The Mammary Glands of the Amazonian Manatee, Trichechus inunguis (Mammalia: Sirenia): Morphological Characteristics and Microscopic Anatomy

Abstract

The mammaries from carcasses of two female Amazonian manatees were examined. Trichechus inunguis possesses two axillary mammaries beneath the pectoral fins, one on each side of the body. Each papilla mammae has a small hole on its apex-the ostium papillare. The mammaries are covered by a stratified squamous keratinized epithelium. The epithelium of the mammary ducts became thinner more deeply in the tissue and varied from stratified to simple cuboidal. There was no evidence of glandular activity or secretion into the ducts of the mammary glands. Anat Rec, 297:1532Rec, 297: -1535

Complete Inactivation of Sebum-Producing Genes Parallels the Loss of Sebaceous Glands in Cetacea

“…We next expanded our search to other mammalian lineages for which conflicting reports on the presence of SGs have previously been published. For example, the T. m. latirostris an exclusive aquatic noncetacean mammal: although Rodrigues et al reported the presence of SGs in the mammary tissue (Rodrigues et al. 2014), others failed to identify the presence of SGs in this species (Sokolov 1982; Graham 2005).…”

“…As such, Cetacea (whales and dolphins), Hippopotamidae, Elephantidae, and Heterocephalus glaber (naked mole rat) were reported to lack SGs; yet, their presence in Manidae (pangolins), Sirenia (manatees and dugongs), and Rhinocerotidae is still disputed, suggesting a complex correlation between SG degeneration and life history traits (fig. 1 B ) (Sokolov 1982; Graham 2005; Rodrigues et al. 2014; Plochocki et al.…”

Transition to an aquatic habitat permitted the repeated loss of the pleiotropic KLK8 gene in mammals

“…First, in the skin of terrestrial mammals, KLK8 activates antimicrobial proteolytic cascades in sweat ( Eissa et al 2011 ). As neither cetaceans nor manatees have sweat glands ( Berta et al 2015 ; Mouton and Botha 2012 ; Rodrigues et al 2014 ), in contrast to the semi-aquatic pinnipeds and terrestrial mammals that have an intact KLK8 gene, the antimicrobial of functions of KLK8 are likely no longer useful for aquatic mammals. Furthermore, the epidermis of KLK8 knockout mouse exhibits delayed recovery from the UVB-induced inflammation ( Kirihara et al 2003 ).…”

Advances in the knowledge of the biology and conservation of the Amazonian manatee (Trichechus inunguis)

“…The morphological aspects of the spermatozoa were also described for the species: spermatozoa measure approximately 60 µm with an oval flattened head and a long midpiece with mitochondrial helix, similar to other sirenians (Amaral et al, 2010b). Both sexes have mammary glands with one teat located on the axillary region, under each flipper, being more developed on adult females (Rodrigues et al, 2014). The milk has high fat content (8.76 -19.73%), apparent absence of carbohydrates, and variation on its content throughout the lactation period (Barbosa, 2011;.…”