How does the (stress) factor light affect the small-spotted catshark (Scyliorhinus Canicula) in late embryonic stages in the Mediterranean Sea

Within the Mediterranean Sea shark populations have decrease over 97 % in the past 200 years. The small spotted catshark (Scyliorhinus canicula) faces local depletion, especially around Maltese waters. With the help of Sharklab-Malta egg cases are recovered from dead females from the fish market in Valletta. The egg cases develop in tanks under similar conditions as the sea in a laboratory. The embryos show a „freeze“ reaction to different possible (life) threatening impulses over the last pre-hatching stages in their egg capsules. The reaction to different illuminance light increases with the age of the embryo. At stage 30 (Ballard et al., 1993) no eye-brain connection is made and with stage 31 reaction to light is implemented and a habituation can be observed over serial impulses. The reaction time decreases to about 4 seconds but does not vanish. Embryological studies bring more insight into the life cycle of the species and helps to understand the impact of environmental stress factors like pollution and changes in temperature and light.

Promotor(s) & Supervisor: Greg Nowell

ISCED Categories

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0511 - Biology", "0521 - Ecology