Early Juvenile Stages Research Articles

Sonic hedgehog (shh) gene from Pseudopleuronectes yokohamae (Teleostei: Pleuronectidae): Molecular cloning, characterization, and expression profile during early embryonic, juvenile, and adult stages.

The hedgehog signaling pathway plays an important role in early development and growth of most vertebrates. Sonic hedgehog (shh) gene is a critical regulator of embryonic development in many species, including humans. However, it is not clear what roles shh can play in the development of fish. In this paper, shh gene was cloned from Pseudopleuronectes yokohamae. The full-length complementary DNA (cDNA) of P. yokohamae sonic hedgehog gene (Pyshh) comprises 3194 bp, with a 1317-bp open reading frame (ORF) that encodes a polypeptide of 438 amino acids with a typical HH-signal domain and Hint-N domain. The conserved sequences of the protein among species were predicted by using multiple sequence comparison. The phylogenetic tree construction showed that PySHH is clustered in a branch of Pleuronectidae. To explore the expression of Pyshh gene in various tissues of P. yokohamae, we used real-time fluorescence quantitative PCR technology to detect it. The results showed that Pyshh gene is widely distributed in various tissues of P. yokohamae juveniles, different tissues of adult males and females, and is particularly expressed in immune organs. The Pyshh gene expression was higher in the muscle and brain of juvenile fish, and higher in bone, gill, and skin of male fish than that of female fish, suggesting that Pyshh might be involved in the formation of immune organs of P. yokohamae. The expression of Pyshh gene significantly upregulated from the gastrula stage to the hatching stage. Western blotting of the expression levels of PySHH during different embryonic development stages revealed that PySHH levels increased gradually during development stages from oosperm stage to hatching stage. These results indicate that Pyshh is highly conserved among species and plays a critical role in the complex process of embryonic development. Its precise regulation is essential for the proper formation of many organs and tissues in the body, and disruptions in its function may have serious consequences for the formation of immune organs in fish.

Effects of low temperature on growth and metabolism of larval green sturgeon (Acipenser medirostris) across early ontogeny.

Southern Distinct Population Segment (sDPS) green sturgeon spawn solely in one stretch of the Sacramento River in California. Management of this spawning habitat is complicated by cold water temperature requirements for the conservation of winter-run Chinook salmon. This study assessed whether low incubation and rearing temperatures resulted in carryover effects across embryo to early juvenile life stages on scaling relationships in growth and metabolism in northern DPS green sturgeon used as a proxy for sDPS green sturgeon. Fish were incubated and reared at 11°C and 15°C, with a subset experiencing a reciprocal temperature transfer post-hatch, to assess recovery from cold incubation or to simulate a cold-water dam release which would chillrearing larvae. Growth and metabolic rate of embryos and larvae were measured to 118days post hatch. Reciprocal temperature transfers revealed a greater effect of low temperature exposure during larval rearing rather than during egg incubation. While 11°C eggs hatched at a smaller length, log-transformed length-weight relationships showed that these differences in developmental trajectory dissipated as individuals achieved juvenile morphology. However, considerable size-at-age differences persisted between rearing temperatures, with 15°C fish requiring 60days post-hatch to achieve 1g in mass, whereas 11°C fish required 120days to achieve 1g, resulting in fish of the same age at the completion of the experiment with a ca. 37-fold difference in weight. Consequently, our study suggests that cold rearing temperatures have far more consequential downstream effects than cold embryo incubation temperatures. Growth delays from 11°C rearing temperatures would greatly increase the period of vulnerability to predation in larval green sturgeon. The scaling relationship between log-transformed whole-body metabolism and mass exhibited a steeper slope and thus an increased oxygen requirement with size in 11°C reared fish, potentially indicating an energetically unsustainable situation. Understanding how cold temperatures affect green sturgeon ontogeny is necessary to refine our larval recruitment estimations for this threatened species.

The embryonic role of juvenile hormone in the firebrat, Thermobia domestica, reveals its function before its involvement in metamorphosis.

