Snow Trout Schizothorax Richardsonii Research Articles

The study of effect of vitamin C and Achyranthes aspera seeds enriched diets on the growth, biochemical composition, digestive enzyme activities and expressions of genes involved in the biosynthesis of fatty acids in Snow trout Schizothorax richardsonii (Gray, 1832)

ABSTRACT Snow trout, Schizothorax richardsonii (Gray, 1832), is an economically important fish in the Himalayan region. Snow trout fry (118.53 ± 5.42 mg) were cultured in flow-through systems for 60 days. Fry were fed with four different diets containing: 0.08% vitamin C (D1), 0.5% Achyranthes aspera seeds (D2), both vitamin C and seeds (D3), and a control (D4). Average weight (271.82 ± 4.90 g) and specific growth rate (1.39 ± 0.03) were significantly higher in fish fed D3 compared to the others. Digestive enzyme activities were significantly higher in D3 compared to the others. EPA content was significantly higher in D2 (110.33 ± 0.94 mg 100 g−1) and D3 (109.87 ± 1.87 mg 100 g−1); DHA (342.70 ± 0.77 mg 100 g−1) and n-3 PUFA (496.17 ± 1.82 mg 100 g−1) contents were significantly higher in D3 compared to the others. The expression of fads2d6 was significantly higher in D3 (6.70-fold) and elovl5 in D2 and D3 (1.51–1.45-fold) compared to the others. Enriched diets improved fish flesh composition.

Dendritic prioritization through spatial stream network modeling informs targeted management of Himalayan riverscapes under brown trout invasion

Abstract With the concept of ‘riverscapes’ long pending to be acknowledged in the ‘landscape‐centric’ legislative framework of Himalayan nations, conservation of native riverine species stays practically unheeded. This necessitates urgent prioritization of stream networks to conserve the lotic taxa under invasion pressures. Himalayan riverscapes are pervaded with the invasive‐exotic brown trout Salmo trutta, posing serious threats to the co‐occurring native, the snow trout Schizothorax richardsonii. Using intensive surveys (218.7 km) and geostatistical stream network models (n = 537), we contrasted snow trout in two stream networks with and without invasives, for assessing differences in their spatial distribution. Our models indicate invasion‐induced relegations of natives from the river mainstem into headwaters, with large sections of mainstem occupied by invasives. Furthermore, a concerningly small percentage of potential habitat left for natives to occupy in the mainstem is threatened, where a 100% overlap of native and invasive trout distributions is predicted. With a higher presence probability for the natives in headwaters of invaded watershed as compared to the non‐invaded watershed, we highlight the headwater streams as potential refugia for the natives under invasion. Synthesis and Applications. Our approach of basin‐scale dendritic prioritization provides immediate management solutions to tackle brown trout invasion threats in Himalaya. We inform decisions on delineation of headwaters as invasion refugia for native fish, with assisted recovery of their fragmented populations in the river mainstems through targeted management of invasives.

Invasive brown trout Salmo trutta induce differential growth strategies in the native snow trout Schizothorax richardsonii of Himalaya: Are natives in unaltered rivers better at picking the gauntlet of invasion?

Brown trout Salmo trutta is a potent global invader and its establishments have progressively altered physiologies, life-histories and niche-availabilities for native fish species. River impoundments further escalate its invasion potential. The Himalayan rivers however, stay uncharted for the effects of brown trout interactions with the native fish fauna. Snow trout Schizothorax richardsonii a Himalayan cold-water native, concerningly overlaps its range with brown trout. To understand its responses to invasion pressures, we investigated brown trout effects on the age and growth of snow trout populations in three rivers with varying levels of perturbation: (a) a dammed and (b) an undammed river with the invasive brown trout in comparison to (c) an undammed river without invasion pressures. We found sympatric snow trout in the undammed river to respond to brown trout invasion with fast life history responses, showing an early age-at-maturity (A50 = 1.2 years) and fast growth with a higher growth constant (K = 0.40 yr−1) and specific rate of linear growth across life. On the contrary, sympatric snow trout in the dammed river showed an explicitly slow life-history by maturing at a higher age (A50 = 2.9 years) and a slow growth, with a lower growth constant (K = 0.26 yr−1) and specific linear growth rates. Our findings suggest that, the snow trout appear to present stronger response to brown trout invasions when the river is unaltered and free from hydropower operations and damming. Further research is strongly warranted from other high-altitude Himalayan basins to delineate the variation in growth strategies exhibited by snow trout in sympatry with the invasives.

