Eleginops Research Articles

Recreational fishing in the lower basin of the Santa Cruz river(Patagonia, Argentina) in the face of damming scenarios

The Steelhead ecotype (Oncorhynchus mykiss) and chinook salmon (Oncorhynchus tshawytscha) have promoted a recreational fishery in the Santa Cruz river, the last large free flowing river of Patagonia. However, two dams are being built upstream in the middle course, potentially affecting the life cycle of these anadromous salmonids. The study describes the dynamics of the recreational fishing of the Santa Cruz river around Piedrabuena city and anglers perceptions, discussing its trends according to possible river connectivity scenarios. The fishery was assessed through a monthly year-round field sampling from April 2018 to April 2019, developing instantaneous angler counts, discriminating fishing methods, effort, and catch per unit effort; also, in situ interviews were used to collect information on anglers’ motivations and perceptions. In addition, information on fishing tournaments was used. Three fishing zones (FZ) were identified near Piedrabuena city: FZ-1, located downstream where anglers used baited hook and line to catch the native marine Patagonian blenny (Eleginops maclovinus); FZ-2, located in the town where baited hook and line, spinning, and fly-cast are used to catch Patagonian blenny and salmonids; FZ-3 located upstream the town, where fishing effort was mainly directed to salmonids employing spinning and fly-cast. Fishing effort showed a seasonal pa�ern with high values from March to May and September to October, agreeing with Steelhead and Chinook salmon runs, respectively. The most relevant motivations for anglers were nonoriented catch variables. Anglers preferred the capture of salmonids over native species, considering dams to be a major threat to fishery. Although a postdamming scenario could allow the adult salmonids to migrate upstream, the current reproduction grounds of Steelhead will be flooded, and juveniles and adults of both species will be hindered in their downstream migration to sea. These aspects seem to seriously compromise the future of these unique fisheries.

Microplastics in stomach contents of juvenile Patagonian blennies (Eleginops maclovinus)

Microplastics are one of the major environmental issues that need to be addressed because they are starting to impact food chains and are also affecting human populations. The size, colour, form, and abundance of microplastics in young blennies of the species Eleginops maclovinus were examined in the current study. While the stomach contents of 70 % of the studied individuals contained microplastics, 95 % of them included fibres. Individual size and the largest particle size that can be eaten, which ranges between 0.09 and 1.5 mm present no statistical correlation. The quantity of particles taken in by each individual does not change with size. The most present microfibers colours were blue and red. Sampled fibres were analysed with FT-IR and no natural fibres were detected, proving the synthetic origin of the detected particles. These findings suggest that protected coastlines create conditions that favour the encounter of microplastics increasing local wildlife exposure to microplastics, raising the danger of their ingestion with potential physiological, ecological, economical and human health consequences.

Chromosome-Level Genome Assembly and Circadian Gene Repertoire of the Patagonia Blennie Eleginops maclovinus-The Closest Ancestral Proxy of Antarctic Cryonotothenioids.

The basal South American notothenioid Eleginops maclovinus (Patagonia blennie or róbalo) occupies a uniquely important phylogenetic position in Notothenioidei as the singular closest sister species to the Antarctic cryonotothenioid fishes. Its genome and the traits encoded therein would be the nearest representatives of the temperate ancestor from which the Antarctic clade arose, providing an ancestral reference for deducing polar derived changes. In this study, we generated a gene- and chromosome-complete assembly of the E. maclovinus genome using long read sequencing and HiC scaffolding. We compared its genome architecture with the more basally divergent Cottoperca gobio and the derived genomes of nine cryonotothenioids representing all five Antarctic families. We also reconstructed a notothenioid phylogeny using 2918 proteins of single-copy orthologous genes from these genomes that reaffirmed E. maclovinus' phylogenetic position. We additionally curated E. maclovinus' repertoire of circadian rhythm genes, ascertained their functionality by transcriptome sequencing, and compared its pattern of gene retention with C. gobio and the derived cryonotothenioids. Through reconstructing circadian gene trees, we also assessed the potential role of the retained genes in cryonotothenioids by referencing to the functions of the human orthologs. Our results found E. maclovinus to share greater conservation with the Antarctic clade, solidifying its evolutionary status as the direct sister and best suited ancestral proxy of cryonotothenioids. The high-quality genome of E. maclovinus will facilitate inquiries into cold derived traits in temperate to polar evolution, and conversely on the paths of readaptation to non-freezing habitats in various secondarily temperate cryonotothenioids through comparative genomic analyses.

Intraspecific variation in reproductive traits and embryo elemental composition of the crab Hemigrapsus crenulatus (Milne Edwards, 1837) across fluctuating coastal environments along Chilean coasts

The estuarine crab Hemigrapsus crenulatus has a wide distribution range along the coast of the South Pacific Ocean (from 20 °S to 53 S°). This decapod is abundant in these coastal and estuarine habitats and plays a key ecological role as prey of the snook fish (Eleginops maclovinus) and kelp gull (Larus dominicanus). Its diet consists of detritus, dead fish, and crustaceans, and the macroalgae Ulva sp. In response to contrasting environmental conditions and anthropogenic impacts along the Chilean coast, H. crenulatus may present intraspecific variations in its reproductive traits and changes in the elemental composition of its embryos, directly affecting its biological fitness. Along the Chilean coast, female individuals were collected during late spring 2019 and early summer 2020 (from November 2019 to February 2020) in six areas of Chile (north: Tongoy (30°S); south-central: Lenga (36°S), Tubul (37°S); south austral: Calbuco (41°S), Castro (42°S), Quellón (43°S). The environmental conditions (i.e. sea surface temperature, precipitation and chlorophyll α) present during each sampling event were also recorded. We evaluated the reproductive parameters of females (fecundity, reproductive output (RO)) as well as their body size (carapace width and dry weight), volume, water content, dry weight, elemental composition (carbon, hydrogen, nitrogen: CHN), and finally the energy content of their embryos. Our results indicated that the environmental conditions of the sea water temperature, precipitation (proxy of water salinity) and chlorophyll α (proxy of food availability) have direct effects on the reproductive parameters of females and the characteristics of their embryos. We observed a low fecundity and high RO in Calbuco and Quellón, where precipitation was high (i.e. diluted salinity) and temperatures and productivity was low. For embryo traits, the highest values of volume and water content were observed in female crabs from the estuarine areas (i.e. Tongoy, Lenga, Tubul), values much higher than those found in the internal sea of Chile (i.e. Calbuco, Castro, Quellón). For the elemental composition, we observed high nitrogen levels and a low C:N proportion in embryos from female crabs from Lenga (a nitrogen enriched area). Fluctuating environmental variables among localities proved to modulate intraspecific variations in females and embryos of H. crenulatus, revealing different reproductive strategies, particularly in the quality and energy investment per embryo, which subsequently influenced successful embryogenesis and larval survival.

Ocean acidification and seasonal temperature extremes combine to impair the thermal physiology of a sub-Antarctic fish

