Costs and benefits of the symbiosis between the anemoneshrimp *Periclimenes brevicarpalis* and its host *Entacmaea quadricolor*

Abstract

ABSTRACT: Shrimp of the species *Periclimenes brevicarpalis* (family Palaemonidae, subfamily Ponloniinae) are obligate associates of sea anemones. To assess the nutritional relationship between the shrimp and one of its hosts, *Entacmaea quadricolor* (family Actiniidae), we conducted 10 replicate 30 d experiments. An experiment comprised 6 treatments: a pair of fed shrimp, a pair of unfed shrimp, a fed pair of shrimp plus an anemone, an unfed pair of shrimp plus an anemone, a fed anemone, and an unfed anemone. Shrimp survival was 6 (of 20) for unfed shrimp lacking an anemone, 17 for fed shrimp lacking an anemone, and 19 for shrimp with a host, whether fed or not. Longevity of unfed anemoneshrimp kept alone (23 d) was significantly less than that of shrimp in the other treatments (28 or 29 d). Larvae were released by all female shrimp with an anemone but by only 7 of 10 unfed and 8 of to fed ones kept alone. Magnitude of growth, interval between molts, and number of larval releases were all dependent on whether a shrimp had been kept with an anemone but were independent of whether it had been fed. Shrimp clipped and ate anemone tentacles: unfed anemones with shrimp lost most or all of their tentacles, and many fed ones did so as well, but anemones kept without shrimp did not. Magnitude of tentacle loss was dependent on whether the anemone had been with shrimp but was independent of whether it had been fed. Thus, there is a benefit to the shrimp from this association and potentially a cost to the anemone, but anemones with shrimp in nature always appear to have normally long and numerous tentacles.