To gain insights into how juvenile hormone (JH) came to regulate insect metamorphosis, we studied its function in the ametabolous firebrat, Thermobia domestica. Highest levels of JH occur during late embryogenesis, with only low levels thereafter. Loss-of-function and gain-of-function experiments show that JH acts on embryonic tissues to suppress morphogenesis and cell determination and to promote their terminal differentiation. Similar embryonic actions of JH on hemimetabolous insects with short germ band embryos indicate that JH's embryonic role preceded its derived function as the postembryonic regulator of metamorphosis. The postembryonic expansion of JH function likely followed the evolution of flight. Archaic flying insects were considered to lack metamorphosis because tiny, movable wings were evident on the thoraces of young juveniles and their positive allometric growth eventually allowed them to support flight in late juveniles. Like in Thermobia, we assume that these juveniles lacked JH. However, a postembryonic reappearance of JH during wing morphogenesis in the young juvenile likely redirected wing development to make a wing pad rather than a wing. Maintenance of JH then allowed wing pad growth and its disappearance in the mature juvenile then allowed wing differentiation. Subsequent modification of JH action for hemi- and holometabolous lifestyles are discussed.

The distribution of the juvenile stages and eggcases of skates (Rajidae) around the British Isles

Abstract Skates (Rajidae) include species of conservation and commercial importance, but there is limited information regarding their ecologically important habitats, including spawning and nursery areas, in northern European seas. Data on the distribution, relative abundance and length composition of skates were collated from scientific trawl surveys, and based on length‐frequency information, length‐at‐hatching and length‐at‐maturity, skates were allocated to length‐based categories representing early‐juvenile stages (EJS) and mid‐juvenile stages (MJS). Citizen science data were used to inform on the occurrence of eggcases. The Great Eggcase Hunt (starting in 2003) citizen science recording project collects georeferenced data for elasmobranch eggcases, primarily from around the British Isles. This provided verified species‐specific data for a total of 227,407 specimens from 11 skate species. Purse Search Ireland (starting in 2005) provided a further 2491 records of 10 skate species from around Ireland. The most frequently observed skate eggcases were from the genus Raja and occurred around much of the British Isles. The EJS and MJS of such species were observed most frequently in inshore waters. Data for EJS were more limited for Raja microocellata and Raja undulata, indicating that the EJS of these species occur in shallower (<20 m) waters. Juveniles of the genus Leucoraja occurred further offshore. Only the eggcases of Leucoraja naevus were recorded regularly, with the eggcase of Leucoraja fullonica described here. The data collated here provide an overview of skate spawning and nursery areas, thus informing fisheries management and marine spatial planning, including the identification and delineation of Important Shark and Ray Areas (ISRAs).

Narrowed gene functions and enhanced transposon activity are associated with high tolerance to ocean acidification in a juvenile subarctic crustacean

Ocean acidification (OA) threatens marine crustaceans, particularly those at high latitudes where conditions are rapidly changing. Red king crab (RKC) support important fisheries in Alaskan waters. RKC early life stages are sensitive to OA when exposure occurs as embryos and juveniles. However, in a supporting study, RKC were surprisingly tolerant of varying OA conditions (pH 7.5, 7.8, & 8.0) when reared long-term from larval hatching to the first crab stage (C1). Here, we examined gene expression in the C1 juveniles to characterize transcriptional activity of these OA-tolerant crabs. Expression of nearly half of all genes (44%) correlated with OA treatment, suggesting a strong molecular response to OA, contrary to the phenotypic results. Downregulated functions were numerous in response to OA, and included reduced energy production, biosynthesis, immune function, and notably lipid and carbohydrate metabolic processes, which suggest a shift in metabolic strategy to protein catabolism, possibly to reduce CO2 production and facilitate acid/base regulation. Only a handful of functions were enriched in OA-induced genes, which were related to transcription regulation, control of growth and cell death, and signaling activity. Transposon activity was high in OA-reared crab, many of which were upregulated at consistent levels, suggesting that transposon mobilization may be a component of the RKC OA-response system. Genetic composition did not differ among OA treatments indicating that transcriptional differences in OA-reared crab were more likely attributed to phenotypic plasticity than selective mortality. Our results suggest that OA-reared RKC have a narrowed, possibly optimized, set of gene functions that enables OA-tolerance through the early juvenile stage. OA-exposure from hatch may benefit RKC and related species by “hardening” them against OA through physiological reprogramming. Future studies should test OA-hardened crabs in additional challenges, as metabolic and immune limitations may ultimately make them more vulnerable to infection or secondary stressors.