To predict the potential impacts of climate change on marine organisms, it is critical to understand how multiple stressors constrain the physiology and distribution of species. We evaluated the effects of seasonal changes in seawater temperature and near-future ocean acidification (OA) on organismal and sub-organismal traits associated with the thermal performance of Eleginops maclovinus, a sub-Antarctic notothenioid species with economic importance to sport and artisanal fisheries in southern South America. Juveniles were exposed to mean winter and summer sea surface temperatures (4 and 10 °C) at present-day and near-future pCO2 levels (~500 and 1800 μatm). After a month, the Critical Thermal maximum and minimum (CTmax, CTmin) of fish were measured using the Critical Thermal Methodology and the aerobic scope of fish was measured based on the difference between their maximal and standard rates determined from intermittent flow respirometry. Lipid peroxidation and the antioxidant capacity were also quantified to estimate the oxidative damage potentially caused to gill and liver tissue. Although CTmax and CTmin were higher in individuals acclimated to summer versus winter temperatures, the increase in CTmax was minimal in juveniles exposed to the near-future compared to present-day pCO2 levels (there was a significant interaction between temperature and pCO2 on CTmax). The reduction in the thermal tolerance range under summer temperatures and near-future OA conditions was associated with a reduction in the aerobic scope observed at the elevated pCO2 level. Moreover, an oxidative stress condition was detected in the gill and liver tissues. Thus, chronic exposure to OA and the current summer temperatures pose limits to the thermal performance of juvenile E. maclovinus at the organismal and sub-organismal levels, making this species vulnerable to projected climate-driven warming.

Neutral and adaptive loci reveal fine-scale population structure in Eleginops maclovinus from north Patagonia.

Patagonia is an understudied area, especially when it comes to population genomic studies with relevance to fishery management. However, the dynamic and heterogeneous landscape in this area can harbor an important but cryptic genetic population structure. Once such information is revealed, it can be integrated into the management of infrequently investigated species. Eleginops maclovinus is a protandrous hermaphrodite species with economic importance for local communities that are currently managed as a single genetic unit. In this study, we sampled five locations distributed across a salinity cline from Northern Patagonia to investigate the genetic population structure of E. maclovinus. We used restriction site‐associated DNA (RAD) sequencing and outlier tests to obtain neutral and adaptive loci, using FST and GEA approaches. We identified a spatial pattern of structuration with gene flow and spatial selection by environmental association. Neutral and adaptive loci showed two and three genetic groups, respectively. The effective population sizes estimated ranged from 572 (Chepu) to 14,454 (Chaitén) and were influenced more by locality than by salinity cline. We found loci putatively associated with salinity suggesting that salinity may act as a selective driver in E. maclovinus populations. These results suggest a complex interaction between genetic drift, gene flow, and natural selection in this area. Our findings also suggest several evolutionary significant units in this area, and the information should be integrated into the management of this species. We discussed the significance of these results for fishery management and suggest future directions to improve our understanding of how E. maclovinus has adapted to the dynamic waters of Northern Patagonia.

Transcriptional modulation of immune genes in gut of Sub-Antarctic notothenioid fish Eleginops maclovinus challenged with Francisella noatunensis subsp. noatunensis

The search for functional foods that improve the immune response has traditionally been focused on lymphoid tissue and the intestinal mucosa. However, it is unknown whether there is a different immune response in different portions of the gut following exposure to a bacterial pathogen. We challenged Eleginops maclovinus intraperitoneally (i.p) with Francisella noatunensis subsp. noatunensis and measured mRNA transcripts related to innate and adaptive immune responses in different parts of the gut (foregut, midgut and hindgut). We used control (i.p only with bacterial culture medium), low dose (i.p of F. noatunensis at 1 × 101 bact/μL), medium dose (i.p of F. noatunensis at 1 × 105 bact/μL) and high dose (i.p of F. noatunensis at 1 × 1010 bact/μL) groups in our experiments. We sampled fish at days 1, 3, 7, 14, 21, and 28 post-injection. We observed tissue-specific expression of TLR1, TLR5, TLR8, MHCI, MHCII and IgM, and transcription of these immune markers was lower in foregut and higher in midgut and hindgut. We detected Francisella genetic material (DNA) in fish stimulated with a high dose from day 1–28 in foregut, midgut, and hindgut. However, we could only detect Francisella DNA in fish stimulated the medium and low dose at later timepoints in the foregut (21–28 days post injection “dpi”) and hindgut (low dose from day 7–28 dpi). Our results suggest that the immune responses to bacterial pathogens occur throughout the gut, but certain segments may be more susceptible to infection because of their cellular morphology (anterior, middle and posterior).

