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) and transmission electron microscopy (TEM). A total of 47 pituitaries were collected from stranded common bottlenose dolphins (Tursiops truncatus). common dolphins (Delphinus delphis), and Atlantic spotted dolphins (Stenella frontalis). as well as from captive common bottlenose dolphins. MRI allowed visualization of the gland’s anatomy and its spatial relationship with the hypothalamus and surrounding structures. A modified skull-opening and pituitary extraction protocol ensured the preservation of the adenohypophysis and neurohypophysis for detailed analysis. Histological, immunohistochemical, and ultrastructural studies confirmed the gland’s structural organization, identifying eight distinct adenohypophyseal cell types: corticotrophs (ACTH), somatotrophs (GH), gonadotrophs (FSH and LH), lactotrophs (LTH), melanotrophs (MSH), thyrotrophs (TSH), follicular cells, and capsular cells. This study presents the first immunolabelling of thyrotrophs in cetacean adenohypophysis and the first detailed ultrastructural characterization of adenohypophyseal cells in cetaceans, providing baseline data for future research. By integrating multidisciplinary techniques, it advances the understanding of dolphin neuroendocrinology and highlights broader implications for cetacean health, welfare, and conservation.

The Franciscana (also known as the La Plata River Dolphin) is a small dolphin that lives in the coastal waters of Brazil, Uruguay, and Argentina. This species is considered the most endangered marine mammal in the western South Atlantic Ocean. Anatomic dissection of the digestive system of 19 animals of different ages, including 2 neonates, 12 juveniles, and 5 adults, was performed. Parameters related to length, breadth, weight, and diameter of the digestive viscera were considered in each case. Our results show that the Franciscana dolphin presents differential characteristics in relation to several parts of the digestive system, including, specifically, the tongue, the teeth, the stomach, and the small intestine. Thus, this paper add precious information to the actual knowledge of this vulnerable marine mammal species in order to improve conservation efforts.

Marine mammals play a critical ecological role as both predator and prey. They are divided into three groups that share similar adaptations to their aquatic life, but that have very different origins and life patterns: sirenians, pinnipeds, cetaceans. The species object of our interest is the South American fur seal or Arctocephalus australis, a carnivore classified within the group of pinnipeds. The objective of the present study was to evaluate whether the anatomical characteristics of the Arctocephalus australis’ digestive system are similar to that of other land-carnivores or if, on the contrary, this species shows anatomical adaptations related to their life in the ocean. The study was carried out on 11 cadavers of the species Arctocephalus australis, made up of two adults and nine juveniles, by means of the anatomical dissection of their entire isolated digestive system. We demonstrate that, with several exceptions, the anatomical characteristics of the digestive system of the Arctocephalus australis are similar to those in other carnivores. Therefore, our data constitute an important contribution for clinical diagnostic and conservation purposes, for both veterinarians and biologists.

Marine mammals are divided into three groups, with similar adaptations resulting from their aquatic lifestyle: sirenians, pinnipeds, and cetaceans. The present work focused on the South American fur seal, or Arctocephalus australis, a carnivore included in the pinnipeds group. We assessed whether the anatomical features of the Arctocephalus australis’ respiratory system are comparable to those of other land-carnivores or whether these individuals show anatomical adaptations related to their ability to dive or their breath-holding capacities. We studied 11 cadavers of Arctocephalus australis, which included adult (n = 2) and juvenile (n = 9) individuals, by anatomically dissecting their isolated entire respiratory system. Although it is generally similar to that in land-carnivores, we demonstrated that the Arctocephalus australis’s respiratory apparatus shows several specific characteristics. Therefore, our results are of great importance for clinical diagnostic and wildlife conservation purposes.

The adrenal glands are central regulators of endocrine function and stress physiology, yet detailed species-specific anatomical baselines remain limited in cetaceans. This study provides a comprehensive gross, histological, morphometric, and ultrastructural characterization of the adrenal glands in 55 short-beaked common dolphins (Delphinus delphis) examined postmortem in the Canary Islands. Adrenal glands were evaluated macroscopically and microscopically, and histological corticomedullary ratios were calculated from mid-transverse sections. Associations with body length, sexual maturity, and cause-of-death category were assessed statistically. Transmission electron microscopy was performed to characterize cortical and medullary cellular ultrastructure. Adrenal weight showed a positive correlation with body length. Histological corticomedullary ratio showed no lateral asymmetry but differed significantly between sexually immature and mature individuals, indicating ontogenetic remodeling of adrenal architecture. In contrast, corticomedullary ratio did not differ significantly between adult dolphins that died from acute events and those with more progressive pathological conditions. Ultrastructural analysis identified characteristic steroidogenic cortical cells and two chromaffin cell populations in the medulla. These findings establish the first integrated anatomical baseline for the adrenal gland in Delphinus delphis, providing essential reference data for comparative anatomy, veterinary pathology, and interpretation of endocrine-related findings in cetaceans.

A juvenile bottlenose dolphin (Tursiops truncatus) was first observed among a group of approximately 12 dolphins on 10 December 2024, repeatedly breaching off Riverhead, Auckland, New Zealand. On subsequent observations, material consistent with fishing debris was seen entangled around the dorsal fin and tail flukes. While most conspecifics departed the area, a larger dolphin remained in close association with the entangled individual. The pair remained within the local area for at least 29 days prior to human intervention efforts to disentangle the animal. During the interim period, the entangled dolphin exhibited progressive deterioration in body condition and reduced activity compared with the free-swimming conspecific. The animal was found dead shortly thereafter. Within 48 hours of death, post-mortem MRI and necropsy were conducted on the cadaver, which was scored as decomposition carcass code 1 (within rigor mortis). These identified an emaciated, sexually immature female bottlenose dolphin. Gross examination revealed severe, multifocal to coalescing lacerations and abrasions affecting the dorsal fin and caudal peduncle, with associated soft-tissue loss and irregular wound margins. Histologically, sections from the dorsal fin laceration showed evidence of severe, subacute to chronic, ulcerative necrosuppurative dermatitis with secondary bacterial infection. Pulmonary tissue samples revealed an acute, severe bacterial pneumonia characterised by neutrophilic infiltration and short bacilli. The liver and spleen showed findings of hepatitis and splenitis, suggestive of bacterial septicaemia. Swab isolates from these pooled tissues identified moderate growth of Erysipelothrix rhusiopathiae and Pseudomonas spp. Collectively, in vivo evidence and post-mortem gross and histopathological findings were consistent with poor body condition resulting from a progressive wasting disease primarily associated with chronic entanglement, leading to chronic active deep infectious necrosuppurative dermatitis and subsequent fatal bacterial septicaemia. Bacterial septicaemia. This case highlights the importance of timely intervention in entanglement events to reduce the risk of secondary complications, including impaired foraging, progressive loss of body condition, and infection. Based on post-mortem findings, death was consistent with bacterial septicaemia in the context of a deep skin lesion to the dorsal fin caused by fishing gear and its subsequent pathological effects. From an animal welfare perspective, the prolonged duration of entanglement, progressive debilitation, and evidence of systemic wasting disease support a period of substantial and sustained welfare compromise prior to death. This incident would be classified as high-intensity, long-duration suffering.