Underwater vocalization and the functional structure of different vibrissae of the ringed seal (Phoca hispida saimensis) of Lake Saimaa, Eastern Finland, were studied. These seals live in darkness under the ice cover for several months during the year. It is known that blind seals are managing well in the lake. Visibility under water in some parts of the area where the seals live is only 2 m. It is suggested that echolocation is used in orientation and feeding. The Saimaa seal has click and click trial underwater vocalizations. However, both the frequency and intensity of the vocalization are low compared with, for example, those of dolphins. The structural adaptations for underwater sound localization are also not well developed. The ringed seal has, however, extremely well‐developed vibrissae. The innervation of one vibrissa is more than 10 times greater than normally found in mammals. The main structural deviations from normal mammalian vibrissae are: (1) an upper cavernous sinus, (2) a groove in the wall of the capsule at the level of the lower cavernous sinus, (3) elasticity of the connective tissue bands fixing the hair root to the capsule in the lower cavernous sinus and especially (4) the structure and innervation of the ring sinus area. Sensory elements are situated upon the glassy membrane on the surface of the outer rootsheath and in the basal cell layer of the outer rootsheath which is like a sensory epithelium. Below this epithelium a layer of liquid or gelatinous material and large amounts of glycogen are found. This sensory epithelium is especially well developed in the superciliary vibrissae. These vibrissae are protruded some millimetres when the seals are attentive. It is suggested that the vibrissae also sense sounds, which are transmitted to the sensory elements by tissue conduction through the capsule wall and via the blood sinuses. The seals may possibly detect compressional waves with the vibrissae.

This study of vertical fatty acid profiles, based on analysis of 58 fatty acids sampled at 3-mm intervals throughout the blubber column of a model marine mammal, the ringed seal (Pusa hispida), revealed three chemically distinct layers. The average depths of the outer and inner layers were quite consistent (approximately 1.5 and approximately 1 cm, respectively). Consequently, the middle layer varied greatly in thickness, from being virtually absent in the thinnest animals to 2.5 cm thick in the fattest. The relative consistencies of the thickness and composition of the layers as well as the nature of the fatty acids making up each layer support the generally assumed function of the various layers: (1) the outer layer is primarily structural and thermoregulatory, (2) the inner layer is metabolically active with a fatty acid composition that is strongly affected by recent/ongoing lipid mobilization/deposition, and (3) the middle layer is a storage site that contracts and expands with food availability/consumption. The remarkable dynamics of the middle layer along with the discrete pattern of stratification found in the vertical fatty acid profiles have important implications for methodological sampling design for studies of foraging ecology and toxicology based on analyses of blubber of marine mammals.

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The milt composition of six freshwater teleosts was studied, and the measured parameters showed clear specific differences between species. The highest spermatocrits and sperm densities were observed in perch, Percafluviatilis, and burbot, Lota Iota, and the lowest in rainbow trout, Salmo gairdneri, and whitefish, Coregonus lavaretus. Fructose concentrations in the seminal plasma were small compared to mammalian values. The glucose concentrations in the seminal plasma were five times higher than those of fructose, and higher in landlocked salmon and rainbow trout than in the other species. The citric acid concentration of all species except whitefish showed a significantly positive correlation to either spermatwrit or sperm density. The role of citric acid in the seminal plasma of fishes was also assumed to be important. The glycerol concentration in the seminal plasma was comparatively high, and highest in whitefish. This was assumed to be related to the high applicability value of glycerol as a cryoprotective agent for whitefish sperm. The high glycerol concentration was also assumed to be related to the lipolytic capacity of the testis in the studied species.

This study investigated the structure and innervation of the vibrissal systems of the pole cat (Mustela putorius), European otter (Lutra lutra) and ringed seal (Phoca hispida) in order to find adaptations to aquatic environment. The number of myelinated nerve fibers of deep vibrissal nerve (DVN) of the entire vibrissal system was considerably greater in the ringed seal (10×, aquatic mammal) and in the otter (4×, semi-aquatic mustelid) compared to the pole cat which is a terrestrial mustelid. Similarly, the number of neural end organs in the vibrissae of ringed seals was about ten times more numerous than in pole cats. The number of the vibrissae in the heads of otters was almost two times more than in pole cats, and all vibrissa groups had similar structures and innervation. The asymmetrically developed carpal vibrissae of otters were, however, more poorly innervated than the vibrissae of the head and had only smooth musculature. In the ringed seal the orientation of lanceolate end organs differed in different vibrissae, indicating the specialization of these vibrissae for different kinds of sensory functions. Ringed seal vibrissae contain structures which obviously are developed as adaptations to an aquatic environment. These include the modified mitochondria of Merkel cells, with Merkel cell-neurite complexes very often associated ciliated cells, liquid filled vesicles or intercellular spaces below the basal cell layer of the outer root sheath at the ring sinus level, a long upper cavernous sinus and a flattened beaded structure of the vibrissa hairs. As the vibrissae of aquatic mammals have analogous functions to the lateral line organ of fishes, we suggest using the term ‘vibrissal sense’ for the vibrissa system of aquatic mammals.