The skin structures and their role in the thermoregulation of the South American fur seal (Arctocephalus australis)

Morphology of sweat glands in the skin of Saimaa (Pusa hispida saimensis) and Baltic ringed (Pusa hispida botnica) seals

The endangered Saimaa ringed seal (Pusa hispida saimensis) is an endemic freshwater subspecies inhabiting Lake Saimaa in Finland. The Baltic ringed seal (Pusa hispida botnica) inhabits the brackish Baltic Sea, which is almost entirely landlocked. Recent research shows that Saimaa and Baltic ringed seals may be genetically even further apart from each other than from other ringed seal subspecies. We documented histologically the integument microstructure of Saimaa and Baltic ringed seals to determine whether the geographic and genetic isolation was manifested as variation in the integument microstructure of these subspecies adapted to icy aquatic environments. The skin structures of these subspecies were similar to those of other phocids. The association of the sweat glands with hair follicles in both subspecies suggested that they were small apocrine sweat glands described previously in terrestrial or aquatic mammals. None of the apocrine glands had large lumina, and some of the ducts were relatively straight and short. Further studies analysing the mode of secretion, for example, apocrine versus eccrine, in the sweat glands are necessary to confirm the types of sweat glands in seals.

The initial steps toward the formation of somatic tissue banks and cell cultures derived from captive Antillean manatee (Trichechus manatus manatus) skin biopsies

The declining population of the Antillean manatee caused by ecosystem degradation and rising pollution has prompted interest in developing conservation strategies for this species. Given this scenario, somatic tissue banks are important tools for acquiring knowledge about the species, as well as for obtaining somatic cells for biotechnological and ecotoxicological applications. Therefore, we aimed to assess the effects of slow freezing (SF) and solid-surface vitrification (SSV) of the dermis of captive Antillean manatees on the histology and ultrastructure of the tissue and cell viability in culture. While the SSV did not change the dermis thickness, the SF maintained the tissue proliferative potential, assessed by the nucleolar organizer region area, similar to noncryopreserved tissues. Moreover, both techniques reduced the number of fibroblasts and increased the percentage of collagen fibers. Nevertheless, only tissues cryopreserved with SF and noncryopreserved tissues were able to produce cells after in vitro culture. Although SF did not alter cell viability and proliferative activity, cells derived from cryopreserved tissues showed decreased metabolism, altered apoptosis, increased levels of reactive oxygen species, and mitochondrial membrane potential compared to cells from noncryopreserved tissues. In summary, we demonstrated for the first time that Antillean manatee somatic tissues can be cryopreserved by SF, and cells can be obtained after in vitro culture. Improvements in cryopreservation conditions, especially vitrification, of somatic samples are needed to increase the quality of somatic tissue banks in this species.

Influence of Intracellular Cryoprotectants on the Conservation of Dermal Somatic Tissues Derived from Antillean Manatees (Trichechus manatus manatus Linnaeus, 1758)

Cryopreservation of somatic tissue has been studied as a tool for the knowledge and conservation of endangered species, such as Antillean manatees. The use of vitrification protocols is an important step in the establishment of biological banks. To decrease the damage caused by this technique, a reduction in the concentration of cryoprotectants has been proposed. Therefore, we aimed to evaluate combinations and concentrations of intracellular cryoprotectants for the conservation of somatic tissues derived from Antillean manatees. Dulbecco's modified Eagle's medium, F-12 composed of 10% fetal bovine serum and 0.25 M sucrose, was supplemented with 3.0 M ethylene glycol (EG) plus 3.0 M dimethyl sulfoxide (DMSO), or 1.5 M EG plus 1.5 M DMSO or 3.0 M EG or 3.0 M DMSO, to produce four solutions for solid-surface vitrification. Noncryopreserved tissues were used as the controls. After warming, tissues derived from four Antillean manatees were evaluated for ultrastructure, histology, and in vitro culture. No differences were observed among the cryopreserved and noncryopreserved tissues in terms of ultrastructure. The dermis thickness of the cryopreserved fragments in solutions containing 3.0 M EG plus 3.0 M DMSO, 3.0 M EG, and 3.0 DMSO was similar to that of the control. Moreover, cryopreservation with 3.0 M EG plus 3.0 M DMSO maintained tissue proliferative capacity potential evaluated by quantification of nucleolar organizing regions. Nevertheless, none of the cryopreserved fragments were able to maintain the number of fibroblasts and the collagen percentage as compared with that of the noncryopreserved fragments. Also, none of the cryopreserved fragments in the different solutions were able to produce cells in vitro. In summary, even reducing the concentration of intracellular cryoprotectants as well as their association did not guarantee the maintenance of cells after in vitro culture. Further studies are needed to optimize the cryopreservation protocols in Antillean manatee somatic tissues.

Anatomy of the sense of touch in sea otters: Cutaneous mechanoreceptors and structural features of glabrous skin

Sea otters (Enhydra lutris) demonstrate rapid, accurate tactile abilities using their paws and facial vibrissae. Anatomical investigations of neural organization in the vibrissal bed and somatosensory cortex coincide with measured sensitivity, but no studies describe sensory receptors in the paws or other regions of glabrous (i.e., hairless) skin. In this study, we use histology to assess the presence, density, and distribution of mechanoreceptors in the glabrous skin of sea otters: paws, rhinarium, lips, and flipper digits, and we use scanning electron microscopy to describe skin-surface texture and its potential effect on the transduction of mechanical stimuli. Our results confirm the presence of Merkel cells and Pacinian corpuscles, but not Meissner corpuscles, in all sea otter glabrous skin. The paws showed the highest density of Merkel cells and Pacinian corpuscles. Within the paw, relative densities of mechanoreceptor types were highest in the distal metacarpal pad and digits, which suggests that the distal paw is a tactile fovea for sea otters. In addition to the highest receptor density, the paw displayed the thickest epidermis. Rete ridges (epidermal projections into the dermis) and dermal papillae (dermal projections into the epidermis) were developed across all glabrous skin. These quantitative and qualitative descriptions of neural organization and physical features, combined with previous behavioral results, contribute to our understanding of how structure relates to function in the tactile modality. Our findings coincide with behavioral observations of sea otters, which use touch to maintain thermoregulatory integrity of their fur, explore objects, and capture visually cryptic prey.