Sperm characteristics in perch Perca fluviatilis L.

Sperm densities in perch Perca fluviatilis males showed a positive correlation with the amount of stripped milt. Sperm flagellum length did not correlate with body mass, but a significant correlation between flagellum length and the total number of sperm produced was found.     

Intraspecies variation of reproductive strategies in perch (Perca fluviatilis)

The variation of reproductive strategies in different populations of perch and intrapopulation groups differing in the rate of growth have been analyzed. Using a bioenergetic approach, the origin and differences between these groups have been studied. It was shown that bioenergetic mechanisms of regulation of the sizes and weight of the eggs lead to formation of the strategy of forced reproduction in the slow-growing group of perch, unlike the reproductive strategy of the fast-growing group of perch characterized by a later reaching of sexual maturity at a greater relative weight of gonads and spawning of larger eggs, which provides for a longer lifespan of larvae. The great number of age groups in the spawning part of this group compensates for a decrease in reproduction in years with unfavorable conditions.     

Swimming activity of perch, Perca fluviatilis L.

The swimming excursions of individual perch, measured automatically, within either cages in Windermere or in a trough on the shore, showed increases at dawn and dusk and in the summer. Similar measurements in troughs in the laboratory showed increased activity following a change from light to dark and vice versa, a pattern that was obliterated by either continuous light or continuous darkness. These results are discussed in relation to water temperature and catches of perch in traps.     

Laboratory experiments on prey selection by perch fry (Perca fluviatilis)

SUMMARY. In laboratory experiments, prey selection of zooplankters by starved perch fry ( Perca fluviatilis ) from Windermere, English Lake District, is temporally variable and there is usually, in the short-term, a persistent succession from one actively selected prey species to another. Provided that the prey is visible, the patterns of prey selection are maintained irrespective of the accessibility of the prey. The fish do not optimize their energy intake per effort. The method of observing predation activity by fish shows qualitative and quantitative prey selection as time progresses in great detail.     

Energetics and metabolic correlates of starvation in juvenile perch (Perca fluviatilis)

Long-term measurements of the diurnal pattern of oxygen consumption were conducted in fasting juvenile perch at 15 and at 20° C. In addition, dry body mass, protein and glycogen concentrations and the activity of two key enzymes of energy metabolism, phosphofructokinase and glutamate pyruvate transaminase, were monitored during the period of food deprivation. The average rate of oxygen consumption decreased during the starvation period, but the regular diurnal pattern of low rates in the dark and high rates in the light was upset by a break around days 7 to 8 at both temperatures. This break coincided with the exhaustion of the glycogen reserves in the muscles and in the liver, indicating that switching to a new energetic fuel was accompanied by a change in the pattern of swimming activity. Choice of the major energy source after exhaustion of the carbohydrate store was substantially influenced by water temperature. A negative correlation was found between the scope for spontaneous activity and the specific rate of oxygen consumption in the dark phase suggesting that the resting rate of metabolism responded more strongly to food deprivation than the rate of spontaneous activity in the light phase.     

河鲈胚胎及卵黄囊期仔鱼发育

为探究河鲈(Perca fluviatilis)早期生活史和发育生物学,采用体视解剖镜、显微镜仔细观察、测量、描述、绘图的方法,连续观察了6个批次河鲈胚胎及卵黄囊期仔鱼发育状况,进行比较分析。结果显示:(1)在水温8~13℃时,胚胎期约需265h,有效积温2540~2880℃.h;水温11~13℃时,卵黄囊期约需6d,有效积温1750~2120℃.h;(2)辐射状次级卵膜将受精卵连成长带形单层网片状,每个胚胎周围有6个胚胎,排列很有规则。胚胎卵黄囊表面有一个大圆形油球。出膜前期可见眼球色素、胸鳍突起;(3)胚胎出膜的不同步主要是由于出膜前期长短不一和孵化水温较低所致。     

Hepatic glucose phosphorylating activities in perch (Perca fluviatilis) after different dietary treatments

