Academic literature on the topic 'Freshwater fishes - Respiratory organs'

Betta sp. is a freshwater ornamental fish which also known as a fighting fish. One of the fundamental organs to support fishes life is respiratory organ. Fighting fish is belongs to the suborder Anabantoidei which means labyrinth fishes group. The aim of the study was to know histology of the respiratory organs of Betta sp. Histological preparations were done using paraffin method, stained with Hematoxylin-Eosin (HE). The result showed that Betta sp. has a respiratory organ common fish i.e gills and additional respiratory organ structure namely labyrinth and pseudobranch that makes Betta sp can survive in a low volume of water. The gill is consists of gill arch, gill raker, gill fillament and gill lamellae. The labyrinth is consist of connective tissue and folded ephitelium. Pseudobranch according to some literature function as an additional respiratory. Functions attributed to the pseudobranch include; regulation of oxygen to the eyes, enzyme production for use in the gas bladder, osmoregulation, and many others.

Monocrotophos, an organophosphate pesticide is used frequently in paddy fields of India. Although its impact of toxicity has been reported in many organisms, its effect on digestive and respiratory organs in Anabas testudineus is scanty. The Present investigation was conducted to evaluate the impact of histopathological and biochemical indices on freshwater fish A.testudineus exposed to sub-lethal concentration (45 ppm) of an organophosphorous pesticide monocrotophos (MT). Severe histoarchitectural and biochemical changes were observed in fishes exposed to monocrotophos when compared to fishes of control group. Exposure of fishes to the pesticide resulted in induction of histological abnormalities in gills, stomach and intestine. This was accompanied with reduction in total protein content and an elevation in catalase activity in gills, stomach and intestine. These structural alterations of the gills, stomach and intestine could affect respiration, digestion and absorption of nutrients which in turn could adversely affect growth and survival of the freshwater fish A. testudineus. The result of this investigation serves as a biomonitoring tool for the effects of organophosphorous pesticide MT on the aquatic biota.

The stress response in teleost fish shows many similarities to that of the terrestrial vertebrates. These concern the principal messengers of the brain-sympathetic-chromaffin cell axis (equivalent of the brain-sympathetic-adrenal medulla axis) and the brain-pituitary-interrenal axis (equivalent of the brain-pituitary-adrenal axis), as well as their functions, involving stimulation of oxygen uptake and transfer, mobilization of energy substrates, reallocation of energy away from growth and reproduction, and mainly suppressive effects on immune functions. There is also growing evidence for intensive interaction between the neuroendocrine system and the immune system in fish. Conspicuous differences, however, are present, and these are primarily related to the aquatic environment of fishes. For example, stressors increase the permeability of the surface epithelia, including the gills, to water and ions, and thus induce systemic hydromineral disturbances. High circulating catecholamine levels as well as structural damage to the gills and perhaps the skin are prime causal factors. This is associated with increased cellular turnover in these organs. In fish, cortisol combines glucocorticoid and mineralocorticoid actions, with the latter being essential for the restoration of hydromineral homeostasis, in concert with hormones such as prolactin (in freshwater) and growth hormone (in seawater). Toxic stressors are part of the stress literature in fish more so than in mammals. This is mainly related to the fact that fish are exposed to aquatic pollutants via the extensive and delicate respiratory surface of the gills and, in seawater, also via drinking. The high bioavailability of many chemicals in water is an additional factor. Together with the variety of highly sensitive perceptive mechanisms in the integument, this may explain why so many pollutants evoke an integrated stress response in fish in addition to their toxic effects at the cell and tissue levels. Exposure to chemicals may also directly compromise the stress response by interfering with specific neuroendocrine control mechanisms. Because hydromineral disturbance is inherent to stress in fish, external factors such as water pH, mineral composition, and ionic calcium levels have a significant impact on stressor intensity. Although the species studied comprise a small and nonrepresentative sample of the almost 20,000 known teleost species, there are many indications that the stress response is variable and flexible in fish, in line with the great diversity of adaptations that enable these animals to live in a large variety of aquatic habitats.

The current study was carried out to evaluate prevalence of endoparasites in freshwater fishes of Chenab River. The fish samples were collected from Chenab River during November 2014 to March 2015. In total, 285 fishes were examined for parasites, of which 75 fishes (26.1% of the total sample) were infected with parasites. Among the species, prevalence of infection was maximum in Rita rita (60%) and in Labeo rohita (37.5%). The minimum prevalence was, however, recorded in Oreochromis aureus (16.7%) and no parasite was found in Mastacembatus armatus. Among the organs, highest prevalence of endoparasites was observed in the intestine (43%) and gall bladder (33.2%). The prevalence of nematode and trematode was found higher (29 and 21%, respectively) in all fishes. It was revealed that the diversity of endoparasites in freshwater fishes is high. Since the use of fish as a ready source of food is increasing, therefore, the overall health status of fish in a system is becoming more valuable.Bangladesh J. Zool. 46(1): 53-61, 2018

