Individual specimens of ctenophores M. leidyi, Beroe sp., B. infundibulum
and P. pileus were collected at Helgoland Roads in the
German Bight (54◦11.3N, 7◦54.0E) from October 2009 to October
2010. The samples were obtained three times per week using
a 500 μm mesh trawl towed by the research vessel Aade and
transferred to the laboratory within 2 h. Specimens were observed
under a dissecting microscope for morphological identification
based on Greve (1975), Faasse and Bayha (2006) and Byern,
Mills and Flammang (2010). Ten intact individuals of each
species were collected each sampling day and were rinsed five
times with sterile seawater (0.2 μm filtered and autoclaved) to
remove transient and loosely associated microorganisms from
the surfaces of the ctenophores. All specimens were checked to
ensure that there were no visible gut contents, stored at −20◦C
and freeze-dried prior to DNA extraction.