Comparative morphology, histology, and cytology of odontocete cetaceans prostates

Histological study of seventeen organs from dugong (Dugong dugon)

Background

Dugongs are marine mammals with a crescent-shaped tail fluke and a concave trailing margin that belong to the family Dugongidae., They are distributed widely in the warm coastal waters of the Indo-Pacific region. Importantly, the population of dugongs has decreased over the past decades as they have been classified as rare marine mammals. Previous studies have investigated the habitat and genetic diversity of dugongs. However, a comprehensive histological investigation of their tissue has not yet been conducted. This study provides unique insight into the organs of dugongs and compares them with other mammal species.

Methods

Tissue sections were stained with Harris's hematoxylin and eosin Y. The histological structure of 17 organ tissues obtained from eight systems was included in this study. Tissue sections were obtained from the urinary system (kidney), muscular system (striated skeletal muscle and smooth muscle), cardiovascular system (cardiac muscle (ventricle), coronary artery, and coronary vein), respiratory system (trachea and lung), gastrointestinal system (esophagus, stomach, small intestine, liver, and pancreas), reproductive system (testis), lymphatic system (spleen and thymus), and endocrine system (pancreas).

Results

While most structures were similar to those of other mammal species, there were some differences in the tissue sections of dugongs when compared with other mammalian species and manatees. These include the kidneys of dugongs, which were non-lobular and had a smooth, elongated exterior resulting in a long medullary crest, whereas the dugong pyloric epithelium did not have overlying stratified squamous cells and was noticably different from the Florida manatee.

Discussion

Histological information obtained from various organs of the dugong can serve as an essential foundation of basal data for future microanatomical studies. This information can also be used as high-value data in the diagnosis and pathogenesis of sick dugongs or those with an unknown cause of death.

Birth-and-death evolution of ribonuclease 9 genes in Cetartiodactyla

RNase9 plays a reproductive function and has been recognized as an important member of the ribonuclease (RNase) A superfamily, a gene family that is widely used as a model for molecular evolutionary studies. Here, we identified 178 RNase9 genes from 95 Cetartiodactyla species that represent all four lineages and 21 families of this clade. Unexpectedly, RNase9 experienced an evolutionary scenario of "birth and death" in Ruminantia, and expression analyses showed that duplicated RNase9A and RNase9B genes are expressed in reproductive tissues (epididymis, vas deferens or prostate). This expression pattern combined with the estimate that these genes duplicated during the middle Eocene, a time when Ruminantia become a successful lineage, suggests that the RNase9 gene duplication might have been advantageous for promoting sperm motility and male fertility as an adaptation to climate seasonality changes of this period. In contrast, all RNase9 genes were lost in the Cetacean lineage, which might be associated with their high levels of prostatic lesions and lower reproductive rates as adaptations to a fully aquatic environment and a balance to the demands of ocean resources. This study reveals a complex and intriguing evolutionary history and functional divergence for RNase9 in Cetartiodactyla, providing new insights into the evolution of the RNaseA superfamily and molecular mechanisms for organismal adaptations to the environment.

The Odontocete Ear Canal-Associated Lymphoid Tissue (ECALT) and Lymph Nodes: Morphological and Pathological Description with Immuno-Phenotypic Characterisation

Simple Summary

The marine mammal immune system is of vital importance for the health of any marine mammal. With changes in the natural environment and with increasing anthropogenic stressors such as pollution, the immune system is challenged to unknown extents. Dolphins and other odontocete cetaceans have been shown to be particularly sensitive to anthropogenic influence in many aspects. In this regard, it is important to understand how these animals cope with novel stressors and how the immune system works and responds. In studying parallel issues related to underwater noise pollution, we looked at the cetacean ear canal and analysed in detail the cells of the immune system. Like the skin, it is likely to be exposed to the external environment and requires a local defence system as a first barrier to incoming threats. We studied the ear-canal associated immune system and describe the cell population using a variety of microscopic techniques. We describe healthy and activated tissue and cases with inflammation of the external ear canal and compare the different physiological states. As such, this study contributes to acquiring a general understanding of the odontocete cetacean immune system.

