Manuel Arbelo

• Associate Professor. DVM. PhD. Dipl ECZM (Wildlife Population Health).
• Professor (Associate) at University of Las Palmas de Gran Canaria

The pituitary gland regulates essential physiological processes in mammals. Despite its importance, research on its anatomy and ultrastructure in dolphins remains scarce. Using non-invasive imaging technology (MRI) and a novel skull-opening and dissection protocol, this study characterizes the dolphin pituitary through immunohistochemistry (IHC) an...

Climate change, overfishing, and other anthropogenic activities can negatively impact the energetic balance and body condition of cetaceans. Still, cetaceans must meet their energetic demands for survival, which are more expensive to maintain in the marine environment. The resilience of cetaceans to negative energy balance periods is unknown. We an...

The Canary Islands are considered a hot spot for marine species biodiversity. Each stranded cetacean has provided important scientific, biological and pathological information. The morphological identification of parasites in these stranded cetaceans is the main aim of the present article. An investigation to identify parasites was carried out in 2...

The European domestic rabbit ( Oryctolagus cuniculus domesticus) is commonly kept as a pet, with increasing popularity among pet owners. Despite the increasing body of information on lagomorph medicine and pathology, comprehensive published compilations of causes of mortality in pet rabbits are limited. We analyzed health disorders, pathology findi...

Introduction The amygdala is a noticeable bilateral structure in the medial temporal lobe and it is composed of at least 13 different nuclei and cortical areas, subdivided into the deep nuclei, the superficial nuclei, and the remaining nuclei which contain the central nucleus (CeA). CeA mediates the behavioral and physiological responses associated...

On the 21st of May 2023, a dead adult male sperm whale (Physeter macrocephalus) of 13 m in length and estimated weight of around 18,000 kg was reportedly stranded at Playa Los Nogales, La Palma, Canary Islands, Spain. A necropsy was performed 48hpm. A 50 cm diameter and 9.5 kg coprolite was found obstructing the caudal colon-rectal lumen. Necro-hem...

Simple Summary The common bottlenose dolphin, Tursiops truncatus, is a worldwide cetacean species essential for marine ecosystems’ health and balance. Understanding the genetic connectivity and structure of different populations is crucial for the correct management and conservation of a species, such as designing Special Areas of Conservation or M...

In this study, an innovative method was developed to detect and quantify phthalates in fresh cetacean blubber. An adaptation of the ammonium formate QuEChERS method was used and adapted as a micro-extraction for small quantities of samples. Significantly, this technique utilized minimal quantities of reagents and salts, with the additional implemen...

Simple Summary Beaked whales are singular and unconventional marine mammals, living in deep offshore waters. There is a scarce, almost absent, number of neuroanatomical studies on these toothed whales. The hypothalamus is a small brain region and it serves as the primary connection between the nervous and endocrine systems. This region is responsib...

Fifty-five skin lesions from 31 stranded cetaceans along the Canary coasts (2011–2021) were submitted to macroscopic, histological, and molecular analyses to confirm infection by cetacean poxvirus, herpesvirus and cetacean morbillivirus. They were macroscopically categorized into eight categories with respective subcategories according to their col...

This case exemplifies the value of integrative science in the study of cetaceans by combining information from different approaches such as at-sea monitoring programmes and stranding networks (from both health and biological perspectives) to clarify uncertainty relevant to the management of these species and the Marine Protected Area.

The nature, etiopathogenesis, and clinicopathologic relevance of the prevalent intracytoplasmic eosinophilic globules (IEGs) within hepatocytes of cetaceans are unknown. This study aims to evaluate the presence and characterize the IEGs in the hepatocytes of cetaceans using histochemical and immunohistochemical electron microscopy, Western blot, le...

The presence of ultraviolet filters (UVFs) and stabilizers (UVSs) was evaluated for the first time in the common bottlenose dolphin (Tursiops truncatus). UVFs and UVSs are compounds of growing concern because their effects on the environment are not completely known. UVFs and UVSs are added to personal care products (PCPs), such as cosmetics and pr...

Nowadays, zoos and aquariums, along with the constant advancement of sociocultural moral values, are proactively committed to ensuring and safeguarding cetacean health standards. This entails developing new approaches to health assessments by embracing minimally invasive sampling methods and enhanced animal handling and management, among other aspe...

In oceanic ecosystems, the nature of barriers to gene flow, and the processes by which populations may become isolated are different from the terrestrial environment, and less well understood. In this study we investigate a highly mobile species (the sperm whale, Physeter macrocephalus) that is genetically differentiated between an open North Atlan...

