Feeding strategy and growth of cyprinids in the littoral zone of Lake Balaton

The growth, diet and feeding strategy of five phytophil or phytolithophil species of Cyprinidae from the littoral habitats of Lake Balaton were investigated by examining their scales and foregut contents. The relationships between the total anterior radii of scales and the standard lengths were represented best by a power function for white bream Blicca bjoerkna , and linear functions for common bream Abramis brama , roach Rutilus rutilus and wild goldfish Carassius auratus gibelio , respectively. The backcalculated mean lengths for the first age groups of common bream, white bream and roach did not differ statistically from those obtained by direct observation on 0 group fish in late November 1995. Compared to other waters, common bream grows slowly, wild goldfish and roach rapidly, while the growth rate of white bream can be considered of medium speed in Lake Balaton. Common bream showed a generalized feeding pattern, consuming mainly chironomid larvae, detritus and Corophium curvispinun . Roach showed a clear shift between specialization for Dreissena and algae. Despite the dense population of D. polymorpha in the lake, the significance of the herbivorous adaptation of roach has not yet been made clear. Wild goldfish consumed mainly detritus but, in the open water region, it shifted to zooplankton. White bream preyed chiefly on D. polymorpha , but showed a mixed feeding pattern and utilized most of the available food resources. Carp had the most specialized feeding strategy and preyed mainly on D. polymorpha . According to the discriminant analysis, the five cyprinids exhibited significant food resource partitioning.     

Structure,development and function of the branchial sieve of the common bream,Abramis brama,white bream,Blicca bjoerkna and roach,Rutilus rutilus

Synopsis The filter feeding organ of cyprinid fishes is the branchial sieve, which consists of a mesh formed by gill rakers and tiny channels on the gill arches. In order to establish its possible role during growth we measured the following morphological gill raker parameters over a range of sizes in three cyprinid fishes, bream, white bream and roach: inter raker distance, bony raker length, raker width, cushion length and channel width. At any given standard length common bream has the largest inter raker distance, roach the lowest and white bream is intermediate. In the comb model of filter feeding the inter raker distance is considered to be a direct measure of the mesh size and retention ability (= minimal size of prey that can be retained) of a filter. For the three species under study there is a conflict between the comb model and experimental data on particle retention. Lammens et al. (1987) found that common bream has a large retention ability whereas roach and white bream have a much smaller one. A new model, the channel model (Hoogenboezem et al. 1991) has been developed for common bream; in this model the lateral gill rakers can regulate the mesh size of the medial channels on the other side of the gill slit. The present data indicate that this model is not appropriate for white bream and roach. At any given standard length white bream and roach only reach 70% of the raker length of common bream, which means that in this model the gill slits should to be very narrow during filter feeding. The gill rakers consist of a bony raker and a fleshy cushion. The bony rakers have a rather long needle-like part outside the cushion in bream, but not in white bream and roach which have blunt gill rakers. Blunt gill rakers are not suited to reduce the diameter of the medial channels. The comb model seems more appropriate for white bream and roach, but doubts about the validity of this simple model remain. The sum of the areas of the medial channels is an approximation of the area through which water flows in the filter. This channel area therefore gives an impression of the capacity or flow rate of the filter. With this capacity estimation and an estimation of energy consumption we calculated an energy ratio of filter feeding. The energy ratio decreases with increasing standard length with an exponent close to the expected exponent of -0.40. The energy ratio is highest in bream, intermediate in white bream and lowest in roach.     

Influence of diurnal rhythms of feeding during intestine total amylolytic activity and activity of alkaline phosphatase in juvenile fish

The total amylolytic activity and activity of alkaline phosphatase in the intestine mucosa of larvae and fries of roach, blue bream, and perch change both during the process of individual development and during the day. Maximal intensities of juvenile feeding was observed primarily in the morning and evening hours. The pattern of diurnal alkaline phosphatase activity correlates to a greater extent to intensity of juvenile feeding, in comparison to the pattern of total amylolytic activity. In planktivorous blue bream, such regularity is more pronounced than in benthivorous roach. The total amylolytic activity in fries of roach, blue bream and perch correlates to fish type of feeding.     

