Patterns of Stimulated Bioluminescence in Two Pyrosomes (Tunicata: Pyrosomatidae).

Area of Science:

• Marine Biology
• Bioluminescence Research
• Animal Physiology

Background:

• Pyrosomes are colonial tunicates known for brilliant, sustained bioluminescence.
• Unlike most luminescent plankton, pyrosomes luminesce in response to light.
• Individual zooids within a colony detect light and trigger bioluminescence.

Purpose of the Study:

• To investigate the luminescence responsivity of Pyrosoma atlanticum and Pyrosomella verticillata.
• To determine the effects of photic, electrical, and mechanical stimuli on pyrosome luminescence.
• To analyze the propagation patterns and characteristics of pyrosome bioluminescence.

Main Methods:

• Photic stimulation with varying wavelengths (350-600 nm) and intensities.
• Electrical and mechanical stimulation to assess rhythmic flashing.
• Image intensification to observe luminescence propagation across colonies.

Main Results:

• Photic stimulation at 475 nm induced maximum bioluminescence.
• P. atlanticum had a half-response constant of 1.1 x 10^7 photons·s^-1·cm^-2, while P. verticillata had 9.3 x 10^7 photons·s^-1·cm^-2.
• Stimulus strength affected zooid recruitment, luminescence duration, and quantum emission.
• Luminescence propagated saltatorily across colonies due to photic triggering.
• Mechanical and electrical stimuli produced rhythmic flashing.

Conclusions:

• Pyrosomes exhibit distinct light-sensing and bioluminescence capabilities.
• Species-specific differences in photic sensitivity exist between P. atlanticum and P. verticillata.
• Stimulus parameters significantly influence the nature and extent of pyrosome bioluminescence.