Entrainment to light of circadian activity rhythms in tench (Tinca tinca)

The present article analyzes locomotor activity rhythms in Tinca tinca. To that end, three different experiments were conducted on 24 animals (20 g body weight) kept in pairs in 60-liter aquaria fitted with infrared sensors connected to a computer to continuously record fish movements. The first experiment was designed to study the endogenous circadian clock under free-running conditions [ultradian 40:40 min LD pulses and constant dark (DD)] and after shifting the LD cycle. Our results demonstrate that tench has a strictly nocturnal activity pattern, an endogenous rhythm being evident in 45.8% of the fish analyzed. The second experiment was conducted to test the influence of different photoperiods (LD 6:18, 12:12, 18:6, and 22:2) on locomotor activity, the results showing that even under an extremely long photoperiod, tench activity is restricted to dark hours. The third experiment examined the effect of light intensity on locomotor activity rhythms. When fish were exposed to decreasing light intensities (from 300:0 lux to 30:0, 3:0, and 0.3:0 lux) while maintaining a constant photoperiod (LD 12:12), the highest percentage of locomotor activity was in all cases associated with the hours of complete darkness (0 lux). In short, our results clearly show that (a) tench is a species with a strictly nocturnal behavior, and (b) daily activity rhythms gradually entrain after shifting the LD cycle and persist under free-running conditions, pointing to their circadian nature. However, light strongly influences activity rhythms, since (c) the length of the active phase is directly controlled by the photophase, and (d) strictly nocturnal behavior persists even under very dim light conditions (0.3 lux). The above findings deepen our knowledge of tench behavior, which may help to optimize the aquacultural management of this species, for example, by adjusting feeding strategies to their nocturnal behavior.     

A three-state MWC analysis of oxygenation in tench (Tinca tinca) hemoglobin

Summary Oxygen equilibria in tench hemoglobin were analysed according to a three-state MWC model. In addition to theT andR states of the traditionally used two-state model, the three-state model introduces an additional state, theS state, when organic phosphates bind to theT-structure hemoglobin. Under conditions covering natural red cell pH values and nucleoside triphosphate-hemoglobin ratios, it was possible to closely fit experimental data to the three-state equation with constant values of the association constantsK _R ,K _T , andK _S , and with only the allosteric constantsL andM varying with effector conditions. Thus, in contrast to a twostate analysis of oxygen equilibria, the three-state analysis was consistent with the basic assumption of the MWC model, that heterotropic ligands only affect allosteric constants and not association constants. The temperature-dependence of the three-state parameter values showed that in the presence of nucleoside triphosphate the dominance of theS state over theT state was most pronounced at low temperatures. Furthermore, the numerical values of the enthalpy and entropy change of oxygenation were lower in theS state than in theT andR states, and the enthalpy and entropy change for the allostericSR transition were much larger than for theTR transition.Abbreviations Hb hemoglobin - Y fractional O₂ saturation - ATP adenosine triphosphate     

Response of the tench (Tinca tinca L.) to potassium nitrate enriched water

When the tench ( Tinca tinca L.) was exposed to a slight increase, 8.5 mg/l, in the potassium content of the water, metabolic and hormonal changes occurred which lasted more than four weeks. An initial phase of lipolysis was followed by a partial consumption of glycogen reserves, which in turn was followed by a phase of gluconeogenesis. Hyperglycaemia persisted throughout the experiment. The ion distribution in erythrocytes and liver changed relatively early; there was no observable change in water content. These changes are similar to those observed during the osmoregulation of fish.     

Influence of dietary composition on growth and energy reserves in tench (Tinca tinca)

The effects of different protein, lipid and carbohydrate diets on growth and energy storage in tench, Tinca tinca L., were studied. Over a 2-month period fish were fed four different diets: control, protein-enriched, carbohydrate-enriched and lipid-enriched. The best growth rates were obtained with the control and protein-enriched diets; the carbohydrate diet produced the worst results (lowest specific growth rate, weight gain, nutritional index and hepatosomatic index). These results suggest that it is not advisable to reduce dietary fish protein below 35%, and that it is not possible to obtain a protein-sparing effect of either lipids or carbohydrates, at least in our experimental conditions. The high-protein diet resulted in the storage of energy excess as muscle proteins and hepatic glycogen. Tench fed the high-carbohydrate diet stored carbohydrates as muscle glycogen and reduced plasma triglycerides. Finally, both liver and muscle lipid content were in positive correlation to dietary lipid.     

Artificial reproduction in 1-year-old tench (Tinca tinca L.)