An association of melanophores appearing at metamorphosis as vehicles of asymmetric skin color formation with pigment anomalies developed under hatchery conditions in the Japanese flounder, Paralichthys olivaceus

The mechanisms for asymmetric skin color formation in the Japanese flounder are studied with particular concerns to causes for pigment disorder (hypomelanosis) occurring under hatchery conditions. For an analysis of normal pigmentation, fish were raised with wild zooplanktons in an indoor hatchery, whilst for hypomelanosis, they were raised with Brazilian Artemia nauplii, a diet used in the hatcheries. Morphological observations, counting of melanophores, histochemical assay of DOPA-positive immature cells (melanoblasts), and radiometric estimation of tyrosinase activities in skins of developing larvae and juveniles indicate that 1) the structural plan for pigmentation in this species is bilaterally symmetric until metamorphosis, utilizing large-sized melanophores (hence larval melanophores) as main vehicles, and 2) an asymmetric coloration characteristic to metamorphosed juveniles is formed by an intensive development of smaller-sized melanophores (hence adult-type melanophores) appearing selectively in the ocular side at the later stages of metamorphosis and by an absence of it in the blind. These findings apparently indicate that 1) two types of melanophores occur in this species which differ with respect to morphological properties and developmental fate, and 2) selective differentiation of adult type melanophores in the ocular side of the body at or after metamorphosis is primarily responsible for an asymmetric coloration of its adult form. The similar assays on the fish fed with Artemia nauplii indicate that defective development of adult-type melanophores results in hypomelanosis in their ocular-sided skins, yielding a pigmentary pattern seen in the blind side of the metamorphosed juveniles with normal pigmentation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regeneration of the skin pigment system during larval development of the clawed frog

We demonstrate regeneration capability of the skin pigment system of clawed frog larvae after local damage to melanophores without skin rupture. The contribution to recovery of pigmentation of the injured area of de novo differentiation of melanophores is compared to contribution of mitotic division of undamaged melanophores localized on the boundaries of the injured area. The regeneration process is observed during various stages of pigment system development of larvae. We establish that, compared to ontogenetic dynamics, pigmentation development in animals is more intense during the regeneration.     

The role of predation and competition in determining the distribution of common bream,roach and white bream in Dutch eutrophic lakes

Synopsis Most of the lakes in The Netherlands are turbid and without vegetation. This is regarded as the result of increasing eutrophication within the last decades. Under these conditions common bream, roach, and white bream are the most common cyprinids. In six shallow (1–3 m), wind exposed lakes the abundance of common bream and roach was linked to the abundance of pikeperch; bream dominated when pikeperch was abundant, but when the latter species was rare, roach was dominant and the biomass of bream was reduced. The biomass of white bream was always relatively low. In lake Tjeukemeer the distribution of roach < 20 cm fork length (FL) and bream was also related to the distribution of pikeperch. Only roach > 20 cm FL managed to coexist with pikeperch in the open water area, whereas roach < 20 cm was confined to the littoral zone where pikeperch was nearly absent. Bream occurred mainly in the open water and avoided the littoral zone where it competed with roach. White bream occupied an intermediate position, occurring in relatively low density both in the littoral zone and in open water. The importance of predation and competition in determining the distribution and abundance of roach and common bream in the eutrophic lakes of The Netherlands is discussed.     

Controlled breeding studies to verify the identity of roach and common bream hybrids from a natural population

The occurrence of post-F1 generation hybrids between common bream and roach in natural populations has still to be qualified. To do this, common bream, roach, F1 and F2 hybrid progeny were produced under controlled conditions. All progeny groups exhibited overlaps in the ranges of their meristic characters. Discriminant analysis of meristic data combined with allozymes allowed identification of post-Fl hybrids. Enzyme electrophoresis showed Fl progeny to be heterozygous at diagnostic loci. Back-crossed F2 progeny had a mixture of homozygosity and heterozygosity at diagnostic loci. Meristic and genetic analysis of fish from a natural population indicated that they were all F1 hybrids. Post-Fl hybridization cannot be ruled out from natural populations because Fl hybrids are known to be fertile. It is suggested that post-Fl hybrids were not detected either because of their low incidence of occurrence or due to biological phenomenon Such as inferior fitness.     

