Teleost is a widely diverse group of fishes and so do their feeding habits. From aquaculture points of view, there have been un-interrupted efforts to optimize feeding rates with protein as the chief ...ingredients in the supplementary diet. However, knowledge on its protein absorption is incomplete so far, to acquire absolute feeding design to mobilize enhanced production of animal-source protein as fish biomass. In this review, the variable protein absorption across digestive tract (DT) in this group of fish has been highlighted. Emphasis is given to outline how DT components, like enterocyte specific absorptive mechanisms, are different in anterior and posterior regions of DT or from the absorptive transporter system. The existence of a transporter-based absorption mechanism brings more variability in the protein absorption in teleosts. At least two such transport systems (Na
+
-dependent and Na
+
-independent) with within-system differences impart more variability to protein absorption. Further, shifting from one stage to another stage of development involves considerable modification of the protein absorptive mechanism in teleosts. Gut microbes may also indirectly facilitate protein absorption in teleosts. Overall, the present review projects a comprehensive understanding of the protein absorption in teleosts that will help to strategize the modulation of feeding technology in fish culture.
•Ensemble species distribution modelling was done for freshwater fish.•Occurrence records of small freshwater fish Amblypharyngodon mola were used.•Climatic, topographic, landcover and soil variables ...were used as predictors.•Upstream precipitation, soil pH and elevation were found to be the key indicators.•Ganges delta region was found to be most suitable habitat.
The key challenge in the fields of conservation and resource management is to track local, regional and global species extinctions and preserve biodiversity through optimization of investment of funds. To fulfil that purpose modelling and mapping habitat suitability of species is becoming essential. The freshwater ecosystem is today one of the most threatened ecosystems and fishes are especially vulnerable for climate change as they have fewer choices for dispersal. The altered thermal regimes, land use and hydrology together cause isolation, fragmentation and changes in distributional patterns of fish. In such landlocked situation, there is utmost need to identify suitable environmental conditions for a species to exist. Indigenous fish is one of the essential components of healthy inland aquatic ecosystems as they fulfil several important ecological functions and form an important part of the aquatic food web. Amblypharyngodon mola is an economically and ecologically important indigenous freshwater fish species of the tropical and subtropical floodplain rivers and wetland habitats of India and Bangladesh. However, lack of knowledge about the key environmental indicators is hindering appropriate management and conservation initiation. Modelling and mapping the distribution of A. mola was done for identifying the key environmental variables and predicting the potential distribution area of the species in current climatic condition. The species occurrence data were accessed from both primary and secondary sources and used after cleaning and removing biasness. Climatic, topographic, landcover and soil variables of 1 km resolution were used as environmental predictors. India and Bangladesh together were used as model background. Ensemble species distribution modelling was done, and the model was validated by area under the curve (AUC) value (>0.7). The result showed that the Ganges delta of lower reach going through West Bengal and Bangladesh is most suitable for A. mola occurrence. Annual upstream precipitation (hydroclim_12), soil pH in water (soil_average_02) and elevation (ele_01) are the key indicators for predicting the habitats suggesting the importance of hydroclimatic, topographic and soil variables in determining the distribution of the fish.
The histological as well as ultramicroscopic structures of olfactory system of an amphihaline migratory fish hilsa Tenualosa ilisha, were studied. The sexually matured riverine fish were collected ...from a common breeding habitat—the Hooghly, a tributary of river Ganga, West Bengal, India. This study revealed that the riverine hilsa has larger olfactory bulb compared to marine hilsa with the olfactory lobes well exposed through nostrils. The olfactory lamellae (OL) are 40–45 in number and posses three distinct layers of sensory cells across each lamellae, namely, outer receptor cells (RC), middle sensory cells, and inner basal cells (BC). Besides the above arrangement, the sensory part of olfactory epithelium (OE) also bears rich microvillous cells exposed to the surface of the OE. The sensory and non‐sensory surfaces on OL are distinguishable, with clear dendritic cells on sensory epithelium and solitary chemosensory cells on non sensory OE. Abundance of both types of cells in the OE is an indication of its chemoattraction ability towards molecules of amino acid origin. The feature of having abundant, dense, and large dendritic knobs on the surface of OE describes resemblance to the typical morphology of the chemosensory septal organs neuron. The expression of four G protein subunits, like Gαs/olf, Gαq, Gαo, and Gαi‐3 in OE indicate that its olfaction is a functional attributes of two olfactory systems, namely main olfactory system and Vomaronasal Olfactory System. Expression of ACIII and PLCβ2 in OE further confirms two signaling pathways involved in odorant reception in hilsa.
