A Multidisciplinary Experimental Study on the Effects of Breeders Diet on Newborn Seahorses (Hippocampus guttulatus)

The global trade in seahorses is increasing and new rearing techniques are currently available for a few species. One of the main bottlenecks in seahorse production is reproductive success, which is dependent upon the administration of high quality diets to breeders. However, little is known about the most adequate diets, on how they should be administered and on how they might affect newborn performance. In this study, three homogeneous groups of adult seahorses Hippocampus guttulatus were maintained in captivity. Each group was fed on one of the following diets since the onset of the breeding period: unenriched adult Artemia (diet A), unenriched adult Artemia and mysidaceans (diet AM) and mysidaceans (diet M). As a positive control, a wild pregnant male was used. The mixed diet AM provided the highest overall breeding success and reasonable fatty acid profiles, and better resembled newborn from a wild male. The use of mysidaceans solely (Diet M) provided the worse results in spite of the high DHA content. Significant differences were observed in newborn characteristics and fatty acid profiles among dietary groups and along the breeding season, especially in total n-3 HUFA and DHA. Monospecific diets including Artemia or mysidaceans very likely suffered nutritional deficiencies, which were reflected in morphological alterations of the muscle tissue (diet A) or abnormal early mortalities in newborn (diet M). Three progressive stages were identified along the whole breeding period: initial mixed capital-income period (100–120 days since the onset of the breeding period), followed by an inflection period (short transitional stage – income sources), and finally a long period characterized by the use of income sources and the progressive exhaustion of body reserves. Special attention should be deserved to the progressive changes in fatty acid profiles along the breeding season, resulting in a decrease in newborn performance. Considering the time required for a diet to be reflected in newborn, we recommend Hippocampus guttulatus breeders to be fed on a high quality diet for at least 3 months prior the breeding period

Acid-Sensing Ion Channels in Zebrafish

The ASICs, in mammals as in fish, control deviations from the physiological values of extracellular pH, and are involved in mechanoreception, nociception, or taste receptions. They are widely expressed in the central and peripheral nervous system. In this review, we summarized the data about the presence and localization of ASICs in different organs of zebrafish that represent one of the most used experimental models for the study of several diseases. In particular, we analyzed the data obtained by immunohistochemical and molecular biology techniques concerning the presence and expression of ASICs in the sensory organs, such as the olfactory rosette, lateral line, inner ear, taste buds, and in the gut and brain of zebrafish

Localization of Neurotrophin Specific Trk Receptors in Mechanosensory Systems of Killifish (Nothobranchius guentheri)

Neurotrophins (NTs) and their signal-transducing Trk receptors play a crucial role in the development and maintenance of specific neuronal subpopulations in nervous and sensory systems. NTs are supposed to regulate two sensory systems in fish, the inner ear and the lateral line system (LLS). The latter is one of the major mechanosensory systems in fish. Considering that annual fishes of the genus Nothobranchius, with their short life expectancy, have become a suitable model for aging studies and that the occurrence and distribution of neurotrophin Trk receptors have never been investigated in the inner ear and LLS of killifish (Nothobranchius guentheri), our study aimed to investigate the localization of neurotrophin-specific Trk receptors in mechanosensory systems of N. guentheri. For histological and immunohistochemical analysis, adult specimens of N. guentheri were processed using antibodies against Trk receptors and S100 protein. An intense immunoreaction for TrkA and TrkC was found in the sensory cells of the inner ear as well as in the hair cells of LLS. Moreover, also the neurons localized in the acoustic ganglia displayed a specific immunoreaction for all Trk receptors (TrkA, B, and C) analyzed. Taken together, our results demonstrate, for the first time, that neurotrophins and their specific receptors could play a pivotal role in the biology of the sensory cells of the inner ear and LLS of N. guentheri and might also be involved in the hair cells regeneration process in normal and aged conditions

Zebrafish and Flavonoids: Adjuvants against Obesity

Obesity is a pathological condition, defined as an excessive accumulation of fat, primarily caused by an energy imbalance. The storage of excess energy in the form of triglycerides within the adipocyte leads to lipotoxicity and promotes the phenotypic switch in the M1/M2 macrophage. These changes induce the development of a chronic state of low-grade inflammation, subsequently generating obesity-related complications, commonly known as metabolic syndromes. Over the past decade, obesity has been studied in many animal models. However, due to its competitive aspects and unique characteristics, the use of zebrafish has begun to gain traction in experimental obesity research. To counteract obesity and its related comorbidities, several natural substances have been studied. One of those natural substances reported to have substantial biological effects on obesity are flavonoids. This review summarizes the results of studies that examined the effects of flavonoids on obesity and related diseases and the emergence of zebrafish as a model of diet-induced obesity