Introduced, invaded and forgotten: allopatric and sympatric native snow trout life-histories indicate brown trout invasion effects in the Himalayan hinterlands

After 150 years of introduction of the brown trout Salmo trutta in Himalaya, the native species’ response to this globally pervasive invader, is still unknown. Here, we investigate the effects of invasion of brown trout on native snow trout Schizothorax richardsonii, one of the most primitive species that co-evolved with the Himalayan orogeny. We contrast two natural river systems which harbour snow trout in the absence (allopatry) and presence (sympatry) of brown trout. We put forth that sympatric snow trout adapted to a ‘fast’ life history with maturation at a smaller length, greater fecundity and smaller egg diameter to cope with brown trout invasion. However, investment in a reproductive-somatic trade off was evident with a disrupted size structure and reduced abundance as compared to the allopatric population. Although the fast life history adaptations of snow trout might increase their competitive ability with invasive brown trout, trading off the somatic fitness in the process seemingly acts as a deterrent to longevity. We attribute the plastic responses of snow trout to their plausible inherent potential of sustenance and recovery from high invasion pressures. The popularity of brown trout as a sport fish in Himalaya however poses extraneous propagule pressure on the snow trout, which warrants quantification through future research.

INFESTATION OF NEMATODE PARASITE FILOCHONA TELEOSTEI IN RELATION TO SIZE, WEIGHT AND AGE OF SNOW TROUT SCHIZOTHORAX RICHARDSONII (GRAY)

Parasitological investigation was conducted to assess the effects of various biotic factors viz. length, weight and age of host on the infection patterns of Filochona teleostei (Singh & Malik, 1992) in snow trout Schizothorax richardsonii (HAM.) from hill streams of Garhwal Himalayas. The statistical analysis was carried out to calculate infection incidence, mean worm burden, regression values and their significance. About 20% fishes (18% male and 22% female) were found infected with nematode parasites. Infection patterns of Filochona teleostei revealed a negative correlation (r= - 0.347 to - 0.734) with length, (r= - 0.499 to - 0.671) with weight and (r= - 0.576) with age of host fish. The age immunity and stronger host resistance developed by the larger fishes are the possible reasons for the decrease in infection in larger and older fishes.

STUDIES ON THE FEEDING OF SNOW TROUT, SCHIZOTHORAX RICHARDSONII (GRAY) BASED ON NATURAL AND ARTIFICIAL DIET

The present paper deals with food analysis and feeding behavior of the snow trout Schizothorax richardsonii (Gray) which is a cold water herbivore fish by nature. It is locally called Asela and is distributed in Himalayan and sub-Himalayan regions of Asia and has considerably attracted the attention of researchers due to its high productivity. The health and growth of fishes is greatly influenced by their nutrition and feeding. It has been observed in the present study that the adult fish naturally feeds on diatoms and algae. An experiment was conducted on artificial feeding of fish by giving three different types of food, i.e., formulated diet as control, periphton based diet and a mixture of both in different artificial raceways. It was observed that the fish conversion ratio (FCR) of the fish pooled in the raceway one (R1), i.e., feeding with formulated was high (6.85) due to balanced nutrients. It is recommended that with the introduction of balance artificial diet may be helpful in increasing the production of S. richardsonii.

Is there always space at the top? Ensemble modeling reveals climate-driven high-altitude squeeze for the vulnerable snow trout Schizothorax richardsonii in Himalaya