Abstract

A changing marine environment with emerging natural and anthropogenic stressors challenges the marine mammal immune system. The skin and adnexa form a first protective barrier in the immune response, although this is still relatively understudied in cetaceans. The cellular and tissue morphology of the nodular and diffuse lymphoid tissue are not fully charted and the physiological responses are not yet completely understood. The odontocete’s external ear canal has a complex relationship with the external environment, with an artificial lumen rendering the inside of the canal a relatively secluded environment. In this work, we studied the odontocete ear canal-associated lymphoid tissue (ECALT) by histo- and immunohistochemistry (HC, IHC) with anti-CD3, anti-CD20, anti-Iba-1, anti-HLA-DR, and anti-vimentin antibodies. The ECALT cellular composition consists mainly of B-lymphocytes with the occasional presence of T-lymphocytes and the dispersed distribution of the macrophages. In cases of activation, the cellular reaction showed a similar pattern with the occasional presence of T-cells, plasma cells, and neutrophils. Nodular lymphoid tissue was generally in line with the description in other odontocetes, although with abundant erythrocytes throughout the entire organ. This study contributes to the understanding of the cellular composition of diffuse and nodular lymphoid tissue in several species of odontocetes, and in association with inflammation of the external ear canal.

Protein Identification of Spermatozoa and Seminal Plasma in Bottlenose Dolphin (Tursiops truncatus)

Proteins play an important role in many reproductive functions such as sperm maturation, sperm transit in the female genital tract or sperm-oocyte interaction. However, in general, little information concerning reproductive features is available in the case of aquatic animals. The present study aims to characterize the proteome of both spermatozoa and seminal plasma of bottlenose dolphins (Tursiops truncatus) as a model organism for cetaceans. Ejaculate samples were obtained from two trained dolphins housed in an aquarium. Spermatozoa and seminal plasma were analyzed by means of proteomic analyses using an LC-MS/MS, and a list with the gene symbols corresponding to each protein was submitted to the DAVID database. Of the 419 proteins identified in spermatozoa and 303 in seminal plasma, 111 proteins were shared by both. Furthermore, 70 proteins were identified as involved in reproductive processes, 39 in spermatozoa, and 31 in seminal plasma. The five most abundant proteins were also identified in these samples: AKAP3, ODF2, TUBB, GSTM3, ROPN1 for spermatozoa and CST11, LTF, ALB, HSP90B1, PIGR for seminal plasma. In conclusion, this study provides the first characterization of the proteome in cetacean sperm and seminal plasma, opening the way to future research into new biomarkers, the analysis of conservation capacity or possible additional applications in the field of assisted reproductive technologies.

The prostate of the bat Artibeus lituratus: Seasonal variations, abiotic regulation, and hormonal control

The prostate is an important gland that contributes to the male reproductive process, producing secretions that are essential for maintaining ideal conditions for the survival of sperm. Studies indicate a wide variation in the occurrence, morphology, and physiology of this gland in mammals, especially in bats, with this variation being related not only to the number of regions and their degree of compaction/lobulation but also to fluctuations in their functioning throughout the year. Thus, the aim of this study was to evaluate the annual morphological and physiological variations of the male prostate of Artibeus lituratus and analyze their responses to annual abiotic variations and hormonal control. Sixty sexually adult males of A. lituratus were analyzed in this study, with five specimens collected monthly. Blood samples were submitted to serum hormone measurements and the prostates were morphologically, morphometrically, and immunohistochemically analyzed. The results indicated that the two prostatic regions (ventral and dorsal) of A. lituratus had different morphology, as well as different physiology and regulation. Annual fluctuations in abiotic factors seemed to influence the dorsal region more than the ventral region. Conversely, variations on testicular factors, such as testosterone and estradiol, influenced the ventral region more than the dorsal region. Despite these differences, both prostatic regions were strongly synchronized to the main reproductive peak of the species in September. The holocrine pattern of the ventral prostate was not directly affected by abiotic factors or by factors released by the testes.