The role of veterinarians is becoming more significant and necessary to support the welfare and health not only of non-traditional companion animals and wildlife animals, but also of humans and the environment. The importance of the One Health/One World concept and its social impact is increasing significantly, accompanied by the notoriety of new e...

Ten species within the genus Nasitrema (subfamily Nasitrematinae, family Brachycladiidae) have been reported infecting a wide variety of odontocetes worldwide, although there is still a lack of information about their presence in beaked whales (BWs). Nasitrema spp. are commonly described inhabiting the pterygoid sinus, the tympanic cavities, and th...

La brucelosis es una enfermedad zoonótica causada por varias especies bacterianas del género Brucella (bacterias Gram negativas intracelulares facultativas) y que está ampliamente estudiada en animales terrestres. Sin embargo, no es así en la brucelosis marina, la cual está producida por las especies B. ceti y B. pinnipedialis, afectando a cetáceos...

Dolphins play a key role in marine food webs as predators of mid-trophic-level consumers. Because of their mobility and relatively long life span, they can be used as indicators of large-scale changes in the ecosystem. In this study, we calculated the trophic position (TP) of 5 dolphin species from the Canary, Madeira and Azores Islands using bulk...

Neuromelanin (NM) is a dark polymer pigment that is located mostly in the human substantia nigra, and in the locus ceruleus, referred to as “the blue spot”. NM increases linearly with age, and has been described mainly in the human brain; however, it also occurs in the neurons of monkeys, horses, giraffes, cattle, sheep, goats, dogs, rats, and even...

Nearly two decades ago, pathologic examination results suggested that acoustic factors, such as mid-frequency active naval military sonar (MFAS) could be the cause of acute decompression-like sickness in stranded beaked whales. Acute systemic gas embolism in these whales was reported together with enigmatic cystic liver lesions (CLL), characterized...

Cetaceans are mammals that underwent a series of evolutionary adaptations to live in the aquatic environment, including morphological modifications of various anatomical structures of the skeleton and their bone mineral density (BMD); there are few studies on the latter. BMD is related to the radiodensity measured through computed tomography (CT) i...

Abstract: Estimating cetacean interactions with fishery activities is challenging (Kuiken, 1996; Moore et al., 2013). Bycatch is responsible for thousands of cetacean deaths per year globally (Young & Iudicello, 2007; Dolman & Moore, 2017). This study updates the data on fishery interaction in stranded cetaceans in the Canary Islands, from the last...

During the last ten years, the IUSA Molecular Pathology Laboratory has set up and/or optimized numerous molecular diagnostic techniques using the polymerase chain reaction (PCR) technique for the accurate detection of marine wildlife pathogens in the Canary Islands, constituting the first systematic Sanitary Surveillance of our marine ecosystem. Th...

Herpesviruses are causative agents of meningitis and encephalitis in cetaceans, which are among the main leading known natural causes of death in these species. Brain samples from 103 stranded cetaceans were retrospectively screened for the presence of herpesvirus DNA in the brain. Molecular detection of Cetacean Morbillivirus was performed in HV p...

Considerable information has been gained over the last few decades on several disease processes afflicting free-ranging cetaceans from a pathologist's point of view. Nonetheless, there is still a dearth of studies on the hearts of these species. For this reason, we aimed to improve our understanding of cardiac histological lesions occurring in free...

Nearly two decades ago, pathologic examination results suggested acoustic factors, such as mid-frequency active naval military sonar (MFAS) could be the cause of acute decompression-like sickness in stranded beaked whales. Acute systemic gas embolism in these beaked whales was published together with enigmatic cystic liver lesions (CLL), characteri...

A retrospective survey for detecting the cetacean morbillivirus (CeMV) was carried out in beaked whales (BWs) stranded in the Canary Islands (1999–2017). CeMV is responsible for causing worldwide epizootic events with the highest mass die-offs in cetaceans, although the epidemic status of the Canarian Archipelago seems to be that of an endemic situ...

Harmful algal blooms (HABs) have been increasingly recorded over the last decades and much work has linked these events to multiple oceanographic and climate disturbances. HABs can affect ecosystems either as events that affect dissolved oxygen, clog fish gills, or smother corals or through the production of biotoxins which affect living marine res...

Simple Summary Characterization, description, and geographical location of harmful bacterial agents in cetaceans are important for population surveillance and health monitoring around the world. This research compiles the pathologic features of nocardiosis in five free-ranging delphinids from the Canary Islands and Andalusia. All examined animals s...