Mountain systems throughout the globe are conspicuously sensitive to on-going climate alterations. This condition is much more detrimental in the Himalaya, where the rate of warming and thus the glacier meltdown is much higher than elsewhere. The Himalayan coldwater species are concerningly most vulnerable to these changes because of their limited thermal range. Whilst climate studies strongly prognosticate the altered distribution of plants and mammals in this region, the impact on coldwater fishes still remains unknown. We used snow trout (Schizothorax richardsonii), a Himalayan coldwater specialist as a model organism to predict the current suitability and climate-driven potential range shift in an ensemble-based modeling framework. We collated occurrence data from a long term, extensive field-based sampling with additional records derived from an in-depth literature survey. A comprehensive input data set including topographic, hydrogeomorphic and climatic variables were used to build correlative species distribution models for the current and future time-periods (2050 and 2070) under three-carbon emission scenarios (Representative Concentration Pathways) by integrating five General Circulation Models. Furthermore, we predicted the elevation-specific range shifts of the snow trout in response to climate change. We predict that a wide-ranging mid-elevation river network is currently suitable for the snow trout in Himalaya, however a significant part of its current distributional range would be lost over time. Our results highlight that snow trout would expand their range upwards into the high-altitude streams with a concurrent predominant range contraction in most of their lagging edges, ultimately creating a high-altitude squeeze. The net habitat loss under three RCP scenarios (RCPs 2.6, 4.5 and 8.5) was estimated to range from 7.41% to 16.29% for the year 2050 which would further increase in the year 2070 ranging from 9.46% to 26.56%. These results provide a strategic information on prioritizing climate-adaptive actions to target the currently suitable habitats and future refugia identified. Our modeling framework also provides a foremost basis to conserve not only the snow trout but also to evaluate the climate impact on several other coldwater species, which are equally vulnerable and ecologically important in the Himalaya.

Molecular characterisation and transcriptional regulation of muscle growth regulatory factors myogenin and myogenic factor 6 in the Trans-Himalayan cyprinid fish Schizothorax richardsonii

In vertebrates, myogenic regulatory factors (MRFs) play an important role in muscle growth through the processes of cell determination and differentiation. Herein, we report the molecular characterisation of two MRFs, myogenin (myog) and myogenic factor 6 (myf6) in Indian snow trout Schizothorax richardsonii. The full length mRNA sequence of Srmyog and Srmyf6 was 1437 and 1296 bp, with an ORF of 762 and 720 bp, encoding a putative protein of 253 and 239 amino acids, respectively. In silico analysis and predicted tertiary protein structure revealed that both these nuclear localized MRFs contained the highly conserved basic helix loop helix motif, to potentially aid in dimerization with functional partners and DNA binding. Phylogenetically, the deduced protein sequences of Srmyog and Srmyf6 closely clustered with high altitude dwelling cyprinids, suggesting common ancestry. Tissue-wise, transcripts of Srmyog and Srmyf6 were abundant in skeletal muscle, affirming their muscle-specific role. Moreover, Srmyog was highly expressed in females as compared to males, whereas Srmyf6 expression was higher in older-bigger individuals as compared to younger-smaller fish. Nutritional status (fed-starved-refed) and diet composition (protein and lipid levels) had no significant influence on Srmyog expression. But, Srmyf6 expression was elevated in fishes re-fed after 3 weeks of starvation and in those fed low protein diet. Only rearing temperature was found to coherently influence Srmyog and Srmyf6 transcripts, with highest expression at 18 °C, which favoured growth. Overall, molecular characterisation of the structure and regulation of these MRFs is the first step taken towards deciphering slow growth in this important Himalayan cyprinid.

Interferon induced Mx protein from Indian snow trout Schizothorax richardsonii (Gray) lacks critical functional features unlike its mammalian homologues

Viral attack within host cells triggers the production of type I interferons and leads to the induction of interferon stimulated genes (ISGs). One of the ISG Mx, encodes type I interferon inducible GTPase that is responsible for the establishment of an anti-viral state within cells. Intriguingly, several isoforms of Mx have been reported in fish, but the structural analysis of fish Mx proteins remains unexplored. For the first time, we have identified and unraveled the molecular structure of Mx protein from Indian snow trout, Schizothorax richardsonii (Gray) a Coldwater fish that inhabits the water bodies in the sub-Himalayan region. The snow trout Mx coding region consists of 2518 nucleotides with an open reading frame (ORF) of 1854 nucleotides. It codes for a polypeptide of 617 amino acids with a predicted molecular weight of 70 kDa. In silico analysis of snow trout Mx protein revealed signature of dynamin family (LPRGTGIVTR) along with a tripartite GTP-binding domain (GDQSSGKS, DLPG, and TKPD). Homology modelling established that the Mx protein is an elongated structure with a G domain, bundle signaling element (BSE) and a GTPase effector domain (GED). Moreover, the GED of Mx contains two highly conserved leucine zippers at the COOH-terminal of the protein suggesting its structural similarity with human homologues. However, snow trout Mx lacks the essential features of its mammalian homologues questioning its functional characteristics. Further, a ligand binding site in the said protein has also been predicted adjacent to the GTPase switch within the G domain.

