractile properties of the anoxic crucian carp heart. Combined, these findings indicate an avoidance of severe extracellular acidosis and adrenergic stimulation are two important factors protecting the intrinsic contractile properties of the crucian carp heart during prolonged anoxia, and thus likely facilitate the ability of the anoxic crucian carp to maintain cardiac pumping.     

Distribution of aldehyde dehydrogenase and alcohol dehydrogenase in summer-acclimatized crucian carp, Carassius carassius L.

The tissue distribution of aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) in summer-acclimatized crucian carp showed almost the same exceptional pattern as previously found in winter-acclimatized specimens. There was a nearly complete spatial separation of ALDH and ADH; in other vertebrates these enzymes occur together. This exceptional enzyme distribution is probably an adaptation to the extraordinary ability of Carassius to produce ethanol as the major metabolic end product during anoxia. Since the crucian carp is less likely to encounter anoxia during the summer, the present results suggest that the crucian carp is unable to switch over to a 'normal' ALDH and ADH distribution in the summer. However, it is also possible that there is an advantage for the summer-acclimatized crucian carp in keeping ALDH and ADH separate, because of occasional anoxic periods.     

An experimental study of body size and food size relations in crucian carp,Carassius carassius

Synopsis In dense, single-species assemblages of crucian carp, competition is intense and results in populations of stunted fish. To explore mechanisms underlying this competition, we measured handling times, return rates, and prey choice for five sizes of crucian carp feeding on six sizes of a standardized food. Handling times increased with prey size and decreased with fish size. Return rates (dry mass ingested per unit handling time) increased dramatically with fish size, and generally decreased with increasing prey size, especially for small fish. Patterns of return rates among size-classes suggested that one or more size-related shifts in feeding efficiency exist for crucian carp; combined with physiological stresses related to winter anoxia, the inability of fish to make these shifts may contribute to size structures observed in high-density populations. Comparisons of relations among fish size, prey size, and return rates for crucian carp and bluegill, Lepomis macrochirus, suggest that similar intraspecific competitive relations exist between generalist species with size-structured populations. Despite differences in return rates among prey sizes, the extent of food selectivity based on prey size exhibited by crucian carp in two types of choice trials was less than predicted. Crucian carp commonly take in several items before mechanically processing food with their pharyngeal apparatus; this multiple prey processing may contribute to disparities between observed choice patterns and those predicted based on return rates for single prey.     

Specific projection of the sensory crypt cells in the olfactory system in crucian carp, Carassius carassius

To study the projection of a special type of sensory neuron called crypt cells in the olfactory system in crucian carp, Carassius carassius, we applied the neural tracer 1,1-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) in the olfactory bulb (OB). Small crystals of DiI were applied in a small area at the synaptic region at the ventral part of the OB, where a population of secondary neurons specific for sex pheromones has been identified. In those samples (4 out of 24) where only axons in the lateral bundle of the medial olfactory tract were stained, the majority (50-66%) of olfactory sensory neurons stained were crypt cells situated in the peripheral layer of the olfactory epithelium. Because this bundle of the tract mediates reproductive behavior, it is conceivable that crypt cells express olfactory receptors for sex pheromones.     

Intermediate stages in the disassembly of synaptic ribbons in cone photoreceptors of the crucian carp,Carassius carassius

Synaptic ribbons are trilaminated plate-shaped presynaptic densities of certain types of receptor cells and neurons. In cone photoreceptors, these structures dissassemble and reassemble in response to light and to a variety of other stimuli. We used the lithium-ionenhanced disassembly and reassembly of synaptic ribbons to characterize structural intermediates in these cyclic changes. A few minutes after exposure of isolated retinas from the crucian carp (Carassius carassius) to lithium, ribbons fragmented into 50-nm-sized dense globular structures. These small spheres were concentrically surrounded by synaptic vesicles attached to them by stalk-like fine bridging filaments. Disassembly always started at the free cytoplasmic edges of the ribbons and proceeded toward the membrane-associated edges. As the disassembly process never started at the membraneanchored site, synaptic ribbons appeared to be polarized structures with functionally different ends. Spheres were subjected to further depolymerization. They disintegrated into clusters of small granular material and disappeared after ca. 45 min of lithium treatment. Spheres were not observed during the reassembly of synaptic ribbons, indicating that the assembly of synaptic ribbons proceeds via smaller subunits.     

Regional distribution of monoamines and monoamine metabolites in the brain of the crucian carp (Carassius carassius L.)

