Monogamy does not last long in Pontonia mexicana, a symbiotic shrimp of the amber pen-shell Pinna carnea from the southeastern Caribbean Sea

► Monogamy in symbionts is expected when hosts are scarce and predation risk is high. ► We tested this prediction using a shrimp symbiotic with a pen-shell in the Caribbean. ► Invariably, shrimps dwell as heterosexual pairs in pen-shell host individuals. ► However, our data suggests that monogamy in this shrimp species does not last long. ► Male shrimps appear to switch among pen-shells in search of receptive females.