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In recent decades, the Amur sleeper (Perccottus glenii) is one of the most impressive east-to-west invaders of European inland waters, but there are insufficient data on its biology in the countries it has entered. Specimens of two sets of samples from November 2015 (n=25) and October 2016 (n=39) were caught in the Danube River channel near Veliko Gradiste (Serbia) by electrofishing. Thirty morphometric and eight meristic characteristics of the collected fish were measured with the aim of describing the general body shape in more detail using the ?point-to-point? method. This is the first attempt to obtain morphometric and meristic characteristics of Amur sleeper caught in Serbia. The results revealed a relatively low variability in the morphometric and meristic characters of the studied population. When compared to other studies, there was a great variability of the studied characteristics between geographically distant European populations that inhabit different water body types. Female fish had more robust bodies compared to males of the same length, while males had longer pectoral, anal and dorsal fins. Additionally, 2+ individuals had more robust heads and jaws, as well as longer anterior parts of the body compared to 1+ individuals of the same size

Accumulation of Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Si, Sr, and Zn was analyzed in gills, liver, gonads, and muscle of European chub (Squalius cephalus), Cactus roach (Rutilus virgo), and pikeperch (Sander lucioperca) from Zlatar reservoir (Serbia) using inductively coupled plasma optical emission spectrometry (ICP-OES). The highest concentrations of Cu in liver as well as Ba, Ca, Fe, Mn, Na, P, and Sr in gills were detected in all fish species, while the lowest concentrations of Cu, Fe, Mn, Na, and Zn were detected in muscle. Pikeperch had significantly lower concentrations of Ba in all tissues compared to the other species, as well as Fe, P, and Sr in muscle, K, Mg, Mn, Sr, and Zn in gills, and Fe in gonads. European chub had significantly higher concentrations of Ca, Cu, and Zn in muscle, Cu in liver, and Cr and Cu in gonads compared to Cactus roach and pikeperch. Cd concentration in one individual of Cactus roach exceeded the maximum allowed concentration. The muscle was exposed to the lowest pressure of metal pollution in all species, and European chub accumulated more metals compared to the other species. There is no significant health risk due to consumption of investigated species. A major hazard index (HI) contributor in all species was Hg. According to the target carcinogenic risk factor (TR), target hazard quotient (THQ), and HI, men are under lower health risk compared to the women. The TR and THQ for As, Cr, Cu, Fe, Mn, Ni, and Zn as well as HI values were higher for European chub compared to the other species. On the other hand, THQ for Hg was highest for pikeperch.

Paper description: We compared a model for spectral sensitivity data designed in our laboratory with the widely used template. Our model was designed with fewer (four) parameters, which we believe brings us closer to understanding the true nature of the absorption curve. In the fitting of spectral sensitivity data it uses non-transformed wavelengths. As a result, the shape of the curve remains the same for a broad range of l max values. Abstract: A four-parameter model of spectral sensitivity curves was developed. Empirical equations were designed for A 1 - and A 2 -based visual pigments with the main a-band maximum absorptions (l max ) from 350 nm, near the ultraviolet, up to 635 nm in the far-red part of the spectrum. Subtraction of the a-band from the full absorbance spectrum left a “b-band” described by a l max -dependent Gaussian equation. Compatibility of our templates with A 1 -and A 2 -based spectra was tested on the electroretinographic (ERG-derived) scotopic action spectra recorded in dogfish shark, eel, Prussian carp and perch. To more precisely estimate the accuracy of our model, we compared it with widely used templates for visual pigments. There was almost no difference between the tested models in fitting the above-mentioned spectral data. One of the advantages of our model is that in the fitting of spectral sensitivity data it uses non-transformed wavelengths and the shape of the curve remains the same for a broad range of l max values. Compared to multiparameter templates of other authors, our model was designed with fewer (four) parameters, which we believe can bring us closer to un derstanding the true nature of the absorption curve. https://doi.org/10.2298/ABS180822052G Received: August 22, 2018; Revised: November 7, 2018; Accepted: November 14, 2018; Published online: November 20, 2018 How to cite this article: Gacic Z, Mickovic B, Gacic L, Damjanovic I. New spectral templates for rhodopsin and porphyropsin visual pigments. Arch Biol Sci. 2018;71(1):103-10.