1. Monoamines (which all demand oxygen for their synthesis) and monoamine metabolites were quantified in 6 brain regions of the extremely anoxia tolerant crucian carp (Carassius carassius L.).2. The norepinephrine levels were generally twice as high as the dopamine levels. No epinephrine was found.3. The major dopamine metabolite seemed to be homovanillic acid. No 3,4-dihydroxyphenylacetic acid was found.4. Serotonin occurred at about the same levels as dopamine. The levels of the main serotonin metabolite, 5-hydroxyindole-3-acetic acid, were about 10% of that of serotonin.5. All three monoamines had a similar distribution, with the highest concentrations in hypothalamus and the lowest in cerebellum and vagal lobes.6. The distribution and levels of monoamines agreed with that of anamniote vertebrates in general, suggesting that the crucian carp has not adapted to anoxia by abandoning or minimizing the use of monoaminergic systems.     

Gender distinction in neural discrimination of sex pheromones in the olfactory bulb of crucian carp, Carassius carassius

Studies on projection of the sensory neurons onto the olfactory bulb in fish have revealed a clear subdivision into spatially different areas that each responded specifically to different classes of odorants. Amino acids induce activity in the lateral part, bile salts induce activity in the medial part, and alarm substances induce activity in the posterior part of the medial olfactory bulb. In the present study, we demonstrate a new feature of the bulbar chemotopy showing that neurons specifically sensitive to sex pheromones are located in a central part of the ventral olfactory bulb in crucian carp. Extensive single-unit recordings were made from these neurons, stimulating with four sex pheromones, 17,20beta-dihydroxy-4-pregnen-3-one, 17,20beta-dihydroxy-4-pregnen-3-one-20-sulfate, androstenedione, and prostaglandin F(2alpha), known to induce specific reproductive behaviors in males of carp fish. All substances were applied separately to the sensory epithelium at a concentration of 10(-9) M. Of the 297 neurons recorded in males, the majority (236 or 79.5%) responded exclusively to one of the four sex pheromones and thus showed a high specificity. Of the 96 neurons recorded from the olfactory bulb in females, only 1 unit showed such a specific activation. These findings reflect remarkable differences between males and females in the discriminatory power of the olfactory neurons toward these sex pheromones. The gender differences are discussed in relation to behavior studies, expression of olfactory receptors, and the convergence of sensory neurons onto the secondary neurons in the olfactory bulb.     

1H-NMR study of the metabolome of an exceptionally anoxia tolerant vertebrate, the crucian carp (Carassius carassius)

The crucian carp (Carassius carassius) can tolerate anoxia for days to months, depending on the temperature. In this study, we applied ¹H-NMR-based metabolomics to polar extracts of crucian carp brain, heart, muscle and liver samples obtained from fish exposed to either control normoxic conditions, acute anoxia (24 h), chronic anoxia (1 week) or reoxygenation (for 1 week following chronic anoxia) at 5 °C. Spectra of the examined tissues revealed changes in several energy-related compounds. In particular, anoxic stress resulted in decreased concentrations of phosphocreatine (muscle, liver) and glycogen (liver) and ATP/ADP (liver, heart and muscle) and increased concentrations of lactate (brain, heart, muscle) and beta-hydroxybutyric acid (all tissues). Likewise, increased concentrations of inhibitory compounds (glycine, gamma-amino butyric acid or GABA) and decreased concentrations of excitatory metabolites (glutamate, glutamine) were confirmed in the anoxic brain extracts. Additionally, a decrease of N-acetylaspartate (NAA), an important neuronal marker, was also observed in anoxic brains. The branched-chain amino acids (BCAA) valine/isoleucine/leucine increased in all anoxic tissues. Possibly, this general tissue increase can be due to an inhibited mitochondrial function or due to protein degradation/protein synthesis inhibition. In this study, the potential and strength of the ¹H-NMR is highlighted by the detection of previously unrecognized changes in metabolites. Specifically, myo-inositol substantially decreased in the heart of anoxic crucian carp and anoxic muscle tissue displayed a decreased concentration of taurine, providing novel insights into the anoxia responses of the crucian carp.     

The effect of starvation on the ultrastructure of the red and white myotomal muscles of the crucian carp (Carassius carassius)

Summary The effect of 16 weeks total starvation on the ultrastructure of the red and white myotomal muscles of the crucian carp (Carassius Carassius) has been investigated. In the white fibres the amount of myofibrillar material fell from 89.6% to 70.7% of the total fibre volume whilst in the red fibres the fall was from 72.2% to 70.3%. The sarcoplasmic reticulum appeared to have become swollen during starvation in both fibre types. In the white fibres the terminal cisternae of some triads seem to have fused. The volume of the red fibres occupied by mitochondria was reduced from 16.2 % to 5.9 %. The concentration of mitochondria in the white fibres was too low to detect any quantitative changes. A marked reduction in the amount of euchromatin material was observed in most white fibre nuclei and many red fibre nuclei. Many of the ultrastructural changes noted in the present study can be correlated with biochemical changes known to occur in the red and white myotomal muscles of fish during starvation. This work was supported by a grant from the Natural Environmental Research Council.     