Increased activity of hepatic glucose phosphorylation was observed in perch after feeding previously fasted fish. When a pellet diet containing 14% carbohydrate was given, most of the increased activity had a low affinity towards glucose (S0.5 = 19.5 mM) and resembled the mammalian glucokinase (Hexokinase IV or D) and the glucokinase-like activity previously observed in salmon liver. In addition, increased activity of a hexokinase with high affinity towards glucose (Km = 0.50 mM) was observed with the pellet diet. An increase in the activity of this hexokinase alone was observed when the fish were fed with filet of cod containing less than 0.2% carbohydrate. Perch with a very high hepatic glucokinase-like activity after eating the pellet diet had high activities of pyruvate kinase and glucose-6-phosphate dehydrogenase, indicating a high capacity of glycolysis and carbohydrate utilization. Simultaneously, the activity of glycogen phosphorylase was strongly reduced while the activity of fructose-1,6-bisphosphatase was not significantly changed. These observations were made with perch captured in the spawning season and brought to the laboratory. Assays of glucose phosphorylation in livers of perch eating the natural diet (insects) in the lake showed no glucokinase-like activity.     

Responses of Acilius sulcatus (Coleoptera: Dytiscidae) to chemical cues from perch (Perca fluviatilis)

In this study we tested the hypothesis that the presence of chemical stimuli from a hungry predator would initiate anti-predator responses, while stimuli from a satiated predator would not. We used chemical stimuli released from starved perch (Perca fluviatilis) and from satiated perch (predator). As prey we used adult Acilius sulcatus (Coleoptera: Dytiscidae). The reaction of the beetles to different predator conditions was tested during daytime. We also tested the reaction to starved perch during the night. A. sulcatus activity decreased when it was exposed to stimuli released from starved perch during daytime when visibility was poor, due to the presence of artificial vegetation. There was, however, no reaction to satiated perch under the same experimental conditions. These results indicate that A. sulcatus can discriminate between chemical cues from hungry and satiated fish predators. When visibility was good and the concentration of chemical cues was constant, the beetles did not react to starved perch in the daytime, but their activity decreased at night in response to stimuli released from starved perch. Visual as well as chemical cues seem to be important for detecting a potential predator. When visibility is good, beetles seem to rely on visual stimuli, while in darkness they seem to use chemical stimuli to detect the presence of predators. Received: 4 October 1996 / Accepted: 7 February 1997     

Haemogregarina pseudemydis n. sp. (Apicomplexa: Haemogregarinidae) and Pirhemocyton chelonarum n. sp. in Turtles from Louisiana*

SYNOPSIS. The blood of each of 95 turtles (8 species) collected from southeastern Louisiana was infected with some or all of the merogonic stages and gametocyte stage of Haemogregarina pseudemydis n. sp. Five species of turtles harbored Pirhemocyton chelonarum n. sp. Turtle Haemogregarina and Pirhemocyton are locality records for Louisiana. Pirhemocyton is reported for the first time in turtles and in the continental U.S.A.     

Complexity of lectins from the hard roe of perch (Perca fluviatilis L.)

Fish eggs are a rich source of lectins, the sugar-binding (glyco)proteins. In this paper we aim to further characterise perch roe lectins using several protein characterisation techniques including affinity chromatography and protein sequencing. Perch roe lectins are comprised of two subunits, subunit A and subunit B which have molecular weights of 12,400 and 12,000, respectively. These subunits form multiple aggregates A_nB_n in which the two subunits are present in differing ratios and, also as an `homogeneous' aggregates of one of the subunits A_n or B_n. Lectins A_n (designated A thereafter) and lectin B_n (designated B thereafter) formed by one type of subunit only (subunit A or B) were isolated in a pure state. Lectin B could also be isolated by spontaneous precipitation occurring during incubation of the perch roe extract at 4°C. Lectin B has a higher affinity for d-glucose than lectin A, whereas both lectins (A and B) have a similar affinity for l-fucose. The N-terminal region of subunit B showed the following amino acid sequence: EPAXPPWGTQFG-, whereas the N-terminus of subunit A was blocked and therefore could not be directly sequenced. Differences between subunits A and B were also found in amino acid composition. This unusual complexity and variability of perch roe lectins is likely to have physiological significance which, as yet, remains to be determined.     