An examination of Homo naledi early juveniles recovered from the Rising Star cave system, South Africa

Background Six Homo naledi early juveniles were recovered from U.W. 101 (Dinaledi Chamber), U.W. 102 (Lesedi Chamber), and U.W. 110 in the Rising Star cave system. Aim This paper develops the information for the H. naledi early juvenile life stage, as defined by a combination of deciduous and permanent dentition, and the eruption of the first permanent molar. Subjects and methods The growing number of young individuals recovered from the Rising Star cave system allows us to gain a better understanding of their variation, or lack thereof, and provides a basis to estimate broad ranges for age at death of the individuals. The individuals are identified and described through craniodental remains and spatial associations. Results and conclusion Our results show that the teeth are remarkably consistent across the localities in their metric and non-metric traits, and our analyses refine previous estimations on dental eruptions with the first permanent molar erupting first in the sequence among permanent teeth.

Post-settlement dynamics of Japanese flounder Paralichthys olivaceus in Tango Bay: Seasonal patterns in growth, mortality, and recruitment potential.

Japanese flounder Paralichthys olivaceus is one of the most valuable coastal flatfish species in East Asia. To investigate post-settlement growth and mortality, juveniles were sampled in Tango Bay (Japan) weekly throughout the settlement period in 2007 and 2008. Otolith (lapillus) microstructure analysis enabled the categorization of juveniles into six biweekly cohorts each year. Later cohorts exhibited higher growth rates possibly because of higher water temperatures. A key observation was the direct relationship between high mortality and high density in mid-season cohorts in both years, pointing to density-dependent mortality. This increased mortality may be attributed to predation, including cannibalism by earlier cohorts. Furthermore, growth-selective mortality was evident soon after settlement, underscoring the vulnerability of slow growers to predation during the early juvenile stage. Although earlier and later cohorts were less abundant but showed promising recruitment potential, the prospective contribution of mid-season cohorts to the adult population remained uncertain. The results clearly highlight the importance of density-dependent mortality in population regulation in post-settlement Japanese flounder.

Copper Stress Causes Shell Morphology Changes in Early Juvenile Anodonta woodiana Based on Geometric-Morphometric Analysis.

In this study, the morphological characteristics of early juvenile shells of Anodonta woodiana, which were exposed to different concentrations of aqueous copper, were analyzed using 10 landmarks to determine morphological changes in the shells. Morphological changes mainly occurred at the top of the shell and front and back ends of the central axis. Stepwise discriminant analysis proved shape differences among experimental and control groups. The results of this study demonstrate for the first time that environmentally relevant copper concentrations cause stress-related morphological changes in A. woodiana in the vulnerable early juvenile stage.

Growth performance, hematological and oxidative stress responses in Nile tilapia (Oreochromis niloticus) exposed to polypropylene microplastics

AbstractThe present study investigated the effect of polypropylene (PP) microplastics on the growth performance, hematological profile and oxidative stress responses in the liver and brain tissues of Oreochromis niloticus juvenile. The microplastic exposure was done by offering microplastic‐incorporated feed to the fish. The feed was prepared by mixing microplastics and the feed in three different ratios; Low (1.5 g/kg), Medium (3.0 g/kg), High (4.5 g/kg), and a control with no plastics in it. The trial was done for 7 weeks. A significant impact on the growth performance of the fish was observed in terms of body weight gain, specific growth rate, metabolic growth rate, protein efficiency ratio and energy retention. All the treatments had a significant difference in growth parameters compared to the control. The results of the hematological profile confirmed erythropoietic impairment in the fishes due to high microplastic exposure which led to an anemic condition in the fishes and mortality in the early juvenile stage. The antioxidant enzyme analysis also shows significant oxidative stress induced in liver and brain tissues in a dose‐dependent manner. Exposure to PP microplastics significantly affected the growth, health and metabolism of O. niloticus. Further studies on genetic and cellular levels should be done to elucidate the wide‐ranging effects of MPs on fish species.

