Feeding Ecology of Fish

Host's defense against external challenges activates an inflammatory response regulated by a set of chemical signals, including hormones. These immunomodulatory hormones, such as corticosterone, testosterone, and melatonin, trigger the systemic immune responses responsible for inflammatory assembly and resolution. This study aimed to investigate the effects of an immune challenge on endocrine and innate immune responses in the bullfrog (Lithobates catesbeianus). Adult males were intraperitoneally injected with lipopolysaccharide (LPS; 2 mg/kg) or saline, and blood samples were collected 6 and 24 h after injection for measurement of neutrophil/lymphocyte ratio, blood leukocyte phagocytosis, plasma bacterial killing ability, and plasma levels of corticosterone, melatonin, and testosterone. Our results showed LPS-induced increased neutrophil/lymphocyte ratio and leukocyte phagocytosis, and decreased melatonin and testosterone plasma levels, which were more pronounced 24 h after injection. Overall, we conclude that LPS intraperitoneal injection can activate the innate immune response and modulate the hormonal profile of the bullfrogs, with effects more pronounced 24 h than 6 h after treatment.

Systemic hormonal and immune regulation induced by intraperitoneal LPS injection in bullfrogs (Lithobates catesbeianus).

The inflammatory response is a complex process that relies on interactions among multiple endocrine and immune modulators. Studies incorporating time-related and integrative endocrine and immune responses to an immune challenge might shed light on the characterization of the phases of the inflammatory response in anurans. The present study investigated time-related changes (1, 3, 6, and 18 h post-challenge) in plasma corticosterone (CORT), melatonin (MEL) and testosterone (T) levels, phagocytosis percentage (PP), plasma bacterial killing ability (BKA), and neutrophil to lymphocyte ratio (NLR) following a lipopolysaccharide (LPS) immune challenge in Rhinella diptycha toads. Our results showed the response to LPS injection was characterized by increased CORT, PP, BKA, and NLR, with a concomitant decrease in plasma MEL and T. Increased CORT was more pronounced at 6 and 18 h, while increased NLR was observed only 18 h post-LPS injection. Meanwhile, plasma MEL and T decreased independently of the time post-LPS injection. Additionally, toads in better body condition showed higher BKA and PP in the LPS-treated group, regardless of the time postinjection. Our results show that toads (R. diptycha) were sensitive to the LPS challenge, mounting an inflammatory response, which started quickly (after 1 h) and developed over time and was influenced by body condition. These results demonstrate a time-related hormonal and immune variation as a consistent pattern of activation of the immune system, as well as of hypothalamic-pituitary-adrenal/interrenal and immune-pineal axes following an immune challenge more deeply studied in mammals, suggesting the evolutionary conservation of the regulatory mechanisms for tetrapod vertebrates.

LPS-induced immunomodulation and hormonal variation over time in toads

This paper reviews several aspects of immunoendocrinology and ecoimmunology in Brazilian species of anurans under investigation for more than a decade, including 1) patterns of annual covariation of circulating steroids, calling behavior and innate immunity, 2) endocrine and immune correlates of calling performance, 3) behavioral and physiological correlates of parasite load, 4) thermal sensitivity of immune function, and 5) endocrine and immunomodulation by experimental exposure to acute and chronic stressors, as well as to endocrine manipulations and simulated infections. Integrated results have shown an immunoprotective role of increased steroid plasma levels during reproductive activity in calling males. Moreover, a higher helminth parasite load is associated with changes in several behavioral and physiological traits under field conditions. We also found anuran innate immunity is generally characterized by eurythermy, with maximal performance observed in temperatures close to normal and fever thermal preferendum. Moreover, the aerobic scope of innate immune response is decreased at fever thermal preferendum. Experimental exposure to stressors results in increased corticosterone plasma levels and immune redistribution, with an impact on immune function depending on the duration of the stress exposure. Interestingly, the fate of immunomodulation by chronic stressors also depends in part on individual body condition. Acute treatment with corticosterone generally enhances immune function, while prolonged exposure results in immunosuppression. Still, the results of hormonal treatment are complex and depend on the dose, duration of treatment, and the immune variable considered. Finally, simulated infection results in complex modulation of the expression of cytokines, increased immune function, activation of the Hypothalamus-Pituitary-Interrenal axis, and decreased activity of the Hypothalamus-Pituitary-Gonadal axis, as well as reduced melatonin plasma levels, suggesting that anurans have a functional Immune-Pineal axis, homologous to that previously described for mammals. These integrated and complementary approaches have contributed to a better understanding of physiological mechanisms and processes, as well as ecological and evolutionary implications of anuran immunoendocrinology.

Immunoendocrinology and Ecoimmunology in Brazilian Anurans.