Specific features of expression of aspartate aminotransferase genes in early development of some cyprinid fishes and their intergeneric F1 hybrids

Temporal parameters of expression of the aspartate aminotransferase gene Aat-1 parental alleles were studied in early development of intergeneric reciprocal F1 hybrids of the bream, roach, and blue bream. When the first AaT-1 expression was timed to the early stages (late blastula-gastrula), the gene parental alleles were activated asynchronously according to the maternal types (blue bream x roach hybrids). When the first Aat-1 expression was timed to later stages (yolk sac resorption), the parental alleles were activated synchronously (bream x roach, roach x bream, and roach x blue bream hybrids). The pattern of activation of embryonic genes is determined by the maternal environment and the influence of allele interactions is not excluded: Aat-f/Aat-sl (bream x roach, roach x bream, and roach x blue bream) and Aat-sl/Aat-med (blue bream x roach).     

Effects of preservation on pigmentation and length measurements in larval lampreys

The effects of two methods of preservation (fixation and storage in 10% formalin, and fixation in 10% formalin followed by storage in 95% alcohol) on pigmentation and morphometric features used for identification of larval Ichthyomyzon lampreys were analysed. Both short‐term (3 weeks) and long‐term (6 months) studies were conducted using digital analysis of images of fresh and preserved lampreys. Six standard morphometric lengths and 10 areas of pigmentation were analysed. All measurements were significantly affected by preservation. Preservative type affected pigmentation and morphometric characteristics differently, and characters were affected to different degrees. Multiple measurements over time showed that almost all changes occurred within 3 weeks of preservation. Regression equations allowed for accurate correction of preservation effects on morphometric measurements, but the effects on pigmentation levels were less predictable. Effects of preservation on larval lampreys need to be considered when comparing fresh and preserved specimens because they influence critical identification features.     

Polymorphism of A, B and C loci of lactate dehydrogenase in European fish species of the Cyprinidae family

In 24 fish species of the Cyprinidae family, belonging to 21 genera, isoenzyme patterns of lactate dehydrogenase (LDH) were determined, which could be classified in the majority of cases into 3 main groups. Isoenzyme patterns in natural hybrids of roach and rudd, roach and bream, roach and bleak were also analysed. In bitterling, polymorphism was observed in B locus of LDH. In white bream polymorphism exists in the A locus. In bream, rudd, silver carp and barbel polymorphism was found in C loci. Isoenzyme patterns indicate that in each case the polymorphism is genetically controlled by two alleles at a single locus. The populations investigated were in Hardy-Weinberg equilibrium. No significant differences were found in the activity of liver LDH in various polymorphic types of C loci of bream and rudd.     

体色异常褐牙鲆皮肤色素及鳞片发育的形态学研究

本文观察比较了体色正常及体色异常褐牙鲆 (Paralichthysolivaceus)皮肤中黑色素胞和鳞片的发生及演变过程。结果显示仔鱼鱼体两侧皮肤中最先出现星状幼体型黑色素胞 ,随着变态发育 ,有眼侧皮肤中成体型黑色素胞逐渐替代幼体型黑色素胞 ;而无眼侧皮肤中 ,幼体型黑色素胞逐渐退化崩解 ,成体型黑色素胞不出现 ,无眼侧皮肤逐渐失去色素变为白色。体色异常现象出现于变态后期 ,白化和黑化现象几乎同时发生。白化个体有眼侧皮肤中成体型黑色素胞不能正常替代幼体型黑色素胞 ,逐渐失去色素形成白色斑块。黑化个体无眼侧皮肤中成体型黑色素胞则非正常地出现 ,逐渐替代幼体黑色素胞形成黑斑。约 30日龄变态完成时 ,体色异常现象已经显著 ,已能明显区分体色正常和异常个体。 6 0日龄左右 ,幼鱼皮肤开始长出形态较为原始的圆鳞。体色正常个体有眼侧皮肤上的圆鳞会逐渐发育成栉鳞 ,无眼侧则维持圆鳞。对比分析体色异常个体的鳞片形态 ,发现有眼侧白化部位的鳞片仍为圆鳞 ,而无眼侧黑化部位的鳞片则发育为栉鳞。同时 ,通过对体色正在恢复中的白化牙鲆的鳞片观察表明 ,伴随着白化部位色素的恢复 ,该部位的圆鳞会逐渐转变为栉鳞。由此推断色素的发生与鳞片的发育密切相关     

Feeding of benthophagous fish in the Chogray Reservoir

Data on feeding of the bream Abramis brama, roach Rutilus rutilus, and white bream Blicca bjoerkna in Chogray Reservoir in 2010 and 2012 are presented. The main diet of bream consists of Chironomidae, and the diet of roach and white bream consists of the bivalve mollusk Dreissena polymorpha.     

