Siphonal eyes of giant clams and their relationship to adjacent zooxanthellae

Journal Article · Thu Jan 01 04:00:00 EST 1981 · Veliger; (United States)

OSTI ID:6701276

Fankboner, P V

Giant clams of the genus Tridacna possess up to several thousand eyes upon the surface of their exposed hypertrophied siphons; this extraordinary number of eyes is unique in the animal kingdom. The siphonal eyes of Tridacna are simple photoreceptors that lack a lens, but possess a pigment cup made of several to many layers of olive-green zooxanthellae. Each eye contains 280 to 350 polygonal retinal cells (15 to 20 ..mu..m in diameter) which bear numerous ciliary blebs. Retinal cell blebs posses a ciliary axoneme composed of 9 x 2 + 0 microtubule doublets which splay outwards from the cilium's basal plate. The ciliary blebs give rise to many microvilli that are believed to be the photoreceptive portion of the retinal cell. Whereas tridacnid eyes possess directional sensitivity, because they lack a lens, they are individually incapable of image discrimination. However, both the ability of giant clams to detect nearby movements and the high density of eyes on the siphonal surface indicate that tridacnid eyes may function cooperatively in small numbers much like the elements of a primitive compound eye. Owing to the transparency of the retinal cells and the biconvex shape of the siphonal eye, it is apparent that Yonge's hypothesis that zooxanthellae surrounding the eye's capsule may derive more sunlight than other similar siphonal tissues is reasonable.

• Research Organization: Simon Fraser Univ., Burnaby, British Columbia
• OSTI ID: 6701276
• Journal Information: Veliger; (United States), Journal Name: Veliger; (United States) Vol. 23:3; ISSN VLGHA
• Country of Publication: United States
• Language: English

Related Subjects

550800* -- Morphology
59 BASIC BIOLOGICAL SCIENCES
ALGAE
ANATOMY
ANIMALS
AQUATIC ORGANISMS
BODY
BODY AREAS
EYES
FACE
HEAD
INVERTEBRATES
MOLLUSCS
ORGANS
PLANTS
SENSE ORGANS
SYMBIOSIS