Francisella noatunensis modulates the hepatic profile of fatty acids in Patagonian blennie Eleginops maclovinus

Fatty acids (FA) have been reported to play a role in the defense against bacterial pathogens. However, studies in fish are limited and no information exists on the modulation of FA of Eleginops maclovinus challenged with the pathogen of aquaculture relevance Francisella noatunensis. We inoculated 144 fish intraperitoneally with 3 doses (low dose [LD]: 1 × 101 bact/μL; medium dose [MD]: 1 × 105 bact/μL; high dose [HD]: 1 × 1010 bact/μL) and a control dose (sterile culture medium, [C]) of the bacteria F. noatunensis and took liver samples at 1, 3, 7, 14, 21, 28 days post-inoculation (dpi). The LD of F. noatunensis did not present significant differences to the C, except for the C20:4n6 (ARA) at day 28, while the MD and HD of F. noatunensis did generate a significant effect of the FA profile of E. maclovinus. We observed a greater modulation after administering the HD of bacteria and detected significant differences from day 3 post-inoculation (P < 0.05). Significantly high levels of C18:0 was detected at day 28 (P < 0.05), while significantly low levels of C14:0, C20:0, C16:1, C18:1n9, C18:2n6; C18:3n3, and C20:5n3 were detected at different dpi of F. noatunensis (P < 0.05). ARA and C22:6n3 (DHA) showed a significant decrease during the first dpi (P < 0.05) but later they showed an increase in their levels, with ARA increasing its levels from day 14 (P < 0.05), while DHA increased its levels only at day 28 (P < 0.05). A large number of FA were highly correlated with each other and multivariate statistical analyzes (PCA and random forest) were able to detect the HD of F. noatunensis as the dose that most affects the FA profile of E. maclovinus, while the LD, MD and C cannot be differentiated in their FA profile. The FA most affected by the challenge with F. noatunensis were C18:2n3 and C18:3n3 (P < 0.05). Our results suggest a relationship between the bioavailability of FA in the liver and the level of the physiological response of E. maclovinus to an experimental challenge with F. noatunensis and suggest that hepatic FA modulation may explain or be part of the high tolerance to bacterial infections reported for E. maclovinus, although more studies are necessary to clarify the roles of the different types of FA on pathogen-host dynamics and its potential use in combating fish pathogenic bacteria.

The fasted and post-prandial physiological responses of the Patagonian blennie Eleginops maclovinus

Eleginops maclovinus is a native species with potential for Chilean aquaculture. Understanding the variations between the post-prandial and fasted metabolic responses can contribute to improving the aquaculture of this species. This study aimed to characterize variations in intermediate metabolism during the course of the day in the liver, serum, and gills of fed and unfed fish. For this, 72 fish were assigned to two experimental groups, “fed” and “fasted”. The first group was fed “ad libitum” at 8.30, while the fasted group was not fed for 24 h. Samples were taken from both groups at 9:00, and every 2 h: 11:00, 13:00, 15:00, 17:00, and 19:00. In the fed group, food spent a long time in the gastrointestinal tract, with a large increase in stomach size and without evidence of complete emptying of the stomach at 19:00 (10.5 h post-feeding). In serum, the levels of amino acids, glucose, and triglycerides presented significant differences with peak levels at different times of day in the fed group. The cortisol in the fasted group presented a diurnal pattern with high levels during the morning and very low levels after 13:00, while in the fed group, the high cortisol variability did not allow a clear pattern to be established. In the liver, the effect of time on the enzymatic activity of the intermediary metabolism was greater compared to the effect of feeding. In the liver, enzyme activity decreased at later hours of the day, while glycogen levels increased at later hours of the day in both groups: but its levels were higher in the fed group. In gills, as well as in the liver, time had a greater effect than feeding on intermediate metabolism, since feeding only had a significant effect on the levels of hexokinase, lactate, and amino acids, suggesting an effect on carbohydrate metabolism. Meanwhile, time significantly affected the levels of Na+, K+-ATPase, glutamate dehydrogenase, aspartate aminotransferase, amino acids, and proteins, suggesting an effect on amino acid metabolism. In conclusion, the intermediate metabolism of E. maclovinus presents variations according to the time of day, with an increased metabolism during the morning and decreased metabolism as the day progresses, especially at the hepatic level. The gill tissue, despite not being a metabolic organ, presents feeding-dependent variations in its metabolism. Additional studies will be required to corroborate if coordinating a feeding strategy during the first hours of the day when metabolism is greater would improve the growth of E. maclovinus.

