Behavioural responses to con- and heterospecific alarm cues by an alien and a coexisting native fish

Hydrobiologia - The monkey goby Neogobius fluviatilis is an invasive Ponto-Caspian fish that enters habitats of the native gudgeon Gobio gobio in European freshwaters, likely belonging to the same...     

Cytochrome P450 1A induction in gudgeon Gobio gobio : Laboratory and Field Studies

The induction of cytochrome P450 1A was studied in gudgeon (Gobio gobio), a common European cyprinid, using both farm-raised and field-caught fish. The effects of sex, reproductive status and past exposure to xenobiotics were assessed. When exposed to beta-naphthoflavone (bNF), reared gudgeon showed a dose-dependent increase of EROD activity with a plateau observed at doses from 20 mg kg-1 (females) and 5 mg kg-1 (males). The sexual difference in EROD activity was related to the gonadosomatic index (GSI) of the female whatever the level of induction. Dose and sex effects were confirmed by the immunodetection of CYP1A protein. More than 1 month was necessary for EROD activity to decrease to baseline levels. A second bNF injection after 32 days gave similar levels of induction, suggesting that EROD induction by bNF was not impaired by a pretreatment. Wild fish were brought from two sites in the Rhone river basin: a low contaminated site (Ain) and a highly contaminated site (Rhone). Wild gudgeon were highly induced by bNF in laboratory conditions, except males from the Rhone site which exhibited EROD levels as high as the EROD plateau found in laboratory conditions. A 2- month depuration period in clean water was necessary for EROD activity in wild gudgeon to decrease to baseline levels. These results provide better knowledge of the main factors of modulation of the induction in gudgeon as well as on the influence of the history of exposure to inducers.     

Studies on Ligula intestinalis Some aspects of the pathology in the second intermediate host

A 3 year survey of a lake, in which 120 roach, Rutilus rutilus , were examined revealed the presence of the plerocercoids of Ligula intestinalis in more than 90 % of the fish. The average number of parasites per fish was 4.2 although fish exceeding 32 g were not ligulosed. Gudgeon, Gobio gobio , of all sizes were affected. Implants of the plerocercoids into small roach, gudgeon and goldfish, Carassius auratus , were successful but not in the case of Perca fluviatilis, Esox lucius and Leuciscus cephalus. The pathological effects of the plerocercoids on roach and gudgeon are described.     

Ligula intestinalis (L.) (Cestoda: Pseudophyllidea): plerocercoid-induced changes in the spleen and pronephros of roach, Rutilus rutilus (L.), and gudgeon, Gobio gobio (L.)

The effects of the plerocercoid of Ligula intestinalis (L.) (Cestoda: Pseudophyllidea) on the major lymphoid organs, the spleen and pronephros, of roach, Rutilus rutilus (L.), and gudgeon, Gobio gobio (L.), are described. The spleen of ligulosed roach showed a significant decrease in weight. Differential cell counts suggested this was due to a reduction in erythrocytes, despite significant increases in macrophages and vacuolated granulocytes. The spleen of gudgeon, which consisted almost entirely of erythrocytes, showed a slight reduction in weight in ligulosed fish. In both roach and gudgeon this decrease was independent of parasite burden. Differential cell counts of the pronephros from ligulosed roach revealed a significant decrease in neutrophils and increase in vacuolated granulocytes. In the pronephros of gudgeon, however, cell counts were unaffected by ligulosis. Ultrastructural observations included an apparent disintegration of vacuolated granulocytes and increased pinocytic activity in specialized endothelial cells in the spleens of ligulosed roach. Also, melano-macrophage centres and melano-macrophages increased in the spleen of ligulosed roach and gudgeon, respectively. The marked changes in spleen weight and differential cell counts in ligulosed roach and lack of such changes in ligulosed gudgeon correlate with the differential response to the parasite by these two fish species.     

Microhabitat use by 0+ and older fishes in a small English chalk stream

The microhabitat use of two size/age classes of fish (0 +, ≥1+) in the River Lee, based on measurements of 14 environmental variables, was studied using point abundance sampling by electrofishing over the summer and autumn of 1995. Microhabitat use by all cyprinid species (barbel Barbus barbus, minnow Phoxinus phoxinus , chub Leuciscus cephalus and gudgeon Gobio gobio ) differed between 0+ and older (≥1+) with lentic, shallow, littoral environments being important for 0+ fishes, whereas deeper, faster areas in mid-channel were important for ≥ 1 + fishes. There was more overlap in microhabitat use by 0+ juvenile cyprinids in the River Lee than in larger systems such as the River Danube (Slovakia/Hungary) and River Great Ouse (U.K.).     