Activities of digestive enzymes in relation to ingested natural food in three carp species of the Himalayan River Ladhiya, northern India

The present investigation was carried out to study gut content and accompanying digestive enzyme profiles of the three carp species, golden mahseer Tor putitora, snow trout Schizothorax richardsonii and hill trout Barilius barila. The fishes were captured from the River Ladhiya, Champawat district, Uttarakhand, northern India. The digestive tract length was on average 1.8 and 2.3 times longer than the body, while members of Bacillariophyceae, Chlorophyceae, Cyanophyceae and Zygnematophyceae made up 95.15% and 99.63% of gut content in the golden mahseer and snow trout, respectively. In hill trout, the digestive tract being only half the body length, gut content was insects (72.73%), eggs of aquatic organisms (22.73%) and nematodes (4.55%). Estimated gut enzyme activities demonstrated that amylase activity was significantly (P < 0.05) higher in golden mahseer and snow trout compared to hill trout, while total protease, trypsin and chymotrypsin activities were all significantly (P < 0.05) higher in the hill trout compared to other species. A strong co-relation was found among relative gut length, food composition and digestive enzyme activities of each species. This may guide the future formulation of feed to these important species of carps kept in farm.

Studies on fecundity of snow trout Schizothorax richardsonii (Gray) from the lotic bodies of Rajouri district (J&amp;K).

The present work embodies studies on the reproductive capacity of Snow trout Schizothorax richardsonii collected from various streams of Rajouri district (J&K). About 50 fishes, ranging from 21.0 to 32.9 cm of total length, were put to the study of fecundity in relation to Fish length, Fish weight, Ovary length, Ovary weight and Ova diameter. The other aspects studied include relationship between Fish length and Ovary length, Ovary weight and Ova diameter. All the parameters were put to regression analysis. The higher values of correlation coefficient (re”0.9) in all the studied parameters indicated a strong correlation between them. However, the relationship between Fecundity and Fish length came out to be the highest indicating the dependence of Fecundity more on the length of fish body than other parameters.

Morphology of adhesive organ of the snow trout Schizothorax richardsonii (Gray, 1832)

This paper describes the morphology and fine structure of adhesive organ (AO) of the snow trout Schizothorax richardsonii (Gray, 1832). The species lives in the sub‐Himalayan streams and rivers, where they adhere to submerged rocks and stones with its AO located beneath the mouth opening. The AO consists of a crescent callus part and a modified labial fold, bearing numerous tubercles. In both parts, the epidermis is exceptionally thick (150–170 µm) and contains keratinocytes rich in bundles of tonofilaments; elsewhere, the epidermis contains single, disperse filaments, mucous cells and other usual cells seen in teleosts. Unlike epidermis elsewhere, the outer 4–5 row cells of the AO epidermis undergo keratinisation and are cytokeratin positive. The individual keratinised cell layers, which are degenerated electron‐dense sheets, lack nuclei and cytoplasmic organelles, but possess filaments embedded in a dense cytoplasmic matrix and few, large mucous‐like granules. Beneath the keratinised layers, keratinocytes are compactly aligned into 20–25 rows. They possess abundant thick bundles of clumped tonofilaments over the entire cytoplasm and peripherally, small mucous granules. Towards the basal epidermis, the cells are elongated and show major cytoplasmic organelles, few tonofilament bundles, but no mucous granules. It is evident that the keratinocytes of the mid‐epidermis are differentiated for the production of tonofilaments. The outer keratinised part of the AO epidermis provides structural support and protection (from damage) during adhesion. It appears that the callus part acts by creating vacuum first, while the tuberculated part of the AO epidermis assists in adhesion to the rocky substratum.