Although it is generally accepted that sexual maturity of tench (Tinca tinca L.) is not reached before 2–3 years of age, a successful experiment on artificial reproduction in 1‐year‐old tench is described. It was possible to obtain semen and eggs from 48% of males and 27.7% females kept in a small concrete tank at a final density of 3 kg m⁻³ and fed on a commercial dry diet. Two hormonal treatments were applied: the first with 1354 degree‐days and the second with 2353 degree‐days. In each experiment, the positive response in males and females was around 80%. Total egg production exceeded 11% of body weight, fertilization rate was above 90% and hatching rates around 50%. These results differ little from those reported for older breeders.     

Enhanced granulocyte phagocytosis at low winter temperature and high summer temperature in the tench (Tinca tinca L.)

Tench were captured in summer and winter when water temperature was 30 ± 3°C and 12 ± 2°C, respectively. Blood granulocytes were assayed for mobility capacity and phagocytic and microbicide capability to Candida albicans at 22°C and 30°C in summer and at 22°C and 12°C in winter. The results showed that tench granulocytes were more active in winter than in summer, and that phagocytic function was greatest at the seasonal temperature (30°C in summer and 12°C in winter) with respect to 22°C. This study suggests the importance of seasonally in the study of temperature effects on fish phagocyte function.     

Genetic structure and divergence of tench Tinca tinca European populations

The tench Tinca tinca is a freshwater species with human-mediated translocations, aquaculture interest and limited information on its genetic structure. mtDNA sequencing analysis of control region and two genes in 50 individuals from five European populations identified two phylogroups, with greater variability than that reported until now, and a hybridization zone in the Danube River region. Restriction analyses of additional samples reveal the complicated genetic structure characteristics of tench's wild and translocated populations, supporting future breeding practices.     

Product quality in different strains of tench (Tinca tinca) tested under controlled environmental conditions

Tench is produced in pond aquaculture in Europe and is highly valued by consumers. However, little is known about the product quality of this species, including body composition and flesh quality which are relevant for processing, storage and marketing. The experimental investigations indicate that tench are favorable in several parameters of body composition, e.g. carcass yield and fillet percentage, when compared with common carp. Organ weights show a trend toward a lower percentage than in other cyprinids. Composition of the tench fillets is similar to that of common carp. However, tench are able to store large amounts of fat on the fillet surface and intramuscularly, significantly affecting the sensorial characteristics. Technological parameters indicate that tench fillet is quite favorable for processing. In most of the samples analyzed, the water‐binding capacity of raw muscle was significantly better than in other species. Owing to a high energy content in tench muscle, the post‐mortem decrease in pH is very pronounced, which may lead to a rapid autolytic degradation of the tissue. When compared with common carp, tench fillets were favorable in terms of appearance due to a lighter flesh. Large variations in several product quality parameters reflect differences in fish size, age, sex, feeding, and genetic origin.     

The haematology of gynogenic tench, Tinca tinca L., and of recessively homozygous colour tench strains

Two wild‐coloured strains of tench (the first meiotic gynogenic generation MeiG₁, and their control diploid half siblings) and three recessively homozygous colour strains (golden, blue and alampic) were examined for the determination of basic haematological indices. The MeiG₁ strain had higher erythrocyte counts than diploid controls or the blue and alampic strains (P < 0.001), and had a higher blood haemoglobin content than all three colour strains (P < 0.001). No differences were detected among strains for haematocrit, mean corpuscular haemoglobin, or mean corpuscular volume. Both the lowest leucocyte count (P < 0.001) and leucocrit value (P < 0.001) were found in the alampic tench, and may result from a negative pleiotropic effect of this recessive homozygous genotype (bbgg). In agreement with previous findings in tench, the differential leucocyte count revealed lymphocytes to be the dominating white blood cells; their rate was about 90% in both the wild‐coloured and blue strains, and less in the other two strains (83–84%). Neutrophil granulocytes were most abundant in the MeiG₁ strain. Eosinophil granulocytes were detected only in the golden strain, and were not common (0.2%).     

Modification of neurosecretory cells in the preoptic nucleus of tench (Tinca tinca) and of various plasm ions following an elevation of water temperature]

Temperature increasing in water is responsible in Tench of on activity decrease in neurosecretory cells of preoptic nucleus, and of an increase in sodium plasmatic concentration. Influence of parameter is discussed.     

