Journal ArticleDOI
Fine structure of the optic cusion in the asteroid Nepanthia belcheri
P. E. Penn,C. G. Alexander +1 more
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The optic cushion of Nepanthia belcheri (Perrier) is a prominent pigmented sense organ situated on the oral surface below the terminal tentacle.Abstract:
The optic cushion of Nepanthia belcheri (Perrier) is a prominent pigmented sense organ situated on the oral surface below the terminal tentacle. The distal region contains up to 170 optic cups, whilst proximally are numerous pyriform glandular cells traversed by supporting fibres. The outer margin of the optic cup is formed by alternating pigmented and photoreceptor cells. The pigmented cells contain numerous densely staining granules of scarlet pigment. The distal ends of the photoreceptors are elaborated into many long microvilli regularly arranged about a modified cilium. There is a clear circumciliary space delimiting the cilium from the microvilli.read more
Citations
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Journal ArticleDOI
Eye evolution and its functional basis
TL;DR: Calculations of the physical requirements for these four sensory tasks show that they correlate with major innovations in eye evolution and thus work as a relevant classification for a functional analysis of eye evolution.
Journal ArticleDOI
Unique system of photoreceptors in sea urchin tube feet.
TL;DR: The data suggest that echinoderms, in contrast to chordates, deploy a microvillar, r-opsin–expressing PRC type for vision, a feature that has been so far documented only in protostome animals.
Book ChapterDOI
Neurobiology of the Echinodermata
TL;DR: The present evidence suggests that any part of the radial nerve cords when receiving significant local sensory input can act to coordinate whole animal behaviour and thus the echinoderms can be considered “brainless”.
Journal ArticleDOI
Photoperiodic regulation of gametogenesis and gonadal growth in the sea star Pisaster ochraceus
TL;DR: Long daylengths (or short nightlengths) in spring and summer apparently synchronize or entrain the initiaion of gametogenesis and gonadal growth in fall and phase shift of all these events was evident within 6 to 9 mo.
Journal ArticleDOI
Photoperiodic Regulation of Gametogenesis in Sea Stars, with Evidence for an Annual Calendar Independent of Fixed Daylength
TL;DR: Gametogenesis and gonadal growth in the west coast sea star Pisaster ochraceus normally begins in the fall and leads to large gonads full of gametes in the spring, when spawning occurs, but the mechanism of the photoperiodic response is fundamentally different.
References
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A low-viscosity epoxy resin embedding medium for electron microscopy.
TL;DR: A low-viscosity embedding medium based on ERL-4206 is recommended for use in electron microscopy and has a long pot life of several days and infiltrates readily because of its low viscosity.
Journal ArticleDOI
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Journal ArticleDOI
Evolution of Photoreceptors
TL;DR: This essay will endeavor to demonstrate the relevance to photoreceptors of the Darwinian dictum: descent with modification to animal and plant photoreceptor structures.
Book ChapterDOI
Structure of Invertebrate Photoreceptors
TL;DR: Eakin this article conducted a tour of the photoreceptors of the human brain and found that they are all constructed on the same plan, a stack of disks, even the receptors of the ancient third eye.