Evidence for the co-existence of separate strains or species of Ligula in Lough Neagh,Northern Ireland

LIGULA (Cestoda: Pseudophyllidea) infections in gudgeon (Gobio gobio) and roach (Rutilus rutilus) differ markedly in the pathology that is observed in the host, particularly with respect to a tissue response and the extent of inhibition of gonadal development. The entire internal transcribed spacer (ITS) region (ITS-1, 5.8S and ITS-2) and the large subunit domains D1-D3 were sequenced and compared in parasites from these fish from Lough Neagh, Northern Ireland, together with a single specimen from minnow (Phoxinus phoxinus) from Wales. Sufficient differences were observed between parasites from R. rutilus and G. gobio to support the suggestion that they may represent different strains/species. In contrast, Ligula from P. phoxinus closely resembled those from R. rutilus. Ligula infections in G. gobio were recorded prior to the introduction of R. rutilus. The co-existence of separate strains or species of Ligula in Lough Neagh probably resulted from the introduction of R. rutilus to these waters, correlated with an increase in the number of great crested grebes (Podiceps cristatus).     

Patterns of diet overlap between populations of non-indigenous and native fishes in shallow ponds

No significant differences in the diet composition were detected for any of the populations of four non-indigenous fish species (brown bullhead Ameiurus nebulosus , pumpkinseed Lepomis gibbosus , topmouth gudgeon Pseudorasbora parva and eastern mudminnow Umbra pygmaea ) and two native fish species (gudgeon Gobio gobio and roach Rutilus rutilus ), between two small shallow ponds and between habitats within the ponds, during late summer. Based on diet composition, groups of size classes within species ('functional groups') were distinguished. For most functional group combinations of exotic fishes, diet overlap values were low. Although chironomid larvae formed the most important food source, differential consumption of chironomid size classes allowed an important degree of niche differentiation between non-indigenous fishes. In contrast, high diet overlap was found between the functional groups of indigenous gudgeon and of several non-indigenous fishes, indicating a high potential for interspecific exploitative competition. The diet of roach consisted almost entirely of non-animal remains (detritus and plant material). The high proportion of such low-energy food in the diet of this species may be indicative for a competition induced niche shift to suboptimal food sources.     

Role of glutathione in functioning of the system of antioxidant protection in fish (review)

Oxidative stress causes damage to cell components by reactive oxygen species (ROS) originating from the effect of various chemical pollutants, such as heavy metal cations, polyaromatic hydrocarbons, organochlorine and phosphororganic pesticides, polychlorine biphenyls, dioxins, and other xenobiotics. To avoid pathological consequences of interaction between biological molecules and high-reactive ROS, cells have a detoxification mechanism that uses glutathione, a nonprotein thiol. Glutathione is a component of cellular protection against the toxic action of xenobiotics and metal cations. In the last decade, the effect of environmental pollutants on changes in glutathione concentrations in tissues of aquatic organisms has been touched on in a large number of works. This review summarizes data of the up-to-date studies on glutathione variability in fish tissues under the effect of biogenic and industrial xenobiotics.     

The use of artificial neural networks to predict the presence of small-bodied fish in a river

1. Discriminant factorial analysis (DFA) and artificial neural networks (ANN) were used to develop models of presence/absence for three species of small-bodied fish (minnow, Phoxinus phoxinus , gudgeon, Gobio gobio , and stone loach, Barbatula barbatula ).
2. Fish and ten environmental variables were sampled using point abundance sampling by electrofishing in the Ariège River (France) at 464 sampling points.
3. Using DFA, the percentage of correct assignments, expressed as the percentage of individuals correctly classified over the total number of examined individuals, was 62.5% for stone loach, 66.6% for gudgeon and 78% for minnow. With back-propagation of ANN, the recognition performance obtained after 500 iterations was: 82.1% for stone loach, 87.7% for gudgeon and 90.1% for minnow.
4. The better predictive performance of the artificial neural networks holds promise for other situations with non-linearly related variables.     

