Properties of IIlex illecebrosus Egg Masses Potentially Influencing larval Oceanographic Distribution

• Main Authors: O'Dor, R. K., Balch, N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: NAFO 1985
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/33870/; https://oceanrep.geomar.de/id/eprint/33870/1/573.pdf

Visual observations and video-tape records of the spawning of captive IIlex illecebrosus show that this species can produce gelatinous egg masses 50 cm or larger in diameter while swimming in open water. Measurements of the density of the eggs and the changes in water density which are necessary to lift egg masses indicate that the masses have densities about 0.005% greater than the water used to make the gel, whereas the eggs are more than 5% denser than typical seawater. The gel thus appears to function as a buoyancy mechanism which prevents eggs from sinking. Measurements of rates of temperature equilibration between egg masses and the surrounding water indicate that complete density equilibration requires many days under most conditions. If spawning occurs pelagically, common oceanographic situations where density increases with depth, due either to decreasing temperature (e.g. North Atlantic Central Water) or increasing salinity (e.g. the Gulf Stream), could allow the egg masses to be suspended in the mesopelagic zone. Such a mechanism, which could retain pelagically-spawned eggs of IIlex and other oegopsids, particularly ommastrephids, in a zone where temperatures are adequate to allow embryonic development, helps to explain why there are so few records of ommastrephid eggs in nature.