Eye development in southern calamary, Sepioteuthis australis, embryos and hatchlings
Bozzano, A and Pankhurst, PM and Moltschaniwskyj, NA and Villanueva, R, Eye development in southern calamary, Sepioteuthis australis, embryos and hatchlings , Marine Biology: International Journal on Life in Oceans and Coastal Waters, 156, (7) pp. 1359-1373. ISSN 0025-3162 (2009) [Refereed Article]
Abstract Eye development, optical properties and photomechanical
responses were examined in embryos and
hatchlings of the southern calamary, Sepioteuthis australis.
This species occurs in shallow coastal waters in Australia
and New Zealand, and the egg masses were collected in
October and December 2004 from Great Oyster Bay, Tasmania.
At the earliest developmental stage the eye of the
squid was comprised of a hemispherical cup of undiVerentiated
neural retina, while presumptive iris cell layers and
lentigenic precursor cells enclosed a posterior eye chamber.
DiVerentiation of the proximal and distal processes was
observed in correspondence with the cornea development
and lens crystallization, and occurred before diVerentiation
of the neural retina, which was complete prior to hatching.
Longer photoreceptor distal processes were Wrst observed
just prior to hatching in the dorsal-posterior retina. After
hatching, this diVerence was much more evident and higher
photoreceptor density was found in the central retina. This
indicates that the eye of S. australis at this age uses diVerent
retina areas for diVerent visual tasks. Optical sensitivity
and resolution suggest that juvenile S. australis are diurnal.
This study also found functional photomechanical
responses of visual screening pigment migration and pupil
constriction in S. australis embryos, although complete
functionality of the pupil at this stage was uncertain.
However, the pupils of squid aged 2 days closed almost
completely under bright conditions, showing that photomechanical
responses were highly developed in the juvenile
squid. These Wndings indicate that squid embryos are able
to perceive visual stimulation, suggesting an early reliance
on vision for survival after hatching.