Fish drift in a Danube sidearm‐system: II. Seasonal and diurnal patterns

Seasonal and diurnal patterns of larval and juvenile fish drift were investigated in the Marchfeldkanal, a man‐made side branch of the Danube River near Vienna, Austria. A clear seasonal pattern with peak densities in mid‐June was found. Species composition varied over time, showed a site specific pattern and was dominated by tubenose goby Proterorhinus marmoratus . Water temperature was the main factor responsible for the increase of drift densities until the median drift date and repeated occurrence of early larval stages in drift indicated repeated spawning for many species. Significant differences in drift densities between different time periods of the day (day, dusk, night and dawn) were found for common bream Abramis brama , barbel Barbus barbus , chub Leuciscus cephalus , tubenose goby and roach Rutilus rutilus . The highest drift rates occurred at night (2200–0400 hours), with 86% of all larvae drifting during the hours of darkness. Fish larvae of different lengths drifting at different phases of the day were found for common bream, bleak Alburnus alburnus and chub, with largest larvae drifting during dusk (chub) and day (bleak and common bream). For bleak, all gudgeon species Gobio spp., tubenose goby, roach and for all cyprinid species combined, one 2 h night sample was found to be sufficient to predict the total 24 h drift.     

Neural crest cell behavior in white and dark embryos of Ambystoma mexicanum: Epidermal inhibition of pigment cell migration in the white axolotl

Melanophores in larvae of the white (dd) strain of the Mexican axolotl (Ambystoma mexicanum) are confined to the dorsal midline of the trunk and dorsal posterior part of the head, whereas those in dark larvae (D_-) are distributed over the flank as well. Our results show that this phenotype of white larvae is the result of the failure of the melanophores or their neural crest precursor cells to migrate laterally due to an inhibition of or a failure in the support of their migration in the subepidermal space by the overlying epidermis. Correlated light and scanning electron microscopy of dissected larvae showed melanophores occupying the subepidermal space on the flank of dark larvae, whereas these cells were restricted to the dorsal midline of white larvae. Grafting experiments in which patches of epidermis, the underlying mesoderm, or both, were exchanged between dark and white embryos suggested that white epidermis alone can prevent the integration of pigment cells on the flank of dark larvae and, conversely, that grafts of dark epidermis alone can support their migration on the flank of white larvae. Mesoderm, when grafted alone, could not be shown to have similar effects.     

Specific features of expression of aspartate aminotransferase genes in early development of some cyprinid fishes and their intergeneric F1 hybrids

Temporal parameters of expression of the aspartate aminotransferase gene Aat-1 parental alleles were studied in early development of intergeneric reciprocal F1 hybrids of the bream, roach, and blue bream. When the first Aat-1 expression was timed to the early stages (late blastula-gastrula), the gene parental alleles were activated asynchronously according to the maternal types (blue bream × roach hybrids). When the first Aat-1 expression was timed to later stages (yolk sac resorption), the parental alleles were activated synchronously (bream × roach, roach × bream, and roach × blue bream hybrids). The pattern of activation of embryonic genes is determined by the maternal environment and the influence of allele interactions is not excluded: Aatf/Aat-sl (bream × roach, roach × bream, and roach × blue bream) and Aat-sl/Aat-med (blue bream × roach).     

Ecological consequences of food partitioning for the fish population structure in a eutrophic lake