Cetacean brain sampling may be an arduous task due to the difficulty of collecting and histologically preparing such rare and large specimens. Thus, one of the main challenges of working with cetaceans’ brains is to establish a valid methodology for an optimal manipulation and fixation of the brain tissue, which allows the samples to be viable for...

The gastrointestinal contents of twelve individuals from six odontocete species that stranded between 2018 and 2019 in the Macaronesian Region (Eastern North Atlantic) were examined for the presence of marine debris. In addition, concentrations of eleven organic persistent contaminants (nonylphenols, bisphenols, phthalates and pesticides) were anal...

The monitoring of herpesvirus infection provides useful information when assessing marine mammals' health. This paper shows the prevalence of herpesvirus infection (80.85%) in 47 cetaceans stranded on the coast of the Valencian Community, Spain. Of the 966 tissues evaluated, 121 tested positive when employing nested-PCR (12.53%). The largest propor...

The global whale population has dramatically declined in the past centuries due to anthropogenic abuse, whereas, climate change, ship strikes, entanglements, pollution, and water debris are currently making an enormous impact on the recovery of all whales on the planet. The prostate is recognized as the only male accessory gland in odontocete cetac...

Poxvirus-like lesions are widely used as a potential health indicator in cetaceans, although for this application, corroboration of Poxvirus skin disease is imperative. Aiming to address skin biopsies intrusiveness, a preliminary investigation of a non-invasive skin sampling procedure to molecularly detect CePV-1 in 12 tattoo-like-lesions from two...

Herpesviruses (HVs) (Alpha- and Gammaherpesvirinae subfamilies) have been detected in several species of cetaceans with different pathological implications. However, available information on their presence in beaked whales (BWs) is still scarce. In this study, a total of 55 BWs (35 Ziphius cavirostris and 20 animals belonging to the Mesoplodon genu...

Estimating cetacean interactions with fishery activities is challenging. Bycatch and chronic entanglements are responsible for thousands of cetacean deaths per year globally. This study represents the first systematic approach to the postmortem investigation of fishery interactions in stranded cetaceans in the Canary Islands. We retrospectively stu...

Hypoxia could be a possible risk factor for neurodegenerative alterations in cetaceans’ brain. Among toothed whales, the beaked whales are particularly cryptic and routinely dive deeper than 1,000 m for about one hour in order to hunt squids and fishes. Samples of frontal cerebral and cerebellar cortex were collected from nine animals, representin...

Infectious and inflammatory processes are among the most common causes of central nervous system involvement in stranded cetaceans. Meningitis and encephalitis are among the leading known natural causes of death in stranded cetaceans and may be caused by a wide range of pathogens. This study describes histopathological findings in post-mortem brain...

ABSTRACT: Testicular neoplasms are extensively described and characterized in domestic animals but reports in wildlife species, including marine mammals, are scarce. This case report describes a testicular seminoma in an adult striped dolphin Stenella coeruleoalba stranded along the coasts of the Canary Islands. Post-mortem computerized tomography...

Fat embolism is the mechanical blockage of blood vessels by circulating fat particles. It is frequently related to traumas involving soft tissues and fat-containing bones. Different techniques have been used for decades to demonstrate histologically fat emboli, being the extremely toxic post-fixation with osmium tetroxide one of the most used techn...

Simple Summary: Hearing is arguably the primary sensory and communication channel for cetaceans. The study of diverse physiological and pathological events involving this system, requires standardized and reliable protocols for processing valuable and scarce samples such as the ears of cetaceans. As part of our research, standardized tissue process...

Background: Alzheimer’s disease results from the interplay of multiple risk factors and their effects. Diving mammals may be routinely exposed to severe hypoxia when submerged. Among toothed whales, the beaked whales are particularly cryptic and routinely dive deeper than 1,000 m for about one hour in order to hunt deep-water squid and fish. We hyp...

Some modifications in the vascular system of marine mammals provide adaptive advantages for diving. This study analyses the organisation of the aortic wall in dolphins, observing artery changes in volume and blood pressure for diving behaviour. Samples of three aortic segments (ascending, thoracic and abdominal) of three dolphin species were proces...

Aggressive encounters involving cetacean species are widely described in the literature. However, detailed pathological studies regarding lesions produced by these encounters are scarce. From January 2000 to December 2017, 540 cetaceans stranded and were necropsied in the Canary Islands, Spain. Of them, 24 cases of eight species presented social tr...

