A star is born again: Methods for larval rearing of an emerging model organism, the False clownfish Amphiprion ocellaris

As interest increases in ecological, evolutionary, and developmental biology (Eco-Evo-Devo), wild species are increasingly used as experimental models. However, we are still lacking a suitable model for marine fish species, as well as coral reef fishes that can be reared at laboratory scales. Extensive knowledge of the life cycle of anemonefishes, and the peculiarities of their biology, make them relevant marine fish models for developmental biology, ecology, and evolutionary sciences. Here, we present standard methods to maintain breeding pairs of the anemonefish Amphiprion ocellaris in captivity, obtain regular good quality spawning, and protocols to ensure larval survival throughout rearing. We provide a detailed description of the anemonefish husbandry system and life prey culturing protocols. Finally, a “low-volume” rearing protocol useful for the pharmacological treatment of larvae is presented. Such methods are important as strict requirements for large volumes in rearing tanks often inhibit continuous treatments with expensive or rare compounds

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Influence et importance relative de facteurs intrinsèques et extrinsèques sur la mortalité des alevins de Sparidés (Pisces) durant la phase d'installation benthique en Méditerranée

La phase d'installation benthique constitue une des périodes les plus critiques du cycle biologique des Sparidés. En effet, durant cette phase, les jeunes poissons de cette famille subissent une très forte mortalité par prédation qui peut décimer jusqu'à 99% des individus présents au moment de la période de colonisation des zones de nurseries. L'objectif de notre étude a été de rechercher l'influence des conditions environnementales sur la mortalité de 2 espèces de Sparidés, Diplodus vulgaris et Diplodus sargus. Nous avons également suivi l'évolution de plusieurs paramètres physiologiques et de la structure génétique de micro-cohortes de ces alevins durant toute la phase d'installation benthique. Les résultats obtenus semblent indiquer que les conditions environnementales et en particulier l'agitation du milieu ne semblent pas avoir d'influence sur les paramètres démographiques intraspécifiques (croissance et mortalité). Nous avons pu noter une évolution caractéristique de certains paramètres physiologiques (tels la disparition des individus parasités; ou l'homogénéisation de la condition nutritionnelle) qui nous permet d'envisager une sélection phénotypique directionnelle en faveur de certains individus. Du point de vue génétique il semble également que des phénomènes sélectifs se produisent, les fréquences alléliques des allèles PGM-80, 6PGD-50 et GPI-70 ayant tendance à diminuer fortement au cours de la phase d'installation benthique. Ces résultats démontrent que la phase d'installation benthique des alevins de sparidés se déroule globalement dans les mêmes conditions d'un point de vue démographique quelque soient les sites de nurseries choisis par les larves.PERPIGNAN-BU Sciences (661362101) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocSudocFranceF

Effects of intracoelomic tagging procedure on white seabream (Diplodus sargus) behavior and survival

The effects of intracoelomic tagging procedure (i.e. implantation by surgical incision into the abdominal cavity or laparotomy) on wild white seabream (Diplodus sargus) were evaluated by the comparison of the behavior of tagged and untagged control fish. Activity budgets were made to examine their behaviors, using an instantaneous scan sampling method. This method consists in recording the occurrence of specific behaviors at a regular time interval. An ethogram was previously established, summarizing the different possible behaviors for white seabream in captivity conditions. The occurrence of the isolated behaviors from the ethogram between tagged and untagged groups and the temporal evolution of these behaviors were tested. The activity budgets of individual fish showed no significant differences, but high variability in behavioral patterns. No differences were detected for the occurrence of the different behaviors between the tagged and control groups, except for socializing behavior. Tagged fish were more often grouped than control fish. One fish lost its tag after 17 days, due to suture shedding (i.e. the loss of surgical monofilament used to close a wound by joining the edges). After 18 days, suture inspection showed that the incision regions had not healed, but no other fish had lost sutures. No mortality was recorded during the experiment, regardless of fish group. After 48 days, the tagged fish presented neither visceral damage nor inflammation. Incision regions presented no inflammation and had totally healed with only one out of the two or three suture points we made persisting for each tagged fish. In conclusion, neither tag presence in the body cavity nor the tagging procedure cause any adverse effects on the behavior and survival of wild seabream in captivity conditions. Therefore, we consider that the monitoring of tagged white seabreams is representative of untagged fish and reflect their natural behavior. Additionally, as white seabream recover quickly after surgery and present no adverse behavioral effects due to intracoelomic tag implantation, we recommend maintaining fish for as short a time as possible in captivity conditions to avoid extra stress, and to release them as soon as they recover from the tagging procedure

Anemonefish Husbandry

Unlike most reef fish families, which are broadcast spawners, damselfishes and anemonefishes are benthic spawners. Indeed, as mentioned in Chapter 6, anemonefishes live in the vicinity of their sea anemone host and lay eggs on a substrate nearby

