Ectosymbiotic behavior of Cancer gracilis and its trophic relationships with its host Phacellophora camtschatica and the parasitoid Hyperia medusarum

Abstract

In southern Puget Sound, large numbers of megalopae and juveniles of the brachyuran crab Cancer gracilis and the hyperiid amphipod Hyperia medusarum were found riding the scyphozoan Phacellophora camtschatica. C. gracilis megalopae numbered up to 326 individuals per medusa, instars reached 13 individuals per host and H. medusarum numbered up to 446 amphipods per host. Although C. gracilis megalopae and instars are not seen riding Aurelia labiata in the field, instars readily clung to A. labiata, as well as an artificial medusa, when confined in a planktonkreisel. In the laboratory, C. gracilis was observed to consume H. medusarum, P. camtschatica, Artemia franciscana and A. labiata. Crab fecal pellets contained mixed crustacean exoskeletons (70%), nematocysts (20%), and diatom frustules (8%). Nematocysts predominated in the fecal pellets of all stages and sexes of H. medusarum. In stable isotope studies, the δ 13 C and δ 15 N values for the megalopae (-19.9 and 11.4, respectively) fell closely in the range of those for H. medusarum (-19.6 and 12.5, respectively) and indicate a similar trophic reliance on the host. The broad range of δ 13 C (-25.2 to -19.6) and δ 15 N (10.9 to 17.5) values among crab instars reflects an increased diversity of diet as crabs develop.The association between C. gracilis and P. camtschatica is unusual because of the ontogenic switch of the symbiont from a primarily kleptoparasitic association to a facultative cleaning association. It is suggested that P. camtschatica incidentially concentrates H. medusarum in its oral arms as the symbionts transfer from its gelatinous prey. Metabolic studies suggest that by riding medusae crabs may be able to develop faster through transport into warmer surface waters while reducing the energetic costs associated with locomotion.KEY WORDS: Symbiosis · Scyphozoa · Commensal crab · Hyperiid amphipod · Cleaning behavior · Stable isotope · Metabolic rate · Fecal pellet Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 315: [221][222][223][224][225][226][227][228][229][230][231][232][233][234][235][236] 2006 1988, Sorarrain et al. 2001, Gasca & Haddock 2004. During their early stages of development, hyperiid amphipods have been established as obligate parasites of gelatinous hosts (Harbison et al. 1977), and Hyperia medusarum Müller is one hyperiid species that remains associated through adulthood and is recognized as a marine parasitoid (Laval 1980). Although much of the life cycle of H. medusarum has been examined, the mechanisms of its winter survival and the dynamics of fall population outbreaks remain unclear.The symbiotic relationships between cnidarians and brachyuran crabs are less clearly defined. Numerous symbioses of this type have been observed in the field and noted in the literature. Crabs are thought to benefit from enhanced mobility and shelter, however specific interactions in these relationships have remained largely uncharacterized.The scyphozoan jellyfish Phacellophora camtsc...

First record of the association between Lychnorhiza lucerna (Scyphozoa, Rhizostomeae) and Cyrtograpsus affinis (Decapoda, Varunidae)

“…Although in this study no crab larvae were found within L. lucerna, the presence of crab larval stages in association with scyphomedusae was reported several times (Corrington, 1972;Graham, 1994;Towanda & Thuesen, 2006), even for the same medusa species (Nogueira & Haddad, 2005). Furthermore, small juveniles and recently moulted individuals of L. spinosa have been found within L. lucerna.…”

“…All of these cases involve medusae of the Class Scyphozoa and crabs belonging to the families Majidae and Portunidae (see references in Nogueira & Haddad, 2005;Towanda & Thuesen, 2006). Therefore, the presence of three specimens of C. affinis within L. lucerna constitutes the finding of a new brachyuran family (Varunidae) in association to medusae of the Class Scyphozoa.…”

“…On the other hand, any potential advantage seems unlikely for the medusae (Corrington, 1972). Based on these hypothetical effects of one species on the other, these associations have been characterized as commensalism or parasitism (see Towanda & Thuesen, 2006).…”

“…Arai, 1997;Towanda & Thuesen, 2006). These animals may profit from the mobile nature of their hosts, allowing otherwise benthic organisms to access to the benefits of a pelagic lifestyle.…”

Stable isotope analysis reveal hidden reliance on scyphozoan jellyfish in a commensal fish: editorial comment on the feature article by D’Ambra et al.

“…The study by D'Ambra and her colleagues joins a limited pool of isotopic studies that also show assimilation of jellyfish host tissues by of commensal crabs and amphipods (Towanda and Thuesen 2006;Fleming et al 2014). As such, the prevailing view that commensal taxa primarily use their hosts as habitat is clearly due for some rethought.…”