Commensalism

Ecclesiastes 3:1-8

' TO EVERYTHING there is a season, and a time for every matter or purpose under heaven: A time to be born and a time to die, a time to plant and a time to pluck up what is planted, [Heb. 9:27.] A time to kill and a time to heal, a time to break down and a time to build up, A time to weep and a time to laugh, a time to mourn and a time to dance, A time to cast away stones and a time to gather stones together, a time to embrace and a time to refrain from embracing, A time to get and a time to lose, a time to keep and a time to cast away, A time to rend and a time to sew, a time to keep silence and a time to speak, [Amos 5:13.] A time to love and a time to hate, a time for war and a time for peace. [Luke 14:26.]'

Commensalism is a biological relationship where one species benefits (the commensal) by getting food, shelter, or transportation, while the other species (the host) is neither significantly helped nor harmed, making it a (+/0) interaction. Examples include barnacles on whales, birds nesting in trees, or shrimp living on sea cucumbers, all gaining advantages without affecting their hosts, though sometimes subtle effects (like increased visibility for the host's food) can occur. 

Key Characteristics

• Benefit to one: The commensal gains resources or protection.

• Neutral for the other: The host experiences no significant positive or negative impact.

• Types of benefit: Can include food, shelter, transport (phoresy), or support. 

Common Examples

• Barnacles & Whales: Barnacles attach to whales for a free ride and access to food in the water, while the whale is mostly unaffected.

• Cattle Egrets & Livestock: Egrets follow grazing animals, eating insects stirred up by their hooves; the cattle are largely indifferent.

• Orchids & Trees: Orchids grow on trees to get sunlight and support, but don't take nutrients from the tree.

• Remora Fish & Sharks: Remoras attach to sharks, getting transportation, protection, and leftover food scraps without bothering the shark. 

Modern Understanding

• While classically defined as neutral, some interactions (like microbesin our gut) can have minor effects or shift to parasitism if the host becomes weak.

• Terms like "synanthropy" describe species (like pigeons) that benefit from human environments.