Sea anemone and clownfish microbiota diversity and variation during the initial steps of symbiosis

International audienceClownfishes and sea anemones form an intriguing long-term association, but the mechanism underlying this symbiosis is not well understood. Since clownfishes seem to cover themselves with sea anemone mucus, we investigated the microbiomes of the two partners to search for possible shifts in their compositions. We used a 16S rRNA gene sequencing strategy to study the dynamics of the microbiota during the association between the clownfish Amphiprion ocellaris and its host Heteractis magnifica under laboratory conditions. The experiment conducted in aquaria revealed that both clownfish and sea anemone mucus had specific signatures compared to artificial sea water. The microbiomes of both species were highly dynamic during the initiation of the symbiosis and for up to seven days after contact. Three families of bacteria (Haliangiaceae, Pseudoalteromonadacae, Saprospiracae) were shared between the two organisms after symbiosis. Once the symbiosis had been formed, the clownfishes and sea anemone then shared some communities of their mucus microbiota. This study paves the way for further investigations to determine if similar microbial signatures exist in natural environments, whether such microbial sharing can be beneficial for both organisms, and whether the microbiota is implicated in the mechanisms that protect the clownfish from sea anemone stinging

Low vulnerability of the Mediterranean antipatharian Antipathella subpinnata (Ellis & Solander, 1786) to ocean warming

info:eu-repo/semantics/publishe

The tropical coral Pocillopora acuta displays an unusual chromatin structure and shows histone H3 clipping plasticity upon bleaching

Background: Pocillopora acuta is a hermatypic coral with strong ecological importance. Anthropogenic disturbances and global warming are major threats that can induce coral bleaching, the disruption of the mutualistic symbiosis between the coral host and its endosymbiotic algae. Previous works have shown that somaclonal colonies display different levels of survival depending on the environmental conditions they previously faced. Epigenetic mechanisms are good candidates to explain this phenomenon. However, almost no work had been published on the P. acuta epigenome, especially on histone modifications. In this study, we aim at providing the first insight into chromatin structure of this species. Methods: We aligned the amino acid sequence of P. acuta core histones with histone sequences from various phyla. We developed a centri-filtration on sucrose gradient to separate chromatin from the host and the symbiont. The presence of histone H3 protein and specific histone modifications were then detected by western blot performed on histone extraction done from bleached and healthy corals. Finally, micrococcal nuclease (MNase) digestions were undertaken to study nucleosomal organization. Results: The centri-filtration enabled coral chromatin isolation with less than 2% of contamination by endosymbiont material. Histone sequences alignments with other species show that P. acuta displays on average ~90% of sequence similarities with mice and ~96% with other corals. H3 detection by western blot showed that H3 is clipped in healthy corals while it appeared to be intact in bleached corals. MNase treatment failed to provide the usual mononucleosomal digestion, a feature shared with some cnidarian, but not all; suggesting an unusual chromatin structure. Conclusions: These results provide a first insight into the chromatin, nucleosome and histone structure of P. acuta. The unusual patterns highlighted in this study and partly shared with other cnidarian will need to be further studied to better understand its role in corals

Low vulnerability of the Mediterranean antipatharian Antipathella subpinnata (Ellis & Solander, 1786) to ocean warming

International audienceAntipatharians (black corals) are major components of mesophotic ecosystems in the Mediterranean Sea. The arborescent species Antipathella subpinnata has received particular attention as it is the most abundant and forms dense forests harbouring high levels of biodiversity. This species is currently categorized as “Near Threatened” in the IUCN Red List, due to increasing fishing pressure and bottom-trawling activities. Yet, the effects of ocean warming have never been investigated for this species, nor for any other antipatharians from temperate regions. Our study aimed at evaluating the effects of increasing seawater temperatures on A. subpinnata, by combining predictive distribution modelling with a physiological tolerance experiment. During the latter, we exposed A. subpinnata for 15 days to different temperature conditions spanning the current seasonal range to forecasted temperatures for 2100, while measuring biological endpoints such as oxygen consumption rates and different signs of stress (tissue necrosis, total antioxidant capacity). Unexpectedly, no stress was found at organism nor cellular level (wide thermal breadth) suggesting low susceptibility of this species to mid-term temperature increase. If the response to the 15-days heat stress is representative of the response to longer-term warming, ocean warming is unlikely to affect A. subpinnata. The species distribution model predicted the presence of A. subpinnata at depths that correspond to temperatures colder than its maximum thermal tolerance (as determined by the physiology experiment). This suggests that the presence of A. subpinnata at shallower depths is not limited by physiological constraints but by other ecological factors including interspecific competition