Expression of TRPV4 in the zebrafish retina during development

Issue Online: 21 May 2012; Version of Record online: 01 February 2012; Manuscript accepted: 22 October 2011; Manuscript received: 23 September 2011The transient receptor potential (TRP) channels are involved in sensing mechanical/physical stimuli such as temperature, light, pressure, as well as chemical stimuli. Some TRP channels are present in the vertebrate retina, and the occurrence of the multifunctional channel TRP vanilloid 4 (TRPV4) has been reported in adult zebrafish. Here, we investigate the expression and distribution of TRPV4 in the retina of zebrafish during development using polymerase chain reaction (PCR), Western blot, and immunohistochemistry from 3 days post fertilization (dpf) until 100 dpf. TRPV4 was detected at the mRNA and protein levels in the eye of zebrafish at all ages sampled. Immunohistochemistry revealed the presence of TRPV4 in a population of the retinal cells identified as amacrine cells on the basis of their morphology and localization within the retina, as well as the co‐localization of TRPV4 with calretinin. TRPV4 was first (3 dpf) found in the soma of cells localized in the inner nuclear and ganglion cell layers, and thereafter (10 dpf) also in the inner plexiform layer. The adult pattern of TRPV4 expression was achieved by 40 dpf the expression being restricted to the soma of some cells in the inner nuclear layer and ganglion cell layers. These data demonstrate the occurrence and developmental changes in the expression and localization of TRPV4 in the retina of zebrafish, and suggest a role of TRPV4 in the visual processing.Depto. de Optometría y VisiónFac. de Óptica y OptometríaTRUEpu

Micro and Nano Plastics Distribution in Fish as Model Organisms: Histopathology, Blood Response and Bioaccumulation in Different Organs

Micro- and nano-plastic (MP/NP) pollution represents a threat not only to marine organisms and ecosystems, but also a danger for humans. The effects of these small particles resulting from the fragmentation of waste of various types have been well documented in mammals, although the consequences of acute and chronic exposure are not fully known yet. In this review, we summarize the recent results related to effects of MPs/NPs in different species of fish, both saltwater and freshwater, including zebrafish, used as model organisms for the evaluation of human health risk posed by MNPs. The expectation is that discoveries made in the model will provide insight regarding the risks of plastic particle toxicity to human health, with a focus on the effect of long-term exposure at different levels of biological complexity in various tissues and organs, including the brain. The current scientific evidence shows that plastic particle toxicity depends not only on factors such as particle size, concentration, exposure time, shape, and polymer type, but also on co-factors, which make the issue extremely complex. We describe and discuss the possible entry pathways of these particles into the fish body, as well as their uptake mechanisms and bioaccumulation in different organs and the role of blood response (hematochemical and hematological parameters) as biomarkers of micro- and nano-plastic water pollution

Piezo 1 and Piezo 2 in the Chemosensory Organs of Zebrafish (<i>Danio rerio</i>)

The ion channels Piezo 1 and Piezo 2 have been identified as membrane mechano-proteins. Studying mechanosensitive channels in chemosensory organs could help in understanding the mechanisms by which these channels operate, offering new therapeutic targets for various disorders. This study investigates the expression patterns of Piezo proteins in zebrafish chemosensory organs. For the first time, Piezo protein expression in adult zebrafish chemosensory organs is reported. In the olfactory epithelium, Piezo 1 immunolabels kappe neurons, microvillous cells, and crypt neurons, while Calretinin is expressed in ciliated sensory cells. The lack of overlap between Piezo 1 and Calretinin confirms Piezo 1’s specificity for kappe neurons, microvillous cells, and crypt neurons. Piezo 2 shows intense immunoreactivity in kappe neurons, one-ciliated sensory cells, and multi-ciliated sensory cells, with overlapping Calretinin expression, indicating its olfactory neuron nature. In taste buds, Piezo 1 immunolabels Merkel-like cells at the bases of cutaneous and pharyngeal taste buds and the light and dark cells of cutaneous and oral taste buds. It also marks the dark cells of pharyngeal taste buds and support cells in oral taste buds. Piezo 2 is found in the light and dark cells of cutaneous and oral taste buds and isolated chemosensory cells. These findings provide new insights into the distribution of Piezo channels in zebrafish chemosensory organs, enhancing our understanding of their sensory processing and potential therapeutic applications

Neurotrophins and Trk Neurotrophin Receptors in the Retina of Adult Killifish (<i>Nothobranchius guentheri</i>)

Specific subpopulations of neurons in nerve and sensory systems must be developed and maintained, and this is accomplished in significant part by neurotrophins (NTs) and the signaling receptors on which they act, called tyrosine protein kinase receptors (Trks). The neurotrophins–tyrosine protein kinase receptors (NTs/Trks) system is involved in sensory organ regulation, including the visual system. An NTs/Trks system alteration is associated with neurodegeneration related to aging and diseases, including retinal pathologies. An emergent model in the field of translational medicine, for instance, in aging study, is the annual killifish belonging to the Nothobranchius genus, thanks to its short lifespan. Members of this genus, such as Nothobranchius guentheri, and humans share a similar retinal stratigraphy. Nevertheless, according to the authors’ knowledge, the occurrence and distribution of the NTs/Trks system in the retina of N. guentheri has never been investigated before. Therefore, the present study aimed to localize neurotrophin BDNF, NGF, and NT-3 and TrkA, TrkB, and TrkC receptors in the N. guentheri retina using the immunofluorescence method. The present investigation demonstrates, for the first time, the occurrence of the NTs/Trks system in N. guentheri retina and, consequently, the potential key role of these proteins in the biology and survival of the retinal cells