Development and application of a bioenergetics growth model for multiple early life stages of an ecologically important marine fish

Spatial and temporal variability in temperature and food availability are key drivers of growth of marine fishes. Growth during the early life stages (ELS's) is tightly coupled to survival, and in turn, can set year-class strength (i.e. annual recruitment) and overall stock productivity of populations and fished stocks. Ontogenetic changes in physiology, dietary preferences, and growth across ELS's can be accounted for within bioenergetics models, but existing models lack resolution within larval and early juvenile stages. We leveraged daily output from a coupled physical-biogeochemical model to force a highly resolved ontogenetic bioenergetics model parametrized for an ecologically important rockfish in the California Current System. Size-at-age predictions closely track empirical growth trajectories of the ELS's. Scenario testing revealed that growth performance is disproportionately driven by changes in temperature compared to food availability. We then expanded the model to incorporate spatial climatological differences in temperature and prey concentration and found that preflexion growth potential is maximized in areas of historical spawning, suggesting the timing and location of reproduction is an adaptive strategy that places larvae in habitat favorable for survival. Growth potential for late-stage larvae (postflexion) is greatest over a broad areal extent, implying that if a particle tracking algorithm was coupled to the bioenergetics model, a wide range of larval dispersal pathways would place postflexion larvae in habitat suitable for rapid growth. Finally, growth potential of pelagic juveniles is maximized over the continental shelf and shelf-break, aligning with high juvenile catch rates from a fisheries-independent survey. In summary, this study (i) serves as a proof of concept that a bioenergetics model with high ontogenetic resolution can reproduce life stage-specific growth trajectories even though the underlying physiology data for model parameterization is imperfect and (ii) can aid future studies aimed at understanding how ecosystem processes interact with ontogenetic growth and changes in year class strength of early life stages of marine fishes.

Upwelling as a stressor event during embryonic development: Consequences for encapsulated and early juvenile stages of the marine gastropod Acanthina monodon

Upwelling phenomena alter the physical and chemical parameters of the sea's subsurface waters, producing low levels of temperature, pH and dissolved oxygen, which can seriously impact the early developmental stages of marine organisms. To understand how upwelling can affect the encapsulated development of the gastropod Acanthina monodon, capsules containing embryos at different stages of development (initial, intermediate and advanced) were exposed to upwelling conditions (pH = 7.6; O2 = 3 mg L−1; T° = 9 °C) for a period of 7 days. Effects of treatment were determined by estimating parameters such as time to hatching, number of hatchlings per capsule, percentage of individuals with incomplete development, and shell parameters such as shell shape and size, shell strength, and the percentage of the organic/inorganic content.We found no significant impacts on hatching time, number of hatchlings per capsule, or percentage of incomplete development in either the presence or absence of upwelling, regardless of developmental stage. On the other hand, latent effects on encapsulated stages of A. monodon were detected in embryos that had been exposed to upwelling stress in the initial embryonic stage. The juveniles from this treatment hatched at smaller sizes and with higher organic content in their shells, resulting in a higher resistance to cracking 30 days after hatching, due to greater elasticity.Geometric morphometric analysis showed that exposure to upwelling condition induced a change in the morphology of shell growth in all post-hatching juveniles (0–30 days), regardless of embryonic developmental stage at the time of exposure. Thus, more elongated shells (siphonal canal and posterior region) and more globular shells were observed in newly hatched juveniles that had been exposed to the upwelling condition. The neutral or even positive upwelling exposure results suggests that exposure to upwelling events during the encapsulated embryonic phase of A. monodon development might not have major impacts on the future juvenile stages. However, this should be taken with caution in consideration of the increased frequency and intensity of upwelling events predicted for the coming decades.