Immune response of Salmo salar (exotic fish) and Eleginops maclovinus (native fish) during Francisella noatunensis horizontal transference

Bacterial transmission between cultured and native fish is potentially of great epidemiological significance. We evaluated horizontal transmission of Francisella noatunensis subsp. noatunensis from Salmo salar (Ss) to Eleginops maclovinus (Em) and vice versa by conducting cohabitation experiments. We detected F. noatunensis DNA in infected fish “Trojans” (fish injected with F. noatunensis ) and cohabitants (non-injected fish in the same tank as trojans) of both species from day 1. Additionally, we detected bacterial replication from day 1 post injection (dpi) in trojan E. maclovinus and day 14 in the other experimental conditions. We also found that hematocrit values in trojan fish were significantly decreased; however, we did not detect any corresponding decrease in cohabitating fish. Furthermore, we found that transcription of genes involved in the innate and acquired immune response in trojan fish and cohabitants, such as TRL1, TRL5, TRL8, MyD88, IL-1β, IL, MHCI and MHCII, especially at 1–3 dpi, and at 7, 14, 21 and 28 dpi in several tissues, with a tissue-dependent response. Finally, we observed an increase in serum IgM Anti- F. noatunensis antibody levels from 14 dpi in trojan fish but not in cohabitating fish. Our results demonstrate that F. noatunensis can be transmitted horizontally from S. salar to E. maclovinus and vice versa. • Bacterial transmission between cultured and native fish could be of great epidemiological significance • The horizontal transmission of F . noatunensis from Salmo salar to Eleginops maclovinus (Em) and vice versa was evaluated. • The Hematocrit values in Trojan fish were significantly decreased. • The transcription of genes involved in the innate and acquired immune response in trojan fish and cohabitants were activated. • Our results demonstrate that F. noatunensis can be transmitted horizontally from S. salar to E. maclovinus and vice versa

Brain immunity response of fish Eleginops maclovinus to infection with Francisella noatunensis

The brain's immune system is selective and hermetic in most species, including fish, favoring immune responses mediated by soluble immunomodulatory factors such as serotonin and the availability of nutrients against infectious processes. Francisella noatunensis coexist with fish such as Eleginops maclovinus, which raises questions about the susceptibility and immune response of the brain of E. maclovinus against Francisella. In this study, we inoculated fish with different doses of Francisella and took samples for 28 days. We detected bacteria in the brain of fish injected with a high concentration of Francisella at all time points. qPCR analysis of immune genes indicated a response mainly in the medium-dose and early expression of genes involved in iron metabolism. Finally, brain serotonin levels were higher than in uninfected fish in all conditions, suggesting possible immunomodulatory participation in an infectious process.

Proximal composition and fatty acid profile of Hemigrapsus crenulatus (H. Milne Edwards, 1837) as one of the main foods of "patagonian blenny"Eleginops maclovinus (Cuvier, 1830).

