Beyond symbiosis: cleaner shrimp clean up in culture.

Thane A Militz,Kate S Hutson

doi:10.1371/journal.pone.0117723

Abstract

Cleaner organisms exhibit a remarkable natural behaviour where they consume ectoparasites attached to “client” organisms. While this behaviour can be utilized as a natural method of parasitic disease control (or biocontrol), it is not known whether cleaner organisms can also limit reinfection from parasite eggs and larvae within the environment. Here we show that cleaner shrimp, Lysmata amboinensis, consume eggs and larvae of a harmful monogenean parasite, Neobenedenia sp., in aquaculture. Shrimp consumed parasite eggs under diurnal (63%) and nocturnal (14%) conditions as well as infectious larvae (oncomiracidia) diurnally (26%). Furthermore, we trialled the inclusion of cleaner shrimp for preventative parasite management of ornamental fish, Pseudanthias squamipinnis, and found shrimp reduced oncomiracidia infection success of host fish by half compared to controls (held without shrimp). Fish held without cleaner shrimp exhibited pigmentation changes as a result of infection, possibly indicative of a stress response. These results provide the first empirical evidence that cleaner organisms reduce parasite loads in the environment through non-symbiotic cleaning activities. Our research findings have relevance to aquaculture and the marine ornamental trade, where cleaner shrimp could be applied for prophylaxis and control of ectoparasite infections.

Highlights

Parasitism has long been considered the most common lifestyle on earth with virtually all living organisms serving as potential hosts [1,2]
Cleaner shrimp consumed two-thirds (63.5 ± 5.3%) of Neobenedenia sp. eggs present in aquaria during the 12 h experimental period (99.5 ± 0.3% of eggs were recovered in handling controls; Fig. 1)
The success of temperate aquatic biocontrols employed for their symbiotic cleaning services demonstrates the potential for cleaner organisms in tropical aquaculture

Summary

Introduction

Parasitism has long been considered the most common lifestyle on earth with virtually all living organisms serving as potential hosts [1,2]. Manipulation of several biotic and abiotic factors in aquaculture, such as food availability, population density, water quality parameters, physical handling and the absence of predation, offsets the natural ecosystem balance [3,4,5]. This manipulation often favours proliferation of parasites with direct life cycles, as stressors may interact with parasites, their hosts, and the host—parasite relationship in myriad ways [6,7]. Aquaculture remains the fastest primary growth industry in the world but is heavily burdened by parasitic outbreaks [8]. Biocontrols have been proposed as a natural means to restore ecosystem balance in PLOS ONE | DOI:10.1371/journal.pone.0117723 February 23, 2015

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