Retinal development and retinomotor responses in perch, Perca fluviatilis L.

The development of the retina of perch, Perca fluviatilis L., was studied for all developmental stages. The density of cones 100 μm-¹ was found to decrease with age, although their actual numbers increased. All premetamorphosed perch had pure-cone retinae, the rods developing at, or after metamorphosis. Retinomotor responses were found to commence after metamorphosis when the rods developed. Visual acuity, measured as the minimum separable angle (α), was observed to improve exponentially with age, and its value was found to depend more on the focal length of the lens, than on the number of cones in the retina. The cones in the unspecialized part of the retina were predominantly of the twin type and were related to single cones in a ratio of 4 : 1.     

Initial purification and characterization of hepatic microsomal cytochrome P-450 from BNF-treated perch (Perca fluviatilis)

1. A procedure was developed for isolating and purifying cytochrome P-450 from hepatic microsomes of BNF-treated perch, using modified versions of the methods of Williams and Buhler (1982. Biochim. biophys. Acta 717, 398-404) and Goks?yr (1985. Biochim. biophys. Acta 850, 409-417). 2. Following chromatography on phenyl-Sepharose CL 4B and DEAE-Sepharose CL-6B, the major peaks, fractions b and c, were resolved into five fractions, possibly representing different isoenzymes, by a FPLC with a strong anion exchange column (Mono Q). 3. These fractions have been characterized on the basis of their spectral, electrophoretic and immunological properties. 4. The purified form of cytochrome P-450 in fraction V from perch liver showed a number of similarities to cytochrome P-450c, the major BNF-inducible cytochrome P-450 in cod liver. 5. Therefore we suggest that this purified form of cytochrome P-450 is a BNF-induced form in perch and that it is closely related to the gene subfamily cytochrome P-450 IA1.     

The variability in numbers of perch Perca fluviatilis L. caught in traps

The variability in the catch of perch traps set in Windermere over the period 1955–70 has been analysed. Altogether 2690 catches in four series have been treated by analyses of variance after a logarithmic transformation. A representative value of the between traps variance from all sources of variation has been used to estimate the reliability of the mean catches based on different numbers of traps. It is shown that many traps are needed to obtain consistent results.     

Exceptionally big individual perch (Perca fluviatilis L.) and their growth

In Lake Windermere (U.K.) where there was a dense, slow-growing population of perch ( Perca fluviatilis L.) which had an l _x of about 180 mm, there co-existed a few individuals with an l _x of 463 mm. Data from 137 of these big perch, mostly caught in gillnets fishing for Esox lucius L., were examined. Their early growth was identical to that of normal perch, but, at an age, varying between individuals, from 1 to 8 and averaging 4 years, their growth accelerated for about 4 years and then followed a von Bertalanffy model with an l _x of 463 mm. They thus had a 'double' growth-curve that is revealed only if individual growth is examined. Acceleration tended to occur in certain calendar years and was correlated with strong year-classes of young perch. Growth was greater in years with warm summer water temperatures. There were no changes in the growth of big perch, after they had achieved 290 mm, during a period of great changes in the population density and an increase in the growth of normal perch < 290 mm. No more big perch were caught in Windermere between 1967 and 1990. Net selection, length-weight relationships, seasonal cycle in gonad weight, and opercular-body length relationship were the same as those of normal perch. The few available data suggest that big perch were piscivorous, feeding largely on small perch. The distribution of sites in the lake where big perch were caught is contagious, catches follow the negative binomial; but within fishings that caught big perch at the same site and time, catches were more evenly distributed than random. It is postulated that most adults would have accelerated their growth if they had sustained piscivory. Similar big perch have been found in other lakes.     

Seasonal variations in some blood parameters in perch, Perca fluviatilis L.