Research Highlights
The olfactory bulb in the amphihaline migratory fish hilsa is big in size, with 40–45 lamellae. Its sensory areas showed multilayered cellular features with prominent sensory as well as microvillous cells, whereas non‐sensory area possesses solitary chemosensory cells. The expression of four G protein subunits, Gαs/olf, Gαq, Gαo, and Gαi‐3 in olfactory epithelium indicates that its olfaction is a functional attributes of two olfactory systems, namely main olfactory system and vomaronasal olfactory system.
The feeding ecology of
was investigated for two consecutive years (2013-2015) from floodplain wetlands in the Subansiri river basin of Assam, North East India. The analysis of its gut content ...revealed the presence of 62 genera of planktonic life forms along with other animal matters. The organization of the alimentary tract and maximum Relative Mean Length of Gut (0.511±0.029 mm) indicated its carnivorous food habit. The peak gastro-somatic index (GSI) in winter-spring seasons and summer-rainy seasons indicated alteration of its feeding intensity. Furthermore, higher diet breadth on resource use (Levins’ and Hurlbert’s) with zooplankton compared to phytoplankton and total plankton confirmed its zooplanktivore habit. The feeding strategy plots also suggested greater preference to zooplankton compared to phytoplankton. The organization of its gill rakers specified a secondary modification of gut towards either carnivory or specialized zooplanktivory. So, the fish may be a carni-omnivore with preference to zooplankton.
The electron microscopic and histological studies of the buccal‐cavity of herbivorous fish Mola (Amblypharyngodon mola) were performed. The studies revealed that the architectures of the buccal ...cavity of A. mola support the herbivory nature of the fish. Both the upper and lower jaws of the fish are rich in mucus glands, unculi, and microridges. The presence of papillae like taste buds in the lower jaw of A. mola indicates the mechanosensory role of the lower jaw during gustation. These features directly support a gustatory feeding behavior associated with filter feeding in this small freshwater fish.
The study revealed new features of Amblypharyngodon mola to explain its feeding habits. The presence of rich mucus glands with microridges indicates its filter‐feeding nature, whereas the occurrence of papillae like taste buds confers the presence of gustatory feeding habits of the fish.
Management of fed-fish culture practices, at present, stands on two broad feed categories, (i) formulated proteinaceous aquafeeds and (ii) the natural resources. Judicious use of the later is gaining ...popularity since it offers sustainability to fish culture. Polyculture often targets phyto- and zooplanktonic resources, but mostly ignores periphyton. This review discusses the works on feed diversification performed independently at different times. Fishes, viz. Cyprinus carpio, Labeo rohita and Amblypharyngodon mola were projected as potential candidates for resource - nutrient management with feed diversification in rice fish culture. With C. carpio the rice fish culture called Aji Gnui Assonii in terrace water-logged rice field of Apatani Plateau, Arunachal Pradesh (India) is referred as self-substrating aquaculture practice. This monoculture practice experiences high carp productivity since there remains surplus of resources below the threshold level in these rice fields. Similarly, L. rohita, explores periphytic resources in ponds when substrates are installed. As a result, filter feeders get more foraging aquatic phase intensifying the resources for exploration in pond. This concept is suggested for rice fields with water depth above 50 cm where rice stems act as substrate. With trenches or refuge canals, resource intensification may be managed for more cultivable fishes in rice fields with <50 cm water depth. This model of resource intensification further allows inclusion of Small Indigenous Fish Species (SIFs)-which are rich source of many micronutrients. Thus, integration of SIFs confers huge potentiality for intensification of nutrients, especially protein and micronutrients in rice fields.