The surface area of Montenegro’s portion of the Black Sea drainage basin is 7075 km2, or 0.9% of the entire basin, and is made up of the rivers Tara, Piva, Lim, Ćehotina and Ibar, and Lake Plav. The major polluters of watercourses are wastewaters and solid waste from inhabited settlements. According to water categorization regulations, the rivers of the Danube Basin in Montenegro are, based on the status quo, classified into four quality classes. Thus, the mid- and lower courses of the larger rivers fall within quality classes II and III. The water quality of the Lim, downstream of Berane, worsens at its exit from Montenegro and falls into quality class III. The Ibar profile downstream of Bać is largely out of a prescribed class. The Ćehotina downstream of Pljevlja is in water quality class III, and occasionally out of a prescribed class. The Tara belongs to the Durmitor National Park, but its water quality is class I only at its most upstream profile; its profiles downstream of Kolašin are from class II to class III. These findings are confirmed by analyses of their aquatic macroinvertebrate communities, i.e. Oligochaeta, as bioindicators of water quality. The ichthyofauna of the Danube Basin rivers in Montenegro comprises 20 fish species. Hydromorphological alterations of watercourses, such as dam construction, have a significant effect on fish populations. Thus, the dam on the Piva river has a negative effect on the fish population, presenting a barrier to migration routes, as is the case with huchen or Danube salmon (Hucho hucho). Bănăduc D, Curtean-Bănăduc A, Pedrotti F, Cianfaglione K, Akeroyd JR, editors. Human Impact on Danube Watershed Biodiversity in the XXI Century. Springer, Cham; 2020. p. 241–56. (Geobotany Studies).

To shed light on thermoadaptive properties of Salmo trutta from lake Plav (Montenegro), we undertook kinetic studies of pyruvate reduction rates and thermal stability analyses of white muscle LDH. We compared these with the data obtained for trout of the same, confirmed by us, Danubian lineage living in rivers and streams of Serbia and Montenegro. We also tested the effect of acclimation in captivity at 4 and 14 °C. The lake trout was of a typical smoltified phenotype (the size, the elongated silver colored body). At physiological substrate concentration, the breaks in the Arrhenius plots (critical temperature - Tc) correlated with acclimation temperatures or habitat water temperatures. Q10 values for temperatures above Tc were close to one, in all cases except 4 °C acclimated trout. At temperatures below Tc Q10 was close to two, except in the case of 14 °C acclimated trout. Lake trout had a highest Q10 values at temperatures below Tc. It was conspicuous that within the entire range of tested temperatures the differences in Q10 resulted from the effect of environmental temperature. Higher Q10 values were obtained with LDH isolated from trout acclimated to 4 °C compared with LDH acclimated to 14 °C. Ea values were much lower at a temperature below Tc compared with temperatures above Tc. Thermal stability of muscle LDH was lower after acclimation to 14 compared to 4 °C, while extremely high thermostability was obtained with the lake trout enzyme. Our data support the concept that Tc values have distinct physiological significance.

Temperature dependence of electroretinogram (ERG) was investigated in 3 fish species occupying different habitats — dogfish shark ( Scyliorhinus canicula ), Prussian carp ( Carassius gibelio ) and European eel ( Anguilla anguilla ). Acute cooling of the shark isolated eyecup from 23 °C down to 6 °C induced suppression of the electroretinographic b-wave — a complete degradation of this component was observed at 6 °C. On the other hand, photoreceptor component of the ERG, the negative late receptor potential was not affected by cooling. The fact that the suppression of the dogfish shark b-wave at low temperatures was as a rule irreversible testifies about breakdown of neural retinal function at cold temperature extremes. Although in vivo experiments on immobilized Prussian carps have never resulted in complete deterioration of the b-wave at low temperatures, significant suppression of this ERG component by cooling was detected. Suppressing the effect of low temperatures on Prussian carp ERG might be due to the fact that C. gibelio , as well as other cyprinids, can be characterized as a warmwater species preferring temperatures well above cold extremes. The ERG of the eel, the third examined species, exhibited the strongest resistance to extremely low temperatures. During acute cooling of in situ eyecup preparations of migrating silver eels from 30 °C down to 2 °C the form of ERG became wider, but the amplitude of the b-wave only slightly decreased. High tolerance of eel b-wave to cold extremes shown in our study complies with ecological data confirming eurythermia in migrating silver eels remarkably adapted to cold-water environment as well.