Ontogeny and social context regulate the circadian activity patterns of Lake Malawi cichlids

Activity patterns tend to be highly stereotyped and critical for executing many different behaviors including foraging, social interactions, and predator avoidance. Differences in the circadian timing of locomotor activity and rest periods can facilitate habitat partitioning and the exploitation of novel niches. As a consequence, closely related species often display highly divergent activity patterns, suggesting that shifts from diurnal to nocturnal behavior, or vice versa, are critical for survival. In Africa’s Lake Malawi alone, there are over 500 species of cichlids, which inhabit diverse environments and exhibit extensive phenotypic variation. We have previously identified a substantial range in activity patterns across adult Lake Malawi cichlid species, from strongly diurnal to strongly nocturnal. In many species, including fishes, ecological pressures differ dramatically across life-history stages, raising the possibility that activity patterns may change over ontogeny. To determine if rest-activity patterns change across life stages, we compared the locomotor patterns of six Lake Malawi cichlid species. While total rest and activity did not change between early juvenile and adult stages, rest-activity patterns did, with juveniles displaying distinct activity rhythms that are more robust than adults. One distinct difference between juveniles and adults is the emergence of complex social behavior. To determine whether social context is required for activity rhythms, we next measured locomotor behavior in group-housed adult fish. We found that when normal social interactions were allowed, locomotor activity patterns were restored, supporting the notion that social interactions promote circadian regulation of activity in adult fish. These findings reveal a previously unidentified link between developmental stage and social interactions in the circadian timing of cichlid activity.

Could extremophilia be a life history strategy in late-stage larvae of Sparodon durbanensis (Family Sparidae)?

Microbialite pools are dynamic, heterogenous environments with extreme physico-chemical variability in terms of temporal temperature, oxygen and salinity fluctuations. Despite this habitat being hypothesised to be an ecological trap for larvae of marine estuary-dependent fishes, late-stage larvae and early juvenile White musselcracker (Sparodon durbanensis) ubiquitously occur in these pools. This study aimed to investigate the relationship between S. durbanensis density, developmental stage, total length and the physico-chemical environment using a multiple linear regression model analysis. Moreover, it aimed to further explore the potential nursery role of these extreme habitats. All larval and early juvenile stage S. durbanensis were collected with hand nets from pools at three representative microbialite sites on the warm temperate coast of South Africa from late summer to late autumn in 2021. A total of 63 pools were sampled with a total of 57 postflexion larvae and 162 early juvenile S. durbanensis specimens collected. Pool temperatures ranged from 16.6 to 37.3 °C with a mean of 24.5 °C, dissolved oxygen concentration ranged from 5.5 to 26.0 mg/L with a mean of 13.5 mg/L, and salinity ranged from 1.3 to 34.8 with a mean of 25.4. Temperature had a significant positive relationship with total length for early juvenile stages, while none of the other predictor variables showed evidence of a significant relationship with total length. Fish density showed a significant relationship with pool volume for both developmental stages where higher densities occurred in smaller pools that were also characterised by the most extreme physico-chemical variability. Late-stage larvae and early juveniles of this marine fish, that does not use estuaries as a nursery area, appears to complete the larval phase under extreme estuarine-like conditions in microbialite pools. Microbialite pools, as well as adjacent non-microbialite rocky shore pools appear to act as a micro-refuge, possibly improving growth rates and reducing the pelagic larval duration due to warmer water temperatures after which fish move into adjacent deeper, low shore pools and gullies. Due to the extreme conditions in microbialite pools, protection from predators during transition from larval to juvenile stages is also afforded.

Enigmatic fish ear stones: Ontogenetic development of saccular otolith in an endemic toothcarp of the Arabian peninsula, Aphaniops kruppi (Teleostei: Aphaniidae)