Clinical blood tests on fish exposed to contaminants are used extensively both in laboratory and field studies. Seasonal variability is examined in some of the parameters commonly used in health assessments. Hematocrit, hemoglobin concentration and inorganic ion concentration were studied in perch, Perca fluviatilis, from a Baltic brackish water area. Seasonal cycles were demonstrated in hematocrit and in chloride, magnesium and potassium ion concentrations. Other parameters studied reacted irregularly or only slightly to the shift of seasons.     

Proposed standard weight (Ws) equation for European perch (Perca fluviatilis Linnaeus, 1758)

Relative weight (W_r) is an important and commonly used condition index that provides a measure of the well‐being of a fish population by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and of the same length in good physiological condition, i.e. the standard weight (W_s). Two methods of calculating the standard weight are proposed in the literature: the RLP method and the EmP method. The aim of this study was to develop a standard weight equation for European perch by means of both methods, using length–weight data from 64 913 fish from 18 countries (across Europe and Oceania). The resulting equations were: log₁₀ (W_s) = ?3.1483 + 1.2663 log₁₀ (TL) + 0.4291 [log₁₀ (TL)]² for the EmP method and log₁₀ (W_s) = ?5.3493 + 3.2152 log₁₀ (TL) for the RLP method. The applicable length‐range of the two W_s equations was restricted to 80–460 mm. A further research aim was to compare the performances of RLP and EmP. The resulting quadratic EmP W_s equation did not exhibit length‐related biases, which suggests that it can be used to compute relative weight for European perch.     

Temperature effects on aerobic scope and cardiac performance of European perch (Perca fluviatilis)

Several recent studies have highlighted how impaired cardiac performance at high temperatures and in hypoxia may compromise the capacity for oxygen transport. Thus, at high temperatures impaired cardiac capacity is proposed to reduce oxygen transport to a degree that lowers aerobic scope and compromises thermal tolerance (the oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis). To investigate this hypothesis, we measured aerobic and cardiac performance of a eurythermal freshwater teleost, the European perch (Perca fluviatilis). Rates of oxygen consumption were measured during rest and activity at temperatures between 5 °C and 27 °C, and we evaluated cardiac function by in vivo measurements of heart rate and in vitro studies to determine contractility of myocardial strips. Aerobic scope increased progressively from 5 °C to 21 °C, after which it levelled off. Heart rate showed a similar response. We found little difference between resting and active heart rate at high temperature suggesting that increased cardiac scope during activity is primarily related to changes in stroke volume. To examine the effects of temperature on cardiac capacity, we measured isometric force development in electrically paced myocardial preparations during different combinations of temperature, pacing frequency, oxygenation and adrenergic stimulation. The force-frequency product increased markedly upon adrenergic stimulation at 21 and 27 °C (with higher effects at 21 °C) and the cardiac preparations were highly sensitive to hypoxia. These findings suggest that at (critically) high temperatures, cardiac output may diminish due to a decreased effect of adrenergic stimulation and that this effect may be further exacerbated if the heart becomes hypoxic. Hence cardiac limitations may contribute to the inability to increase aerobic scope at high temperatures in the European perch (Perca fluviatilis).     

Competition for minerals between Acanthocephalus lucii and its definitive host perch (Perca fluviatilis)

Concentrations of various essential and toxic elements (Ba, Ca, Co, Cu, Fe, Mg, Mn, Sr, Zn and Al, Ag, Cd, Cr, Ni, Pb, Tl) were analysed by inductively coupled plasma mass spectrometry in the acanthocephalan Acanthocephalus lucii and in different tissues of its host Perca fluviatilis. Nearly all the elements were found in significantly higher concentrations in the acanthocephalan than in the host tissues. Spearman correlation analysis revealed several strong inter-element associations within the organs of perch and within the parasites. Furthermore, statistical analysis revealed different competitive interactions. The concentrations of several essential elements (Ba, Ca, Fe, Mn, Sr and Zn) within the parasites decreased with an increasing number or weight of worms inside the intestine of the host. Additionally, the levels of some elements in the perch liver were negatively correlated with the weight of A. lucii in the intestine. Thus, it emerged that not only is there competition for essential elements between acanthocephalans inside the gut but there is also competition for these elements between the host and its parasites.