An examination of the fish population in the River Trent, Nottinghamshire using angler catches

During this study, anglers caught over 580 kg of fish, comprising over 29 500 individuals of 14 species. Nine times as many gudgeon, Gobio gobio , as roach, Rutilus rutilus , were caught. Gudgeon represented 35.94% of the total catch weight compared with 44.64% for roach. The mean total catch per man-hour was 8.9 fish and the mean catch rate was 176 g per man-hour. Population estimates for fish longer than 12 cm for all species other than gudgeon and bleak, Alburnus alburnus , gave fish densities of 0.21 fish m⁻², the roach population was 0.15 m⁻², and that for dace Leuciscus leuciscus , 0.02 m⁻². The population density for all sizes of all species caught was estimated to be 2.25 fish m⁻².
The fish biomass available to the angler was 447 kg ha⁻². The rate of exploitation of the fishery over the period of sampling was high at 17%, representing an annual exploitation rate of 94%.     

Meiobenthos provides a food resource for young cyprinids

Young individuals of the bottom-biting (i.e. sediment-ingesting) common carp Cyprinus carpio and gudgeon Gobio gobio consumed significant amounts of nematodes in laboratory experiments, whereas the selective-feeding roach Rutilus rutilus did not. In mesocosm enclosure experiments in the field, C. carpio strongly decreased the nematode abundance within 4 days, whereas the bottom-biting bream Abramis brama did not affect the abundance until after 14 days. In controlled experiments with a known number of prey, C. carpio but not A. brama significantly reduced the number of nematodes, and G. gobio reduced the nematode abundance dependent on the size of the fish, with smaller fish causing a greater reduction. Cyprinus carpio consumed the nematodes and did not just mechanically kill them in the sediment, as shown by dissection of the fish intestine. Morphometric analysis of the branchial baskets indicated that the mesh width of C. carpio, but not of A. brama, is suitable for consuming meiobenthos. The results indicate that the meiobenthos is a food resource for certain bottom-feeding freshwater fishes.     

Investigation of Paradiplozoon homoion (Monogenea, Diplozoidae) life cycle under experimental conditions

Diplozoids (Diplozoidae, Monogenea) are fish ectoparasites with a direct life cycle without intermediate hosts. Their free swimming larva, the oncomiracidium, hatches from eggs, invades a fish host and metamorphoses into a post-oncomiracidial larval stage, the diporpa. Later, two diporpae fuse and live as a pair in cross-copulation during their adult life. An experimental study was designed to investigate the life cycle of Paradiplozoon homoion (Monogenea, Diplozoidae) parasitizing their common fish hosts, gudgeon (Gobio gobio). A total of 35 gudgeon parasitized by diplozoids were collected from their natural environment of the Vlára River, Czech Republic, and kept together in tanks with 41 non-parasitized gudgeons reared in a laboratory environment. In total, 100 adult specimens of P. homoion were collected from the Vlára River gudgeon and a new parasite generation was expected to be observed on fish reared in the laboratory environment. Eight days after the first diplozoid eggs appeared on fish gills, the presence of diporpae with one or two pairs of clamps was noted. The appearance of the first juveniles was recorded at the same time as diporpae. Development of P. homoion from egg to sexually mature adult stage took 33 days at a constant temperature of 20 degrees C. The development of eggs in adults of the second generation was observed 2 days after the first observation of these adults. The behavior of oncomiracidia was also studied and this free swimming stage of diplozoids survived for 22 h in the absence of a host. When host fish were experimentally infected by oncomiracidia, diporpae were found attached to the fish gill apparatus within 2 h of infection.     

Molecular phylogeny of the genus Gobio Cuvier, 1816 (Teleostei: Cyprinidae) and its contribution to taxonomy

The phylogenetic relationships among gudgeons that represent most nominal taxa within Gobio gobio sensu lato were examined by mitochondrial and nuclear genome sequencing. The molecular analyses confirmed the separate generic status of Gobio as a monophyletic group and revealed 15 Eurasian lineages divided into two main clades, the Northern European and the Ponto-Caspian. The validity of eleven nominal taxa as distinct species was confirmed, gudgeons from the Volga River basin were described as a new species G. volgensis, and three revealed phylogenetic lineages were submitted for a comprehensive revision as "species-in-waiting". The species G. gobio showed a wide range extending from the British Isles to the Black Sea coast and overlapped the areas of several other species. Four pure lineages were detected in the middle Danube River basin. The Crimean Peninsula was found to be a region with the occurrence of individuals of hybrid origin. This region will require special investigation to define species participating in hybridization events, and to establish further steps for the conservation of endemic native gudgeon species. A simple diagnostic method, based on different lengths of the PCR products, called "S7indel diagnostics" is presented for further taxonomic investigations in the genus Gobio.     

