The theme of the 2025 franking labels is Treasures of the sea. Capturing life below the surface, the four labels portray four fascinating species of the Baltic Sea.
Bladderwrack (Fucus vesiculosus) is the largest algae of the Baltic Sea. Thanks to its air bladders, it stands upright in the water. Belts of bladderwrack offer shelter and food to many other species and are sometimes referred to as the "forest of the Baltic Sea".
The blue mussel (Mytilus edulis) also plays a significant role in the ecosystem of the Baltic Sea, and their presence is a good indicator of the health of the marine environment. The blue mussel has a triangular shell, the colour of which shifts from dark blue to black. The mussels that live in the Baltic Sea are a cross between two marine species and grow to only 1–4 cm long due to the low salinity.
The jellyfish (Aurelia aurita), a native species of the Baltic Sea, is pale pink and translucent and consists of almost 100% water. The thin, threadlike tentacles lining the bell margin have stinging cells (nematocysts) that help the jellyfish capture zooplankton. The circular gonads seen through the top of the bell are reproductive glands.
The three-spined stickleback (Gasterosteus aculeatus) is a small fish, which grows to 4–10 cm in length and can be recognized by the three sharp spines on its back in front of the dorsal fin. Acquiring a red mating costume during the June breeding season, the male stickleback also builds a nest on the seabed and takes care of the eggs until they hatch.
A series consists of four self-adhesive franking labels of four motifs. The denomination is the same on all four franking labels.
