The Existence of Bacteria in the Luminescent Organs of Loligo duvauceli

This study aims to reveal the symbiosis between bacteria and luminescent organs of the Loligo
duvauceli in the bioluminescence process. This research was conducted with the assumption that
bioluminescence is not an innate ability of the organ itself. Bioluminescence occurs because of the
mutual symbiosis between squid and bacteria that live in these organs. The symbiosis between
bacteria and squid occurs in the form of horizontal symbiosis, where the bacteria originate from
external environment and form symbiosis with its host after the squid hatched from the egg. This
research focused on each of the aspect of the squid and bacteria, of which then the interdependence
was analyzed by organ histology as a light source using the Scanning Electronic Microscope (SEM)
and Transmission Electronic Microscope (TEM) on the squids, aged 1-2 days after hatch. The results
showed that the luminescence organ was fully formed at one day old juvenile, and gradually
developed along with the growth of the individual. The study also found that bioluminescent
appendage in one day old juveniles did not have symbiont bacteria. Bioluminescence bacteria begin
to be found in small colonies in two days old juveniles and in adult individuals. The presence of
bacteria in the squid luminescence organ occurs in the form horizontal symbiosis. This means that the
bacteria originate from external environment and enter into the appendage through ciliated canals
after the squid hatched. Bacteria need an enclosed container to colonize with a high cell density, as a
condition of achieving quorum sensing. Bacteria need special substrates to maintain the ability to
produce light. The light emitted by squid comes from bacterial activity. Symbiotic interactions between
bacteria and squid produce light in a process called bioluminescence. Bioluminescence is used by
squid as a defense strategy through disguises and as a communication mechanism between
individuals of the opposite sex. The results of this research study concluded that the presence of
bacteria in squid luminescence organs occurs in the form of horizontal symbiosis. The symbiosis
between luminescence bacteria and squid is classified as mutualistic symbiosis