Ecological and Developmental Dynamics of a Host-Parasite System Involving a Sea Anemone and Two Ctenophores

Abstract

The lined sea anemone Edwardsiella lineata has evolved a derived parasitic life history that includes a novel body plan adapted for life inside its ctenophore hosts. Reputedly its sole host is the sea walnut, Mnemiopsis leidyi, a voracious planktivore and a seasonally abundant member of many pelagic ecosystems. However, we have observed substantially higher E. lineata prevalence in a second ctenophore species, the ctenophore predator Beroë ovata. The interplay among these 3 species has important conservation consequences as M. leidyi introductions are thought to be responsible for the severe depletion of numerous commercial fisheries in the Mediterranean basin, and both E. lineata and B. ovata have been proposed as biological controls for invasive M. leidyi. Over a 3-yr period (2004-2006), we collected 8,253 ctenophores from Woods Hole, Massachusetts, including M. leidyi, B. ovata, and a third ctenophore, Pleurobrachia pileus, and we recorded E. lineata infection frequencies, parasite load, and parasite location. We also conducted laboratory experiments to determine the likely mechanisms for parasite introduction and the effect of each host on parasite development. We observed peak E. lineata infection frequencies of 0% in P. pileus, 59% in M. leidyi, and 100% in B. ovata, suggesting that B. ovata could be an important natural host for E. lineata. However, in laboratory experiments, E. lineata larvae proved far more successful at infecting M. leidyi than B. ovata, and E. lineata parasites excised from M. leidyi exhibited greater developmental competence than parasites excised from B. ovata. Although we show that E. lineata is efficiently transferred from M. leidyi to B. ovata when the latter preys upon the former, we conclude that E. lineata larvae are not well adapted for parasitizing the latter species and that the E. lineata parasite is not well adapted for feeding in B. ovata; these developmental and ecological factors underlie the host specificity of this recently evolved parasite.

Sterile Surfaces of <i>Mnemiopsis leidyi</i> (Ctenophora) in Bacterial Suspension—A Key to Invasion Success?

“…Such parasites mature in fish predators of ctenophores and commonly occur with remarkable prevalence and infestation intensity [16]. Mnemiopsis leidyi uniquely harbors the parasitic vermiform larva of the sea anemone Edwardsiella lineata (although it will transfer to the ctenophore predator Beroe ovata via predation [17]). Little is known about the host-specificity of symbionts and knowledge on how the host is affected by the symbiotic association is essentially lacking.…”

Parasitic anemone infects the invasive ctenophore Mnemiopsis leidyi in the North East Atlantic

“…The highest number of parasites observed in a single Mnemiopsis was 11. Multiple infections may have resulted from the sampling methodology, but were also observed in the field and is well documented in the literature (Crowell 1976;Reitzel et al 2007). During 2008, the percentage of Mnemiopsis with internal parasites ranged from 0 to 6.3%, and the percentage of parasites found outside hosts averaged 50 ± 43% (mean ± SD).…”

“…Similar to E. lineata from the North American east coast (Reitzel et al 2007), the larvae were most commonly found attached to the pharynx region of the Mnemiopsis (Fig. 3a).…”

“…In the native habitat of the ctenophore, parasitic infections from the sea anemone Edwardsiella lineata are common and parasitized Mnemiopsis have significantly lower, sometimes negative growth rates. Prevalence can be higher than 50% (Crowell 1976;Reitzel et al 2007) and as a consequence parasite infection may be one of the factors that contribute to population control (Bumann and Puls 1996). Here we report of the first occurrence of parasitic sea anemone larvae in M. leidyi from the NE Atlantic, together with densities of the parasite and the host ctenophore during 2007 and 2008.…”

Symbionts of marine medusae and ctenophores

“…Bumann & Puls (1996) implied that this parasite might be the only parasite affecting the host populations. Reitzel et al (2007) have intensively investigated the infection of the parasitic stage of E. lineata on three species of ctenophores off Wood Hole on the coast of the northern Atlantic during summer and early winter. The hostspecificity was very strict in the following order: Beroe ovata Bruguière (highest prevalence 100%) Ͼ M. leidyi (60%) Ͼ Pleurobrachia pileus (Müller) (0%).…”