Successful bottom planting of indigenous macroalgae Saccharina latissima aimed at coastal restoration purposes require the mass production in controlled conditions of strongly fixed, healthy sporophytes followed by optimal transfer techniques in order to ensure viability and vigor of the young seedlings about to be directly introduced in the coastal environment. Early development of S. latissima submitted to different combinations of substrate type (natural vs artificial brick-shaped substrate), gametophyte spraying method (water-based vs binder-based) and water velocity (0.1 vs 0.2 m s-1) was evaluated during a growth trial that lasted 42 days. Overall, all experimental groups (8 in triplicate) reached the targeted length of 15 mm between 35-42 days post-seeding. No strong indications that the proposed 2×2×2 factorial design generated long lasting effects on growth and development indicators were observed (thallus length, SGR and % coverage). The observation of no persistent difference in the growth response of S. latissima under all experimental conditions, demonstrates that it is well suited for mass production of seedlings. Our results and evidenced-based practices led us to conclude that the use of an artificial substrate in combination with a binder-based gametophyte pulverization and the application of a velocity 0.2 m s-1 during early-growth could be adopted in a standardized protocol. We argue that 1) artificial substrates (uniform shape, stackable and rough surface) will most likely allow better use of a vessel’s open deck space and adherence of the developing holdfast; 2) the use of a binder may slow down the dehydration of the propagules and promote adhesiveness to the substrate during rearing, handling and transfer operations and under varying flow rates or wave actions respectively and 3) highest velocity should promote the selection of propagules with strongest attachment and thus possibly limit post-transfer dislodgement. We suggest further studies should 1) focus on identifying optimal gametophyte concentration at the spraying step, in order to reduce production costs and maximise productivity of seedling operations and 2) include biomass determination (g of tissue per cm2) in combination to the semi-quantitative density evaluation (% coverage) based on image-analysis, in order to improve our global assessment of growth.

Landmark-based geometric morphometrics is widely used to study the morphology of the endocast, or internal mold of the braincase, and the diversity associated with this structure across vertebrates. Landmarks, as the basic unit of such methods, are intended to be points of correspondence, selected depending on the question at hand, whose proper definition is essential to guarantee robustness and reproducibility of results. In this study, 20 landmarks are defined to provide a framework to analyze the morphological variability in squamate endocasts. Ten species representing a cross-section of the diversity of Squamata from both phylogenetic and ecological (i.e., habitat) perspectives were considered, to select landmarks replicable throughout the entire clade, regardless of the degree of neuroanatomical resolution of the endocast. To assess the precision, accuracy, and repeatability of these newly defined landmarks, both intraobserver and interobserver error were investigated. Estimates of measurement error show that most of the landmarks established here are highly replicable, and preliminary results suggest that they capture aspects of endocast shape related to both phylogenetic and ecologic signals. This study provides a basis for further examinations of squamate endocast disparity using landmark-based geometric morphometrics.

Vertebrate endocasts are widely used in the fields of paleoneurology and comparative neuroanatomy. The validity of endocranial studies is dependent upon the extent to which an endocast reflects brain morphology. Due to the variable neuroanatomical resolution of vertebrate endocasts, direct information about the brain morphology can be sometimes difficult to assess and needs to be investigated across lineages. Here, we employ X-ray computed tomography (CT), including diffusible iodine-based contrast-enhanced CT, to qualitatively compare brains and endocasts in different species of squamates. The relative position of the squamate brain within the skull, as well as the variability that may exist in such spatial relationships, was examined to help clarify the neurological regions evidence on their endocasts. Our results indicate that squamate endocasts provide variable representation of the brain, depending on species and neuroanatomical regions. The olfactory bulbs and peduncles, cerebral hemispheres, as well as the medulla oblongata represent the most easily discernable brain regions from squamate endocasts. In contrast, the position of the optic lobes, the ventral diencephalon and the pituitary may be difficult to determine depending on species. Finally, squamate endocasts provide very limited or no information about the cerebellum. The spatial relationships revealed here between the brain and the surrounding bones may help to identify each of the endocranial region. However, as one-to-one correspondences between a bone and a specific region appear limited, the exact delimitation of these regions may remain challenging according to species. This study provides a basis for further examination and interpretation of squamate endocast disparity.

