Lack of differences in anatomical structures of the head associated with thermoregulation between Saimaa (Pusa hispida saimensis) and Baltic ringed seals (Pusa hispida botnica)

Prompted by our previous findings of several subtle but distinct differences in some anatomical aspects of the Saimaa (Pusa hispida saimensis) and Baltic ringed seals (Pusa hispida botnica), particularly in the head region, we investigated the osteological and arterial architecture of the nasal conchae and the ophthalmic rete of through computer tomography, magnetic resonance imaging, arterial silicone injections, dissection, histological examination, and comparison of skull specimens. The conchal and ophthalmic retia, involved in the thermoregulation of mammals, were similar in their anatomical structure to those reported from other pinnipeds and did not differ between the ringed seal subspecies. The endangered status of the Saimaa ringed seal prevented invasive investigation methods helpful for linking anatomical findings to functional properties. However, with silicone models, we were able to confirm the existence of delicate structures such as a separate vibrissal arterial circulation and the lateral and medial posterior ciliary arteries.