TITLE:
Sterile Surfaces of Mnemiopsis leidyi (Ctenophora) in Bacterial Suspension—A Key to Invasion Success?
AUTHORS:
Sven Hammann, Anthony Moss, Martin Zimmer
KEYWORDS:
Ctenophora, Immune Response, Invasive Species, Space-For-Time, Symbiotic Interactions
JOURNAL NAME:
Open Journal of Marine Science,
Vol.5 No.2,
April
24,
2015
ABSTRACT: Seawater is a dense
microbial suspension with >106 prokaryotic and >104 eukaryotic propagules
per milliliter. Hence, submerged surfaces get immediately covered by
biofilm-forming colonizers upon contact with seawater. Since biofilms may
reduce individual fitness through decreasing motility and attractiveness or
increasing shearing stress by water currents and infection risk by pathogens,
marine organisms have evolved countermeasures to regulate the number of
surface-colonizers; alternatively they tolerate settlement and
biofilm-formation. Antimicrobial defense mechanisms co-evolved with potentially
colonizing microbes. By contrast, non-native animals (neozoa) are confronted
with novel microbial colonizers upon colonizing a new habitat, and are expected
to be less well protected against surface-colonization. Here we present results
of a thorough screening of the epithelial surface of the ctenophore Mnemiopsis leidyi, being
non-native in European marine environments, for epithelial bacteria and
archaea. Neither light- and electron-microscopic inspection nor PCR-screening
for bacterial and archaeal DNA of 134 adult specimens from different collection
sites in the Western Baltic revealed any presence of prokaryotes on the surface
epithelium of comb jellies in a recently invaded environment. A limited number
of bacterial associates became evident from whole-body extracts of both
juvenile and adult comb jellies. Their taxonomic diversity, however, was
significantly lower in adult than in juvenile specimens, suggesting a
maturation of anti-microbial defense upon ontogenetic development. The
mechanisms underlying the effective defense of Mnemiopsisagainst microbial
colonization, however, remain unknown. Based on our findings, we propose 1) to
make use of invasion events as natural space-for-time experiments on how
symbiotic interactions change upon environmental change; and 2) to study basal
metazoan animals, such as ctenophores, to understand the evolutionary basics of
symbiont-host interactions.