Phylogenetic relationships of silver crucian carp Carassius auratus gibelio, C. auratus cuvieri, crucian carp C. carassius, and common carp Cyprinus carpio as inferred from mitochondrial DNA variation

PCR-RFLP analysis of the ND3/ND4L/ND4 and 12S/16S rRNA regions and nucleotide sequence variation of the cytochrome b gene were used to study the mtDNA divergence in species of the family Cyprinidae, to examine the phylogenetic relationships of the species, and to identify their taxonomic status. The results indicated that an ancestral form diverged into silver crucian carp and crucian carp after its separation from the common carp lineage. The divergence of continental Carassius auratus gibelio and Japanese C. auratus cuvieri occurred more recently. Two well distinguishable mtDNA phylogroups, suggesting divergent evolution, were observed in continental C. auratus gibelio populations. The divergence was possibly related to the formation of two silver crucian carp groups with different types of reproduction, triploid gynogenetic and diploid gonochoric. At the same time, the results supported the high probability of current genetic exchange between the forms. In view of these findings and high morphological similarity of the two forms, they were not considered to be separate species.     

Hybridization of crucian carp, Carassius carassius (Linnaeus, 1758), in Ukrainian reservoirs and genetic structure of hybrids

Hybridization of crucian carps Carassius carassius in polyspecific crucian populations of reservoirs of Ukraine and genetic structure of the hybrids were investigated using biochemical gene marking and cytometric procedure. The fact of wide hybridization between C. auratus and C. carassius was proved to be true by large number of hybrids which can form populations consisting only from hybrid individuals. Hybrids C. auratus x C. carassius were diploid, tryploid and in exceptional cases tetraploid; females and males which most likely breed by hybridogenesis. Besides, some clonal hybrids C. carassius x C. gibelio-1 appearing as tetraploid females, and one triploid female C. carassius x Tinca tinca were revealed. It is supported that hybridization of alien C. auratus with endemic C. carassius became one of mechanisms of replacement and depressions of populations of the last.     

Seasonality of dihydropyridine receptor binding in the heart of an anoxia-tolerant vertebrate, the crucian carp (Carassius carassius L.)

Prolonged anoxia tolerance of facultative anaerobes is based on metabolic depression and thus on controlled reduction of energy-utilizing processes. One proposed survival mechanism is the closing of ion channels to decrease energetic cost of ion pumping (Hochachka PW. Science 231: 234-241, 1986). To test this hypothesis, the involvement of L-type Ca2+ channels in seasonal anoxia tolerance of the vertebrate heart was examined by determining the number of [methyl-3H]PN200-110 (a ligand of L-type Ca2+ channel alpha-subunit) binding sites of the cardiac tissue and the density of Ca2+ current in ventricular myocytes of an anoxia-resistant fish species, the crucian carp. In their natural environment, the fish were exposed for > 3 mo of hypoxia (O2 < 2.5 mg/l) followed by almost 8 wk of anoxia that resulted in abrupt depletion of cardiac glycogen stores in late spring. Unexpectedly, however, the number of [methyl-3H]PN200-110 binding sites did not decline in hypoxia/anoxia as predicted by the channel arrest hypothesis but remained constant for most of the year. However, in early summer, the number of [methyl-3H]PN200-110 binding sites doubled for a period of approximately 2 mo, which functionally appeared as a 74% larger Ca2+ current density. Thus the anoxia tolerance of the carp heart cannot be based on downregulation of Ca2+ channel units in myocytes but is likely to depend on suppressed heart rate, i.e., regulation of the heart at the systemic level, and direct depressive effects of low temperature on Ca2+ current to achieve savings in cardiac work load and ion pumping. The summer peak in the number of functional Ca2+ channels indicates a short period of high cardiac activity possibly associated with reproduction and active perfusion of tissues after the winter stresses.     

