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Red sea urchins lining the seafloor can “see”….

Sea urchins may use the entire surfaces of their bodies—from the ends of their “feet” to the tips of their spines—as huge eyes.

Scientists had already known the marine invertebrates react to light without any obvious eye-like structures—raising the question of how the animals see.

Previous genetic analysis of the California purple sea urchin had revealed that the animals possess a large number of genes linked with the development of the retina—the light-sensitive tissue lining the inner eyeball in people and other vertebrates.

This and other research suggested that sea urchin might rely on light-receptor cells randomly scattered across their skin, which collectively function like retinas.

Scientists had theorized the animals’ spines simulate the light-blocking pigmented cells found in most animals’ eyes. Because light-receptor cells in the retina can soak up light from every direction, pigmented cells work to block light from the back and the sides so animals can “see” what’s in front of them.

Now, however, the scientists have found two distinct groups of bristly, light-receptor cells concentrated at the bases and tips of the purple sea urchin’s 1,400-plus tube feet. These long, suction-tipped tubes, located on the undersides of sea urchin bodies, help the organisms move.

The team suspects that sea urchins use their tube feet as retinas and the rest of their bodies to shield against the extra incoming light, said researcher Maria Ina Arnone, a developmental biologist at Anton Dohrn Zoological Station in Naples, Italy.

Prior studies did find the number and placement of spines on a sea urchin could affect how sharp its vision might be, and this new find “might well be part of the picture,” Arnone added.

SeaUrchin-kit

Ocean Care Solutions Sea Urchin first aid kit..don’t get stung without it!!

Australian Bull Ray….Stingray

The Australian bull ray has a disc that is wider than it is long. The snout is blunt with a skirt-shaped inter nasal flap as well as a single fleshy lobe that surrounds the snout and almost reaches the pectoral fins. The medium-sized eyes are located on the sides of the head and the spiracles are large. The pectoral fins which make up the “wings” of this ray originate below the eyes. The margins of the pectoral fins are deeply concave and the tips are highly angular. There is a small dorsal fin that originates over or just behind the pelvic fin rear tips and is anterior to the spine on the tail. The tail is elongate and whip-like and has a venomous stinging spine located just behind the dorsal fin.
Stingray first aid kits available through DFA, on line or at your favorite retail beach/dive shop…don’t get stung without it!!