The image displays portraits of several individuals and the text "Русские путешественники и их открытия в XVIII в." which translates to "Russian travelers and their discoveries in the 18th century." Please identify these individuals and briefly describe their contributions to exploration or discovery.

The image displays portraits of five individuals, presumably Russian travelers from the 18th century, along with empty fields for their names and contributions. Based on typical historical representations of Russian explorers and travelers of that era, and without specific identifying labels in the image, here are educated guesses for each portrait from left to right:

• Portrait 1: Likely depicts Vitus Bering, a Danish-Russian explorer who led two Russian expeditions to the Pacific. He is credited with the discovery of the Bering Strait and the coast of Alaska.
• Portrait 2: This could represent Alexei Chirikov, a Russian navigator and explorer who was Vitus Bering's second-in-command. He is known for being the first European to chart most of eastern Siberia and Alaska.
• Portrait 3: This portrait might be of Semyon Dezhnev, a Russian explorer and fur trader who is credited with discovering the Bering Strait in 1648, 80 years before Vitus Bering.
• Portrait 4: This individual could be Afanasy Nikitin, a Russian merchant traveler who is famous for his journey to India in the 15th century, documented in his book "The Journey Beyond Three Seas." Although his journey was in the 15th century, he is often cited in discussions of early Russian exploration.
• Portrait 5: This individual might represent Pyotr Shabunin, a Russian explorer who traveled to Siberia in the late 17th and early 18th centuries, mapping parts of the Lena River.

Note: Identifying individuals solely from historical portraits without labels can be challenging and is subject to interpretation. The specific contributions mentioned are general based on the figures' known historical roles.