Dolphin Morbillivirus: a lethal but valuable infection model

Recent selection created distinctive variability patterns on MHC class II loci in three dolphin species from the Mediterranean Sea

The major histocompatibility complex (MHC) includes highly polymorphic genes involved in antigen presentation, which is crucial for adaptive immune response. They represent fitness related genetic markers particularly informative for populations exposed to environmental challenges. Here we analyse the diversity and evolutionary traits of MHC class II DQA and DQB genes in the dolphins Stenella coeruleoalba and Grampus griseus from the Mediterranean Sea. We found substantial nucleotide and functional diversity, as well as strong evidence of balancing selection indicated by allele and supertype frequencies, Tajima's D statistics and dN/dS tests. The Risso's dolphin, considered the least abundant in the region, showed the effect of divergent allele advantage at the nucleotide and functional-peptide levels. An outstanding polymorphism was found in the striped dolphin, particularly intriguing in the DQA gene where the Ewens-Watterson test detected a selection sweep that occurred in recent history. We hypothesize that morbillivirus, which has recurrently invaded Mediterranean populations over the last decades, exerted the detected selective pressure.

Is pomegranate husk scald during storage induced by water loss and mediated by ABA signaling?

BACKGROUND

Husk scald (HS) is a physiological disorder limiting the marketability of pomegranate fruit during long-term storage. Herein we propose that HS is triggered by water loss and mediated by ABA signaling. Therefore, pomegranate fruit were stored at three different storage temperatures (3.5, 7 and 11°C) and 96.5% ± 2.3% relative humidity (RH) evaluating weight loss (WL), abscisic acid (ABA), respiration rate (RR), total phenolics (TP), total anthocyanin (TA), antioxidant activity (AA), exocarp electrolyte leakage (EL), malondialdehyde (MDA), color attributes, browning index and visual quality of fruit.

RESULTS

HS appeared after 3 months of storage at 11 °C, less at 7°C and non-present at 3.5°C. Incidence of HS occurred along with higher WL, RR, EL, MDA, and ABA content. Conversely, TP, TA and AA decreased significantly. WL increased with water vapor pressure deficit (VPD) at higher temperatures. After 93 days, 11 °C fruit reached ~10% WL while ABA increased to ~150 μg kg^-1 . However, 3.5 and 7 °C fruit, reached 5 and 7% WL while ABA was ~31 and 75 μg kg^-1 , respectively.

CONCLUSION

Herein, we propose a mechanistic model of HS development where water stress induces ABA as a primary signaling molecule that triggers the HS response mediated by reactive oxygen species (ROS). Accumulation of ROS induces phenolic biosynthesis and oxidative stress promotes loss of membrane compartmentalization that induces phenolic degradation. Ultimately, husk scalding becomes visible due to the oxidation of phenolics into brown pigments. © 2022 Society of Chemical Industry.

SARS-CoV-2, a Threat to Marine Mammals? A Study from Italian Seawaters

Zoonotically transmitted coronaviruses were responsible for Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), causing the dramatic Coronavirus Disease-2019 (CoViD-19) pandemic, which affected public health, the economy, and society on a global scale. The impact of the SARS-CoV-2 pandemic permeated into our environment and wildlife as well; in particular, concern has been raised about the viral occurrence and persistence in aquatic and marine ecosystems. The discharge of untreated wastewaters carrying infectious SARS-CoV-2 into natural water systems that are home to sea mammals may have dramatic consequences on vulnerable species. The efficient transmission of coronaviruses raises questions regarding the contributions of virus-receptor interactions. The main receptor of SARS-CoV-2 is Angiotensin Converting Enzyme-2 (ACE-2), serving as a functional receptor for the viral spike (S) protein. This study aimed, through the comparative analysis of the ACE-2 receptor with the human one, at assessing susceptibility to SARS-CoV-2 for different species of marine mammals living in Italian waters. We also determined, by means of immunohistochemistry, ACE-2 receptor localization in the lung tissue from different cetacean species, in order to provide a preliminary characterization of ACE-2 expression in the marine mammal respiratory tracts. Furthermore, to evaluate if and how Italian wastewater management and coastal exposition to extreme weather events may led to susceptible marine mammal populations being exposed to SARS-CoV-2, geomapping data were carried out and overlapped. The results showed the potential SARS-CoV-2 exposure for marine mammals inhabiting Italian coastal waters, putting them at risk when swimming and feeding in specific risk areas. Thus, we highlighted the potential hazard of the reverse zoonotic transmission of SARS-CoV-2 infection, along with its impact on marine mammals regularly inhabiting the Mediterranean Sea, while also stressing the need for appropriate action in order to prevent further damage to specific vulnerable populations.

