Saimaa Ringed Seal Research Articles

Vitamins A1 (Retinol), A2 (3,4-Didehydroretinol) and E (α-Tocopherol) in the Liver and Blubber of Lacustrine and Marine Ringed Seals (Phoca hispida sp.)

Concentrations of vitamins A1 (retinol), A2 (3,4-didehydroretinol) and E (α-tocopherol) in the liver and blubber of ringed seals from Lake Saimaa (Phoca hispida saimensis), Lake Ladoga (P. h. ladogensis), the Baltic Sea (P. h. botnica) and Spitsbergen (P. h. hispida) were determined by high-performance liquid chromatography. The freshwater seals had much lower levels of vitamin A1 but higher levels of vitamin A2 than the marine seals. The concentrations of vitamin E in the livers of the subspecies studied were high compared with earlier reports of seals, but the ranges were large. The livers of the marine seals contained more vitamin E than the livers of the freshwater seals, but the levels in the blubber were uniform in all populations, except in old specimens from the Baltic. The differences between the freshwater and marine seals are suggested to be due mainly to diet. The ratios of A1 to A2 in the liver and blubber and in the fish diet were similar for the marine seals and for the freshwater seals (but differed in the marine and freshwater populations), which suggests no great differences in the absorption, transport and metabolism of the two analogues. Blubber was an important storage site for the vitamins studied, and age-dependent increases were detected, especially for vitamin E. In the 2-month to 2-year-old ringed seals of Lake Saimaa, however, the vitamin E concentration in the blubber was not affected by age.

DIVING BEHAVIOR OF THE SAIMAA RINGED SEAL (PHOCA HISPIDA SAIMENSIS NORDQ.)

The activity and diving patterns of four adult Saimaa ringed seals (Phoca hispida saimensis, a landlocked subspecies living in Lake Saimaa, Finland) were examined during spring, summer, and autumn by the use of VHF-transmitters. Over 17,000 dives were registered. The duration of the dives and diving patterns differed among individuals. The mean duration of dives increased from spring to autumn; e.g., in one individual the mean dive duration increased from 6 min in June to 10.5 min in October. The haul-out periods of one individual in May to early June made up 46.2% of its total activity budget, but in another individual in July to August the haul-out periods made up only 11% of the budget and the seal was submerged for 80% of the time. Periods of successive long duration dives (>10 min) were observed in three individuals in summer and autumn. The longest dive measured was 23 min. The duration of the periods containing long dives was often over three hours (maximum six hours) and the mean duration of the dives about 15 min. These long duration dives are assumed to be aerobic resting dives. Generally, the dives of the Saimaa ringed seal appear to be of longer duration than previously assumed.

Fatty acid composition of fats around the mystacial and superciliary vibrissae differs from that of blubber in the saimaa ringed seal ( Phoca hispida saimensis)

1. 1. Adipose tissues associated with the mystacial and superciliary vibrissae of the Saimaa seal ( Phoca hispida saimensis) contained 31% of hexadecenoic acid (16:1ϖ7), which was almost twice the already high amount in blubber. The amount of tetradecenoic acid (14:1ϖ5) was also double that in blubber. 2. 2. At the same time the levels of long-chain highly unsaturated docosapentaenoic (22:5ϖ3) and docosahexaenoic acids (22:6ϖ3) were only two-thirds of those found in blubber. 3. 3. It is suggested that the excess of low-melting monoenoic fatty acids (14:1 and 16:1) in adipose tissues near the vibrissae might not be compensation for the low supply of dietary polyunsaturated fatty acids in these tissues, but that the self-induced excess of monoenoic fatty acids ensured the proper functioning of these well-developed sense organs.

Fatty acid composition in liver and blubber of the saimaa ringed seal ( Phoca hispida saimensis) compared with that of the ringed seal ( Phoca hispida botnica) and grey seal ( Halichoerus grypus) from the baltic

1. 1. The main differences in fatty acid composition of blubber between the Saimaa seal ( Phoca hispida saimensis) and the Baltic seals ( Phoca hispida botnica and Halichoerus grypus) were, that in fresh water the proportions of polyunsaturated C18 acids and arachidonic acid (20:4ε6) were high. 2. 2. The trend became more evident when data on ringed seals from northern oceans were compared with the present data. 3. 3. The proportions of exogenous 20:1 and 22:1 were extremely low in ringed seals from Lake Saimaa and in Baltic seals compared with seals living in oceans.

Diving in darkness: whiskers as sense organs of the ringed seal (Phoca hispida saimensis)

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.

Heavy metals and high pup mortality in the Saimaa ringed seal population in eastern Finland

Hair nickel, mercury, cadmium, lead and chromium concentrations were measured from still-born ringed seal pups and from other ringed seal groups from Lake Saimaa in Finland. Nickel concentration was significantly higher in the hair samples of still-born pups as compared to live-born pups and to adult seals. There was assumed to be some connection between the stillbirth of the pups and nickel concentration of the hair. Mercury concentration of the natal hair of pups was significantly higher than the mercury concentration of the first adult hair but no clear connection between stillbirth and mercury pollution was observed. No differences were observed in cadmium, lead and chromium concentrations of the hair of still-born and other ringed seal groups.

Levels of organochlorine compounds in an inland seal population in eastern Finland

Fourteen Saimaa ringed seals ( Phoca hispida saimensis) were studied for PCB, DDT, chlordane and chlorophenol compounds in blubber, liver, muscle, heart and kidney in Lake Saimaa, eastern Finland, in 1977–1981. Both PCBs and total DDT increased on average from a good 5 mg kg −1 in extractable fat of blubber in a new-born to a good 65 mg kg −1 in sexually mature specimens, the maximum being 93 and 104 mg kg −1 respectively. Concentrations of PCBs and tDDT in blubber and liver were most clearly dependent on the age and weight of the seal. Chlordanes were found in all 14 specimens (mean 0.59 mg kg −1 in blubber), trichlorophenol in one, tetrachlorophenol in two and pentachlorophenol in all three specimens studied. Although some of the Saimaa seals had reached quite high levels of both PCBs and tDDT, the present results do not indicate that the steady decrease of the Saimaa seal population during the last two decades would have been caused by these toxins, at least not in isolation.