Aeromonas hydrophila is an opportunistic microorganism. It is a secondary biological agent that contributes to the occurrence of fish diseases and its deterioration. This research was undertaken to determine the prevalence of A. hydrophila in some freshwater fishes collected from three different fish markets of Dhaka City and to test their antibiotic susceptibility. Total bacterial count and total aeromonas on different aeromonas selective media were enumerated using serial dilution technique. Bacterial isolates were characterized to identify A. hydrophila using biochemical tests and with comparison to reference strain (ATCC 7966). The lowest Aeromonas count was detected to be 2.83±0.40×102 cfu/g in Anabas testudineus and the highest was 1.03±0.153×103 cfu/g in Oreochromis mossambicus. On market basis highest aeromonas count was found in Anando Bazar (8.10±1.09×102 cfu/g) and lowest in Hatirpool Bazar (5.63±0.90×102 cfu/g) with no significant difference. Maximum susceptibility to amikacin and gentamicin was observed whereas all of the isolates were found resistant to a commonly used antibiotic amoxycillin. The obtained results point that antimicrobial susceptibility was more or less similar regardless of the origin of the samples collected. All the fishes investigated in this study contained A. hydrophila in their different organs.

The semen cryopreservation in cryotubes reduces the time needed for filling, freezing and thawing of the samples, while optimizing the procedures for artificial fertilization. However, no study has yet been performed with tambaqui semen in this container. The aim of this study was to evaluate the influence of cryotubes (1.6 and 4.5 mL) and thawing time (60ºC/70s and 60ºC/90 s) on the quality and fertility of tambaqui cryopreserved semen. For that, semen samples were diluted in freezing solution (1:9) composed with 75% glucose 290 mOsm , 10% methylglycol and 5% egg yolk, and frozen in liquid nitrogen vapor (in a dry shipper), and stored in liquid nitrogen (-196 °C). The semen samples was thawed at 60ºC in bath water during 70s or 90s and the semen quality was evaluated (Total motility - MT; Progressive motility - MP; Curvilinear velocity - VCL; Straight-line velocity - VSL and Average path velocity - VAP). In this study was also determined the time viability of spermatozoa thawed, maintained under refrigeration at 5°C, and assessed over 24 hours. Besides the kinetic parameters were evaluated sperm morphology and membrane integrity of spermatozoa. The fertilizing capacity of semen was evaluated from the samples thawed in the best time. All parameters of sperm kinetic showed higher values when the semen samples were thawed in 90 s compared to 70 s, independently of cryotube type. No significant differences were observed in sperm kinetic parameters after thawing between samples frozen in 1.6 ml and 4.5 mL cryotubes, except for total motility that was higher in 1.6 mL (47 ± 14% ) compared with 4.5 mL cryotubes (40 ± 11%), independently of thawing time. After activation, the spermatozoa significantly reduced the values of kinetic parameters within 37 seconds, except the MT which remained constant during this period. Relying on the sperm parameters evaluated (VCL, VSL, VAP and membrane integrity for both cryotubes and MT, MP and morphology only for 1.6 mL cryotube) the frozen semen maintained the quality during 3h after thawing. The fertilization rate obtained with fresh semen (74±6%) was higher than cryopreserved semen (1.6 mL - 45±9% and 4.5 mL - 41±12%). The two cryotubes did not differ in this parameter. A high correlation (p <0.05) was observed between fertility and sperm kinetics parameters (MT - 89%, MP - 86%; VCL - 79%; VSL - APV and 69% - 78%). It is concluded that 1.6 and 4.5 mL cryotubes can be used in the cryopreservation of tambaqui semen being recommended to be thawed at 60°C for 90s and their use in fertilization procedures within 3 hours after thawing since kept at 5°C.
A criopreservação de sêmen em criotubos reduz o tempo necessário para o envase, congelamento e descongelamento das amostras, além de otimizar os procedimentos de fertilização artificial. No entanto, nenhum estudo ainda foi realizado com o sêmen de tambaqui neste recipiente. Assim, o objetivo do presente trabalho foi avaliar a influência do tipo de criotubo (1,6 e 4,5 mL) e do tempo de descongelamento (60ºC/70s e 60ºC/90s) sobre a qualidade e fertilidade do sêmen de tambaqui criopreservado. Para isso, amostras de sêmen foram diluídas em solução de congelamento (1:9 v/v) composta por 75% de glicose 290 mOsm, 10% de metilglicol e 5% de gema de ovo, sendo envasadas em criotubos de 1,6 e 4,5 mL, congeladas em vapor de nitrogênio líquido no botijão dry-shipper (-175ºC) e armazenadas em botijão criogênico a -196°C. Para avaliação do tempo de descongelamento do sêmen, os criotubos foram imersas em água a 60°C durante 70 s ou 90 s e a qualidade espermática imediatamente avaliada (Motilidade total - MT; Motilidade progressiva - MP; Velocidade curvilinear - VCL; Velocidade em linha reta - VSL e Velocidade média da trajetória - VAP). Neste estudo foi determinado também o tempo de viabilidade dos espermatozoides descongelados, mantidos sob refrigeração a 5°C e avaliados durante 24 horas. Além dos parâmetros de cinética espermática foram avaliadas a morfologia e a integridade da membrana plasmática dos espermatozoides. A capacidade de fertilização do sêmen foi avaliada a partir das amostras descongeladas no melhor tempo. Todos os parâmetros de cinética espermática apresentaram valores superiores quando as amostras de sêmen foram descongeladas por 90s em relação ao tempo de 70s, independentemente do tipo de criotubo. Não foram observadas diferenças significativas nos parâmetros de cinética espermática pós-descongelamento entre as amostras congeladas nos criotubos de 1,6 e 4,5 mL, com exceção da MT que foi superior nos criotubos de 1,6 mL (47±14%) em comparação com os criotubos de 4,5 mL (40±11%), independentemente do tempo de descongelamento. Após ativação, os espermatozoides reduziram significativamente os valores dos parâmetros de cinética dentro de 37 segundos, exceto a MT que se manteve constante neste período. Baseando-se na maior parte dos parâmetros espermáticos avaliados (VCL, VSL, VAP e Integridade da membrana plásmatica para ambos os criotubos e MT, MP e Morfologia espermática somente para o criotubo de 1,6 mL) o sêmen congelado manteve sua qualidade durante 3h após o descongelamento. A taxa de fertilização obtida com o sêmen in natura (74±6%) foi superior ao sêmen criopreservado (1,6 mL - 45±9% e 4,5 mL - 41±12%). Os dois criotubos não diferiram entre si neste parâmetro. Uma alta correlação significativa (p<0,05) foi observada entre a fertilização e a cinética espermática (MT - 89%; MP - 86%; VCL - 79%; VSL - 69% e VAP - 78%). Conclui-se que os criotubos de 1,6 e 4,5 mL podem ser utilizados na criopreservação do sêmen de tambaqui, sendo recomendado seu descongelamento a 60°C por 90s e seu uso em procedimentos de fertilização dentro de 3 horas após o descongelamento desde que mantido a 5°C.