Topographical relation between the olfactory bulb and the olfactory tract in tench (Tinca tinca L)

Electrical activity was recorded from single cells in the olfactorybulb when electrically stimulating the medial and lateral olfactorytract and when stimulating the olfactory epithelium with aminoacids. Bulbar units excited by stimulation of the medial olfactorytract were found in the medial and middle parts of the bulb.Neurones in the dorso-lateral part of the bulb were excitedby stimulation of lateral tract. Units inhibited by stimulationof the lateral or medial olfactory tracts had a reversed distributionwith the majority found in the medial or lateral parts of thebulb respectively. The chemicals tested induced changes in thedischarge of units mainly situated in the lateral part of thebulb.     

Difference in blood and water diffusion distance in gill lamellae of diploid and triploid tench Tinca tinca (L.)

Image analysis of sagittal sections of gill lamellae of diploid and triploid tench Tinca tinca revealed the blood and water diffusion distance in diploids (2·07 μm) to be significantly higher than that of their triploid siblings (1·46 μm; P < 0·01). Lamellae of diploids compared to triploids were found to be significantly shorter (105·84 v. 132·11 μm) and thicker (18·47 v. 14·21 μm; all at P < 0·05) than those of their triploid siblings but with similar mean sectional areas (1965·44 v. 1910·86 μm²).     

PCR–RFLP analysis of mitochondrial DNA in tench Tinca tinca

Polymorphism was detected at ND1, ND6, D‐loop and cyt b segments of mtDNA in 105 tench (Tinca tinca L.), using the polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) technique and five composite haplotypes were identified. The diversity indices and the results of the population comparisons revealed that the identified markers provide a powerful tool for further studies on this species.     

Response of juvenile tench Tinca tinca (L.) to the anaesthetic 2-phenoxyethanol

The response of tench Tinca tinca aged 40–171 days post‐hatch (22–49 mm TL) to the anaesthetic 2‐phenoxyethanol was studied at 25°C. The lowest effective concentration of 2‐phenoxyethanol increased with age, while the highest safe concentration decreased. The fish aged 40 days post‐hatch required a significantly (P ≤ 0.05) shorter time to become anaesthetized than did older fish. The recovery time after 15 min of exposure to 2‐phenoxyethanol at 0.45 g dm^?3 was significantly shorter in the 40‐day‐old fish than in older fish. In juveniles of the same age, induction time or recovery time did not depend on their size or condition (Fulton's coefficient). At 25°C, 2‐phenoxyethanol at 0.5 g dm^?3 may be used to efficiently and safely anaesthetize T. tinca juveniles.     

A performance test with five different strains of tench (Tinca tinca L.) under controlled warm water conditions

Growth performance tests were carried out with a total of five different strains of tench (Tinca tinca L.) originating from the Czech Republic (4) and Germany (1). Tench larvae and juveniles were reared in closed recirculating systems for 446 to 452 days, respectively. At the end of each test, the tench strains showed differences in performance, e.g. specific growth rates (SGR) from 2.13 to 2.52, feed conversion ratios (FCR) from 1.75 to 3.65 kg feed per kg weight gain, and survival rates from 64.4 to 81.0%. Thus, appropriate strain selection appears to have the potential to remarkably increase productivity of the species. The highest SGR was observed in the Vodnany 96 strain in the first trial and the best FCR in the Tabor strain in the second trial. However, the rearing conditions in the recirculating systems were not optimal for tench; many fish with deformed bones (head, fins, spine) were observed in all strains, particularly in the faster‐growing strains.     

Successful gonadal development and maturation of tench (Tinca tinca L.) in small concrete ponds

The experiments were performed in a tench farm from autumn until the spawning season (June–July). Tench broodstocks from natural habitats were maintained in 25 × 6 × 1 m concrete ponds and fed on commercial trout pellets. Females and males were separated and maintained under natural photoperiod and temperature conditions at densities around 2 kg m^?2. Water flow throughout was supplied at the rate of 15 L s^?1. When females showed external signs of advanced gonadal development, induction of spawning was made by luteinizing hormone releasing factor (LH‐RH) synthetic analogue administration at three different periods of the reproductive season (June–July). A single intramuscular injection (20 μg kg^?1 body weight) was administered to 110 mature females selected from a total of 150. The females were stripped 42 h (22°C) after hormone administration. The mean rate of stripped females to the number injected was 77%. Mean relative egg weight in relation to the weight of the stripped females was 5.61%. More than 90% of the males provided semen without hormonal induction. Differences in egg production and external egg quality were observed at different times of the spawning period. It was proven that tench maintained in small concrete tanks and fed on artificial diets were able to reach gonadal maturation.