Overwinter feed restriction followed by spring refeeding is proposed as a strategy to improve productivity and sustainability of Arctic charr production. A 257-day experiment was conducted with different feeding regimes to evaluate compensatory growth response in growth and physiological state of juvenile fish (150-200 g) reared under seasonal temperature and photoperiod. Five experimental groups in replicates were created based on frequency (C = continuous and P = periodic) and feed restriction level (0, 50 and 100%): C100%, P50%, C50%, P0% and C0%. After a period of acclimation of one month, two distinct phases of the growth trial were conceived: a restriction period (102 days) followed by a refeeding period (126 days). The growth (SGR's, organ indexes (HSI, CSI, ISI and VSI), FCE and FI) and pyloric caeca digestive (TRYP, CHY) and metabolic (LDH and CS) enzyme activity, stress levels (cortisol, HSP70 and hematocrit), morphometric traits (body mass, length and K) and muscle proximate composition were evaluated at different intervals. Our results indicate that 1) a limited period of food restriction (P0%) or a prolonged starving (C0%) enabled the observation of a complete growth compensation after 86 and 126 days post-refeeding respectively with improved feed conversion efficiency (FCE of 1.20 for P0% and C0% compared to 1.06 for the control); 2) Arctic charr under a fair level of food reduction applied either periodically (P50%) or continuously (C50%) can achieve similar growth than un-restricted fish; 3) during the refeeding period, lower variability in growth was successfully induced (C100% > P50% > C50% > P0% > C0%); 4) rapid size or mass adjustment of key digestive organs such as pyloric caeca and intestine is associated with feed restriction and refeeding (reduction and increase in relative size respectively); 5) enzymatic activities of TRY, LDH and CS measured at the last sampling of the restriction phase indicate some level of adjustments that quickly receded to levels similar to the control group (9 days post-refeeding); 6) lipid content value was significantly higher in fish from the C100% group in comparison to C50%, P0% and C0% groups at the end of the restriction phase, indicating that lipid depletion is a prerequisite to compensatory growth induction and 7) in comparison to the control un-restricted fish, the stress levels, as estimated by stress markers (cortisol, HSP70 or hematocrit) were not affected by the level of feed restriction. Feed restriction has been successfully used to promote compensatory and catch-up growth. Here we suggest that studies are however required to further explore to which extent feed-restriction could induce vulnerability of Arctic charr, during sub-optimal growth conditions. Finally, defining the best sequence of feed restriction and refeeding should ensure implementation of production and benefit while maintaining optimal health conditions.

SummaryClimate changes can promote disease outbreaks, but their nature and potential impacts in remote areas have received little attention. In a hot spot of biodiversity on the West Antarctic Peninsula, which faces among the fastest changing climates on Earth, we captured specimens of two notothenioid fish species affected by large skin tumors at an incidence never before observed in the Southern Ocean. Molecular and histopathological analyses revealed that X-cell parasitic alveolates, members of a genus we call Notoxcellia, are the etiological agent of these tumors. Parasite-specific molecular probes showed that xenomas remained within the skin but largely outgrew host cells in the dermis. We further observed that tumors induced neovascularization in underlying tissue and detrimentally affected host growth and condition. Although many knowledge gaps persist about X-cell disease, including its mode of transmission and life cycle, these findings reveal potentially active biotic threats to vulnerable Antarctic ecosystems.

Abstract Neorthacheta dissimilis Malloch (Diptera: Scathophagidae) is a poorly known scathophagid fly that feeds and develops on iris (Iridaceae). A survey of its occurrence was performed at the Montréal Botanical Garden (Montréal, Québec, Canada) in 2018, 2019, and 2020. Iris species and cultivars from two subgenera, Iris and Limniris, were evaluated for larval infestation. When pooled for subgenera and years, data from 18 Iris classes revealed high levels of infestation per flower stalk, ranging from 34% to 100%. When analysed per bud or flower, levels of infestation remained high, ranging from 19% to 100%, but generally was lower than for flower stalks as the unit of replication. The mean number of N. dissimilis larvae per infested flower or bud was higher for the subgenus Limniris (1.13) than for the subgenus Iris (1.03), with a maximum of four N. dissimilis larvae per flower being observed. These figures are worrying for horticulturalists because the insect is prevalent and causes either abortion or aesthetic damages to iris flowers.

