It has all the hallmarks of a successful sitcom: a busy, near-sighted, workaholic landlord and a lazy tenant who is forced to help out, often begrudgingly, to earn his keep. Except this sitcom takes place beneath the sea and involves animals instead of people – namely a type of small fish called a goby and a snapping shrimp.
The shrimp is the workaholic landlord. It has constructed a small burrow in the sand on the sea floor and it has recruited a tenant, the goby. The goby, however, does no domestic work whatsoever, so why does the shrimp allow the goby – and only the goby – to become a lodger? As it turns out, the shrimp is virtually blind and it relies on the good eyesight of the goby to keep watch for predators whilst it is outside the burrow.
The goby spends a lot of time hanging out at the entrance to the burrow. The shrimp takes this opportunity to leave the safety of its home, perhaps to plough out sand, do some maintenance work or even grab a clawful of food from the garden of algae it grows just outside. The shrimp keeps in contact with the fish at all times using its long antennae. If the goby becomes alarmed, perhaps by the sudden appearance of a predator, it will flick the shrimp’s antennae with its tail. This tells the shrimp to dart back into the burrow, which it promptly does.
It is clear that both parties gain from this relationship: the shrimp gets a warning of approaching danger and the goby gets a safe place to live that it would otherwise be unable to construct. The goby rarely ventures too far from the burrow and, even if it does, the shrimp spends its time unloading sediment within the burrow entrance, only venturing outside again once the goby has returned and contact has been re-established.
Occasionally, of course, living with another animal can be tiresome. The shrimp is obsessed with construction work, continuously expanding its burrow, and that means venturing outside on a regular basis. But the goby, if well-fed, is reluctant to leave the safety of the burrow for what it probably deems as an unnecessary reason, and so the shrimp must harass and hustle the little fish until it complies.
Despite the occasional disagreements, though, both species tend to live together in relative peace. And this isn’t just a relationship of convenience – it’s downright essential. If the two species were ever isolated permanently, neither the fish nor shrimp are likely to survive. Not exactly what you want happening at the end of your sitcom.