Differential regulation of AMP-activated kinase and AKT kinase in response to oxygen availability in crucian carp (Carassius carassius)

We investigated whether two kinases critical for survival during periods of energy deficiency in anoxia-intolerant mammalian species, AMP-activated kinase (AMPK), and protein kinase B (AKT), are equally important for hypoxic/anoxic survival in the extremely anoxia-tolerant crucian carp (Carassius carassius). We report that phosphorylation of AMPK and AKT in heart and brain showed small changes after 10 days of severe hypoxia (0.3 mg O2/l at 9 degrees C). In contrast, anoxia exposure (0.01 mg O2/l at 8 degrees C) substantially increased AMPK phosphorylation but decreased AKT phosphorylation in carp heart and brain, indicating activation of AMPK and deactivation of AKT. In agreement, blocking the activity of AMPK in anoxic fish in vivo with 20 mg/kg Compound C resulted in an elevated metabolic rate (as indicated by increased ethanol production) and tended to reduce energy charge. This is the first in vivo experiment with Compound C in a nonmammalian vertebrate, and it appears that AMPK plays a role in mediating anoxic metabolic depression in crucian carp. Real-time RT-PCR analysis of the investigated AMPK subunit revealed that the most likely composition of subunits in the carp heart is alpha2, beta1B, gamma2a, whereas a more even expression of subunits was found in the brain. In the heart, expression of the regulatory gamma2-subunit increased in the heart during anoxia. In the brain, expression of the alpha1-, alpha2-, and gamma1-subunits decreased with anoxia exposure, but expression of the gamma2-subunit remained constant. Combined, our findings suggest that AMPK and AKT may play important, but opposing roles for hypoxic/anoxic survival in the anoxia-tolerant crucian carp.     

Studies on resistance characteristic and cDNA sequence conservation of transferrin from crucian carp, Carassius auratus

Transferrin (Tf) is a kind of non-heme β-globulin with two iron ions (Fe³⁺)-binding sites. To prove Tf’s physiological functions, Fe³⁺-proteins, serum iron contents, and total iron-binding capabilities were tested for Tfs of crucian carps (Carassius auratus) and sliver carps (Hypophthalmichthys molitrix). The above results demonstrated that sliver carps shared 1/3 Tf alleles with crucian carps; Tf of crucian carps had stronger Fe³⁺-binding ability and transportation ability in plasma than that of sliver carps. In addition, the results of oxygen consumption experiments indicated that crucian carps had the higher oxygen utility rate than sliver carps. For acute hypoxia exposure assay, normoxic gas mixture, hypoxic gas mixture A, and hypoxic gas mixture B were used to induce oxygen-regulated gene expression of crucian carps in acute hypoxia. The results of quantitative real-time PCR revealed that mRNA levels of Tf gene, Tfr gene and ATPase gene were down-regulated in acute hypoxia but mRNA level of LDHa gene was up-regulated in acute hypoxia. The results of crucian carp Tf-cDNA sequence analysis showed that cDNA regions of two Fe³⁺-binding sites were T₇₄₇–T₁₀₂₆ and T₁₇₃₇–A₁₈₈₄ based on the principle of bioinformatics. The sequence conservation of two Fe³⁺-binding sites was higher than that of the other five regions, which were confirmed according to the subregion model of Tf-cDNA sequence.     

Identification of natural hybrids of gibel carp Carassius auratus gibelio (Bloch) and crucian carp Carassius carassius (L.) from lower Dyje River floodplain (Czech Republic)

Morphometric and genetic variation were examined in parental Carassius auratus gibelio and Carassius carassius individuals, and their natural hybrids. Of meristic traits, only the number of gill rakers clearly distinguished hybrids (39·4 ± 1·4) from parental C. a. gibelio (48·3 ± 0·7) and C. carassius (28·6 ± 1·1). MtDNA sequences showed that the hybrids were descendants of female C. a. gibelio . Microsatellite analysis confirmed the presence in hybrids of variants typical of C. a. gibelio and C. carassius .     

Genetic polymorphism and isoenzyme patterns of lactate dehydrogenase in tench (Tinea tinea), crucian carp (Carassius carassius) and carp (Cyprinus carpio)

Isoenzyme patterns and the polymorphism of lactate dehydrogenase (LDH) were investigated in 3 fish species of family Cyprinidae, i.e. tench ( Tinea tinea ), crucian carp ( Carassius carassius ) and carp ( Cyprinus carpio). The isoenzyme patterns were tissue and species specific. In crucian carp subunits with different electro-phoretic mobility are present, which are genetically controlled from the B¹, B², A¹, A²and C loci, while the set of loci in carp is B¹, B², A, C¹and C²and in tench B, A, C. The locus B of LDH in tench, the locus B²in crucian carp, and the loci B¹, C¹and C²in carp are polymorphic and have two different alleles in each case. The polymorphism did not affect the total LDH activity in the tissues. All the populations investigated were in Hardy-Weinberg equilibrium. The genetic control of the polymorphism in B¹and C¹loci in carp was proved by test matings. The polymorphism in B loci tested in erythrocytes may be utilized as genetic markers in the fish breeding.