Chronological age and reservoir characteristics as predictors of trait composition in Neotropical reservoir fish assemblages

One of the main impacts on aquatic environments is the alteration of flow regime, usually caused by dam construction. This impact changes the dynamics and functioning of the environment. We aimed to evaluate changes in the composition of functional traits of fish assemblages from 29 reservoirs of different chronological ages. We assessed if there were any alterations in trophic state of these reservoirs according to their ages (chronological variable). Then, we evaluated the relationship between functional traits and environmental/chronological variables. Results showed that reservoir age is a predictor of fish assemblage functional traits composition. In older reservoirs, there was a predominance of omnivorous species, with multiple spawning and parental care. However, herbivorous species, with total spawning and medium size, had their abundance reduced. Also, it was possible to identify the influence of depth and water retention time on the composition of functional traits. By showing that although age has an influence on composition, the intrinsic characteristics of each reservoir are very important in evaluating the impacts of these projects. Therefore, the findings presented provide insights into what may happen to functional traits of fish assemblages with ageing of reservoirs.     

Intermediary metabolic response and gene transcription modulation on the Sub-Antarctic notothenioid Eleginops maclovinus (Valenciennes, 1930) injected with two strains of Piscirickettsia salmonis

Pathogen interactions with cultured fish populations are well studied, but their effects on native fishes have not been characterized. In Chile, the disease caused by bacterial species Piscirickettsia salmonis represents one of the main issues and is considered to be one of the important pathogens in the field of aquaculture. They have been found to infect native fish. Therefore, it is necessary to understand the impact of P. salmonis on native species of local commercial value, as well as the potential impact associated with the emergence of antibiotic-resistant strains of P. salmonis. Due to this purpose, the native fish Eleginops maclovinus was used in our study. Fish were randomly distributed in tanks and intraperitoneally inoculated with two strains of P. salmonis. No mortality was recorded during the experiment. Cortisol, glucose and total α-amino acid levels increased in fish injected with AUSTRAL-005 strain compared to sham-injected and LF-89-inoculated fish. Moreover, results showed an increase in the activity of carbohydrates and lipids metabolism in liver; and an increase in the carbohydrates, lipids and total α-amino acid metabolism in muscle after injection with AUSTRAL-005. Our results suggest that P. salmonis modulates the physiology of E. maclovinus and the physiological impact increase in the presence of the antibiotic-resistant strain AUSTRAL-005.     

Rapid sequence modification in the highly polymorphic region (HPR) of the hemagglutinin gene of the infectious salmon anaemia virus (ISAV) suggests intra-segmental template switching recombination

The ISAV has a genome composed of eight segments of (–)ssRNA, segment 6 codes for the hemagglutinin–esterase protein, and has the most variable region of the genome, the highly polymorphic region (HPR), which is unique among orthomyxoviruses. The HPR has been associated with virulence, infectivity and pathogenicity. The full length of the HPR is called HPR0 and the strain with this HPR is avirulent, in contrast to strains with deleted HPR that are virulent to varying degrees. The molecular mechanism that gives rise to the different HPRs remains unclear. Here, we studied in vitro the evolution of reassortant recombinant ISAV (rISAV) in Atlantic salmon head kidney (ASK) cells. To this end, we rescued and cultivated a set of rISAV with different segment 6-HPR genotypes using a reverse genetics system and then sequencing HPR regions of the viruses. Our results show rapid multiple recombination events in ISAV, with sequence insertions and deletions in the HPR, indicating a dynamic process. Inserted sequences can be found in four segments of the ISAV genome (segments 1, 5, 6, and 8). The results suggest intra-segmental heterologous recombination, probably by class I and class II template switching, similar to the proposed segment 5 recombination mechanism.     

Transpositional feeding rhythm of loach <Emphasis Type="Italic">Misgurnus anguillicaudatus</Emphasis> from larvae to juveniles and its ontogenesis under artificial rearing conditions

The diel feeding rhythm and ontogenesis during early life stage of loach Misgurnus anguillicaudatus were investigated under experimental conditions (light: L 06:00–18:00, D 18:00–06:00 h). Morphological and behavioral developments of loach from newly hatched to 40 days after hatching were observed. Larvae were able to prey on daphnia 3–4 days after hatching at 23 ± 0.5°C. As the larvae grew, they showed an increasing feeding capacity and a distinct feeding rhythm. Feeding intensity and incidence for day-4 larvae were highest at 10:00 and 16:00 h. The highest levels of feeding intensity for day-12 larvae occurred at 08:00, 12:00, and 18:00 h as did feeding incidence. By day 20, when the larvae metamorphosed, the highest levels of feeding intensity occurred at 06:00, 18:00, and 24:00 h and were concurrent with the highest feeding incidence. After metamorphosis, feeding capacity had again increased considerably and, in contrast to the earlier stages before day 20, feeding intensity for day-30 juveniles peaked at 05:00 and 20:00 h, about 1–2 h after the maximum feeding incidence. The feeding rhythm of loach juveniles at day 40 was almost the same as the day-30 juveniles. The estimated maximum daily feeding rates were 43.1%, 33.4%, 19.0%, 12.8%, and 5.8% of body weight on days 4, 12, 20, 30, and 40, respectively. Thus, loach was found to have different feeding rhythms in the pre- and post-metamorphosis stages, with the highest feeding activity in daytime during the larval planktonic stage before metamorphosis, and intensely nocturnal feeding behavior during the juvenile benthic stage after metamorphosis.     

In silico and gene expression analysis of the acute inflammatory response of gilthead seabream (Sparus aurata) after subcutaneous administration of carrageenin

Fish Physiology and Biochemistry - Inflammation is one of the main causes of loss of homeostasis at both the systemic and molecular levels. The aim of this study was to investigate in silico the...     

Management practices and their association with Mycobacterium tuberculosis complex prevalence in red deer populations in Southwestern Spain

Intensification of game management may increase the prevalence of tuberculosis (TB) in wildlife despite eradication programs implemented in cattle herds in the same areas. In this cross-sectional study, we investigated the association between wild game management practices and the presence of tuberculosis in red deer populations in Southwestern Spain. Five hundred and fifty-one animals were examined by necropsy to detect tuberculosis-like lesions in the main lymph nodes. Prevalence, as determined by TB-like lesions, was estimated to be 5.1% of animals, with 77% of TB-like lesions confirmed by PCR. Our results suggest that population density, in addition to factors which promote the local aggregation of animals, is factors associated with increased prevalence of TB in red deer populations. We suggest that management practices including supplementary feeding, fencing, water ponds and interaction with domestic livestock should be revised in order to prevent TB in wild deer both.     

High stocking density and food restriction have minimum impact on size dispersal of cultured Senegalese sole (Solea senegalensis, Kaup 1858) juveniles. Evidence for individual growth being regulated by population structure

The individual growth being regulated by population structure was studied in cultured populations of Senegalese sole (Solea senegalensis Kaup) juveniles. Soles constituting an initial population were individually tagged and their specific growth rates (SGR) registered after two months of growth. Fish were then graded in order to achieve four new subpopulations based in their previous growths and cultured for other additional 60 days. Three subpopulations consisted of individuals that had previously shown an average SGR (% day⁻¹) of 1.04 ± 0.3, 0.66 ± 0.1 and 0.18 ± 0.1, respectively. A fourth sole subpopulation was established from randomly selected juveniles to constitute the ungraded control group. Growth of the three subpopulations originally graded according to high (1.04% day⁻¹), medium (0.66% day⁻¹) and low (0.18% day⁻¹) SGR soles, was always similar (P > 0.05) at any time (close to 0.60% day⁻¹). SGR distributions along time revealed a tendency of the three subpopulations to achieve similar growth rate dispersals to that of the ungraded group after 60 days of culture.The individual growth of sole juveniles was also determined in populations that were subject to increased stocking density and food restriction. Soles stocked at high density (N = 110 fish tank⁻¹; 30.97 ± 0.8 kg m⁻²) showed an increased growth standard deviation when compared with individuals kept at low density (N = 20 fish tank⁻¹; 6.20 ± 0.2 kg m⁻²). In contrast, it was found that population growth dispersal was unaffected in soles fed at a daily ration of either 0.25% or 1.0% of their biomass. Minimum consequences on overall size dispersal in terms of ΔCV were found when high stocking and restricted food ration conditions were compared to control groups. Overall results from this work indicate that individual growth of captive juvenile soles was mainly regulated at a population level, existing a strong tendency to achieve a social arrangement in terms of growth. High stocking density and low feeding ration assay suggests that potentially competitive rearing conditions do not contribute to increase population size dispersal during intensive production of S. senegalensis.     

Insulin and IGF-I receptors and tyrosine kinase activity in carp ovaries: changes with reproductive cycle

Insulin and insulin-like growth factor I (IGF-I) receptors from carp ovaries were semipurified with wheat germ agglutinin at different moments of the reproductive cycle and their binding characteristics and tyrosine kinase activity were studied. Specific receptors for insulin and IGF-I were found. IGF-I receptors presented higher binding (23.8 ± 1.5%), number of receptors (965 ± 20fm/mg) and affinity (K_D 0.24 ± 0.03nM) than those shown for insulin receptors (4.1 ± 1%, 530 ± 85fm/mg and 0.85 ± 0.1nM, respectively). Insulin and IGF-I receptors have a tyrosine kinase activity which is not different from that found in muscle of the same species. Seasonal changes were found in binding, with maximum values for insulin and IGF-I reached at the end of pre-spawning period (June). However, while IGF-I binding was observed in all stages, insulin binding decreased in autumn and disappeared in winter, which suggests a different role for the two peptides in ovarian physiology.