The Patagonian blenny (Eleginops maclovinus) is species endemic to South America with physiological characteristics that would facilitate its incorporation into Chilean aquaculture. However, there is currently no specific artificial food that can be used to raise E. maclovinus. In light of this problem, this study describes the proximal composition and fatty acid profile of the crab Hemigrapsus crenulatus, one of the main foods of E. maclovinus. The purpose of the study is to serve as basic information for the development of a specific artificial diet for juveniles of this fish species. The proximal analysis of the complete body of H. crenulatus indicates that it is mainly composed of ash (35.9%), proteins (32.2%), glucides (19.8%) and minor lipids (3.6%). The fatty acid profile is 40.7% PUFAs, 29.7% MUFAs and 29.5% SAFAs, and the most abundant acids are Eicosapentaenoic (18.8%), Oleic (6.8%) and Palmitic (16.6%), respectively. H. crenulatus has highest level of proteins, lipids and PUFAs among the species of the Brachyura infraorder.

The evolutionary puzzle solution for the origins of the partial loss of the Cτ2 exon in notothenioid fishes

Cryonotothenioidea is the main group of fishes that thrive in the extremely cold Antarctic environment, thanks to the acquisition of peculiar morphological, physiological and molecular adaptations. We have previously disclosed that IgM, the main immunoglobulin isotype in teleosts, display typical cold-adapted features. Recently, we have analyzed the gene encoding the heavy chain constant region (CH) of the IgT isotype from the Antarctic teleost Trematomus bernacchii (family Nototheniidae), characterized by the near-complete deletion of the CH2 domain. Here, we aimed to track the loss of the CH2 domain along notothenioid phylogeny and to identify its ancestral origins. To this end, we obtained the IgT gene sequences from several species belonging to the Antarctic families Nototheniidae, Bathydraconidae and Artedidraconidae. All species display a CH2 remnant of variable size, encoded by a short Cτ2 exon, which retains functional splicing sites and therefore is included in the mature transcript. We also considered representative species from the three non-Antarctic families: Eleginopsioidea (Eleginops maclovinus), Pseudaphritioidea (Pseudaphritis urvillii) and Bovichtidae (Bovichtus diacanthus and Cottoperca gobio). Even though only E. maclovinus, the sister taxa of Cryonotothenioidea, shared the partial loss of Cτ2, the other non-Antarctic notothenioid species displayed early molecular signatures of this event. These results shed light on the evolutionary path that underlies the origins of this remarkable gene structural modification.

Comparison under controlled conditions of the life cycle of Lepeophtheirus mugiloidis and Caligus rogercresseyi , parasites of the Patagonian blenny Eleginops maclovinus

Eleginops maclovinus, a potential species for the diversification of the aquaculture in Chile, has been reported as a natural host of Caligus rogercresseyi, a parasite that severely affects salmon grown in sea cages in southern Chile, and also as an important host for Lepeophtheirus mugiloidis. In order to contribute to the biological knowledge of L. mugiloidis, adult lice were collected from infested E. maclovinus in the field to compare with the life cycle of C. rogercresseyi. The study showed that the life cycle of L. mugiloidis was similar to the life cycle recently reported for L. salmonis, comprising eight stages of development, with only two chalimus stages, differing from C. rogercresseyi which has four chalimus stages and does not present preadult stages. L. mugiloidis reached the adult stage at 467ºD, while C. rogercresseyi reached the adult stage at 382ºD. The average size of females of L. mugiloidis was 44% larger than males, different from C. rogercresseyi, where females were 13.4% larger than males in samples collected from the field and 9.9% in samples produced under laboratory conditions.

Horizontal transmission of Piscirickettsia salmonis from the wild sub-Antarctic notothenioid fish Eleginops maclovinus to rainbow trout (Oncorhynchus mykiss) under experimental conditions.

Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a bacterial disease that affects farmed salmonids, causing high mortalities and significant economic losses in the Chilean salmon farm industry. Given the Chilean native fish species Patagonian blenny, Eleginops maclovinus, lives in the vicinity of salmon farms, it is relevant to clarify the epidemiological role that this species could play in the transmission and/or dissemination of this pathogen. This study aimed to evaluate the bidirectional transmission of P.salmonis between the Patagonian blenny and Oncorhynchus mykiss (rainbow trout), via a cohabitation challenge model. The results of this study demonstrated the transmission of the bacteria from Patagonian blennies to rainbow trout, considering the specific mortality in cohabitant rainbow trout, reaching 46%: the necropsy of these specimens, evidencing the characteristic pathological lesions of the disease and the positive results of the qPCR analysis for P.salmonis, in the same individuals. In contrast, no mortalities of Patagonian blenny specimens were recorded in the challenged experimental groups. This study is the first report showing the horizontal transmission of P.salmonis from a native non-salmonid species, such as the Patagonian blenny, to a salmonid species, generating the disease and specific mortality in rainbow trout, using a cohabitation challenge.

Cold Adaptation in Antarctic Notothenioids: Comparative Transcriptomics Reveals Novel Insights in the Peculiar Role of Gills and Highlights Signatures of Cobalamin Deficiency

Far from being devoid of life, Antarctic waters are home to Cryonotothenioidea, which represent one of the fascinating cases of evolutionary adaptation to extreme environmental conditions in vertebrates. Thanks to a series of unique morphological and physiological peculiarities, which include the paradigmatic case of loss of hemoglobin in the family Channichthyidae, these fish survive and thrive at sub-zero temperatures. While some of the distinctive features of such adaptations have been known for decades, our knowledge of their genetic and molecular bases is still limited. We generated a reference de novo assembly of the icefish Chionodraco hamatus transcriptome and used this resource for a large-scale comparative analysis among five red-blooded Cryonotothenioidea, the sub-Antarctic notothenioid Eleginops maclovinus and seven temperate teleost species. Our investigation targeted the gills, a tissue of primary importance for gaseous exchange, osmoregulation, ammonia excretion, and its role in fish immunity. One hundred and twenty genes were identified as significantly up-regulated in Antarctic species and surprisingly shared by red- and white-blooded notothenioids, unveiling several previously unreported molecular players that might have contributed to the evolutionary success of Cryonotothenioidea in Antarctica. In particular, we detected cobalamin deficiency signatures and discussed the possible biological implications of this condition concerning hematological alterations and the heavy parasitic loads typically observed in all Cryonotothenioidea.

Fatty acid biomarkers in three species inhabiting a high latitude Patagonian fjord (Yendegaia Fjord, Chile)

The study of fatty acid biomarkers in trophic structures at sub-polar latitudes is fundamental in describing energy fluxes across ecosystems characterized by complex inter-specific interactions. Due to the presence of certain essential fatty acids obtained exclusively from predator–prey interactions, fatty acid biomarkers are widely used to identify trophic interactions. This study analyzed fatty acid compositions in three species inhabiting a relatively pristine Patagonian fjord. This fjord is geographically difficult to access, so there are very little sampling opportunities, biological and oceanographic information. In the three species collected (Ctenodiscus australis (Loven in Lutken 1871) (Echinodermata, Asteroidea, Ctenodiscidae); Munida gregaria (Fabricius 1793) (Arthropoda, Malacostraca, Munididae); Eleginops maclovinus (Cuvier 1830) (Chordata, Actinopterygii, Eleginopsidae)) along this remote area were evaluated their fatty acid trophic markers as a tool to differentiate dietary components and dietary habits. The study reported significant differences in the amount of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA), with the highest concentrations of all fatty acids in M. gregaria. The last suggests that M. gregaria is considered as a good quality food source or biological component that might support the fjord trophic web in the Southern Hemisphere. The results describe diet compositions in sampled species, and differences among species for fatty acid compositions and proportions. This provides an initial basis for future modeling or projecting how benthic ecosystems of fjords and Patagonian channels respond to food intake, particularly in environments associated with glacial systems characterized by a low phytoplankton biomass and greater sensitivity to climate variability.

