Shrimp

Shrimp are the decapod crustaceans that evolution keeps returning to—a body plan so successful that the infraorder Caridea alone contains over 3,000 species, with additional 'shrimp' forms arising independently in other lineages. Like crabs with carcinisation, the shrimp body plan represents an evolutionary attractor: elongated body, swimming appendages, rostrum (pointed projection), and the characteristic tail-flip escape response. Multiple lineages have converged on this form because it works.

The Cleaning Station Economy

Cleaner shrimp operate biological markets parallel to cleaner wrasse—maintaining fixed 'stations' where client fish queue for parasite removal. The shrimp signals availability through rhythmic swaying; clients signal readiness by adopting specific postures with fins spread and gill covers open. The cleaner enters the client's mouth, picks parasites from between teeth and gills, and exits unharmed.

The market dynamics are sophisticated. Research shows cleaner shrimp preferentially service larger clients (who carry more parasites and offer longer cleaning sessions). Clients that have been cheated (bitten for mucus rather than cleaned) avoid returning to that station. Reputation effects constrain cheating just as they do in wrasse cleaning mutualisms.

The convergent evolution of cleaning mutualism in both shrimp and wrasse—distant lineages independently evolving identical market structures—suggests that certain economic arrangements are biological attractors, not cultural inventions.

The Pistol Shrimp's Sonic Weapon

Pistol shrimp (Alpheidae) possess one of the most remarkable weapons in nature: an enlarged claw that snaps shut with such speed that it creates a cavitation bubble reaching temperatures briefly exceeding the sun's surface. The collapsing bubble produces a sonic boom loud enough to stun prey. The snap occurs faster than can be tracked by the naked eye—the claw accelerates at over 40,000 g.

Many pistol shrimp form obligate mutualistic partnerships with gobies—the shrimp maintains the shared burrow (it cannot see well), while the goby provides predator surveillance (it can see but cannot dig). Neither thrives alone; together they create a defensible position with both construction and security capabilities.

Brine Shrimp and Extreme Environment Tolerance

Brine shrimp (Artemia salina) demonstrate extremophile tolerance—surviving in salt concentrations that would kill most marine life. Their eggs can enter cryptobiosis (suspended animation) for years, surviving desiccation, radiation, and temperature extremes that destroy normal cells. This resilience enables colonization of hypersaline lakes worldwide.

The brine shrimp strategy represents bet-hedging at the extreme: produce dormant eggs that can wait indefinitely for favorable conditions. When the environment is hospitable, they hatch and reproduce rapidly. When conditions deteriorate, the eggs persist while all active individuals die. The population survives through its dormant fraction, not its active one.