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Abralia sp. and Abraliopsis
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Last Updated 10.25.2005

Studies done on Abraliopsis and Abralia trigonura revealed similar patterns of counterillumination. These species are able to regulate the color of their light emission to match that of the down dwelling light. During the daytime, the squid are in deep, cold waters where the sun’s light will appear blue-ish. The nocturnal nature of these species require this type of flexibility as they must move substantial distances upwards through the water column to get to mesopelagic water where they can forage for food. Water near the surface is warmer and the moonlight that refracts through it appears green. Both species mimicked moonlight and sunlight colors, although Abraliopsis more closely with the former and A. trigonura more closely with the latter. In both of these cases, temperature triggered the change in emission spectra or color. Differences in the color of the downwelling light caused no change in the squid’s ventral illumination. Plausibly, squid similar to these that lack extraocular photosensitive vesicles compensate by being sensitive to temperature changes in the water (Young 1980).

Abralia veranyi, commonly known as the Eye Flash Squid, is another small species with a mantle length of about 4 cm. It is widely distributed throughout the Atlantic Ocean, and in the Mediterranean and Sargasso Seas. This species has been valuable in research to document the pattern and distribution of photophores within the mantle. Herring and his collaborators were able to describe the functional ranges of the photophores and bioluminescent behavior (Herring 1992).

Figure (top): Abralia trigonura Photographed by Richard Young.

Figure (above): Abralia veryani Photographed by Roger Hanlon.

Figure (left): Abralia veryani Photographed by Roger Hanlon.