On the three visual pigments in the retina of the firefly squid, Watasenia scintillans

Section: The Evolution Of Multifocalitymentioning

confidence: 99%

Early evolution of multifocal optics for well-focused colour vision in vertebrates

Gustafsson

Collin

Kröger

2008

“…Many cephalopods have horizontal slit (octopuses) or W-shaped pupils (some squids and cuttlefishes), despite the fact that most species are monochromats (Williamson, 1995). Even the firefly squid (Watasenia scintillans Berry 1911), one of a few cephalopod species known to have several visual pigments (Seidou et al, 1990), has a monofocal lens (Kröger and Gislén, 2004) and, interestingly, a circular pupil (Kinya Narita, personal communication). LCA is compensated for by a banked retina (Kröger and Gislén, 2004).…”

Section: T Malmström and R H H Krögermentioning

confidence: 99%

Pupil shapes and lens optics in the eyes of terrestrial vertebrates

Malmström

Kröger

2006

103

SUMMARY Animal eyes that are primarily used under low-light conditions usually have optical systems of short depth of focus, such that chromatic defocus may lead to considerable blurring of the images. In some vertebrates, the problem is solved by multifocal lenses having concentric zones of different focal lengths, each of which focuses a different relevant spectral range onto the retina. A partially constricted circular pupil would shade the peripheral zones of the lens, leading to the loss of well-focused images at relevant wavelengths. The slit pupil, however, allows for use of the full diameter of the lens even in bright light. We studied species of terrestrial vertebrates from a variety of phylogenetic groups to establish how widespread multifocal lenses are and how pupil shapes are adapted to the optical systems. We found that multifocal lenses are common from amphibians to mammals, including primates. Slit pupils were only present in animals having multifocal optical systems. Among the felids, small species have multifocal lenses and slit pupils, while large species have monofocal lenses and round pupils. The Eurasian lynx, a cat of intermediate size, has an intermediate eye design. The functional significance of the absence of multifocal optical systems in large felids remains mysterious, because such systems are present in other large-eyed terrestrial vertebrates. Multifocal optical systems in nocturnal prosimians suggest that those animals have colour vision despite being described as cone monochromats.

“…The photoreceptors are long cells that contain only one visual pigment (Bellingham et al, 1998;Brown and Brown, 1958), making cephalopods almost certainly color blind, which has been confirmed in a number of behavioral studies (Marshall and Messenger, 1996;Messenger, 1977). There is one known exception: the firefly squid Watasenia scintillans, which has three visual pigments (Michinomae et al, 1994;Seidou et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Do cephalopods communicate using polarized light reflections from their skin?

Mäthger

Shashar

Hanlon

2009

SummaryCephalopods (squid, cuttlefish and octopus) are probably best known for their ability to change color and pattern for camouflage and communication. This is made possible by their complex skin, which contains pigmented chromatophore organs and structural light reflectors (iridophores and leucophores). Iridophores create colorful and linearly polarized reflective patterns. Equally interesting, the photoreceptors of cephalopod eyes are arranged in a way to give these animals the ability to detect the linear polarization of incoming light. The capacity to detect polarized light may have a variety of functions, such as prey detection, navigation, orientation and contrast enhancement. Because the skin of cephalopods can produce polarized reflective patterns, it has been postulated that cephalopods could communicate intraspecifically through this visual system. The term 'hidden' or 'private' communication channel has been given to this concept because many cephalopod predators may not be able to see their polarized reflective patterns. We review the evidence for polarization vision as well as polarization signaling in some cephalopod species and provide examples that tend to support the notion -currently unproven -that some cephalopods communicate using polarized light signals.