In this study we aimed to analyze the reproductive biology of Bagre bagre from zangaria fishery in Peru island, Reserva Extrativista de Cururupu, Maranhao, Brazil. The Bagre bagre, is second species of fish most abundant in this fishery (16.82%), had its reproductive biology studied for over a year (September/2014 to August/2015), with monthly collections in two types the zangarias. A total of 320 specimens of Bagre bagre was captured. Overall, 170 were females and 150 males. The size of the females it ranged between 13 and 55 cm, while the size of the males sit ranged between 14.8 and 38 cm. The first maturity calculated size was 15.9 cm for females and 21.2 cm for males. Analyzing the frequency of maturation stages and gonadosomatic relationship, it we found that the reproductive period of the species was between the months of December and March.

http://www.agraria.pro.br/ojs-2.4.6/index.php?journal=agraria&page=article&op=download&path%5B%5D=agraria_v11i4a5402&path%5B%5D=4939

Biologia reprodutiva do Bagre bagre capturado pela pescaria de zangaria - DOI:10.5039/agraria.v11i4a5402

Anurans can be naturally infected by the bacterium Escherichia coli (Migula, 1895) Castellani and Chalmers, 1919, which contain lipopolysaccharides (LPS) in their external membrane. LPS affects rep...

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LPS-induced alterations in reproductive organs and liver pigmentation in the toad Rhinella diptycha (Bufonidae)

Editor: Rubens M. Lopes Research involving fish stocks' reproductive aspects has social, economic, and biological importance; (Pinheiro, 2010; Véras and Almeida, 2016). Studies dealing with mean fish length at first sexual maturity are essential to assess and manage the exploited fish population and determine the minimum permissible size for capture, since some marine species have been overfished (King and McFarlane, 2003; Chellappa et al., 2010). According to Pinheiro (2010), the mean length at first sexual maturity represents the mean fish size when 50% of the individuals are ready to enter a new cohort, actively participating in the reproductive process. This work's objective was to estimate the mean length at first sexual maturity of economically important fishes in the Brazilian Northeast coast, thus improving the biological understanding of these species in the light of more efficient stock management. Samples from the following species were captured from 2013 to 2019, through artisanal fishery brought to the municipality of Raposa, in the state of Maranhão, Brazil (Figure 1): Genyatremus luteus (478 individuals 182M; 296F), Micropogonias furnieri (190 individuals 107M; 83F), Oligoplites palometa (172 individuals 97M; 75F), Nebris microps (95 individuals http://dx.doi.org/10.1590/S2675-28242020068311

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Length at first sexual maturity of economically important fishes in the Brazilian Northeast Coast

The feeding habit of lane snapper Lutjanus synagris was analyzed qualitatively and quantitatively, related to seasonality, its ontogenetic development, and the relationship between food and biotic and abiotic conditions on the Amazon Coast of Maranhao, between June 2018 and May 2019 Numerical, gravimetric, and ecological index methods were used to show the relative importance or preference of a category or food item in the diet The food composition was studied related to the sex, size of the predator and seasonality Of 359 stomachs sampled, 54 were empty due to regurgitation and presented a vacuity coefficient (Cv%) of 1504% In the analysis of diets between the sexes, it was possible to identify a greater participation of fish (3043%) and Crabs (2610%) for females, Shrimp (3623%) and Organic Matter Not Identified (OMNI) (1884%) in males The diet showed spatial differences in length distributions The analysis of stomach contents showed the presence synthetic materials (mesoplastics ranging from 50 mm to 25 cm) in 552% of the samples The main food items found were from the Brachyura and Caridea species The results clearly demonstrate that lane snapper prefers benthic prey, presenting a carnivorous and generalist-opportunistic habit Its diet is also composed of demersal-pelagic species, such as Cephalopods and Teleost fish

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FEEDING HABITS OF Lutjanus synagris (TELEOSTEI: LUTJANIDAE) IN THE AMAZON COAST OF THE NORTHEAST REGION OF BRAZIL

Percepção ambiental dos usuários em duas praias do Nordeste do Brasil: a problemática da poluição

RESUMO O trabalho consiste na avaliação dos aspectos reprodutivos da guaravira, Trichiurus lepturus através da pesca comercial no município de Raposa MA. Após identificados, pesados e medidos, os 144 exemplares foram seccionados na parte ventral para a retirada e classificação macroscópica das gônadas. Para a confirmação dos estágios maturacionais e do sexo predeterminados pela análise macroscópica das gônadas, foram realizados com uma parcela das amostras análises histológicas dos tecidos gonadais. A análise macroscópica das gônadas dos exemplares estudados, mostra quatro estágios de maturação para ambos os sexos, sendo eles: imaturo, em maturação, maduros e esvaziado. Durante o período de estudo, as gônadas de T. lepturus se encontraram com frequência, aproximada de 4,86% das no estágio imaturo, enquanto isso, as gônadas em maturação registraram frequência de 7,64%, entretanto, 47,92% esteve madura e por fim, 39,58% se encontraram esvaziadas. Os resultados do presente estudo como, o índice gonadossomático, fator de condição e estágios de desenvolvimento gonadal, podem fornecer informações sobre os aspectos reprodutivos que servem para subsidiar medidas de conservação, bem como, as condições reprodutivas dos estoques pesqueiros dessas espécies na região.

Jailza Freitas

Papers

LPS-induced alterations in reproductive organs and liver pigmentation in the toad Rhinella diptycha (Bufonidae)

Length at first sexual maturity of economically important fishes in the Brazilian Northeast Coast

FEEDING HABITS OF Lutjanus synagris (TELEOSTEI: LUTJANIDAE) IN THE AMAZON COAST OF THE NORTHEAST REGION OF BRAZIL

Percepção ambiental dos usuários em duas praias do Nordeste do Brasil: a problemática da poluição

Estudo dos aspectos reprodutivos do trichiurus lepturus (linnaeus, 1758) na Costa Maranhense, Brasil