Histological Assessment of Selected Blood Vessels of the Phocid Seals (Northern Elephant and Harbour Seals)

Morphological Structure of the Aortic Wall in Deep Diving Cetacean Species: Evidence for Diving Adaptation

This study analyses the aortic wall structure in nine cetacean species with deep diving habits belonging to four Odontoceti families: Ziphiidae, Kogiidae, Physteridae, and Delphinidae. Samples of ascending, thoracic and abdominal aorta were processed for histological and morphometric studies. The elastic component was higher in the proximal aortic segments, and the muscular elements increased distally in all cases. Morphometric analyses showed that all families presented a decrease in the thickness of the arterial wall and the tunica media along the aorta. The reduction was dramatic between ascending and thoracic aorta in the Physeteridae specimens; meanwhile, the other three families showed a more uniform decrease between the ascending, thoracic and abdominal aorta. The decline was not correlated with a reduced elastic or lamellar unit thickness but with a loss of lamellar units. The organization of the elements in the aortic wall did not show essential modifications between the four families, resembling the structure described previously in the shallow and intermediate diving dolphins. Our findings support that the difference in the morphometric characteristics of the different segments in the aortic wall is likely related to the diving habit more than the absolutes values of any other parameter.

Cardiac Structures in Marine Animals Provide Insight on Potential Directions for Interventions for Pediatric Congenital Heart Defects

Despite recent advances in pediatric diagnosis and surgical intervention, mortality and morbidity continue to be a prevalent issue in both Tetralogy of Fallot (ToF) and Hypoplastic Left Heart Syndrome (HLHS). Therefore, novel approaches to studying both of these conditions is warranted. Investigating cardiac anatomical features of different species in the animal kingdom similar to the defects and complications present in ToF and HLHS (as well as others) could serve as a new avenue for improving the management of congenital heart diseases (CHD). This review reveals that although structures found in HLHS and ToF are pathological, similar structures are found in diving mammals and reptiles that are adaptive. Pathologic aortic dilation in CHD resembles the aortic bulb present in diving mammals, but the latter is more elastic and distensible compared to the former. The unrepaired HLHS heart resembles the univentricular heart of non-crocodilian reptiles. Right ventricle hypertrophy is pathological in HLHS and ToF, but adaptive in crocodilians and diving mammals. Lastly, the increased pulmonary resistance due to pulmonary stenosis in ToF is comparable to increased pulmonary resistance in crocodilians due to the presence of an active valve proximal to the pulmonary valve. Some of these anatomical structures could potentially be adapted for palliative surgery in children with HLHS or ToF. Moreover, further investigating the underlying molecular signals responsible for the adaptive tissue responses seen in other species may also be useful for developing novel strategies for preventing some of the complications that occur after surgical repair in both of these CHDs.

Morphological features of the venous bed of the heart of the Baikal seal

The article describes the features of venous blood outflow from the heart in the Baikal seal. The objects for the study were corrosion preparations of 11 hearts of the Baikal seal aged from 1 month to 10 years. In our research we used the methods of preparation, filling of vessels with the use of "Kudo" mounting foam, photographing and sketching the branching of vessels. It was established that in the Baikal seal, the outflow of venous blood occurs through the prominent coronary sinus and the large, intermediate, oblique vein of the left atrium, the middle and right heart veins that flow into it. In 18.2% of hearts, a coronary valve was found at the border of the great heart vein and the coronary sinus. The great heart vein begins above the apices of the heart and is formed from the fusing of the 6-11 collateral veins of the wall of the right ventricle, the venous pericardial plexus, and 9-16 branches on the side of the left ventricle. The most variable is the intermediate (marginal) branch, which in most cases has only one branch, however, in 18.2% of cases there are two ones or in 9.1% of cases, there are intermediate branches with a common trunk. The middle vein of the heart is located in the sub-sinus sulcus and anastomoses with the branch of the great vein of the heart, in 9.1% of cases, the valve of the coronary sinus was found at the border with the coronary sinus. The right veins of the heart have 5-6 branches, among which the marginal ones are the most prominent. 27.3% of Baikal seals have a venous sinus formed from the fusion of the middle and right coronary veins, as well as a duct connecting the large cardiac vein with this sinus.

Morphological structure of the aortic wall in three Delphinid species with shallow or intermediate diving habits: Evidence for diving adaptation

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 processed for histological and morphometric studies. The three dolphin species used, striped dolphin (Stenella coeruleoalba), Atlantic spotted dolphin (Stenella frontalis) and common dolphin (Delphinus delphis), have shallow or intermediate diving habits. Our results indicated that the components of the aortic wall of the dolphins had different dispositions in the three selected segments. The aortic wall decreased in thickness along its length due to a loss of the lamellar units in the tunica media and a thinning of the main elements of the lamellar units along the artery. The life stage had little influence on the thickness of the aortic wall except for the ascending aorta. The weight, body length, species or sex of the specimen did not significantly influence the thickness of the wall or the lamellar units. In summary, the histological and morphometric aortic structure in dolphins, in relation to the studied parameters, seems to be similar to that previously described of terrestrial mammals such as pigs, except for a larger difference in the proportion of lamellar units between the ascending and thoracic segments.