Epidermal sensory structures of adults and juveniles of amphihaline migratory fish hilsa
Tenualosa ilisha
were studied from two habitats, i.e., freshwater (FW) and marine water (MW). Every year, ...adults and sexually mature hilsa migrate upstream from marine habitat to riverine freshwater habitat for breeding. This report provides evidences of chemoreception on their upstream migration through several characteristic features on their body, especially on the head and oral cavity. Scanning electron microscopy (SEM) reveals that freshwater adult hilsa (FH) has abundant solitary chemosensory cells (SCCs) on the snout epidermis (around the openings of the epidermal pit) and upper lip, whereas marine water adult hilsa (MH) moderately possesses such sensory structures. The juveniles returning to marine water completely lack SCCs. Immunohistochemical studies revealed the expression of PLC β2 on the snout of FH and tongue of both FH and MH. Further analysis (immunofluorescence, immunoblot and densitometry) of the epidermis confirms the presence of chemosensory structures through strong expression and localization of G-proteins (Gαq and Gα s/olf) from the snout as well as tongue in freshwater hilsa. The SEM also confirms the presence of two types of taste buds in FH, viz. type I (TB I) and type III (TB III). Whereas TB I and TB III are observed on the upper palatine and lips, most of the TB III are located on the tongue region of freshwater and marine hilsa. The juvenile hilsa are devoid of such structures. The presence of dense and rich SCCs and taste sensory cells in adults could be a characteristic feature for strong sensory reception to recognize odour and food-related environmental cues from habitats where they often migrate.
Two teleosts (Rohu, Labeo rohita and Koi, Anabas testudineus), both with contrasting feeding habits (herbivorous versus carnivorous) were studied for amylase and protease activity concerning ...different regions of their digestive tracts. Significant differences in enzymatic activity across different regions of the digestive tracts were observed. Rohu, with three equal regions of the stomachless gut, showed the highest amylolytic activity at the posterior digestive tract but the highest proteolytic activity is limited to mid region. Contrary to such observation, Koi with three distinct regions of the digestive tract (stomach, pyloric caeca and intestine), the pyloric caeca exhibited the highest specific activity for both amylase and total protease. The optimum pH and temperature conditions were determined concerning the activity for both amylase and protease.
Saccharomyces cerevisiae is an established model organism with a well characterized genome. However, this model presents a unique problem due to a very resistant cell wall which develops in the late ...stationary phase resulting in sub-optimal extraction of proteins from such cells using majority of the cell lysis protocols. In this study, several methods from the literature with modifications thereof for lysis of S. cerevisiae cells were analyzed for their suitability for redox proteomics and biological activity studies of both exponential and late stationary phase cultures. The protocols applied are glass bead lysis, sonication, their combinations, alkali extraction, hot-SDS extraction methods and their modifications. The glass bead lysis method showed low yield but could be convenient in cases where in vitro processing steps post extraction is required or if only hydrophilic proteins are of interest. Hot-SDS and alkali extraction protocols yielded higher amount of proteins and these methods are potentially suitable for Western blotting and redox proteomic studies but allow no post-processing treatment(s) on the extracts which may be required for aging- and oxidative stress-related or other studies.
•Proteins were extracted from different strains of Saccharomyces cerevisiae.•Cells of Saccharomyces cerevisiae were of young and old (chronological) ages.•Maximum yield was obtained using the modified alkali method.•The hot-SDS method should be useful for redox proteomics studies.•The glass bead lysis method is optimum if in vitro processing is required.
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