AbstractOtolith morphology in the toothcarps of the family Aphaniidae is an important source of taxonomic information. However, little is known about the ontogenetic variation in otolith morphology. In this study, the development of otolith morphology in different life stages of Aphaniops kruppi, an endemic toothcarp of the Arabian Peninsula, is described and discussed. The results reveal (i) a significant correlation between standard length and otolith size (length) in larval and early juvenile stages, (ii) clear differences in otolith morphology between larvae/early juveniles and adults, and (iii) a temporal link between the appearance of the sulcus on the otolith's inner face and lifestyles, that is demersal in larvae and early juveniles, and pelagic in adults. Moreover, our new data on otoliths of Ap. kruppi propose that otoliths of larvae or early juveniles of Ap. kruppi can be recognized by adults not only because of their small size but also based on their short and rounded rostrum and antirostrum and shallow, wide excisura. As the above‐mentioned characteristics are also found in the otoliths of juveniles and larvae of several other studied aphaniids, it can be concluded that otoliths are not diagnostic at the species level in Ap. kruppi, and this holds for other closely related species.

Survival and Growth in MultipleSize‐Classesof Hatchery Red Drum over Three Simulated Seasons

AbstractThe Texas Parks and Wildlife Department's (TPWD) Marine Stock Enhancement Program has introduced an average of 20 million fingerling Red DrumSciaenops ocellatusinto bays across Texas annually since 1983. Red Drum fingerlings are released during seasons outside of wild juvenile Red Drum recruitment, exposing them to conditions that they would not normally encounter as early stage juveniles in the wild. Furthermore, releases encompass a wide range of sizes outside of the target release size of 35 mm (20–60 mm), implying that survival and growth in the wild may vary with body size and body condition upon release. This study determined the impacts of season and initial release size on overall growth rate, body condition, and survival of Red Drum fingerlings by exposing two discrete size‐classes to a laboratory simulation of conditions expected to be encountered in the wild for 1 month after harvest from grow‐out ponds. Fish with an initial size of 35 mm TL or greater had higher overall survival over all three seasons of release than smaller fingerlings; however, final body condition (Fulton'sK) was not significant across size‐classes. Growth rates of both size‐classes were highest in summer, indicating that elevated temperatures can benefit fish within the full range of release sizes. Fitted multiple linear regression modeling also determined that water temperature and size‐class were significant indicators of estimated growth rate. In addition, growth rates in wild fish as estimated from TPWD fisheries‐independent samples were consistently lower than those in experimental fish of both size‐classes during all three simulated seasons. This research suggests that releasing larger‐sized (>35‐mm TL) Red Drum may significantly improve survival, especially during seasons with more variable temperature conditions at the beginning and end of the TPWD hatchery release season.

The development of the digestive system and the fate of the yolk syncytial layer in postembryogenesis of Stenodus leucichthys nelma (Teleostei).

Stenodus leucichthys nelma is an economically important species for cold-water aquaculture. Unlike other Coregoninae, S. leucichthys nelma is a piscivore. Here, we describe in detail the development of the digestive system and the yolk syncytial layer from hatching to early juvenile stage using histological and histochemical methods to determine their common and specific characteristics and to test the hypothesis that the digestive system of S. leucichthys nelma rapidly acquires adult features. The digestive tract differentiates at hatching and starts to function before the transition to mixed feeding. The mouth and anus are open, mucous cells and taste buds are present in the buccopharyngeal cavity and esophagus, pharyngeal teeth have erupted, the stomach primordium is seen, the intestinal epithelium with mucous cells is folded and the intestinal valve is observed; the epithelial cells of the postvalvular intestine contain supranuclear vacuoles. The liver blood vessels are filled with blood. The cells of exocrine pancreas are loaded with zymogen granules, and at least two islets of Langerhans are present. However, the larvae remain dependent on maternal yolk and lipids for a long time. The adult features of the digestive system develop gradually, the most significant changes take place approximately from 31 to 42 days posthatching. Then, the gastric glands and pyloric caeca buds appear, the U-shaped stomach with glandular and aglandular regions develops, the swim bladder inflates, the number of islets of Langerhans increases, the pancreas becomes scattered, and the yolk syncytial layer undergoes programmed death during the larval-to-juvenile transition. During postembryonic development, the mucous cells of the digestive system contain neutral mucosubstances.

Large offspring have enhanced lifetime reproductive success: Long-term carry-over effects of weaning size in gray seals (Halichoerus grypus).