Structure, gene expression, and evolution of primate glutathione peroxidases

Glutathione peroxidases (GPxs) are a family of enzymes that scavenge peroxides generated in cells. We carried out molecular cloning for cDNAs of four GPx isozymes (GPx-1 through 4) in primate species. The essential residues for the function of these isozymes were well conserved. A phylogenetic tree of GPx isozymes of primates and other mammals showed that GPx-4 diverged first, followed by GPx-3, GPx-2, and GPx-1. Expression of mRNAs for GPx-2 through 4 in various tissues of Japanese monkey was analyzed by Northern blot hybridization. GPx-2 mRNA was detected at 1.7 kb, exclusively in the stomach and small intestine. GPx-3 mRNA was detected at 1.8 kb, intensively in the kidney and adrenal gland, and weakly in the cerebellum, heart, and lung. GPx-4 mRNA was detected at 1.1 kb, very intensively in the testis and weakly in lung, heart, and cerebellum. These results showed that GPx isozymes were expressed under tissue-specific regulations.     

Can life‐history traits predict the fate of introduced species? A case study on two cyprinid fish in southern France

1. The ecological and economic costs of introduced species can be high. Ecologists try to predict the probability of success and potential risk of the establishment of recently introduced species, given their biological characteristics.
2. In 1990 gudgeon, Gobio gobio , were released in a drainage canal of the Rhône delta of southern France. The Asian topmouth gudgeon, Pseudorasbora parva, was found for the first time in the same canal in 1993. Those introductions offered a unique opportunity to compare in situ the fate of two closely related fish in the same habitat.
3. Our major aims were to assess whether G. gobio was able to establish in what seemed an unlikely environment, to compare populations trends and life-history traits of both species and to assess whether we could explain or could have predicted our results, by considering their life-history strategies.
4. Data show that both species have established in the canal and have spread. Catches of P. parva have increased strongly and are now higher than those of G. gobio .
5. The two cyprinids have the same breeding season and comparable traits (such as short generation time, small body, high reproductive effort), so both could be classified as opportunists. The observed difference in their success (in terms of population growth and colonization rate) could be explained by the wider ecological and physiological tolerance of P. parva .
6. In conclusion, our field study seems to suggest that invasive vigour also results from the ability to tolerate environmental changes through phenotypic plasticity, rather than from particular life-history features pre-adapted to invasion. It thus remains difficult to define a good invader simply on the basis of its life-history features.     

Spatial and temporal variations in fish populations in the upper Thames estuary

Between February 1989 and August 1990, the upper Thames estuary contained 23 species of fish. Fish numbers were higher and relatively constant in the uppermost part of the estuary. Number of species was augmented in summer from fresh water and from downstream, coinciding with high temperature, low flow and high salinity. The eight most abundant species contributed to 98·5% of the total number. Flounder Pleuronectes flesus , dace Leuciscus leuciscus and perch Perca fluviatilis , recruited from May to August, and common goby Pomatoschistus microps , roach Rutilus rutilus and chub Leuciscus cephalus , from August to November. The upper estuary (salinity 0·34–2·96 p.s.u.) formed a species transition area between the freshwater but salinity-resistant roach, chub, and gudgeon Gobio gobio upstream, and the estuarine eurhyhaline common goby and flounder downstream. The three-spined stickleback Gasterosteus aculeatus and cyprinids were more abundant at upstream while perch was more abundant at downstream sites. High abundances of gudgeon, chub and roach were associated with high transparency and dissolved oxygen and low salinity, while high abundances of perch were associated with high salinity and low transparency. Dace and three-spined stickleback were associated with high dissolved oxygen and low pH, and common goby with high pH. Flounder showed no clear preferences.     

Shear stress enhances glutathione peroxidase expression in endothelial cells

Hemodynamic forces have profound effects on vasculature. Laminar shear stress upregulates superoxide dismutase (SOD) expression in endothelial cells. SOD converts superoxide anion to H(2)O(2), which, however, promotes atherosclerosis. Therefore, defense against H(2)O(2) may be crucial in reducing oxidative stress. Since glutathione peroxidase (GPx-1) reduces H(2)O(2) to H(2)O, the regulation of GPx-1 expression by mechanical stress was examined. Cultured bovine aortic endothelial cells (BAECs) were subjected to laminar shear stress and stretch force. Shear stress upregulated GPx-1 mRNA expression in a time- and force-dependent manner in BAECs, whereas stretch force was without effect. Furthermore, shear stress increased GPx activity. L-NAME, an inhibitor of nitric oxide synthase, did not affect shear stress-induced GPx-1 mRNA expression. The ability of laminar shear stress to induce GPx-1 expression in endothelial cells may be an important mechanism whereby shear stress protects vascular cells against oxidative stress.