Pikeperch (Sander lucioperca), European catfish (Silurus glanis), burbot (Lota lota), and common carp (Cyprinus carpio) were collected from the Danube River (Belgrade section, Serbia), and samples of liver, muscle, and gills were analyzed for Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES) to highlight the importance of species and tissue selection in monitoring research, contaminant studies, and human health research. The Kruskal-Wallis test revealed significant differences between fish species in regard to metal levels in liver, muscle, and gills. The principal component analysis (PCA) indicated that the studied fish species could be grouped on the basis of the level of analyzed elements in liver and gills. The Mann-Whitney test showed two subsets (one comprising two piscivorous species, pikeperch and catfish, and the other, two polyphagous species, burbot and carp) in regard to Cr and Hg levels in liver (higher levels in piscivorous species), as well as B, Fe, and Hg in gills (B and Fe with higher levels in polyphagous and Hg in piscivorous species), and As in muscle (higher levels in polyphagous species). Carp had distinctly higher levels of Cd, Cu, and Zn in liver in comparison to other three species. None of the elements exceeded the maximum acceptable concentrations (MAC). However, since Hg levels are close to the prescribed MAC levels, the consumption of these fishes can be potentially hazardous for humans.

In this study, 20 heavy metals and trace elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, Ni, Pb, Si, Se, Sr and Zn) were analyzed in different tissues (muscle, liver, intestine, feather and bone) of the great cormorant (Phalacrocorax carbo) and in different tissues (muscle, liver, gills, kidney and gonad) of their main prey (common carp—Cyprinus carpio and Prussian carp—Carassius gibelio) during the nesting season. Cormorant and fish specimens were collected at the Ecka Fishing Farm (Serbia) and from the nearby river. Principal components analysis (PCA) showed that cormorant livers were differentiated from other four tissues by higher concentrations of Hg, Fe, Cu and Mo, feathers by higher concentrations of Al and Si, and bones by higher concentrations of Sr and Mg. Differentiation among the three age classes of cormorants was observed only with regard to elemental concentrations in their feathers: subadult cormorants were differentiated by higher Hg and Zn concentrations, while the adults were separated by higher concentrations of Fe. In comparison with their prey (common carp and Prussian carp) cormorants were differentiated by higher concentrations of Fe, Hg and Cu in the muscle. Toxic mercury concentrations above 4 μg g−1 dw were determined in the liver of juvenile cormorants, as well as in the liver and feathers of subadults. Hg concentrations were significantly correlated among all studied tissues. Cormorant had significantly higher concentrations of Fe and Hg in muscle and liver than two studied fish species.

Three localities, representing three distinct coastal areas, were investigated: 1. the mouth of the Sutorina River; 2. the mouth of the Jaska River; 3. the mouth of the Bojana River (right branch). Regarding the composition of young mullet assemblages, Lisa saliens, Lisa ramada and Lisa aurata were dominant at the first locality; L. aurata and Chelon labrosus at the second; and at the third L. ramada was clearly dominant, Mugil cephalus occupied the subdominant position, while L. aurata was absent. The seasons of the first appearance of migratory fry were October, April, November, October and July, for M. cephalus, C. labrosus, L. ramada, L. aurata and L. saliens, respectively. Migratory periods varied from 2 (C. labrosus) to 7 (L. ramada) months.

In spectral sensitivity studies, electroretinograms (ERG) were recorded from the in situ eyecup of immobilized perch (Perca fluviatilis) electrofished in the floodplain zone of the Danube River. It is shown that the ERG b-wave is a good indicator of spectral sensitivity, although it reflects the activity of photoreceptors indirectly. With a maximum around 542 mm, the scotopic spectral sensitivity of perch obtained using fitted amplitude-log intensity functions for threshold calculation and two models developed in our laboratory for computer-assisted fitting of spectral sensitivity curves did not differ from the sensitivity determined using the microspectrophotometric and isolated pigment methods (maximum around 541 nm).

The action spectrum of the electroretinographic (ERG) b-wave and the unmasked late receptor potential (LRP) were measured under a variety of conditions (isolated eyecup, detached retina, b-wave recording in fresh preparations, LRP measurements after low-temperature aging, dark and light adaptation). It was shown that in the dogfish, Scyliorhinus canicula (L.), eyecup spectral sensitivity matched closely the pigment 502 spectral curve like other rhodopsin-possessing marine species. The ERG b-wave is as good an indicator of spectral sensitivity as the unmasked LRP that directly reflects the responsiveness of photoreceptors. Differences in spectral sensitivity were not revealed between dogfish preparations studied under a variety of conditions (isolated eyecup vs. detached retina; b-wave recording in fresh preparations vs. LRP measurements after low-temperature aging; dark vs. light adaptation). We developed a new model for spectral sensitivity data.

