Common Seal vs Concentric Boulder Lichen

Phoca vitulina compared with Porpidia crustulata

Key Differences

Common Seal is Near Threatened while Concentric Boulder Lichen is Vulnerable.

Taxonomic Classification

Rank	Common Seal	Concentric Boulder Lichen
Kingdom	Animalia (動物)	Fungi (菌界)
Phylum	Chordata (脊索動物)	Ascomycota (子嚢菌門)
Class	Mammalia (哺乳類)	Lecanoromycetes (チャシブゴケ菌綱)
Order	Pinnipedia (Seals & Sea Lions)	Lecideales (Lecideales)
Family	Phocidae (True Seals)	Lecideaceae
Genus	Phoca (Harbor Seals)	Porpidia
Species	Phoca vitulina	Porpidia crustulata

Conservation Status

Common Seal

NT — Near Threatened

Population: ~500.0K

Trend: Stable →

Concentric Boulder Lichen

VU — Vulnerable

Physical Characteristics

Attribute	Common Seal	Concentric Boulder Lichen
Diet	Carnivore	—
Average Lifespan	30 years	—
Average Length	1.7 m	—
Average Weight	80.0 kg	—

Habitat & Geographic Range

Common Seal

Habitat

Typically found in diverse ecosystems where prey species are available.

Range

Found across Europe (7 countries) and North America (United States). Listed as Near Threatened, this species requires ongoing monitoring to prevent population decline.

Concentric Boulder Lichen

Habitat

Native to Europe and North America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Denmark, Norway, Portugal, Sweden, and United States. Currently classified as Vulnerable on the IUCN Red List, this species faces significant conservation challenges across its range.

Common Seal

最も広く分布する鰭脚類であるゴマフアザラシの近縁種・ゼニガタアザラシ（Phoca vitulina）は、北大西洋と北太平洋の温帯・亜北極沿岸に生息する。成体は最大130kgに達し、海での魚・イカ・甲殻類の捕食と海岸や岩場での休息にほぼ同じ時間を費やす。大きく表情豊かな目は低照度での水中視覚に適応している。シャチ・サメ・ホッキョクグマにとって重要な食料源である。

Concentric Boulder Lichen

<em>Porpidia crustulata</em>, commonly known as the Concentric Boulder Lichen, is a crustose lichen in the family Porpidiaceae formed through a symbiotic relationship between a fungal partner (mycobiont) and photosynthetic green algae (photobiont). Like all crustose lichens, it grows tightly appressed to its substrate—typically siliceous or acidic rock surfaces including boulders, cliff faces, and pebbles in open, well-lit habitats—forming thin, grayish to pale thalli marked by scattered black apothecia (reproductive discs). <em>Porpidia crustulata</em> derives nutrition entirely through photosynthesis conducted by its algal partner, requiring no external organic food source. The species has been documented in Denmark, Norway, Portugal, Sweden, and the United States, suggesting a broad boreal to temperate distribution across the Northern Hemisphere. It is currently classified as Vulnerable by the IUCN, indicating significant conservation concern, likely linked to threats including air pollution, acidification, quarrying of rocky habitats, and changes in land use that reduce the availability of suitable substrates. Crustose lichens are typically slow-growing, long-lived organisms with limited capacity for rapid range shifts in response to environmental change. Biological traits such as individual lifespan, growth rates, and reproductive output remain poorly documented at the population level.