Capture myopathy (CM), is a syndrome that occurs as the result of the stress during and after capture, handling, restraint, and transport of wild animals. Although CM has been described for many species of cetaceans, characterization of the acute cardiac injury - an important component of this syndrome - are still scarce. In this study, we firstly...

Capture myopathy (CM) is described in wild animals as a metabolic syndrome resulting from the extreme stress suffered during and after capture, handling, restraint, and transport. Although CM has been characterized in many species of cetaceans, descriptions of cardiac injury—an important component of this syndrome, and, according to previous author...

The main objective of wildlife forensic investigation is to recognize pathologic changes and cause of death. Even though it may not always be possible to determine the specific illness and/or etiology, the description and subsequent interpretation of the injuries provide an invaluable understanding of pathology in cetacean post-mortem investigation...

Background: Brucella spp. isolation is increasingly reported in cetaceans, although associated pathologies, including lesions of the musculoskeletal and nervous systems, are less frequently described. Concerning the nervous system, Brucella sp. infection causing meningitis, meningoencephalitis or meningoencephalomyelitis have been extensively repo...

The prostate is the only male accessory gland in cetaceans. However, little is known about this organ in these species. Anatomical and histological characteristics of the prostate have been described in only a few cetacean species, further, one study reported a high incidence of prostatic pathologies in cetaceans that may impair reproduction. The o...

Background: Free-living cetaceans are exposed to a wide variety of stressful situations, including live stranding and interaction with human beings (capture myopathy), vessel strikes, and fishing activities (bycatch), which affect their wellbeing and potentially lead to stress cardiomyopathy (SCMP). Methods: Here, the authors aimed to characterise...

Strikes between vessels and cetaceans have significantly increased worldwide in the last decades. The Canary Islands archipelago is a geographical area with an important overlap of high cetacean diversity and maritime traffic, including high-speed ferries. Sperm whales (Physeter macrocephalus), currently listed as a vulnerable species, are severely...

Immunology of marine mammals is a relatively understudied field and its monitoring plays an important role in the individual and group management of these animals, along with an increasing value as an environmental health indicator. This study was aimed at implementing the knowledge on the immune response in cetaceans stranded along the Italian coa...

Western blot analysis was performed by loading 4 μg of human tonsil (Hu), 2.5 ug of striped dolphin (SC) and bottlenose dolphin (TT) cell membrane extract from lymph node onto an 12% SDS polyacrylamide gel. (A) CD5 monoclonal rabbit antibody (Biocare medical, USA product CRM 328) at a dilution of 1:500. (B) CD20 polyclonal rabbit antibody (Thermo S...

Cetacean morbillivirus (CeMV) is a major natural cause of morbidity and mortality in cetaceans worldwide and results in epidemic and endemic fatalities. The pathogenesis of CeMV has not been fully elucidated, and questions remain regarding tissue tropism and the mechanisms of immunosuppression. We compared the histopathologic and viral immunohistoc...

Main microscopic findings in prescapular, pulmonary, mediastinal and mesenteric lymph nodes of striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from Canary Islands (Spain) and Italy, and Guiana dolphins (Sotalia guianensis) from Brazil. (DOCX)

Main microscopic findings in the respiratory system of striped dolphins (Stenella coeruleoalba) and Atlantic bottlenose dolphins (Tursiops truncatus) from the Canary Islands (Spain) and Italy, and Guiana dolphins (Sotalia guianensis) from Brazil. (DOCX)

Template for recording histopathological findings in the central nervous system, including prosencephalon, mesencephalon and rhombencephalon. (DOCX)

Template for recording histopathological findings in the respiratory system. (DOCX)

Gross and microscopic pathologic findings, and most probable cause(s) of stranding and/or death (COD) in Guiana dolphins (Sotalia guianensis), striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) included in this study. (DOCX)

Main microscopic findings in central nervous system of striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from Canary Islands (Spain) and Italy, and Guiana dolphins (Sotalia guianensis) from Brazil. (DOCX)

Main microscopic findings in spleen of striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from Canary Islands (Spain) and Italy, and Guiana dolphins (Sotalia guianensis) from Brazil. (DOCX)

Bottlenose dolphin (Tursiops truncatus) brain; Mediosagittal aspect. A) Areas for neuroanatomical sampling (indicated as black rectangles) in striped dolphins (Stenella coeruleoalba) and bottlenose dolphins from the Canary Islands (Spain). AcL, anterior cerebellar lobe; H, hypothalamus; Hy, hypophysis; Met, metencephalon; My, myelencephalon; OrL, o...

