Symbiotic Relationship
Symbiotic relationships in monocentrid fishes and sepiolid squid appear to have evolved separately. The most prolific of these relationships is with the Hawaiian bobtail squid (Euprymna scolopes).
Free-living A. fischeri in the ocean inoculate the light organs of juvenile squid and fish. Ciliated cells within the light organs selectively draw in the symbiotic bacteria. These cells promote the growth of the symbionts and actively reject any competitors. The bacteria cause these cells to die off once the light organ is sufficiently colonised.
The light organ of certain squid contain reflective plates that intensify and direct the light produced, due to proteins known as reflectins. They regulate the light to keep the squid from casting a shadow on moonlit nights, for example. Sepolid squids expel 90% of the symbiotic bacteria in its light organ each morning in a process known as "venting". Venting is hypothesised to provide the free-living inoculum source for newly hatched squids.
Read more about this topic: Aliivibrio Fischeri
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