The biological integrity of aquatic ecosystems has become threatened by the effects of eutrophication, acidification as well as increased organic and inorganic chemical loads. It is necessary to identify the effects of xenobiotics before the onset of death in an exposed organism or deteriorating changes at population level. Biochemical and physiological indicators such as enzymes and stress proteins could be used as a valuable tool for detecting chemical exposure and evaluating their effects on aquatic organisms. The use of selected enzymes in different organs/tissue was evaluated as possible indicators of stress in fish, in their natural environment as well as under controlled laboratory conditions. During the field assessment of enzymes it was found that selected enzymes could be used as indicators of pollution between high flow and low flow seasons when pollution conditions are more concentrated. However, the various enzymes are non-specific indicators of stress and could therefore, be influenced by environmental changes, handling and struggling in the nets. Exposure to sub-lethal and lethal iron concentrations caused significant differences between the levels of enzymes in exposed and control Oreochromis mossambicus, indicating that the use of enzymes under controlled laboratory conditions, toxicity testing is more effective. The demand for sensitive and specific biological assays needed to be satisfied. Heat shock induction after sub-lethal iron exposure was investigated in the reproductive organs/gonads of O. mossambicus. After the refinement of the standard protocol for the assessment of Heat shock protein 70 (HSP 70) it was found that HSP 70 induction are more intense in male individuals than in female individuals. Higher protein concentrations were also found in female reproduction organs possibly due to the presence of vitellogenin. The use of HSP 70 as a diagnostic tool to monitor cell damage after sub-lethal iron exposure was less effective due to several factors including (1) the selection of the target organ, (2) the different stages of sexual development between individuals, (3) the selection of the exposure toxicant and (4) the presence of another stress protein in female gonads. Most researchers use the Atomic Absorption Spectrophotometry (AAS) method to determine the metal content in fish organs/tissues. During this research it was attempted to find a more time effective, rapid, less hazardous and more economic method to determine metal content in fish organs/tissues. After comparison between the AAS method and Scanning Electron Microscope Energy Dispersive X-ray (SEM-EDX) microanalyses the AAS method was found to be the most effective method to determine metal content in fish organs/tissues. SEM-EDX microanalyses techniques need more refined sample preparation, calibration and operation skills.
Prof. J.H.J Van Vuren