Bioenergetic traits of three keystone marine species in the food web of a pristine Patagonian fjord

The Patagonian fjords are high-latitude aquatic ecosystems, highly sensitive to climate change and play a key role in the exchange of organic matter and carbon flows between terrestrial and marine environments. The bioenergetic composition of species living in these ecosystems are fundamental to understanding the distribution, seasonal variations, and exchange of organic matter within benthic communities. This study reports on the bioenergetic characteristics (lipids, protein, glucose, and energy content) of three keystone species with different life-style and feeding habits: a benthic sea star (Ctenodiscus australis); squat lobster (Munida gregaria); and a Patagonian notothenioid (Eleginops maclovinus). Samples were obtained from the Yendegaia Fjord (54°40'S - 68°50′W) in Chilean Patagonia. Our results indicate that M. gregaria has higher concentrations of lipids, proteins, glucose, and total energy compared to either E. maclovinus or C. australis. The predominance of lipids in all species is possibly related to physiological characteristics and feeding strategies. Also, may be associated with the availability of food and environmental conditions typical of a fjord ecosystem and the reproductive stage in that they were collected. These results suggest that marine animals inhabiting glacially influenced environments with low temperature and low productivity, requires a convergent physiological strategy characterized by high levels of energy storage (i.e. lipids) for metabolism and key bioenergetic processes such as growth and reproduction.

Evolution of chaperome gene expression and regulatory elements in the antarctic notothenioid fishes.

Confined within the cold-stable Southern Ocean, Antarctic notothenioid fishes have undergone an evolutionary loss of the inducible heat shock response (HSR), while facing perpetual low-temperature challenges to cellular proteostasis. This study examines how evolution in chronic cold has affected the shared cellular apparatus that mediates proteostasis under normal and heat stressed states. To deduce Antarctic-specific changes, we compared native expression levels across the full suite of chaperome genes and assessed the structural integrity of two crucial HSR regulators - Heat Shock Factor 1 (HSF1) that activates HSR, and heat shock elements (HSEs), the binding sites for HSF1 - between Antarctic fishes and the basal temperate notothenioid Eleginops maclovinus. Native expression levels of Antarctic fish chaperomes showed very modest changes overall, contrary to the common view of constitutive upregulation in the cold. Only a few cytosolic HSP70 genes showed greater transcription, with only the ancestrally-inducible HSPA6 strongly upregulated across all Antarctic species. Additionally, the constant cold has apparently not relaxed the selective pressures on maintaining HSF1 and HSEs in Antarctic fish. Instead, we found HSF1 experienced intensified selective pressure, with conserved sequence changes in Antarctic species suggesting optimization for non-heat-stress functional roles. HSEs of the HSP70 gene family have largely remained conserved in canonical sequence motifs and copy numbers as in E. maclovinus, showing limited impact of relaxed selective pressure. This study shows that evolution in chronic cold has led to both subtle and distinctive changes in the cellular apparatus for proteostasis and HSR, with functional consequences amenable to experimental evaluation.

Experimental transmission of Caligus rogercresseyi between two different fish species.

Caligus rogercresseyi is the dominant sea louse parasite affecting the salmon and trout industry in southern Chile. This parasite has a wide range of native and endemic fish hosts. The Patagonian blenny Eleginops maclovinus, which is parasitized mostly by the caligid species Lepeophtheirus spp. and C. rogercresseyi, is presumably responsible for the transmission of C. rogercresseyi to salmonids. The aim of this study was to characterize the transmission of parasites between different fish species and parasite cohort development under laboratory conditions. Parasite abundances and intensities were quantified. Transmission of parasites from Patagonian blenny to Atlantic salmon Salmo salar was lower (~9%, mainly corresponding to C. rogercresseyi) than from salmon to Patagonian blenny (14.7-26.9%, where only C. rogercresseyi were observed). This suggests that the transmission of C. rogercresseyi from salmon individuals is higher than the transmission from a native fish. Parasite cohorts developed successfully on both fish species, but apparently under different developmental rates. Water temperature, oxygen, and juvenile abundances were the variables that better explained cohort development success and variation in C. rogercresseyi adult abundances over time.