Abstract
Despite being among the largest and most charismatic species in the marine environment, considerable gaps remain in our understanding of the behavioural ecology of manta rays (Mobula alfredi, M. birostris). Manta rays are often sighted in association with an array of smaller hitchhiker fish species, which utilise their hosts as a sanctuary for shelter, protection, and the sustenance they provide. Species interactions, rather than the species at the individual level, determine the ecological processes that drive community dynamics, support biodiversity and ecosystem health. Thus, understanding the associations within marine communities is critical to implementing effective conservation and management. However, the underlying patterns between manta rays, their symbionts, and other hitchhiker species remain elusive. Here, we explore the spatial and temporal variation in hitchhiker presence with M. alfredi and M. birostris throughout the Maldives and investigate the factors which may influence association using generalised linear mixed effects models (GLMM). For the first time, associations between M. alfredi and M. birostris with hitchhiker species other than those belonging to the family Echeneidae are described. A variation in the species of hitchhiker associated with M. alfredi and M. birostris was identified, with sharksucker remora (Echeneis naucrates) and giant remora (Remora remora) being the most common, respectively. Spatiotemporal variation in the presence of manta rays was identified as a driver for the occurrence of ephemeral hitchhiker associations. Near-term pregnant female M. alfredi, and M. alfredi at cleaning stations, had the highest likelihood of an association with adult E. naucrates. Juvenile E. naucrates were more likely to be associated with juvenile M. alfredi, and a seasonal trend in E. naucrates host association was identified. Remora were most likely to be present with female M. birostris, and a mean number of 1.5 ± 0.5 R. remora were observed per M. birostris. It is hoped these initial findings will serve as the basis for future work into the complex relationships between manta rays and their hitchhikers.
Highlights
Symbiosis, when considered biologically, describes a physically close and long-term association between two different species [1,2,3]
Juvenile E. naucrates were more likely to be associated with juvenile M. alfredi, and a seasonal trend in E. naucrates host association was identified
Juvenile E. naucrates were more likely to be associated with juvenile M. alfredi, most likely because juvenile manta rays spend most of their time in protected lagoons and other shallow water nursery habitats [27, 66], increasing the chance of long-term associations between the two species for reasons already discussed in this study
Summary
Symbiosis, when considered biologically, describes a physically close and long-term association between two different species [1,2,3]. Algae-coral, anemonefish, and cleaner-client mutualisms all provide traditional examples [6,7,8,9], where at least one of the interacting species is obligately dependant on the association for all, or part, of its life-history [1, 10]. While some interactions have resulted in significant behavioural adaptions and coevolution, the competitive life of a marine species can encourage short-term and opportunistic associations in order to gain food or protection [11,12,13,14,15]. Pilot fish (Naucrates doctor) are known to commonly associate with large-bodied vertebrates such as sharks, rays and turtles [17], presumably for protection from predation [14]
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