POSTMORTEM FINDINGS IN CETACEANS FOUND STRANDED IN THE PELAGOS SANCTUARY, ITALY, 2007-14

Between 2007 and 2014, 83 cetaceans were found stranded along the Ligurian coast of Italy, in the Pelagos Sanctuary, the largest marine protected area in the Mediterranean basin. Forty-nine (59%) were submitted to complete or partial necropsy, depending on the conservation status of the carcass. Based on gross and histological pathology and ancillary testing, the cause of death was determined and categorized as anthropogenic or natural (i.e., nonanthropogenic) in origin for 33 animals (67%) and of undetermined origin in the remaining 16 (33%). Natural causes of death, accompanied by either poor or good nutritional status, were attributed to 29 animals (59%), whereas four (8%) were diagnosed with an anthropogenic cause of death, consisting of interaction with fishing activities. Infectious and noninfectious disease was the most common cause of death, involving 29 cetaceans (59%). These data are valuable for understanding health and mortality trends in cetacean populations and can provide information for establishing policies for cetacean conservation and management in such an important protected area of the Mediterranean basin.

Trace elements in striped dolphins (Stenella coeruleoalba) from the Eastern Mediterranean: A 10-years perspective

Concentrations of Hg, Se, Cd, Cu, Zn, Fe, Mn and As, in kidney, liver, muscle and blubber from 7 specimens of Stenella coeruleoalba, stranded along the Israeli Mediterranean coast (IMC) from 2006 to 2011 (2011-series) were determined and compared to previous data on S. coeruleoalba from the IMC (2001-series). No differences were observed in essential and toxic elements concentrations, between the two series, except for hepatic Mn which was higher in the latter. Hg/Se molar ratios in blubber, kidney and liver increased linearly with log Hg concentrations, while muscle was more heterogenic in this respect. Means (±SD) of hepatic Hg concentrations (134±89 and 181±200mgkg(-1), from the 2011 and 2001 series, respectively) were similar to that found in 2007-2009 specimens from Spain, possibly reflecting the relatively high natural background levels of mercury in the Mediterranean Sea.

Cetacean Morbillivirus-Associated Pathology: Knowns and Unknowns

The present minireview deals with the pathology of Cetacean Morbillivirus (CeMV) infection in free-ranging cetaceans. In this respect, while "classical" CeMV-associated lesions were observed in the lung, brain, and lymphoid tissues from striped dolphins (Stenella coeruleoalba) and pilot whales (Globicephala melas) which were victims of the 1990-1992 and 2006-2008 epidemics in the Western Mediterranean, an apparent reduction in CeMV neurovirulence, along with a different viral antigen's tissue and cell distribution, were found during the 2010-2011 and the 2013 outbreaks in the same area. Of remarkable concern are also the documented CeMV ability to induce maternally acquired infections in wild cetaceans, coupled with the progressively expanding geographic and host range of the virus in both Hemispheres, as well as in conjunction with the intriguing forms of "brain-only" morbilliviral infection increasingly reported in Mediterranean-striped dolphins. Future research in this area should address the virus-host interaction dynamics, with particular emphasis on the cell receptors specifying viral tissue tropism in relation to the different cetacean species and to their susceptibility to infection, as well as to the CeMV strains circulating worldwide.

Retrospective seroepidemiological investigations against Morbillivirus, Toxoplasma gondii and Brucella spp. in cetaceans stranded along the Italian coastline (1998-2014)

This study reports the results of seroepidemiological investigations carried out against Morbillivirus, Toxoplasma gondii and Brucella spp. on blood serum samples collected from 70 cetacean specimens found stranded along the Italian coastline between 1998 and 2014. A total number of 23 serum samples (32.8%) obtained from Stenella coeruleoalba, Tursiops truncatus, Balaenoptera physalus and Globicephala melas harboured anti-Morbillivirus neutralizing antibodies. Ten sera (16%) collected from S. coeruleoalba and T. truncatus were found positive against T. gondii, while no antibodies against Brucella spp. were found. These data reveal that stranded cetaceans provide a unique opportunity for monitoring the health status of free-ranging animals living in the Mediterranean Sea, in order to investigate the level of exposure of cetacean populations to selected infectious agents representing a serious threat for aquatic mammals.

Cetacean strandings in Italy: an unusual mortality event along the Tyrrhenian Sea coast in 2013

An unusual mortality event involving cetaceans, mainly striped dolphins Stenella coeruleoalba (Meyen, 1833), occurred along the Tyrrhenian Sea coast of Italy during the first 3 mo of 2013. Based on post-mortem analyses carried out according to body condition on 66 dolphins (54% of stranded animals), several hypotheses to explain the causes of this mortality event were proposed. Although no definitive conclusions can be drawn, dolphin morbillivirus was deemed the most likely cause, although other infectious agents (including Photobacterium damselae damselae and herpesvirus) or environmental factors may also have contributed to this recent mortality event.