This study examines the potential effects of linseed oil as a total replacement for fish oil in the formulated diet of Arctic charr, brook charr and their reciprocal hybrids. Muscle fatty acid composition, growth performance and feed utilization were evaluated on four experimental groups submitted to two different dietary lipid sources (100% linseed oil or 100% fish oil). Growth performance, feed utilization, muscle lipids and protein content were not affected by dietary linseed oil. Lipid source significantly affected muscle fatty acid profile. The replacement of fish oil by linseed led to an average reduction in 20:5n3 and 22:6 n3 (25.5% and 18.4% respectively) and an increase in 18:3n3 (177%) (mean values calculated for the four experimental groups). Muscle fatty acid profile was primarily influenced by feed content. Hybridization between the closely related species did not appear to affect the expression of key enzymes for HUFA biosynthesis. Our results show that linseed can be used as a fish oil replacement in charr without any significant impact on growth, feed utilization or muscle lipid and protein content.

Simple SummarySpotted wolffish, a cold-water fish species, is a high potential candidate marine fish species for the diversification of the aquaculture sector in Norway, Canada, and Iceland. A review of the state of advancement of all aspects of its reproduction is proposed. Species-specific life-history and reproduction traits are discussed in parallel with relevant information originating from past R&D activities and the current state of knowledge regarding rearing environmental conditions and practices possibly affecting broodstock performances.The first artificially fertilized spotted wolffish (Anarhichas minor) eggs hatched in Norway in the mid-1990s as this species was considered by Norwegian authorities to be a top candidate species for cold-water aquaculture in the North Atlantic regions. Previous research conducted in Norway (since 1992) and Canada (since 2000), focused on identifying key biological parameters for spotted wolffish cultivation which led, respectively, to the rapid establishment of a full commercial production line in northern Norway, while Québec (Canada) is witnessing its first privately driven initiative to establish commercial production of spotted wolffish on its territory. The control of reproduction can be viewed as a major requirement to achieve the development of performant strains using genetic selection tools and/or all-year-round production to bring about maximal productivity and synchronization among a given captive population. Although the basic reproduction aspects are more understood and controlled there are still some challenges remaining involving broodstock and upscaling of operations that limit the achievement of a standardized production at the commercial level. Quality of gametes is still considered a major constraint and it can be affected by multiple factors including nutrition, environmental conditions, handling practices, and welfare status. Internal insemination/fertilization and the protracted incubation period are challenging as well as the establishment of a health monitoring program to secure large-scale operations. The profound progress achieved in the control of reproduction, sperm handling, and cryopreservation methods for this species is presented and discussed. In this review, we also go into detail over the full range of up-to-date cultivation practices involving broodstock and identify areas that could benefit from additional research efforts (i.e., broodstock nutrition, health and welfare, scaling-up egg and larval production, genetics, and development of selective breeding programs).

AbstractThe requirements to rear spotted wolffish, Anarhichas minor, a cold water, demersal fish, native to the north Atlantic Ocean, have been developed over the past 25 years (since 1990s) and it now is commercially produced in one fish farm in Norway with additional plans for commercial development in the near future in Quebec, Canada. Spotted wolffish have numerous attributes that make them a desirable species to culture in the United States including, but not limited to: having a high value; desired by consumers and chefs; not supplied by U.S. or Canadian fisheries; an established broodstock available in neighboring Quebec; well‐developed hatchlings that do not require live feed; high rearing density tolerance; and low disease susceptibility. Here, we review the advancements made in broodstock management and spawning, egg incubation, juvenile rearing, and on‐growing of fish, as well as future research and development needs. Areas requiring further focus include reducing variability in gamete production; nutritional studies at all life stages; health expertise; genetic selection; and further refinement of standard operating procedures at the commercial level for all life‐stages. Given the state of advancement of wolffish cultivation and the existence of a commercial operation in Norway, we propose that spotted wolffish is commercially ready for production in the United States with the primary barrier being a steady source of eggs to supply emerging pilot‐scale or commercial operations.

Chemoreception plays a central role in the survival and reproduction of many animals in aquatic environments. Fishes use three chemosensory systems, the olfactory system, the diffuse chemosensory system, and the taste (gustatory) system. While these are present in the sea lamprey, a majority of chemosensory research has focused on olfaction. This review summarizes current knowledge of the lamprey chemosensory systems, including stimuli, receptors, neural pathways and behavioural roles of the chemosensory stimuli. A description of the olfactory sensory neurons located deep within the nostril, of synaptic pathways within the brain and of modulatory mechanisms that underly the translation of olfaction to movement are included. The lamprey diffuse chemosensory system may enable solitary chemosensory cells on the skin of the mouth, nostril, gill, and tailfin to function as sentinels for rapid responses to chemical stimuli. While little is known abouth the lamprey taste system, taste buds are located within the pharynx, thus enabling chemosensory responses to material that has entered the body cavity. Knowledge and understanding of function of these three chemosensory systems supports the management of sea lamprey populations.