An individual's size in early stages of life may be an important source of individual variation in lifetime reproductive performance, as size effects on ontogenetic development can have cascading physiological and behavioral consequences throughout life. Here, we explored how size-at-young influences subsequent reproductive performance in gray seals (Halichoerus grypus) using repeated encounter and reproductive data on a marked sample of 363 females that were measured for length after weaning, at ~4 weeks of age, and eventually recruited to the Sable Island breeding colony. Two reproductive traits were considered: provisioning performance (mass of weaned offspring), modeled using linear mixed effects models; and reproductive frequency (rate at which a female returns to breed), modeled using mixed effects multistate mark-recapture models. Mothers with the longest weaning lengths produced pups 8 kg heavier and were 20% more likely to breed in a given year than mothers with the shortest lengths. Correlation in body lengths between weaning and adult life stages, however, is weak: Longer pups do not grow to be longer than average adults. Thus, covariation between weaning length and future reproductive performance appears to be a carry-over effect, where the size advantages afforded in early juvenile stages may allow enhanced long-term performance in adulthood.

Sex-specific karyotyping of Garcinia indica (Thouars) Choisy for differentiation of male and female trees at an early juvenile stage

Sex-specific karyotyping of Garcinia indica (Thouars) Choisy for differentiation of male and female trees at an early juvenile stage

Insulin-like growth factor II, a marker gene for determining the optimum dietary protein level in clownfish Amphiprion ocellaris.

In vivo study was conducted to determine the role of insulin-like growth factors (IGF-II) related to dietary protein utilization. For this early juvenile stage of marine false clownfish Amphiprion ocellaris, 300 numbers of 20-day-old larvae (initial body weight of 18.2±0.027 mg/fish) were used as an experimental animal. Animals were fed for 12 weeks with different dietary protein levels (35, 40, 45, 50, and 55%), using Spirulina maxima as a major protein source. Proximate compositions and amino acid profile of the formulated diet were analyzed by the standard methods. Eventually, significant (P<0.05) mean, body weight gain, absolute growth rate, specific growth rate, and feed conversion ratio were obtained in the fishes fed with 50% of dietary protein, whereas, poor growth performance was noticed in 35% of the dietary protein level fed juveniles. The growth-responsible gene IGF-II expression studies showed the significant upregulation in the growth of the juveniles at 2.05±0.11 for 40%, 3.13±0.20 for 45%, 4.97±0.13 for 50%, and 4.33± 0.24 for 55%, which were higher than the control group 35%. The study concluded that 50% of dietary protein level is optimal for better growth indices in clownfish; A. ocellaris juveniles and IGF-II can be used as a potential marker gene to assess the growth indices in A. ocellaris.

Life stage-specific glycosylation of extracellular vesicles from Schistosoma mansoni schistosomula and adult worms drives differential interaction with C-type lectin receptors DC-SIGN and MGL.

Schistosomes can survive in mammalian hosts for many years, and this is facilitated by released parasite products that modulate the host's immune system. Many of these products are glycosylated and interact with host cells via C-type lectin receptors (CLRs). We previously reported on specific fucose-containing glycans present on extracellular vesicles (EVs) released by schistosomula, the early juvenile life stage of the schistosome, and the interaction of these EVs with the C-type lectin receptor Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN or CD209). EVs are membrane vesicles with a size range between 30-1,000nm that play a role in intercellular and interspecies communication. Here, we studied the glycosylation of EVs released by the adult schistosome worms. Mass spectrometric analysis showed that GalNAcβ1-4GlcNAc (LacDiNAc or LDN) containing N-glycans were the dominant glycan type present on adult worm EVs. Using glycan-specific antibodies, we confirmed that EVs from adult worms were predominantly associated with LDN, while schistosomula EVs displayed a highly fucosylated glycan profile. In contrast to schistosomula EV that bind to DC-SIGN, adult worm EVs are recognized by macrophage galactose-type lectin (MGL or CD301), and not by DC-SIGN, on CLR expressing cell lines. The different glycosylation profiles of adult worm- and schistosomula-derived EVs match with the characteristic glycan profiles of the corresponding life stages and support their distinct roles in schistosome life-stage specific interactions with the host.