Several classes of second-order retinal neurons have been studied electrophysiologically in European eel (Anguilla anguilla) from two different localities, Lake Seliger in Russia and the coastal waters of the Adriatic Sea in Montenegro. The majority of L-horizontal cells (68 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Pronounced color-opponent properties, often taken as pointing to the capacity of color vision, were identified in one amacrine cell, apparently of the "blue/yellow" (or "blue/green") type. Microspectrophotometric measurements revealed two different spectral classes of cones with absorption maxima at about 525 and 434 nm. The existence of green-sensitive and blue-sensitive cone units was thus revealed by both electrophysiological and microspectrophotometric techniques.

The first record of Pseudorasbora parva in the Balkan region was in 1977 in Sasko Lake, Montenegro and in 1978 it was found in Serbia. Since then, this species has spread to almost all lowland rivers and has become a permanent member of the ichthyofauna in Serbia and Montenegro.

One of the purposes of this study was to examine whether b-wave measurements can be used in the evaluation of scotopic spectral sensitivity in Prussian carp measurements when the eyes were surgically deprived of cornea, lens, and most of the vitreous. Another goal was testing the new fitting procedure for A2-based photopigments. Using fitted amplitude-log intensity functions for threshold calculation, and two models for computer-assisted fitting of spectral sensitivity curves, no significant differences in λ max were found between rod photopigments and b-wave-based spectral sensitivity.

Several classes of second-order neurons have been electrophysiologically explored in immature European eels (Anguilla anguilla) from two distant and ecologically different localities (in Russia and Yugoslavia). The majority of L-horizontal cells (58 explored) had both rod and cone inputs, an uncommon phenomenon among teleosts. Spectral sensitivity characteristics of a number of horizontal and bipolar cells indicated that yellow-sensitive and green-sensitive cones coexist in the retina of the European eel, and that rods and green-sensitive cones contain similar visual pigments. Pronounced color-opponent properties, often taken as the capacity of color vision, were identified in one amacrine cell, apparently of the B:Y (or B:G) type. Differences in retinal structure and responsiveness between eels from the two localities, presumably due to differences in local conditions for growth, were less important than between eels of the yellow and silver stage. © 1998 Elsevier Science Inc. All rights reserved.

About 10000 huchen larvae, obtained by artificial spawning, were introduced on 28 May 1995 into the River Tresnjica, a tributary to the River Drina, using procedures applied routinely by local fishing associations. During next two months, only 33 fry were caught in the river. Nevertheless, valuable information has been obtained for the first time on young huchens in the Drina basin. The fry apparently selected slower or almost stagnant water habitats outside the main river course. The variability of prey organisms found in fry stomachs decreased with fry length. Larger and particularly motile prey, especially mayfly larvae, gradually dominated the fry diet. Also for the first time, we document homing instinct in huchens with mark‐recapture information: one out of the nine adults, tagged after spawning, was recaptured the following year at the same spawning site.

The characteristics of glass eel migration at the mouth of river Bojana have been investigated by seasonal field studies from February to April 1998. Samples were collected by two fyke nets, one on each riverside, for 12 hours each night. A total of about 3,300 individuals were caught. In this work we present the results obtained from three successive migration waves in 1998. The data obtained on the number of eels caught during one migration wave, as a function of time, had two components: a bell-shaped curve, lasting 7-14 days, over which an impulse (sudden burst in the number of caught eels, during 1-2 days) was observed. We propose a mathematical model for total number of captured eels within one migration wave. Impulse components were observed during the first and second migration waves. After their removal, the remaining experimental data of the three migration waves were fitted with normal distribution functions. A decrease in the values of fitting parameters as a function of time (migration wave number) was obtained. Our data indicate multiple causes for the observed migration waves.

Summary Whereas earlier Amur sleeper (Perccottus glenii) findings in the Danube River were only single specimens, data reported in this study represent the first record on establishment of a local population. An overview of the spread of the Amur sleeper in the Danube River basin is also presented.

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