In the highly eutrophic lake, Frederiksborg Slotssø, the diet composition of the bream (Abramis brama L.) and roach (Rutilus rutilus L.) populations was examined during three periods with different food availability. The length range of bream and roach was 9–34 cm (TL) and 5–18 cm (TL), respectively. The relative food composition was examined for 2 cm and 1 cm length intervals of bream and roach, respectively. During all three periods, bream shifted from benthic cladocerans (Alona sp.) to zooplankton and chironomids within a transitional length of 15.0–20.0 cm. These foodshifts were coupled with a change in feeding behaviour from particulate to filter feeding. The biomass of chironomids was too low to sustain the consumption of larger bream (>20.0 cm) which initiated feeding in the pelagic zone even in periods when the mean length and biomass of the preferred zooplankton, Daphnia cucullata, were low. In contrast to bream, roach fed mainly on zooplankton. With increasing size, roach progressively shifted to larger zooplankton species due to the increasing mesh size of their branchial system. The importance of benthic animals in the diet of roach was minor due to low feeding efficiency on prey buried in the sediment. Detritus appeared in the diet of bream and roach in periods of low availability of animal food items. Feeding on detritus may provide an energetic advantage to bream and roach and increase the carrying capacity for these species in lakes, where detritus is highly abundant. Especially for the larger fish due to the decrease in their relative metabolic demands. However, the ability of bream to filter feed and with increasing size to retain food items smaller than those retained by roach may be the main mechanism for the dominance of bream over roach in highly eutrophic lakes.     

三种普通欧洲鲤科鱼类(拟鲤、粗鳞鳊和欧鳊)人工杂交F1代形态学观察

对反交试验获得的18个月的拟鲤、粗鳞鳊和欧鳊F1代进行了鉴定.对不同于拟鲤、粗鳞鳊和欧鳊三种鱼的可量和可数形态特征分析表明,拟鲤×欧鳊和拟鲤×粗鳞鳊杂交种比粗鳞鳊×欧鳊杂交种与它们的双亲更容易区分.拟鲤杂交种间具有很多形态上的相似性,例如,上侧虹膜在拟鲤为红色,杂交种则介于双亲之间.在粗鳞鳊×欧鳊杂交种中也可以观察到居间类型.拟鲤×粗鳞鳊和拟鲤×欧鳊各自的杂交种可以通过眼睛的大小、较少的侧线鳞数和2行咽喉齿等特征相区分.粗鳞鳊×欧鳊杂交种与另外两个杂交种相比,具有更多的臀鳍分支鳍条数和一个中央具一黑线的虹斑.三个种进行杂交再获得的互交种通常不易区分.     

Larvae and juveniles of the plunderfishes <Emphasis Type="Italic">Artedidraco shackletoni</Emphasis> and <Emphasis Type="Italic">A.</Emphasis><Emphasis Type="Italic">skottsbergi</Emphasis> (Notothenioidei,Artedidraconidae) from the Indian sector of the Southern Ocean

Early life stages of Artedidraco skottsbergi and A. shackletoni were collected off Adélie Land. The morphology and pigmentation pattern of nine larvae and juveniles of A. skottsbergi between 17.2 and 21.4 mm in standard length (SL), and of two juveniles of A. shackletoni measuring 25.1 mm SL were described. A. skottsbergi was characterized by a heavily pigmented body, except for the caudal peduncle, with distinctively dense pigmentation on the ventrolateral half of the body and caudal section (17.2–17.9 mm SL). Furthermore, they had no pigmentation on the pectoral fin base until they attained 21.4 mm SL. Juvenile A. shackletoni had a heavily pigmented body except for the ventral side of the abdomen and the anal fin base. The proximal part of the dorsal fin and most of the anal fin were covered with melanophores. Although knowledge of larval and juvenile Artedidraco species is limited, the distribution of melanophores on the fins, pectoral fin base and caudal peduncle at each developmental stage may be useful for species identification.     

Observations on morphological and biochemical features of some cyprinid hybrids

Roach, rudd and bream and hybrids between roach x rudd and roach x bream have been examined morphologically and by electrophoretic separation of their serum proteins. Identification by both methods agree and it is suggested biochemical methods of identification may be of value in cases of difficulty when distinguishing hybrids by morphological methods.     

Melanophore appearance in wild and red tilapia embryos

Red tilapia has aroused interest in many countries for its commercial potential. This tilapia strain combines a desirable coloration and appearance with other advantageous farming characteristics. To study the early appearance of melanophore pigmentation in tilapia, a red tilapia strain originating from Thailand and a wild type coloration of Oreochromis niloticus were used as broodstock to produce artificially wild x wild and red x red progenies. The larvae were assessed periodically up to the first feeding and were recorded. Wild type fish showed a regular appearance of stellate melanophores. In the red strain, the pattern of chromatophores varies from total absence of black spotting to different degrees of macromelanophore distribution. Comparison between red and wild types showed that these two tilapia can be easily scored at day 7. Further, we present indications that the pigmentation over the body develops independently of the initial degree of pigmentation.