Template for recording histopathological findings in the lymphoid system (lymph nodes, spleen). (DOCX)

Cetacean morbillivirus (CeMV; Paramyxoviridae) causes epizootic and interepizootic fatalities in odontocetes and mysticetes worldwide. Studies suggest there is different species-specific susceptibility to CeMV infection, with striped dolphins (Stenella coeruleoalba), bottlenose dolphins (Tursiops truncatus), and Guiana dolphins (Sotalia guianensis)...

Mass stranding events (MSEs) of beaked whales (BWs) were extremely rare prior to the 1960s but increased markedly after the development of naval mid-frequency active sonar (MFAS). The temporal and spatial associations between atypical BW MSEs and naval exercises were first observed in the Canary Islands, Spain, in the mid-1980s. Further research on...

This study describes the pathologic findings and most probable causes of death (CD) of 224 cetaceans stranded along the coastline of the Canary Islands (Spain) over a 7-year period, 2006–2012. Most probable CD, grouped as pathologic categories (PCs), was identified in 208/224 (92.8%) examined animals. Within natural PCs, those associated with good...

Tissues submitted for microbiological analysis and results from a subset of 224 stranded and necropsied cetaceans. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘natural pathology associated with significant loss of nutritional status’. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘vessel collision’. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘pathology associated with good nutritional status’. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘neonatal and perinatal pathology’. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘intra- and interspecific traumatic interactions’. (DOCX)

Biological and epidemiological data of 224 stranded and necropsied cetaceans. Sex: female (F), male (M). Age: fetus (F), neonate (N), calf (C), juvenile (Jv), subadult (Sad), adult (Ad). Stranding date (SD; mm/dd/yy). Type of stranding (TS). Stranding location, island (IS): Gran Canaria (GC), Fuerteventura (FT), Lanzarote (LZ), Tenerife (TF), La Go...

Details of immunohistochemical analyses performed on formalin-fixed, paraffin-embedded tissue sections from selected cetacean species, including primary antibody (Ab), manufacturer, clonality, dilution, pretreatment, incubation, secondary Ab, manufacturer, and visualization system. CD: Cluster of differentiation; CK: cytokeratin; GFAP: glial fibril...

Main morphologic and etiologic diagnoses in animals included in ‘interaction with fishing activities’. (DOCX)

Main morphologic and etiologic diagnoses in animals included in ‘foreign body-associated pathology’. (DOCX)

Many studies have been conducted to understand the role of spontaneous diseases in cetacean conservation, focusing in particular on the interaction between the pathogen and its host. These interactions may be influenced by pollutants, but conclusive evidence of the influences of pollution in the development of a disease is not usually evident durin...

Marine pollution, overrepresented by plastic, is a growing concern worldwide. However, there is little knowledge on occurrence and detrimental impacts of marine debris in cetaceans. To partially fill in this gap of knowledge, we aimed to investigate the occurrence and pathologies associated with foreign bodies (FBs) in a large cohort of cetaceans (...

Background: In the last 20 years, Cetacean Morbillivirus (CeMV) has been responsible for many die-offs in marine mammals worldwide, as clearly exemplified by the three dolphin morbillivirus (DMV) epizootics of 1990-1992, 2006-2008 and 2011 that affected Mediterranean striped dolphins (Stenella coeruleoalba). Systemic infection caused by DMV in the...

The earliest evidence of cetacean morbillivirus (CeMV) infection dates from 1982, when the dolphin morbillivirus strain (DMV) was identified in bottlenose dolphins Tursiops truncatus stranded in the mid-Atlantic region. Since then, CeMV has been detected globally in at least 26 species of mysticetes and odontocetes, causing widespread mortality and...

We report the gross and microscopic findings and molecular identification of fungal hyphate infection in a juvenile female Atlantic spotted dolphin Stenella frontalis found dead off Arguineguin, Gran Canaria (Canary Islands, Spain). On necropsy examination, the animal had a large cranial intrathoracic mass and multiple variably-sized nodules throug...

Neurodegenerative diseases, such as Alzheimer’s disease, should be investigated in toothed whales and considered as a possible cause of stranding. In the study, we showed the preliminary results on the beta amyloid (Aβ) peptide and phosphorylated tau protein expression, the pathological hallmarks of AD, in different species of toothed whales.

The locus coeruleus (LC) is the largest catecholaminergic nucleus and extensively projects to widespread areas of the brain and spinal cord. The LC is the largest source of noradrenaline in the brain. To date, the only examined Delphinidae species for the LC has been a bottlenose dolphin (Tursiops truncatus). In our experimental series including di...