Marine Ecosystems Research Department - jamstec japan agency ...

Japan Marine Science and Technology Center
Marine Ecosystems Research Department
materials such as plant pigment are fluorescent, which
is a big problem. Laminariaceae (Kombu) has been
eaten since ancient times, and is known to have various
health benefits. It has recently been found to contain
the anticancer macromolecular polysaccharide
such as fucoidan, so it is an extremely useful and beneficial
plant. In this research, we aim to establish a
efficient method to measure the genome size using
fluorophotometry and measure the genome size of
Laminariaceae growing in warm and cold waters.
In fiscal we collected Laminariaceae seaweeds
(sporophytes, n) from their field, released zoospore
(n) and cultivated the gametephytes (n) in order to
examine the suitable stages for measurements of
genome size. We also examined some pigment
removal methods to exclude non-DNA sources of fluorescence
from samples, and carried out preliminary
genome size measurement. From these results, we
found out that zoospore released from mature sporophytes
can be used for the measurement. As the measured
values of genome size in both Laminariaceae seaweeds
and the control Arabidopsis thaliana being varied
in the preliminary measurements, we realized that
further adjustment for preparation of samples and
search for suitable controls are needed.
Research on the relationship between shape, swimming
and stomach contents in jellyfish species
Period: FY-FY
Jellyfish play a key role within ecosystems as predators,
but little is known about their predatory behavior.
From research into the relationship between jellyfish
shape and swimming pattern using behavioral
models, reportedly species with shallow umbrellas are
suited for continuous swimming, whereas those with
deeper umbrellas are suited for neutral drifting, but
this has not been fully verified. It is not difficult to see
that if the swimming pattern differs, the animals they
prey on will also differ. So in this research we have
established the following hypothesis relating to jellyfish
shape, swimming pattern and prey, and seek to
verify this hypothesis using surface species.
Shallow umbrella continuous swimming
greater opportunity to encounter abundant small
prey prey on smaller animals
Deep umbrella neutral drifting greater opportunity
to encounter strong-swimming prey prey
on larger animals
We believe this research will shed light on the
largely unknown predatory behavior of jellyfish
species, and enable us to infer the type of prey they
feed on from their shape and swimming pattern.
We believe we will then be able to apply this to the
mid- and deepwater jellyfish species, which are difficult
to collect.
This research consists of () observe the shape of
specimens, () observe and measure swimming
actions and speed through video, () estimate the rate
at which jellyfish encounter prey, and () analyze jellyfish
stomach contents. This research covers several
species of jellyfish. In fiscal , as the first step of
the research we focused on () establishing collection
methods that would minimize the damage to specimens,
and () examining methods of analyzing stomach
content.
Production of a plankton net with an enlarged cod
end section has enabled us to collect samples in good
condition. We discovered the best method of sampling
and fixing for observing stomach content in each category.
The Leptomedusae disgorge when fixed, so there
is also a need to fix each jellyfish and collect the disgorged
material as well. On the other hand, the
Anthomedusae rarely disgorge, so there is no need to
fix individual jellyfish. We found that Spirocodon
saltator (order Anthomedusae) and Aequorea
coerulescens (order Leptomedusae) mainly feed on,
respectively, copepods and Rathkea octopucutata.
We gave a presentation on a part of our research at
the Spring Plankton Symposium. This presentation
was summarized in the Feeding Ecology of Jellyfishes,
and was submitted and accepted for inclusion in the
Bulletin of Plankton Society of Japan.
59