Display Settings:

Format

Send to:

Choose Destination
We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
J Exp Biol. 2008 Feb;211(Pt 3):292-9. doi: 10.1242/jeb.012864.

Shadow response in the blind cavefish Astyanax reveals conservation of a functional pineal eye.

Author information

  • 1Department of Biology, University of Maryland, College Park, MD 20742, USA. yossy@umd.edu

Abstract

The blind cavefish Astyanax mexicanus undergoes bilateral eye degeneration during embryonic development. Despite the absence of light in the cave environment, cavefish have retained a structurally intact pineal eye. We show here that contrary to visual degeneration in the bilateral eyes, the cavefish pineal eye has conserved the ability to detect light. Larvae of two different Astyanax cavefish populations and the con-specific sighted surface-dwelling form (surface fish) respond similarly to light dimming by shading the pineal eye. As a response to shading, cavefish larvae swim upward vertically. This behavior resembles that of amphibian tadpoles rather than other teleost larvae, which react to shadows by swimming downward. The shadow response is highest at 1.5-days post-fertilization (d.p.f.), gradually diminishes, and is virtually undetectable by 7.5 d.p.f. The shadow response was substantially reduced after surgical removal of the pineal gland from surface fish or cavefish larvae, indicating that it is based on pineal function. In contrast, removal of one or both bilateral eye primordia did not affect the shadow response. Consistent with its light detecting capacity, immunocytochemical studies indicate that surface fish and cavefish pineal eyes express a rhodopsin-like antigen, which is undetectable in the degenerating bilateral eyes of cavefish larvae. We conclude that light detection by the pineal eye has been conserved in cavefish despite a million or more years of evolution in complete darkness.

PMID:
18203983
[PubMed - indexed for MEDLINE]
PMCID:
PMC3584714
Free PMC Article

Images from this publication.See all images (6)Free text

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk