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Retinal Development and Ommin Pigment in the Cranchiid Squid Teuthowenia pellucida (Cephalopoda: Oegopsida).

Evans AB, Acosta ML, Bolstad KS - PLoS ONE (2015)

Bottom Line: Granules of the pigment ommin, normally located in the screening layer positioned at the base of the photoreceptors, were also observed at the outer end of the photoreceptor segments throughout the retina in young and mid-sized specimens.Early developmental stages of this species, dwelling in shallow waters, may therefore rely on migratory ommin to help shield photoreceptors from excess light and prevent over-stimulation.The oldest, deeper-dwelling specimens of T. pellucida examined had longer photoreceptors, and little or no migrated ommin was observed; we suggest therefore that short-term adaptive mechanisms for bright light conditions may be used primarily during epipelagic, early life stages in this species.

View Article: PubMed Central - PubMed

Affiliation: Institute for Applied Ecology New Zealand, Auckland University of Technology, Auckland, New Zealand.

ABSTRACT
The cranchiid Teuthowenia pellucida, like many deep-sea squid species, possesses large eyes that maximise light sensitivity in a nearly aphotic environment. To assess ontogenetic changes in the visual system, we conducted morphometric and histological analyses of the eyes using specimens from New Zealand collections. While the ratio between eye diameter and mantle length maintained a linear relationship throughout development, histological sections of the retina revealed that the outer photoreceptor layer became proportionally longer as the animal aged, coincident with a habitat shift into deeper, darker ocean strata. Other retinal layers maintained the same absolute thickness as was observed in paralarvae. Granules of the pigment ommin, normally located in the screening layer positioned at the base of the photoreceptors, were also observed at the outer end of the photoreceptor segments throughout the retina in young and mid-sized specimens. Early developmental stages of this species, dwelling in shallow waters, may therefore rely on migratory ommin to help shield photoreceptors from excess light and prevent over-stimulation. The oldest, deeper-dwelling specimens of T. pellucida examined had longer photoreceptors, and little or no migrated ommin was observed; we suggest therefore that short-term adaptive mechanisms for bright light conditions may be used primarily during epipelagic, early life stages in this species.

No MeSH data available.


Related in: MedlinePlus

Cross-section at the equator of adult (ML 130 mm) T. pellucida retina showing no migrated ommin in any region and peripheral-central changes in photoreceptor thickness.Scale bar is 100μm. Arrows indicate length of outer photoreceptor segment. Abbreviations as in Figs 2 and 3.
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pone.0123453.g004: Cross-section at the equator of adult (ML 130 mm) T. pellucida retina showing no migrated ommin in any region and peripheral-central changes in photoreceptor thickness.Scale bar is 100μm. Arrows indicate length of outer photoreceptor segment. Abbreviations as in Figs 2 and 3.

Mentions: Central photoreceptors were also longer than photoreceptors located toward the retina’s periphery in the majority of examined specimens (Fig 4). This was consistent with the findings of Matsui et al. [7], who observed that photoreceptor length is greatest in areas where the most light reaches the retina, and similar to observations on the vertebrate inverted retina, where photoreceptor length has been reported to change by region (central—peripheral) and as a function of light—dark adaptation [20]. In T. pellucida, the longer outer segments found centrally suggest that the retinal area directly in the axial length is structured to gather the most incoming light.


Retinal Development and Ommin Pigment in the Cranchiid Squid Teuthowenia pellucida (Cephalopoda: Oegopsida).

Evans AB, Acosta ML, Bolstad KS - PLoS ONE (2015)

Cross-section at the equator of adult (ML 130 mm) T. pellucida retina showing no migrated ommin in any region and peripheral-central changes in photoreceptor thickness.Scale bar is 100μm. Arrows indicate length of outer photoreceptor segment. Abbreviations as in Figs 2 and 3.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430533&req=5

pone.0123453.g004: Cross-section at the equator of adult (ML 130 mm) T. pellucida retina showing no migrated ommin in any region and peripheral-central changes in photoreceptor thickness.Scale bar is 100μm. Arrows indicate length of outer photoreceptor segment. Abbreviations as in Figs 2 and 3.
Mentions: Central photoreceptors were also longer than photoreceptors located toward the retina’s periphery in the majority of examined specimens (Fig 4). This was consistent with the findings of Matsui et al. [7], who observed that photoreceptor length is greatest in areas where the most light reaches the retina, and similar to observations on the vertebrate inverted retina, where photoreceptor length has been reported to change by region (central—peripheral) and as a function of light—dark adaptation [20]. In T. pellucida, the longer outer segments found centrally suggest that the retinal area directly in the axial length is structured to gather the most incoming light.

Bottom Line: Granules of the pigment ommin, normally located in the screening layer positioned at the base of the photoreceptors, were also observed at the outer end of the photoreceptor segments throughout the retina in young and mid-sized specimens.Early developmental stages of this species, dwelling in shallow waters, may therefore rely on migratory ommin to help shield photoreceptors from excess light and prevent over-stimulation.The oldest, deeper-dwelling specimens of T. pellucida examined had longer photoreceptors, and little or no migrated ommin was observed; we suggest therefore that short-term adaptive mechanisms for bright light conditions may be used primarily during epipelagic, early life stages in this species.

View Article: PubMed Central - PubMed

Affiliation: Institute for Applied Ecology New Zealand, Auckland University of Technology, Auckland, New Zealand.

ABSTRACT
The cranchiid Teuthowenia pellucida, like many deep-sea squid species, possesses large eyes that maximise light sensitivity in a nearly aphotic environment. To assess ontogenetic changes in the visual system, we conducted morphometric and histological analyses of the eyes using specimens from New Zealand collections. While the ratio between eye diameter and mantle length maintained a linear relationship throughout development, histological sections of the retina revealed that the outer photoreceptor layer became proportionally longer as the animal aged, coincident with a habitat shift into deeper, darker ocean strata. Other retinal layers maintained the same absolute thickness as was observed in paralarvae. Granules of the pigment ommin, normally located in the screening layer positioned at the base of the photoreceptors, were also observed at the outer end of the photoreceptor segments throughout the retina in young and mid-sized specimens. Early developmental stages of this species, dwelling in shallow waters, may therefore rely on migratory ommin to help shield photoreceptors from excess light and prevent over-stimulation. The oldest, deeper-dwelling specimens of T. pellucida examined had longer photoreceptors, and little or no migrated ommin was observed; we suggest therefore that short-term adaptive mechanisms for bright light conditions may be used primarily during epipelagic, early life stages in this species.

No MeSH data available.


Related in: MedlinePlus