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Transparency in the eye region of an ostracod carapace ( Macrocypridina castanea , Myodocopida)

DOI: 10.1098/rsta.2018.0267 DOI Help

Authors: A. R. Parker (University of Oxford) , B. P. Palka (Cardiff University) , C. Purslow (Cardiff University) , S. Holden (DSTL Porton Down) , P. N. Lewis (Cardiff University) , K. M. Meek (Cardiff University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Philosophical Transactions Of The Royal Society A: Mathematical, Physical And Engineering Sciences , VOL 377

State: Published (Approved)
Published: February 2019
Diamond Proposal Number(s): 5745 , 8028

Abstract: Many myodocopid ostracods are unusual in that they have well-developed compound eyes yet must view their environment through a shell. The cypridinid Macrocypridina castanea is relatively large among ostracods (about 5–10 mm) and is a pelagic predator. This species possess highly pigmented shells with a transparent region lying just above the eye. Here we examine the ultrastructure and transparency of this window using electron microscopy, serial-block face scanning electron microscopy and X-ray diffraction analysis and optical modelling. An internal, laminar stack was identified within the window region of the shell that formed a more regular half-wave reflector than in non-window regions, and where the distance between molecules in the chitin–protein fibrils decreases as compared to the non-window area. This results in excellent transmission properties—at around 99% transmission—for wavelengths between 350 and 630 nm due to its half-wave reflector organization. Therefore, blue light, common in the mid and deep sea, where this species inhabits, would be near-optimally transmitted as a consequence of the sub-micrometre structuring of the shell, thus optimizing the ostracod's vision. Further, pore canals were identified in the shell that may secrete substances to prevent microbial growth, and subsequently maintain transparency, on the shell surface.

Journal Keywords: transparency; see-through shell; optimized vision in low light; myodocopid ostracod; Macrocypridina; deep sea

Subject Areas: Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography